Last week, we learned about the death of Peter Higgs, a physicist and discoverer of the particle that bears his name. The Large Hadron Collider was built to find and describe the particle. Today, we’ll look back at the life of Peter Higgs and his particle.

Human transcription provided by GMR Transcription

Fraser Cain:               
Astronomy Cast Episode 716: The God Particle – Remembering Peter Higgs. Welcome to Astronomy Cast, our weekly facts-based journey through the cosmos where we help you understand, not only what we know, but how we know what we know. I’m Fraser Cain. I’m the publisher of Universe Today. With me, as always, is Dr. Pamela Gay, a senior scientist for the Planetary Science Institute and the director of CosmoQuest.

Hey, Pamela. How you doing?

Dr. Pamela Gay:        
I am doing well. I am still trying to get my sleep back on schedule after having a bunch of our CosmoQuest community mods come out and hang out during the eclipse week and all the events around that. It was a tremendous event, and it was so good to see so many people face-to-face, including some I had never met in person. At one point, we had 14 humans and four spare dogs in the house during the leadup to the eclipse as everyone was prepping.

Fraser Cain:               
Wow. Well, your house can absorb that.

Dr. Pamela Gay:        
It can.

Fraser Cain:               
Yeah.

Dr. Pamela Gay:        
Although, keeping the dogs separated as necessary was a fascinating game of gates.

Fraser Cain:               
Right. But we were off last week because we were enjoying the eclipse and victory for both of us.

Dr. Pamela Gay:        
Yes.

Fraser Cain:               
We both saw totality, clear skies. It was perfect. So, yay us.

Dr. Pamela Gay:        
We did it. We did it. No need to ever travel again for an eclipse.

Fraser Cain:               
No way. I wanna see more. But it was amazing. And I think for everybody out there who’s listening to this, if you did get a chance to see it, congratulations. If you didn’t get a chance to see it, the cosmic geometry continues, and you will get more chances in the future and some travel ideas. So, keep trying out there. And, yeah. Yeah, I’m so glad that we got a chance to see it after 2017 –

Dr. Pamela Gay:        
Yeah.

Fraser Cain:               
– when we didn’t get a chance to see it.

Dr. Pamela Gay:        
We tried. We tried.

Fraser Cain:               
Yeah.

Dr. Pamela Gay:        
The universe mocked us.

Fraser Cain:               
Yes. Last week, we learned about the death of Peter Higgs, a physicist and the discoverer of the particle that bears his name. The Large Hadron Collider was built to find and describe the particle. Today, we look back at the life of Peter Higgs and his particle. All right, Pamela. Who is Peter Higgs?

Dr. Pamela Gay:        
He was a British theoretical physicist who every single thing I found to read described him as shy, as filled with creativity and curiosity, and just not wanting to be a famous person, but willing to explain science to anyone and break down the concepts as much as was needed to help them understand.

He’s not someone I ever met, but after all the reading I did for this episode, I really am sad I never met him. There aren’t enough personable theoretical physicists who actually can break things down because, most of the time, they’re just working at such a high level that bringing it down to even the level of an observational astronomer isn’t something that happens.

Fraser Cain:               
But let’s talk about his, I don’t know, discovery. What’d you call it, his theory?

Dr. Pamela Gay:        
His background.

Fraser Cain:               
Yeah, yeah. His background, but also leading up to his – man, what’s the right word? I guess, his theory of that there should be a particle that connects mass to the universe. Was he the person that figured this out?

Dr. Pamela Gay:        
So, he was one of them. And so, basically, this is the story of everything working exactly the way it’s supposed to. He went to a private school when he was in high school, or a magnet school; I’m not quite what the right words are.

Fraser Cain:               
Yeah, I know. It’s like public school means not what you think it is, and private school doesn’t mean what you think it means.

Dr. Pamela Gay:        
Right. Right, not in England. No.

Fraser Cain:               
Right, right, right. So, did he go to the one where the regular people go to or the one where people pay for them to go to?

Dr. Pamela Gay:        
He went to the one that Paul Dirac had gone to, and that’s the key point.

Fraser Cain:               
Okay.

Dr. Pamela Gay:        
He went to the same high school. I think that’s the closest explanation word, that Paul Dirac had graduated well before him. But he knew about Paul Diran because was an alumni, and he decided that he wanted to follow in Paul Dirac’s footsteps and become a physicist. He moved to the city of London so that he could go to a more exclusive, finishing off the rest of high school, before starting university. And so, this really starts by being this is someone who had a role model, and that role model inspired them to do great things with their life.

So, first of all, win; I like this story already. He then bounced around. Did his undergraduate. Hitchhiked for a while. Fell in love with the city of Edenborough while hitchhiking, which is just pleasing. It was the ’50s. It was safer back then. Got his PhD when he was 25. Did the same thing that still happens today. He bounced around. He was a lecturer here, a lecturer there.

And when he was 35, he submitted a paper to physics letters that outlined how mass – which at that point in time couldn’t be explained. Like, everything we knew about particle physics at that point in time said a lot of the key particles should not have any mass. But they have mass. And so, there was this very deeply confusing issue.

Fraser Cain:               
And at this point, there was the standard model of particle physics that had a lot of the bits and pieces already figured out.

Dr. Pamela Gay:        
Yeah. It wasn’t as complete.

Fraser Cain:               
Right. Right. We knew about the proton, the neutron, the electron –

Dr. Pamela Gay:        
Yeah.

Fraser Cain:               
– but also the quarks and the various particles, the subatomic particles –

Dr. Pamela Gay:        
Yeah.

Fraser Cain:               
– some of which had been confirmed in both particle accelerators and others which hadn’t. But everyone just assumed they had to be there.

Dr. Pamela Gay:        
Right.

Fraser Cain:               
It was just a matter of time before they were found.

Dr. Pamela Gay:        
And so, he was working on trying to understand how symmetries get broken, how you make space for mass to exist. And he put together a theory that brought together both the boson that would go on to hold his name and a scaler field that permeated all of space and time that particles couple with through that boson. And it’s through that coupling that objects end up having what we discern as having mass in our laboratories.

And the paper was soundly rejected. And I love this part of the story because he submits the work; the paper gets rejected from a journal that was published out of CERN. So, the laboratory that would eventually be the one that discovers the Higgs boson said, “No science for you. Do not believe.”

Fraser Cain:               
Yep.

Dr. Pamela Gay:        
And he added one paragraph to the paper. Submitted it to a different journal, Physics Review, and it got published. Now, here is where he is such an awesome human.

So, his work was not the only work on trying to understand this. There were three different teams at the time that were all working on this at the same time. And throughout his entire life, he always gave credit to all the other teams. And so, you see it called the Higgs field. You see it called by a variety of other different names. And he made sure every time he referred to it he listed everyone involved, usually by an alphabet soup of all their names, which is about the nicest thing a human being could do.

And in preparing for this episode, I was rewatching – and I didn’t make it all the way through – but I was rewatching Particle Fever, which is a documentary.

Fraser Cain:               
That’s a great documentary.

Dr. Pamela Gay:        
Yeah.

Fraser Cain:               
Yeah.

Dr. Pamela Gay:        
It’s by David Kaplan. It’s available not for streaming, but you can purchase it or rent it pretty much everywhere. And he’s not playing a major role in it. And so, while they have all these other physicists where they’re like, “This human only writes papers with three authors because Nobel Prizes can only go to three people” –

Fraser Cain:               
Right.

Dr. Pamela Gay:        
– Peter Higgs is like shown crying when they find the – well, he’s not doing this. He’s wiping away tears. But Peter Higgs is just like, they found it. He’s so sweet, so nice. And they catch him crying. And everyone else is just like, ughhh, because they weren’t the ones getting the Nobel Prize. And here he is, the day – this is my favorite story so far.

So, everyone knows when they’re gonna be making the calls for the Nobel Prize. The people who are nominated often have an idea. They don’t know who’s gonna be the winner, but they know to stay home and stay next to the phone. And Peter Higgs went out for a walk and left his phone at home because he didn’t wanna deal with it. And it was one of his neighbors as he’s walking home that lets him know.

Fraser Cain:               
Right.

Dr. Pamela Gay:        
“Dude, you got the Nobel Prize in physics.” And it’s just awesome.

Fraser Cain:               
So, he had predicted this particle and the field and the interactions between these two. And I think that’s the key.

Dr. Pamela Gay:        
Yeah.

Fraser Cain:               
You know, it’s very easy to just say, oh, there’s gotta be some field that contributes to mass. There’s gotta be some particle that makes mass. But to recognize this connection –

Dr. Pamela Gay:        
Yeah.

Fraser Cain:               
– between the particle, the boson, and the field. And there’s some great analogies to describe how the Higgs boson would work. Do you have a favorite?

Dr. Pamela Gay:        
I do. I read this initially in Scientific America back in the ’90s. So, the way to think about the Higgs boson and the Higgs field is, if you’re trying to walk through a room and you’re a nobody – you have to mass – you just fly through the room because there’s nothing slowing you down. You have nothing dragging you. You have nothing connecting you. Zoom, you’re through the room. Now, if you have a few friends, you might get slowed down because they’re like, “Hey, how’s it going?”

Fraser Cain:               
Right. Right.

Dr. Pamela Gay:        
“Hey, how’s the trip?”

Fraser Cain:               
“What do you think about this?” Yeah. “What do you think about this?”

Dr. Pamela Gay:        
Yeah. Yeah.

Fraser Cain:               
I want you to meet this person.

Dr. Pamela Gay:        
And so, this is someone who has – or something that has a little bit of mass. They have a few bosons coupling them to the Higgs field, and this slows down their passage

Now, the more famous you are, or the more massive you are, the more you have dragging you down by coupling you to that field. And so, more massive objects have a stronger coupling. They have more Higgs bosons tying them to that Higgs scaler field. And so, there’s no direction to the field. It’s just everywhere all the time. And we all get stuck to it by these Higgs bosons. And I for one could do with a few fewer Higgs bosons.

Fraser Cain:               
Right. But like Taylor Swift trying to move through that party would make no progress.

Dr. Pamela Gay:        
Yeah. And that is a massive particle.

Fraser Cain:               
A very massive particle. Yeah. Yeah, that’s great.

So, he predicts the particle, predicts the field. But how did this get translated into what is one of the greatest scientific experiments in human history?

Dr. Pamela Gay:        
Well, this is a combination of really good promotion by another Nobel Prize winner, and also the entire field trying really hard to check all the boxes in the standard model trying to find all the things.

So, first, we have Leon Lederman, who won his Nobel Prize for work on neutrinos, who wrote a book that he intended to call the God – four-letter word I’m not going to say on air – particle. And his publisher was like, no. No, Leon, we cannot do that. And so, the God – four-letter word that I’m not going to say on air – particle became the book The God Particle.

Fraser Cain:               
Right.

Dr. Pamela Gay:        
And poor Higgs was –

Fraser Cain:               
But it was the God Damn Particle, right?

Dr. Pamela Gay:        
Yeah, now you’re gonna say the word on air that I –

Fraser Cain:               
I’m gonna say it. Yeah, that’s fine.

Dr. Pamela Gay:        
Okay, fine. You do it.

Fraser Cain:               
Yeah. Yeah.

Dr. Pamela Gay:        
So, Leon Lederman was gonna name his book The God Damn Particle. His publisher was like, no. No, we cannot do that. And one of the reasons it was called that is because it was so frustrating to find. It’s such a massive particle.

Fraser Cain:               
Right. Right. So, the name is not like its incredible purpose in the universe.

Dr. Pamela Gay:        
No.

Fraser Cain:               
It’s how frustrating it’s been to find this thing that the most powerful particle accelerators, which have been trying to find it, have failed because they don’t have enough energy.

Dr. Pamela Gay:        
Yeah.

Fraser Cain:               
You don’t have the right tool to get to this stupid, illusive particle.

Dr. Pamela Gay:        
Yeah. And then, of course, because Leon Lederman had done that a lot of people were like, oh, we’re going to make this the most important particle ever because it is what gives the universe mass; and with mass, gravity can evolve all the things. And so, it’s not so much a backronym as a backroname, where they gave it all the import after it had been done by a publisher trying to –

Fraser Cain:               
Yeah.

Dr. Pamela Gay:        
Yeah. But I think that because of the book, because of the popularity of the idea, that probably helped with keeping the funding turned on to make this happen. So, the idea that we need to build bigger and bigger and bigger particle accelerators had been around for a while. Here in the United States, we’ve been trying to build the Super Collider – Super Colliding Super –

Fraser Cain:               
Superconducting Super Collider.

Dr. Pamela Gay:        
Thank you. In Texas. And then Congress canceled it after it had mostly been dug, after they had taken all of the land from the farmers via eminent domain. They sold the land to real estate people who built McMansions, and they actually filled in the tunnel instead of using it for geologic research, which had been proposed. So, that was just a hot mess. US was not going to find this particle.

And CERN was like, okay. We’re a multinational consortium. We have partners from nations that are all but at war with each other. And we’re still in the name of science going to use the wealth of all of these nations, the intellectual capabilities of all of these nations, to work together to build a accelerator capable of sending particles at higher and higher velocities and collecting them in these instruments, ATLAS being the key to finding the Higgs boson. And full disclosure, when I was a baby student at Michigan State University, I spent a summer weaving fiber for instruments for ATLAS.

Fraser Cain:               
Oh, wow.

Dr. Pamela Gay:        
So, my skin cells are probably somewhere in ATLAS.

Fraser Cain:               
This is personal.

Dr. Pamela Gay:        
Yeah. Yeah. So, I just listened to audio books all summer and attached fibers very carefully over and over, hundreds and hundreds of them. This is what undergraduates in physics do. But this is just an idea of how many members of the physics community, in the astronomy community have been part of building this.

There were thousands of students. There were hundreds of graduate students. There were probably hundreds of PhDs, just fewer hundreds, working on all levels of this experiment from the electronics, to the optics, to the control systems. It was a truly global endeavor to find the reason my bathroom scale makes me sad in the morning.

Fraser Cain:               
Right. So, let’s talk about the experiment then. What was the Large Hadron Collider at CERN – what was sort of some of the key parts to this experiment?

Dr. Pamela Gay:        
So, they needed to get a extremely large amount of energy, tens of electron volts, confined in the tiniest of volumes. And the reason they need to do this is so that energy could then turn into the ever-so-briefly-lived Higgs boson. So, Higgs bosons have a mean lifetime – and I have to look at my screen for this – of between 1.2 and 4.6 times 10 to the -22 seconds.

Fraser Cain:               
Right.

Dr. Pamela Gay:        
So, 0.0 – write that zero 21 times –

Fraser Cain:               
Right.

Dr. Pamela Gay:        
– 1.2 to 4.6.

Fraser Cain:               
Right. That is a very tiny amount of time. A fraction of a fraction, of a fraction of a second.

Dr. Pamela Gay:        
Yeah. So, they not only needed to get 125 gigaelectron volts divided by C-squared, which is the crazy units that we use in particle physics, of energy confined in one small area; they also had to have instruments capable of measuring the trails made by the particles created in that energy combined in that small area, all at once.

And so, the way this was done was they were accelerating protons. They needed to get them going super, super fast. They needed to then make them go smash, as you do. And then one of the biggest features of ATLAS was layers upon layers of fiber optics of varying kinds, width, color sensitivities that would then be able to channel the energy through the photomultiplier tubes that could sense the light, the flickers of energy of these particles coming in and out of existence. And they did it.

What was amazing is there’d been hints that this was the correct energy. There’d been hints that things had previously been seen at Fermi National Lab when they were running some of their high-energy experiments. They had to turn off Fermi’s experiments while they were working on upgrading their things. Then they upgraded everything at CERN. CERN was the place that ultimately did the experiment.

And it’s hoped with the next generation of the CERN accelerator and all of its instruments that they’ll be able to see more than just a signal created by these things, but they’ll actually start to be able to measure more and more of their properties and hopefully be able to start doing things like prove once and for all that the supersymmetric particles are or aren’t there –

Fraser Cain:               
Right.

Dr. Pamela Gay:        
– and find any particles that may or may not be dark matter.

So, it’s not that they did CERN just to find the Higgs boson. The Higgs boson helped, and Leon Lederman’s book popularizing the Higgs boson really helped. But this is fundamental physics. This is what we do. We go, okay, we have a theory. The theory says all these particles are going to exist. We’re now going to make sure all those particles actually exist because if they don’t the theory is wrong.

Fraser Cain:               
Yeah.

Dr. Pamela Gay:        
And this was the last of the core particles that should be discoverable. There’s a graviton out there that we probably will never find, if it exists. But this was the last of the particles we knew we could find if we could just turn the energy up to 11.

Fraser Cain:               
Right. Right. And there’s like a real beauty to that. I mean, was it 2012 –

Dr. Pamela Gay:        
Yeah.

Fraser Cain:               
– they announced the findings. But for a couple of years leading up to that, we knew that they were on the right track.

Dr. Pamela Gay:        
It was gonna work.

Fraser Cain:               
They were finding with higher levels of – it was going to work. They had found it. It was really a matter of exactly trying to pin down the mass of this particle. But how did the physics community, and I guess how did Higgs – I mean, you mentioned earlier on he wiped away tears from his eyes.

Dr. Pamela Gay:        
He cried.

Fraser Cain:               
Yeah. Yeah. So, how did that sort of change his perspective on what he had originally proposed?

Dr. Pamela Gay:        
So, he’s a shy human, so finding things like that wasn’t something I was able to do. He was the kind of person who showed up to these events, looked spectacularly happy in front of giant pictures of ATLAS. And then when people were like, I don’t understand. He just explained the physics.

This was a human being that, as near as I can tell from everything I read, his true joy came in understanding our universe, having the theory proven true, but then it wasn’t all about, oh, look at me. It was, hey, let me explain the science to you. My favorite description was he’s someone who’s shyness was overcome by explaining physics to others.

Fraser Cain:               
That’s wonderful.

Dr. Pamela Gay:        
I wish I had met him. I really do.

Fraser Cain:               
Yeah. Yeah, that sounds amazing. So, I guess, what comes next? What do you think is his legacy for physics and the future of particle accelerators?

Dr. Pamela Gay:        
So, he had some ideas on dark matter that will either get proven or disproven. But, mostly, he’s been retired and following along for the past few years. And his legacy is all the particle physicists who he inspired, who he taught, who are going to be the humans working to figure out what is dark matter, what is dark energy. He worked as a professor at the University of Edenborough. He got to be at the place he loved when he went hitchhiking. And he trained generations of students, and that in a lot of ways is the best legacy anyone could have, other than, of course, the Nobel Prize.

Fraser Cain:               
I love the idea of an international physics community coming together to do this basic research work.

Dr. Pamela Gay:        
Yeah.

Fraser Cain:               
On the one hand, the particle that interacts with a scaler field, that is the source of mass in the universe –

Dr. Pamela Gay:        
Yeah.

Fraser Cain:               
– it seems very esoteric. And, yet, it is this basic building block of us to understand better the true nature of the cosmos. And who knows if there will ever be practical use for it. But we do know that we have one less mystery out there.

Dr. Pamela Gay:        
And let this also be a lesson about history remembers the workers, the helpers. And this is a human who was one of three different collaborations who proposed what became the Higgs mechanism, the Higgs boson, and the Higgs field. And, well, pretty much everyone and everything refers to them as Higgs boson, Higgs mechanism, Higgs field. He was like, no. He called it the ABEGHHK’tH mechanism –

Fraser Cain:               
Correct.

Dr. Pamela Gay:        
– for Anderson, Brout, Englert, Guralnik, Hagen, Higgs, Kibble, and Hooft.

Fraser Cain:               
Right. Right.

Dr. Pamela Gay:        
He gave credit to everyone.

Fraser Cain:               
Every time.

Dr. Pamela Gay:        
Yeah.

Fraser Cain:               
What a gentleman.

Dr. Pamela Gay:        
So, yeah. Be the helper.

Fraser Cain:               
Thank you, Peter Higgs. And thank you, Pamela.

Dr. Pamela Gay:        
And thank you to all the people out there who make this show possible. We would not be here without you. And I regret to say the names for this week were not listed. So, I’m going to really, really hope that the names for April are good enough, and I’m going to read the April 3rd names. And I will make sure that everyone else who should’ve been read today, all of our $10.00-and-up – we break you across the month – people get acknowledged.

So, our $10.00 patrons whose names are going to be read are David, Everson, Michael Procha, Jon Thase, Berry Gowan, Steven Veit, Jordan Young, Jeanette Wink, Nanoflips, Andrew Poelstra, [inaudible] [00:27:04], Brian Cagle, David Truog, Gerhard Schwarzer, David, Buzz Parsec, Laura Kittleson, Robert Palsma, Les Howard, Jack Mudge, Joe Hollstein, Alexis, Gordon Dewis, Richard Drumm, Adam Annis-Brown, Frank Tippin, Greg Davis, William Andrews, and Gold.

And if you too would like to hear me stumble horribly over your name and be extremely grateful for you while doing it, join at the $10.00-and-up level. Thank you, all, so much.

Fraser Cain:               
All right. Thanks, everyone. We’ll see you next week.

Dr. Pamela Gay:        
Bye-bye.

Ice is ice, right? You know, what you get when water freezes. Well, maybe here on Earth. But across the Universe, water can be squeezed together at different temperatures and pressures, leading to very different structures. Today we’ll talk about the different forms that ice can take.

This episode is brought to you by BetterHelp. Give online therapy a try at betterhelp.com/ASTRONOMY and get on your way to being your best self.

Show Notes | Transcript

Crystallinity of the Ice (UCLA)

How to Make Clear Ice Cubes for Your Cocktails (Liquor.com)

You’re Doing It Wrong: The Guide to Making Perfect Pasta (Smithsonian Magazine)

Iceland Has Got a sparkling Ice Diamond Beach on Breiðamerkursandu (Guide to Iceland)

Centaurs (Swinburne University)

Scientists discover a new type of amorphous ice (Cosmos Magazine)

Scientists created a weird new type of ice that is almost exactly as dense as water (Live Science)

Ganymede (NASA)

Europa (NASA)

Enceladus (NASA)

Kuiper Belt Objects (Swinburne University)

An orbital dance may help preserve oceans on icy worlds (Phys.org)

Why do astronomers call Uranus and Neptune ice giants? (Astronomy)

Europa’s heaving ice might make more heat than scientists thought (Brown University)

What color is an iceberg? (NOAA)

Cat’s Cradle by Kurt Vonnegut Jr. (Goodreads)

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(This is an automatically generated transcript)

Frasier Cain [00:01:43] Astronomy Cast episode 675 Exotic Forms of Ice. Welcome to Astronomy Cast, a weekly facts based journey through the cosmos where we help you understand not only what we know, but how we know what we know. I’m Fraser Cain, I’m the publisher of Universe Today. With me is Doctor Pamela Kane, a senior scientist for the Planetary Science Institute and the director of Cosmic Quest. Hey, panel, how you doing? 

Pamela Gay [00:02:04] I am doing well. It is, odd to be recording this episode on a beautiful spring day, but on the day that I added it to our, show line up, it was a nasty, cold, cold, horrible Midwestern day. And, it just I was inspired. 

Frasier Cain [00:02:23] Well, it’s snowed here. This morning’s so perfectly appropriate. Although you it my my wife described it as a snow cone fight like it was. It did not last long. Gloopy blobs of snow blasting around to. No was not, you know, nice light, fluffy snow drifts. But it was just like someone was pouring gloop down from the sky. It was this is this, this spring. Climate change. Ice is ice, right? You know what you get when water freezes? Well, maybe here on Earth, but across the universe, water could be squeezed together at different temperatures and pressures, leading to very different structures. Today we’ll talk about the different forms that ice can take. All right. So in preparing for this show, one of the things that I didn’t even realize is that the kind of ice that we’re familiar with is actually the minority in the universe. 

Pamela Gay [00:03:25] What? It’s it’s it’s one of these things where, like, growing up, you’re you’re taught over and over in school that ice is the one solid that is bigger than, in volume than the liquid that it forms from. And you’re told all these things. Right. And it turns out that what we’re learning is the special case in which liquid water is able to freeze at a rate that allows crystals to form. And as the oxygen molecules come together to form these six sided crystals with the hydrogen atoms oriented, however, they will the volume gets bigger because the the molecules have to space themselves out to form these crystals. And, and the thing is that very special circumstance of liquid to ice that allows crystals to form isn’t gonna happen everywhere in the universe. 

Frasier Cain [00:04:41] Right? So we’ve got a habitable world where you have liquid water under air pressure. 

Pamela Gay [00:04:49] Yeah. 

Frasier Cain [00:04:50] And as the temperature drops below freezing, then you get these crystals able to form inside the water, float to the top and continue growing to form sheets of, of ice. So. So what is that called? 

Pamela Gay [00:05:08] A crystal in ice. 

Frasier Cain [00:05:09] Crystals on ice. Okay. So yeah. So from when it whenever you like, if you’re going to serve someone to drink, you ask them, would you like some crystal and ice cubes in your drink. 

Pamela Gay [00:05:20] Right. 

Frasier Cain [00:05:21] Well, if you want to go skating at the crystal and ice skating rink. 

Pamela Gay [00:05:27] What I love is there are pubs and bars around the world that have gone to great extremes to figure out how exactly you should freeze ice to get perfectly clear ice cubes, because the the goal is to get all the crystals aligned just so that you don’t have any defects. Just like a diamond, you judge it for its clarity. Well, a diamond is a crystal, an ice is a crystal. And apparently we sometimes judge our ice by its clarity. 

Frasier Cain [00:06:02] What’s the trick? How do you make ice clearer than cloudy eye? 

Pamela Gay [00:06:07] So it’s a combination of, how quickly you freeze it and, just making sure that it is pure water free of defects. And I think I remember reading that you start with hot water and then let that go. And I don’t know why that would be possible. 

Frasier Cain [00:06:29] And there’s something like you have to agitate it, I think. 

Pamela Gay [00:06:34] So you get the air bubbles out. 

Frasier Cain [00:06:36] To get the air bubbles out. Yeah. So you have to keep you have to keep slowly mixing it to get all the air bubbles out, because they’ll cause little blobs of cloud inside that will then make it not clear. Yeah. Yeah. 

Pamela Gay [00:06:47] And a quick side PSA. So I’ve gone through life not knowing why people said use, cold water to make pasta and things like that because it’s it’s not really going to make a big difference on how quickly things boil. And it’s because the cold water going through your pipes doesn’t pull the irregularities off the sides of the pipes, so you actually get softer water from the cold tap than from the hot tap. So if you don’t want as many kidney stones, use the cold water. Yeah, that totally blew my mind. I heard that a few weeks ago. That’s really, you know. 

Frasier Cain [00:07:24] Well, in in my in our new place, we’ve got a pretty big problem with, with hard water. So before, I never had hard water and now I have hard water. Now I’m learning these terrible lessons. As for cleaning the gunk off of faucets and things like that. But I had no idea. That’s really interesting. Okay. Yeah. Now, the the clearest ice that I’ve ever seen was in Iceland. There’s this. Oh, if you take a tour, there’s this. This lake where where glaciers are dropping blobs of ice into the lake, and then they go out into the ocean, and then the ocean wears them down a bit, and then barfs them back up onto the shoreline. And you walk along and they’re just these chunks of glass of diamond. It seems like they’re beautiful. And then you bring one back to the bar and they’ll mix them into your drinks if you want. So it’s, it’s a it’s an amazing experience. Like, like I think seeing geysers and waterfalls and all that was great. But seeing these, these shards of glass, of glass like ice. Yeah. On the shore. And I guess the, you know, something, I guess the enormous pressure of the glacier helped clear the the ice out. All right. So we’ve talked about crystalline ice. Boring. But so let’s talk about the other kind of ice. 

Pamela Gay [00:08:45] So I first learned about this, and I trying to understand the different theories on why objects like centaurs out around Jupiter’s orbit, between Jupiter and Saturn, are able to sometimes become active at that particular distance. A icy object shouldn’t be getting enough energy from the sun to be thermally excited. And so there’s ideas that in some cases, it’s landslides release energy that causes activity. But another idea is as objects move into the inner solar system, while things don’t get warm enough to melt crystalline ice, they do get warm enough to transition ice from what’s called amorphous ice to crystalline ice, which is a process that releases energy. 

Frasier Cain [00:09:42] To what is amorphous ice. 

Pamela Gay [00:09:44] It is ice that comes in many different kinds of density structures, where basically you have water molecules that are so cold that if you put them all in a cup, they wouldn’t form water, but they’re so cold that they can’t orient themselves to form crystals. So you end up with all these water molecules collecting together. The closest analogy I can think of is like dust gathering together. And as these molecules of ice come together without any orientation being dictated upon them, you get amorphous ice. So not crystalline is amorphous. 

Frasier Cain [00:10:34] Right? Right. And so if you were to like take a magnifying glass and look at crystalline ice, you would see all these molecules lined up perfectly, but with amorphous ice. 

Pamela Gay [00:10:46] All over the. 

Frasier Cain [00:10:46] Place. They’re all over the place. But it’s not a liquid. 

Pamela Gay [00:10:49] No. And this is where it’s. It’s so weird because I. There was there was this truly, truly delightful study. And and I’m always amazed at how researchers get permission to do it. And it’s not so much permission, but the creativity and and the funding to do certain things, or permission to use equipment to do certain things. I don’t really think this is a funding issue. Water’s kind of like comes out of the tap. Researchers took. Water froze it at at extreme pressures and extremely low temperatures in the vicinity of ball bearings, steel ball bearings, and essentially beat the tar out of it. And and it turns out that if you have ice and you beat the bejesus out of it, like literally take a container with ball bearings in it and shake it and shake it and shake it and shake it so that you don’t so much have a snow cone as you have snow, but then you put this under extreme pressure. What you have is all these disorganized ice crystals that are a powdery substance that can be considered as solid, but can behave more like a liquid. It’s right here. Weird. 

Frasier Cain [00:12:29] But I guess that’s what like on Earth, as we mentioned, you’ve got reasonable temperatures crossing the line between freezing and end and I guess not freezing. And then and then you got the air pressure. But in worlds like Europa and Enceladus, as you descend down into worlds like Jupiter, you’ve got varying both temperature and pressure, both vastly greater and vastly lower than what we have on Earth. So and these give us some of these weird forms of amorphous ice. All right. We’re gonna talk about that some more in a second, but it’s time for a break. 

Pamela Gay [00:13:14] This episode is brought to you by BetterHelp. I saw an amazing quote the other day from social media. Someone had simply posted, I want to learn to be the adult here. Adult on telecoms. As I reflect back on my last week of zoom meetings and writing and work, I realized I need to learn to be the adult here. Adult when I’ve had too much coffee, and I need to learn how to say I’ve been programing, it’s going to take me a second to switch gears. I need to both learn to give myself space and learn when I should just put myself in timeout until the caffeine and lack of sleep is replaced with solid and actual sleep. It is sometimes such stupid things that prevent us from being our absolute best. As I’ve mentioned, I’ve turned to BetterHelp to get help in the past, and the entire process for getting matched with a therapist was super straightforward. I filled out an online questionnaire on my phone and was matched with a licensed therapist the very next day. They also allow you to switch therapists at no additional charge. Between talking to someone and interacting through all their online tools. I was able to learn new things and I hope, become a better version of myself. Discover your potential at BetterHelp. Visit betterhelp.com/astronomy today to get 10% off your first month. That’s BetterHelp. H e lp.com/astronomy. 

Frasier Cain [00:15:03] And we’re back to. So let’s talk about this and then give me some examples of amorphous ice here in the solar system in various places and how it might have formed and, and sort of just how behaves. 

Pamela Gay [00:15:18] So the most obvious one is what I mentioned. We have these objects that are not rocky asteroids are not comets because their orbit hasn’t carried them into the inner solar system yet. These are objects that formed out in the outer outer solar system. So out beyond 50 A.U. and where they formed was so cold that as ice crystals came together, they didn’t form crystals. And as gravity pulled all of these ice crystals together, it created greater and greater pressure. And so you have these objects that are made of amorphous ice. And as they migrate towards the inner solar system, they eventually get enough energy that the ice rearranges itself into crystalline ice. And we see these outbursts. Now that is kind of cool. It isn’t scary at all. And it’s like, Yeah, that totally makes sense. Yeah. Now, when you carry this research a little bit further. And start looking at worlds in the outer solar system and thinking about that ball bearing experiment. We have worlds like Ganymede that while you can’t really compare them to ice in a small container with ball bearings being beat up, they they do get struck by asteroids, which has a similar compression force. So what you can imagine is asteroid comes in or comet comes in, some source of force comes in, strikes the surface of the world. So Ganymede, one of these other icy worlds at the surface, some of that energy is going to lead to melting, but ultimately there’s going to be compression waves that move through the world and have the ability to transition ice from crystalline ice to amorphous ice. Now, over time, this pressure is going to get released through the world. It’s a tectonic force, just like pressure inside of of the place where two plates come together will eventually release as an earthquake. And. New research is theorizing that over time, the release of that pressure from ice going from crystalline to amorphous. When it goes back to crystalline. This can cause some of the massive cracks, some of the strange quakes and other formations that we’ve seen on the surfaces of these worlds, and previously couldn’t completely explain because they didn’t have tectonics like we have here on Earth. 

Frasier Cain [00:18:18] And so you’ve got I mean, when we think about Europa, like we know that the surface looks very icy and maybe it is crystalline ice at the at that point, but then you’ve got. Tens of kilometers of ice stacked on top of each other. So you can imagine the sorts of pressures that this ice is under, under 20, 30, 50km of pressure of all of this ice coming down on top of it. It must be. 

Pamela Gay [00:18:48] Extreme and well. 

Frasier Cain [00:18:50] And then there is that kind of in rippling back up and causing some of these, these cracks to make their way back up. 

Pamela Gay [00:18:57] Europa and Enceladus are their own kind of special case. They they have more heat inside of them than, Ganymede does. And this additional heat allows ocean currents. Especially with Europa, it’s looking like to actually affect, to create drag forces, to build up torque forces on the ice above that is generating a lot of these structures we see. And the ice, it’s it’s still being debated whether it is consistently tens of kilometers thick or in some places, just a few kilometers thick, with, water being able to seep out. Now, with Ganymede, you’re looking at a world that doesn’t have the same tremendous amount of heat built up in the core. While it may have subsurface oceans, it is going to have significantly thicker ice on the surface. And it’s in these cases with the significantly thicker ice, such as with with Kuiper belt objects in particular, that we’re going to be looking at having this amorphous ice potentially getting formed during collision events where there was once crystalline ice, and then that flipped back from amorphous to crystalline again, that releases energy. 

Frasier Cain [00:20:19] So what about some of the like, the most massive places in the solar system? When you think about as you descend down through the cloud tops of the of the giant planets of Jupiter, Saturn, Uranus, Neptune, I mean, they’re called ice worlds. Yeah, because they have ice like Neptune and Uranus. Like if you brought them to Earth and just sort of spread them out, they would be made of ice. They’d be made of the kinds of material that forms ice, different kinds of ice. So, yeah, what can those planets get up to as you descend down into them? 

Pamela Gay [00:20:59] So this this is yet another form of amorphous ice where the different structures are defined by the, the density of the ice. And, essentially the chaos of how the molecules aren’t aligned with one another. And. They they’ve been doing wild things like using lasers to smash things together, to try and get an understanding of what kinds of ices are existing at these pressures and temperatures, where the temperatures are. It’s a gas body with a lot of gravity compressing inwards. It’s higher temperatures here. So here you have high pressures creating the ice because of pressure. And then. The temperature is above what we’re used to thinking of for freezing. So here again we’re looking at something that think of the molecules more as dust grains that are confined together to form ices in a situation that just doesn’t exist on our planet. And what is really amazing me, is the creativity. And I’m just going to say this over and over, the creativity of the researchers to understand this stuff, where they they are like, okay, so we see this thing, how do we get water on our planet? That is that one atmosphere and that human survivable temperatures. How do we make the water molecules suffer the way they suffer? Right. And how do we explain the colors? One of the weirdest new releases I’ve seen is researchers have really been struggling to try and understand how Europa has the colors that we see. And just like you can get different gem colors by having the crystalline structure include different impurities, whether it be lead or zinc or whatever impurities makes your different colored gems. Well, it turns out that if you have water molecules where you have different ratios of the H2O combined with salts, the ratio of the number of water molecules to salt molecules that are together forming a different kind of crystal. These different kinds of crystals can produce different colors. So while it’s crystal in ice on Europa, it’s now starting to be thought that when we’re seeing these, these gorgeous, brightly colored lines where there’s cracks, that is extremely salty water that has frozen into a crystalline structure, that is a combination of salt molecules and water molecules forming their own structure that just happens to scatter red light. 

Frasier Cain [00:24:15] And like I know that the thinking for like Europa was that this might be some kind of or the hope, whether this is some kind of organic molecule that is being mixed in, that you’ve got some kind of long chain carbon molecules that are mixed in with the ice, and maybe this is evidence of life, but what you’re saying was hope. Yeah. But maybe I mean, who knows. But the but the but it seems like in fact, it’s just salt mixed with water. And it’s forming crystals that are taking on these, these strange shapes. And I think what’s really interesting about a place like Europa is that when you reach the surface, whatever you created is going to last because it’s so far away from the sun, so it’s not going to sublimate. Yeah, you’re you’re far enough away from Jupiter that the tidal interactions, all of the heating that’s coming from that, that’s happening down inside the world. But the stuff that’s reaching the surface is hard as rock, literally. And now it’s being exposed to space, micrometeorites, other debris and stuff that could be raining down on it. But it’s not like it’s going to be sublimating in the same way that that you would get if you moved Europa close to the sun. 

Pamela Gay [00:25:33] And it’s just amazing to to realize that just like carbon, we’re all familiar with how it’s able to be like regular everyday pencil lead versus, forming complex structures with buckyballs versus forming, diamonds of various colors based on what pollutants are in the crystals. Well, water really does the exact same thing where we have the amorphous structure. That’s a lot like your pencil lead. We have the crystalline pure structure that you sometimes see in pubs. That’s crystal clear. We have the salt crystals that are a whole variety of different colors, depending on the ratio of salts to water molecules, which are forming our different color crystals. It it’s all the same chemistry, but occurring at different pressures and temperatures with different molecules or atoms in the case of carbon. 

Frasier Cain [00:26:37] So the thing that I recommend is, is do a search for that. I guess ball bearing ice. Yeah. Experimentally. Yeah. Yeah. And you can really see that the, the lab setup that they had, it’s, it’s quite amazing to see these fairly large ball bearing. Mashing ice to produce the strange shape. And as he said, write the creativity. Do you like how do we replicate an environment that is completely alien to Earth here on Earth? 

Pamela Gay [00:27:06] We’re going to super freeze water and beat the bejesus out. 

Frasier Cain [00:27:10] And punish it with a steal until I guess. Did you ever. Was it Cat’s cradle theory that Kurt Vonnegut told story? 

Pamela Gay [00:27:18] And I didn’t read? 

Frasier Cain [00:27:19] Yeah. And there was this thing called ice nine in that, that that scientists had made this material called ice nine. And the thing that it did was anything it had touched turned into more ice nine and so turned the entire planet into ice nine and then proceeded to attempt to turn the entire universe into ice nine at the at the speed of light. And so, yeah, I don’t think. 

Pamela Gay [00:27:42] That ice doesn’t do that. Just, you know. 

Frasier Cain [00:27:45] Just because it’s a science fiction story doesn’t mean it’s true. Now, if you make strange matter now or now, we’re talking about, you know, not ice, you can’t get that version of ice. 

Pamela Gay [00:27:55] And it’s important to note that if you take a regular ice crystal and you super freeze it slowly, it’s just going to sit there going, hi, I’m ice. You have to do something to it to break the crystal structure, to get the amorphous ice, or have it freeze super fast so the crystal structure doesn’t have a chance to form. So that idea of contagious ice structure is not a concern. 

Frasier Cain [00:28:23] Right? All right. Well, thanks, Pamela. 

Pamela Gay [00:28:26] Thank you, Fraser. And as always, thank you so much to all of our patrons out there through Patreon.com slash astronomy Cast. You allow us to pay the folks behind the scenes Allie Beth Rich who make this show possible. This week I would like to thank a selection of our patrons, planetary Andrew Stevenson, cameras, Ian, Paul Hayden, James Roger, Alex Rain, Gabriel Galvin, Sean Mattes, Glenn McDavid, Arctic fox, Karthik Vaca, trauma and Stephen coffee, Brian Kilby, Dean Kurien, dump truck, Lu Zealand, Bart Flaherty, the air major. John Drake, Benjamin Davies, Nate that Wyler, Benjamin Carrier, the lonely sand person knew la Sam Brooks and his mom Jason cards. Lucas, Robert. Handle, Kim. Barron, Paula. Esposito, Bob. Zach ski, Gordon. Turner, Ron. Thorsen. Arts. Lots. Hall. Arthur. Lots. Hall, Mark H. Whittock, Hal McKinney, Bruno Latz, Reuben McCarthy, time Lord, IRA, Daniel. Donaldson, Frank. Stewart, Wil. Hamilton, Ian. Abdullah, Jeff and Jeff MacDonald. And if you would like to listen to this show with no ads, go join our Patreon and get your own special access feed. 

Frasier Cain [00:29:50] Thanks everyone and we’ll see you next week. 
Pamela Gay [00:29:52] Goodbye. Astronomy cast is a joint product of Universe Today and the Planetary Science Institute. Astronomy cast is released under a Creative Commons Attribution license. So love it, share it, and remix it, but please credit it to our hosts, Fraser Cain and Doctor Pamela Gay. You can get more information on today’s show topic on our website. Astronomy. Cars.com. This episode was brought to you. Thanks to our generous patrons on Patreon. If you want to help keep the show going, please consider joining our community at Patreon.com Slash Astronomy Cast. Not only do you help us pay our producers a fair wage, you will also get special access to content right in your inbox and invites to online events. We are so grateful to all of you who have joined our Patreon community already. Anyways, keep looking up. This has been Astronomy Cast.

It’s been over 20 years since astronomers first discovered that the expansion of the Universe is accelerating thanks to dark energy. And in these decades, astronomers still don’t have much evidence for what could be causing the increased expansion rate. Maybe there’s something else going on to explain it.

Show Notes | Transcript

Escape Velocity Space News (CosmoQuest)

PODCAST: Ep. 4: The Search for Dark Matter (Astronomy Cast)

PODCAST: Ep. 11: A Universe of Dark Energy (Astronomy Cast)

The Dark Energy Survey

The Nancy Grace Roman Space Telescope (NASA JPL)

South Pole Telescope (University of Chicago)

Physical Review Letters (APS)

Hot new early dark energy: Towards a unified dark sector of neutrinos, dark energy and dark matter (Physics Letters B)

Casimir Self-Interaction Energy Density of Quantum Electrodynamic Fields (Physical Review Letters)

Dark matter (CERN)

Dark Energy (Hubblesite)

Doppler Shift (Swinburne University)

Equation of state (cosmology) (Wikipedia)

Hubble’s Exciting Universe: Measuring the Universe’s Expansion Rate (Hubblesite)

Planck (ESA)

WMAP- Content of the Universe (NASA)

Supernovae Were Discovered in all These Galaxies (Universe Today)

What are Cepheid Variables? (Universe Today)

Carnegie Supernova Project II: The Slowest Rising Type Ia Supernova LSQ14fmg and Clues to the Origin of Super-Chandrasekhar/03fg-like Events (The Astrophysical Journal)

Research team discovers unique supernova explosion (Phys.org)

Planck and the cosmic microwave background (ESA)

Hydrogen Epoch of Reionization Array (HERA)

FOLLOW-UP: What is the ‘zero-point energy’ (or ‘vacuum energy’) in quantum physics? Is it really possible that we could harness this energy? (Scientific American)

First principle (Wikipedia)

WMAP Inflation Theory (NASA)

Could a Dark Energy Phase Change Relieve the Hubble Tension? (Universe Today)

Michael S. Turner (University of Chicago)

What is the Casimir effect? (Scientific American)

The Nobel Prize

The Higgs boson (CERN)

Particle Fever (2013) (IMdB)

Back to Top

Transcriptions provided by GMR Transcription Services

Fraser Cain:                 Astronomy Cast Episode 669, Challenges to Dark Energy. Welcome to Astronomy Cast, our weekly facts-based journey through the cosmos where we help you understand not only what we know but how we know what we know. I’m Fraser Cain, the publisher of Universe Today. With me as always is Dr. Pamela Gay, a senior scientist for the Planetary Science Institute and the director of Cosmo Quest. Hey, Pamela, how you doing?

Dr. Pamela Gay:         I am doing well. The third episode of our new TV show aired Saturday and we got it to the station 90 minutes before it was due, due to computer crashes, because computers know.

Fraser Cain:                 Yeah.

Dr. Pamela Gay:         But if you haven’t checked it out yet, it’s Escape Velocity Space News. It airs on Now Media and I am gonna be putting together a podcast version and loading that up later today.

Fraser Cain:                 Congratulations, that’s amazing. It’s been over 20 years since astronomers first discovered that the expansion of the universe is accelerating thanks to dark energy. And in these decades, astronomers still don’t have much evidence for what could be causing the increased expansion rate. Maybe there’s something else going on to explain it.

                                    If you go back into the archive of Astronomy Cast shows, one of the first episodes that we did was Dark Matter and then after that was Dark Energy, like within the teens anyway and we’ve brought it up a couple of times since them, but I had been expecting in the 15 years that we’ve been doing this show that we would have something more to say on the matter. But to be honest, not much has been figured out, apart from some really interesting new surveys, like the Dark Energy Survey Telescope, the development and eventual launch of the Nancy Grace Roman Telescope. We still have no idea what this is.

Dr. Pamela Gay:         One of the things that actually caught me by surprise is I was expecting to spend today talking about the new results from the Dark Energy Survey and the South Pole Telescope, and there are actually two really cool papers that have both come out in Phys Rev Letters in the past couple of months that are both clearly the, hi, we’re theorists, we have predictions, there are only two of us on this paper, please give us the Nobel Prize when our predictions prove true.

Fraser Cain:                 Right.

Dr. Pamela Gay:         And so, we may be getting to the point that theorists are starting to figure out how to get a handle on things, and they’re finding answers that may also help confine dark matter, which is kinda cool.

Fraser Cain:                 Well, that’s great. So, then, I guess, what is the evidence for dark energy?

Dr. Pamela Gay:         Basically it comes down to when you measure the distance to a supernova and you measure the rate at which that galaxy is moving away from us using doppler shifts. We find that the universe is actually accelerating over time, which is not something that was in anyone’s predictions but it was in the math in the form of a constant to the equations of state for the universe. When Einstein originally came up with these equations there was an integration factor, when you integrate you have to add a constant, and he assumed that the constant would have a value that caused the universe to be static.

A few years later, Hubble came along, found the universe is expanding. Now we have a constant that makes sense for that. But it turns out that if you have a universe that is accelerating apart, that is a value for the equations of state, and so now what we’re finding is, in order to explain the geometry of our universe, which is flat, flat, flat, very flat, and an accelerating universe, you have to have 70% of the universe made of something that isn’t observable matter, that’s about 4-1/2 percent of the universe, that isn’t dark matter that gets observed through gravitational lensing, gets observed through rotation curves of galaxies, gets observed through the motions of galaxies and clusters, that’s 27-ish percent and instead you have dark energy.

Fraser Cain:                 So, this measurement really relies on how good the measurements to those type 1A supernovae are.

Dr. Pamela Gay:         Yes. And it also comes down to, once we realized, okay, so we have from the Planck Observatory the flat geometry and then you combine it with everything else and you look at the mass density of the universe, the only way to explain the mass density of the universe is to have this extra stuff as well. So, you can get to dark energy from a couple of different ways but to get at the value that we’re seeing, yes, that came very clearly from the 1998 observations that the universe is accelerating with time and its expansion.

Fraser Cain:                 And we did some coverage on a new database that came out a couple of months ago, where astronomers had gone through and like recalibrated, normalized all the data for about 1,000 total type 1A supernova measurements and if anything, have gotten even more accurate.

Dr. Pamela Gay:         Yeah.

Fraser Cain:                 You overlap the Cepheid variables with type 1A supernovae, the distance ladder is beautiful, the error bars are ever shrinking and the amount of dark energy in the universe is zeroing in on this. They’re really nailing this number.

Dr. Pamela Gay:         And one of the wild things about this is we keep trying to find an excuse that maybe further back in the universe these kinds of supernovas, due to the change in the chemistry, would have different properties, and we do keep observationally finding random exceptions. There was a super cool type 1A supernova that went off while inside of another star, which is one way to blow up a white dwarf.

Fraser Cain:                 You can imagine that would pollute the results a little bit.

Dr. Pamela Gay:         Right. But these one-offs that we’re finding are super cool but they are one-offs. The vast majority of the type 1A supernovae are just boring white dwarfs that ate more than they could hold without changing states.

Fraser Cain:                 Right. And so I guess one possibility is that the type 1A supernovae aren’t the standard candles that astronomers had always believed but the evidence is continuing to build that yes, indeed, they are.

Dr. Pamela Gay:         Yeah.

Fraser Cain:                 Except for these ones where one star blows up from inside another star.

Dr. Pamela Gay:         Yeah.

Fraser Cain:                 Right.

Dr. Pamela Gay:         And so, I mean it’s just like saying most human adults are between five foot and six foot, yes, there are people who are only three foot and there are people who are only seven foot, but the vast majority of us are between five and six foot. So, yeah, it’s averages.

Fraser Cain:                 So, then, let’s talk about some of the largescale surveys that have been developed to try to get to the heart of dark energy. Not necessarily explain it, I guess, but at least to confirm it, map it, try and nail down its parameters.

Dr. Pamela Gay:         So, the big one with the obvious name is the Dark Energy Survey, which was done from down in Chile where they observed with extreme sensitivity vast swaths of the sky with the goal of looking to see how the structure of the universe evolved with time. So, the idea here is, we know that the universe started out as pretty much smooth distribution of particles. It wasn’t even anything more fancy than particles initially, with slight over and under densities that were created by soundwaves moving through the early universe.

                                    That mostly smooth distribution that we can measure in the cosmic microwave background, then had to collapse down into galaxies, stars at the smallest scales, but then clusters of galaxies, walls of galaxies, super clusters at the largest scale and it does that over time. And we have models that basically say okay, here is the CMB, here is the modern universe, let’s fill in in between and the Dark Energy Survey was designed to get at the more recent few billion years.

                                    The next survey that is super exciting to look at is HERA, which is being done in the radio, looking at the redshifted 20-centimeter line of cold hydrogen, that the detectors for this, they’re looking at wavelengths of light that instead of being just 20 centimeters are instead many, many feet, so, longer than us. And in these longer wavelengths we are able to start seeing how cold hydrogen was distributed in the early universe, start piecing together how cold gas clumped and then got re-ionized in the era of re-ionization.

                                    And between these different surveys, we’re working our way through measuring what was the structure over time so that we can better confine our models and say, okay, was the amount of dark energy constant over time. Was there some sort of a phase transition? Was there a kick somewhere? And these are the kinds of questions that folks are trying to answer, is what observables can dark energy give us that will help us confine our theories?

Fraser Cain:                 And so, in addition to the type 1A supernovae measurements, they’re able to now look at these galaxy clusters and then on top of that they’re looking at the concentrations of these regions of hydrogen gas. And so, you’ve got like three independent lines of observation that theoretically should allow you to map out the amount of dark energy.

Dr. Pamela Gay:         Yes.

Fraser Cain:                 And is the assumption that they’re gonna find it? Like I know the Dark Energy Survey is still partway through its survey. You didn’t even mention the Nancy Grace Roman, it’s gonna be launching in 2025, and –.

Dr. Pamela Gay:         Well, you don’t count your satellites until they’re orbiting.

Fraser Cain:                 Fine, fine, okay. Pamela, put your hands over your ears. Audience, the Nancy Grace Roman, one of its main jobs is going to be to characterize dark energy, doing kinda the same thing that the Dark Energy Survey is but from space. So, this is classic, right. Like if you don’t have an easy answer then you build more instruments, more observatories. You keep trying to characterize the nature of the problem, building hypotheses, testing them against your observations, removing bad ideas one after the other and hopefully trying to pin down the final thing. So, we may never know what’s causing dark energy but we’ll have it measured to Six Sigma accuracy.

Dr. Pamela Gay:         Well, and the other side of it is the particle physics side. So, we know that dark energy, whether it’s a force, an energy, a field theory, whatever it is, puts into every cubic meter of space basically a proton-ish worth of energy. And so, how do you explain that energy existing? And by better understanding the quantum mechanic side of the universe, the particle physics, the vacuum energy, are sterile neutrinos actually a thing or not, this is another way of coming at the fullness of the universe by looking at the smallest factors inside of it.

Fraser Cain:                 All right. So, I guess, you found a few papers that have been proposing some alternative explanations that would explain the observations but not necessarily be new energy that’s being injected into every cubic meter of the universe, which I guess sounds satisfying. Like the fact that energy is appearing out of nowhere, that’s unnerving, so what are they proposing?

Dr. Pamela Gay:         So, the first paper in here, I have to look at my notes, the first paper came out from Martin Sloth and Florian Niedermann, where they’re looking at new early dark energy. And the idea here is our universe has undergone phased transitions in terms of the energy of the entire universe. So, the first massive phased change occurred in the first fractions of a second, where we essentially went from every basically molecule sized bit of the universe expanding out via inflation, which we also don’t know what is, to be about the size of the observable universe according to some ways of looking at it.

                                    And this massive, fairly instantaneous epic of inflation may have only been one of two phased transitions or there could have been a later phased transition that, if there testable ideas are right, leads through first principles to having a cosmological constant of 72, which is within error bars of what we see for the modern universe, and fixes the discrepancy we see with the old universe.

Fraser Cain:                 And so, sorry, so like, the idea of inflation –.

Dr. Pamela Gay:         Yes.

Fraser Cain:                 Happening in just the first fraction of the Big Bang was developed I think back in the ’70s –.

Dr. Pamela Gay:         Yeah.

Fraser Cain:                 To help explain a lot of the problems with the Big Bang. Like the Big Bang beautifully explains the universe as we see it today, but there are these flaws in the theory. How can vastly separated parts of the universe be similar temperature, there’s a bunch of these ideas. And so, one of the theories is that, in fact, there was this period of rapid inflation that carried everything away from each other really quickly and then it settled down.

                                    So, I think baked into modern cosmology is already this idea, as you say a phased changed, a dramatic change in the expansion rate of the universe. So, it doesn’t seem that surprising that there could then have been others later on.

Dr. Pamela Gay:         Right.

Fraser Cain:                 So, when would have this other, they’re calling it, what, early, what are they calling it, early –?

Dr. Pamela Gay:         They’re calling it new, early dark energy.

Fraser Cain:                 Dark energy. Right, okay.

Dr. Pamela Gay:         So, NEDE is the abbreviation.

Fraser Cain:                 New early dark energy, right. And so when would this have occurred in the timeline of the universe?

Dr. Pamela Gay:         This still would have occurred during what they refer to as the dark times prior to the release of the cosmic microwave background. And it fits in with the way – Michael Turner, who is a prominent cosmologist, now professor emeritus from the University of Chicago, he says there’s basically these three unknown pillars of cosmology, inflation, dark energy which he actually named, dark matter. And so, this looks at that early period, makes some solid predictions for temperature details that we should be able to see with enhanced continuing to look at the cosmic microwave background, which tells us everything apparently.

                                    But it also makes some finite predictions for what kinds of neutrinos should be out there, and what kinds of specific particles we can expect to find, thus, also perhaps explaining dark matter. So, we have one coherent theory spelled out in a letter-sized research article making concrete predictions. It seems good and just needs tested now but it’s not the only one out there.

Fraser Cain:                 All right. Well, let’s talk about the other one, then.

Dr. Pamela Gay:         So, the other one is by Alexander, and I’m going to mispronounce this and I am sorry, this appears to be a Ukrainian last name, Tkatchenko, and the other one is Dmitry Federov. And they look at the vacuum energy of the universe, and vacuum energy is something we know is real because of the Casimir effect, which is just one of the best named effects in particle physics. The dude’s name was Casimir but it just sounds cool to say.

                                    And what the Casimir effect says is if you take two plates that are capable of conducting electrons and you put them extremely close together but you’re not actually running charge through them and they’re not being exposed to any fields, nothing should happen I a vacuum. But the reality is, if you put these two plates just a couple nanometers apart within a vacuum, they will either attract or repel due to the constant creation and destruction of virtual particles that are in their creation and destruction, creating a field. So, if you have a proton spring into existence as a virtual particle between these two plates, that proton has a field and it creates the effect.

Fraser Cain:                 Right.

Dr. Pamela Gay:         And we see this.

Fraser Cain:                 Right. And if I understand, like the Casimir effect, because the gap is so small the virtual particles of only certain sizes can pop into existence outside or as a field.

Dr. Pamela Gay:         Right.

Fraser Cain:                 Outside the plates and then they are pushing inward, there is essentially a field on the outside and not so much field on the inside and it’s pushing on these plates. And once you move the plates farther and farther apart, now there’s room for the fields to appear both in between the plates and outside the plates.

Dr. Pamela Gay:         Yeah.

Fraser Cain:                 And then that force goes away. And it sort of shows you the presence of this vacuum energy that is everywhere. And it’s been beautifully measured, so no one argues with the existence of vacuum energy. The assumption, though, is that this energy cancels out, goes away very quickly and doesn’t provide any ongoing force to the universe.

Dr. Pamela Gay:         And that’s one school of thought. Another school of thought is, no, it’s totally providing dark energy-like forces, but when they do all the maths, they have consistently come up with an amount that is too large by a factor of 10 to the 120 for the theories that I like the best and that are among the prominent theories. And the best case for getting it down has, until this paper as far as I know, been 10 to the 30th. And when you’re off by somewhere between 10 to the 30 and 10 to the 120, it really doesn’t matter.

Fraser Cain:                 That’s a lot. Yeah.

Dr. Pamela Gay:         It’s a lot. And this is where these two researchers, Tkatchenko and Fedorov, they said, well, okay, what if the vacuum energy has a polarizability, that the particles can actually have alignments that affect what can and can’t come into existence and annihilate. And they make again solid predictions that should be testable if we go looking with new technology that we don’t currently have laying around.

And it’s just one of those nice, simple, elegant ideas of we know stuff can be polarized. We know particles can be aligned. What if just the universe as a whole has this polarizability characteristic to it that we just hadn’t been including? And again, with this research, it makes set predictions on what to go look for. It looks at the particles that are out there and says, okay, here is what to see in particular physics and I don’t know which team I’m rooting for more. I like the polarizability one.

Fraser Cain:                 Why choose?

Dr. Pamela Gay:         Well, I mean that’s – it’s two theory papers making predictions. Both of them have only two authors. Both papers are clearly gearing up for a Nobel Prize. It’s always good to cheer for people but I guess I’ll cheer for both.

Fraser Cain:                 Yeah. When you think about the winning Nobel Prizes, many of them start this way.

Dr. Pamela Gay:         Yes.

Fraser Cain:                 That a theorist puts together a paper and says there should be a particle called the Higgs boson, right, and then 30 years later experimenters are finally able to find it, and this is the same thing. So, I mean I guess if dark energy makes you uncomfortable already –.

Dr. Pamela Gay:         This doesn’t help.

Fraser Cain:                 Buckle up. Yeah.

Dr. Pamela Gay:         Yeah.

Fraser Cain:                 You still got another 30 to 50 years of searching and scanning and trying theories to try and narrow in on an answer to it.

Dr. Pamela Gay:         And if you want to get a feel for what it’s like within the field of particle physics to watch people so clearly chasing Nobel Prizes, watch the moving Particle Fever, it is very delightful. It shows the good, the bad and the ugly of scientists being scientists, and just the joy that comes from people getting to see their dreams come true through instrumentation.

Fraser Cain:                 I will check that out.

Dr. Pamela Gay:         It’s really cool.

Fraser Cain:                 Yeah, that’s awesome. All right. Well, thanks, Pamela. I hope within the lifetime of Astronomy Cast we will do the show we finally know what dark energy is. After we do the show where we say we finally know what dark matter is, we will do both those shows. This is my promise to all of you.

Dr. Pamela Gay:         And this is where it’s just sort of like we can hope, and when that finally happens is that when we retire?

Fraser Cain:                 No, no.

Dr. Pamela Gay:         Okay.

Fraser Cain:                 Because there will be there will be a hundred new mysteries that are even –.

Dr. Pamela Gay:         We keep going until we die.

Fraser Cain:                 Yeah, there will be a hundred new mysteries that are even more complicated and more troubling, so, no, that’s how this whole process works. All right, Pamela, thanks a lot.

Dr. Pamela Gay:         Thank you. And thank you to all the patrons out there. I don’t actually have a thing of names, I just discovered, to pull out because it’s the very beginning of the month and the list hasn’t been generated yet but I do want to say thank you to all of you. We have been reading the names of just a subset of you on air, it’s one of the perks associated with the different levels but we love all of you, whether you’re a $1.00 a month contributor or a $100.00 a month contributor. You allow us, through our ongoing efforts, year after year to allow us to pay our humans and keep the show going, and occasionally replace cables from my camera when they die. So, thank you.

Fraser Cain:                 I will take this opportunity then to sort of mention a trend, a disturbing trend that you who are a fan of educational content should be aware of and that is artificial intelligence generated content.

Dr. Pamela Gay:         Yeah.

Fraser Cain:                 That more and more websites are moving to this model of getting ChatGPT and other artificial intelligence to generate en masse the material and this trend is going to accelerate.

Dr. Pamela Gay:         Yeah.

Fraser Cain:                 And it’s just another career that is gonna be –.

Dr. Pamela Gay:         Go away.

Fraser Cain:                 Go away, sunsetted. The career of the science communicator and that’s because it’s way cheaper to let a large language model generate explainer content. And hopefully, Pamela and I have value and place in this society as more and more of this content shifts into being generated by enormous databases. I know it sounds shocking and surprising but this is where it’s all gonna go and it’s gonna happen startlingly fast. So.

Dr. Pamela Gay:         We have had people write in and say, hey, why don’t you switch over to using ChatGPT to generate your scripts.

Fraser Cain:                 Right.

Dr. Pamela Gay:         It’s already people are suggesting it.

Fraser Cain:                 Yeah, yeah.

Dr. Pamela Gay:         And we won’t do that.

Fraser Cain:                 Yeah. I will get ChatGPT to recommend ideas but I won’t –. See, here’s the key, there are no scripts, that’s the trick.

Dr. Pamela Gay:         Right, right.

Fraser Cain:                 So, how could we have a script if there are no scripts? Smart. Anyway. So, if the work that we’re doing, like if the loss of science communicators at the mainstream media was already troubling to you, now they’re coming for all science communicators. So, if supporting the work that we do is important to you to make sure that we can keep doing the show, paying the people on the team, keeping the servers running, all of that, join our Patreon.

Dr. Pamela Gay:         Thank you.

Fraser Cain:                 Patreon.com/astronomycast. Thanks, everyone, and we’ll see you next week.

Dr. Pamela Gay:         Bye-bye.

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Astronomers have made extremely accurate measurements of the expansion rate of the Universe and come up with different results. And the error bars for the observations don’t overlap, so there’s something strange going on. What’s the answer and how can the Crisis in Cosmology be resolved?

Show Notes | Transcript

See Comet ZTF (C/2022 E3) Dash Between Big and Little Dippers (Sky & Telescope)

Comet Hale-Bopp (NASA JPL)

Comet Hyakutake (NASA JPL)

Comet NEOWISE, the best comet of 2020 (EarthSky)

Comet McNaught over the Pacific Ocean (ESO)

Hubble Tension Headache: Clashing Measurements Make the Universe’s Expansion a Lingering Mystery (Scientific American)

Hubble telescope refines universe expansion rate mystery (Space.com)

Megaparsec (Swinburne University)

Messier 87 (NASA)

Andromeda galaxy: All you need to know (EarthSky)

Ask Ethan: Is there a better way to measure cosmic time? (BigThink)

Type Ia Supernova (Swinburne University)

How do astronomers measure the brightness of something? (Astrobites)

Luminosity (Swinburne University)

Standard Candle (Swinburne University)

What are Cepheid Variables? (Universe Today)

Gravitational Lensing (Hubblesite)

Dr. Adam Riess (Space Telescope Science Institute)

Astronomical deep-sky photometry and spectroscopy (BBC Sky at Night)

Gaia (ESA)

Baryon Acoustic Oscillations (NASA)

COBE (NASA)

Planck (ESA)

LAMBDA – ΛCDM Model of Cosmology (NASA)

Astronomers Grapple with JWST’s Discovery of Early Galaxies (Scientific American)

How Did Inflation Happen — and Why Do We Care? (Space.com)

The Big Bang (NASA)

IMPROVING MEASUREMENTS OF THE COSMIC EXPANSION WITH GRAVITATIONAL WAVES (LIGO)

Cosmic Inflation Theory Faces Challenges (Scientific American)

Sloan Digital Sky Survey

The Dark Energy Survey

JWST (NASA)

Back to Top

Transcriptions provided by GMR Transcription Services

Fraser Cain:                 AstronomyCast, Episode 668, “The Crisis in Cosmology.” Welcome to AstronomyCast, your weekly facts-based journey through the cosmos, where we help you understand not only what we know, but how we know what we know. I’m Fraser Cain, the publisher of Universe Today. With me, as always, is Dr. Pamela Gay, a senior scientist for the Planetary Science Institute and the director of CosmoQuest. Hey, Pamela, how you doing?

Dr. Pamela Gay:         I am doing well. How are you doing?

Fraser Cain:                 Doing great. Yeah, nothing to report.

Dr. Pamela Gay:         That, I think, in 2023, is really the best any of us could ever ask for.

Fraser Cain:                 Yeah, the weather is fine, the snow is gone, I’m getting out and doing a bunch of hikes and stuff in the nature, even though it’s wintertime, but still, garden’s coming along.

Dr. Pamela Gay:         Dang.

Fraser Cain:                 I saw the comet last night. It sucks, but…

Dr. Pamela Gay:         Oh well.

Fraser Cain:                 Yeah, it’s gotten quite diffuse at this point, so although it’s bigger and brighter, it’s also more of just a cloud.

Dr. Pamela Gay:         It’s spread out, so the light from any given place – its surface brightness is really low.

Fraser Cain:                 That’s right, so you really don’t get that nice, little, tight nucleus with the tail, you just get this – what looks like a little cloud in the sky. But still, it’s easy to find. It’s so easy to find because it was right beside Ursa Minor, right beside the Little Dipper, and then, it’s moving towards Cassiopeia. So, if you have never seen a comet – you can’t see it with your eyes, but you can see it in a pair of binoculars or a small telescope. It’s easy to find, and that’s nice, as opposed to one where it’s in a fairly difficult constellation to discover. But unfortunately, completely inaccessible now to the folks in the Southern Hemisphere, so this one is just for the folks in the north. So, if you haven’t already –

Dr. Pamela Gay:         Who do not have cloud like the Midwestern folks in the north.

Fraser Cain:                 Right, yeah. It’s gonna peak in just a couple of days from now, so now is your chance, and then it’s just gonna get – but it mostly sucks. I always compare comets to Hale-Bopp and Hyakutake, and people are even like, “Oh, didn’t you like Comet NEOWISE?” I’m like, no.

Dr. Pamela Gay:         No.

Fraser Cain:                 No, it sucked. I could see it with my eyes. That does not a good comet… That is necessary – sufficient but not necessary? Anyway, just barely being able to see a comet with the unaided eye does not – you do not declare victory in the comet world. No, you want the one that is gigantic –

Dr. Pamela Gay:         The tail.

Fraser Cain:                 The tail spans multiple handspans across the sky, that you can see it even in light-polluted skies. That’s a comet, and everything else the universe is sending our way right now is mediocre, and I reject them. So, no, NEOWISE sucked, McNaught sucked, this one sucks. We demand better. I will wait, but I’ve been patient for too long. Come on, comet!

Dr. Pamela Gay:         I…I can’t argue with that. All of that is true. It’s all true.

Fraser Cain:                 Yeah. For people who are like, “Oh yeah, Comet NEOWISE was fine,” no, it wasn’t! It wasn’t, and you’re settling. You deserve better. I deserve better. We deserve better comets. The universe can provide it; it’s done it in the past. It’s time to put up or shut up. All right.

Dr. Pamela Gay:         Yeah…

Fraser Cain:                 Astronomers have made extremely accurate measurements of the expansion rate of the universe and come up with different results, and the error bars of the observations don’t overlap, so there’s something strange going on. What’s the answer, and how can the crisis in cosmology be resolved? So, what is the crisis in cosmology?

Dr. Pamela Gay:         So, some people call it the Crisis, some people call it the Hubble Tension. A lot of us just put “WTF?” and call it a day. So, what’s happening is before the supernova teams did such an amazing job of measuring the present expansion rate of the universe, we were like, “Nah, the universe is expanding somewhere between 50 kilometers per second per megaparsec to 100 kilometers per second per megaparsec,” and I had so many profs that were like, “Just use 100. It makes the numbers easier.” It was pleasing.

Fraser Cain:                 Right. Just so people understand this idea, that you take a megaparsec of space, which is about 33 million lightyears of space, and when you think about that, that is the distance between us and faraway galaxies, like Andromeda’s really close. We’re talking about galaxies that are 30 million lightyears away, like M87 is kind of in that – when you think about the supernova image. Every second that goes by, those objects are now 100 kilometers farther apart, or 50 kilometers farther apart.

Dr. Pamela Gay:         And it is a function of how far something is away from you, so the further something is away, the faster it appears to be moving away from you. A lot of people use a raisin bread analogy on this because the raisins stay the same size as the bread dough expands, so two raisins that start really close together will end up a little further apart, two raisins that are really far apart initially will end up seriously far apart by the time that bread is done rising.

Fraser Cain:                 And why is knowing the expansion rate of the universe important?

Dr. Pamela Gay:         It’s one of those things that allows us to put together all the rest of our cosmological ideas of how you go from our universe being a single point to expanding out, to forming hydrogen and helium, trace amounts of lithium and beryllium, to – the whole story is tied up, and it slowed down or it sped up, and understanding what rate we’re going now, since there’s no accelerator pedal that we know about, what we see has to be defined by the physics of our universe, and we can start to define all that physics of the universe if we know this one number that refuses to be measured.

Fraser Cain:                 I apologize, I was off by a factor of 10 there, so, sorry, and you should have caught me – it’s surprising you didn’t – but a megaparsec is 3.3 million lightyears, not 33, so Andromeda, roughly, is in that ballpark range. So, apologies.

Dr. Pamela Gay:         Yes. The way I think about it is someone in Andromeda looking back at us would be seeing Neanderthals.

Fraser Cain:                 Right, but astronomers don’t think in lightyears, they think in megaparsecs, so if I get off by a factor of 10, that’s fine by you because you don’t even think about it, so apologies in –

Dr. Pamela Gay:         It’s true.

Fraser Cain:                 Yeah, the general public thinks in lightyears while astronomers only think in parsecs and megaparsecs, but yeah, so, apologize, let’s continue. So, why – you were discussing why knowing the expansion rate of the universe is important.

Dr. Pamela Gay:         It basically just gives us this reference point that we can work all the other maths back from.

Fraser Cain:                 So, how long the universe has been around for?

Dr. Pamela Gay:         How long the universe has been around for, basically –

Fraser Cain:                 What will happen in the future…?

Dr. Pamela Gay:         The one that gets me is by understanding the current expansion rate, we can actually figure how fast the universe went from being a mostly smooth distribution of gases to forming galaxies, to forming galaxy clusters. The rate at which we formed large-scale structure, at a certain level, hinges on how fast our universe is expanding. It’s everything.

Fraser Cain:                 Right. And so, in the olden days, we used to get “How old is the universe?” and people would say, “Well, it’s kind of somewhere between 10 and 20 billion years old,” and that’s that range of measurement. If you get 50 kilometers per second per megaparsec, you get one age of the universe because you just measure how long the universe is expanding, but if you get 100, you get a different one, and they are very different, and knowing that is important. So, how do astronomers measure the expansion rate of the universe at the close and at the far?

Dr. Pamela Gay:         So, there are two totally different suites of mechanisms. The “local time” way of doing it is we look for supernovae, which give off a set amount of light if they’re Type 1A supernovae – explode a white dwarf star, and you get essentially the same explosion over and over and over again, with errors that we’ve discussed in other episodes.

Measure how bright that explosion appears, measure how fast the galaxy the supernova is in is moving, and this tells you the distance using measured brightness and known luminosity, and it tells you the expansion rate by looking at the Doppler shifting. So, we’re literally measuring how much the colors of the different bands of atomic lines have been shifted by the galaxy’s motion, and that gets us a velocity.

Fraser Cain:                 Right. And so, we have all of these standard candles, from the Cepheid variables, to the supernova, to – I saw a list. There must have been 30 potential standard candles overlapping, going from – some of which are very well known, others of which are poorly known, but you go from local measurements using parallax that overlaps with Cepheid variables that overlaps with Type 1A supernova, and you just get this really beautiful, smooth measurement, and what number did we get from the local methods of measuring the expansion rate of the universe?

Dr. Pamela Gay:         So, we’re getting around 70 kilometers per second per megaparsec, and this is using not just supernovae, but as you point out, there’s a bunch of other methods. So, folks are looking at red giants, they’re looking at planetary nebulae, they are looking even at the distant gravitationally lensed galaxies that we’re able to see multiple versions of using crazy geometry when we can see the galaxies’ lenses do the same thing at different times. All these methods are giving us definitely over 70, and narrowing in on 74, so it seems pretty constant.

Fraser Cain:                 Right, and the error bars are really tightening up. The quality of the observations is exquisite. I talk to a lot of astronomers, and they talk about how good of a job they’ve done with those observations, and they just gush.

Dr. Pamela Gay:         The SHOES survey by Adam Reiss – they’re quoting an error of 1.3%, and they are basically going from the nearby Cepheids that they have taken some of the most precise photometry of that anyone has ever taken, then using Gaia parallax data, and then working all the way out. How often does anything in astronomy get done with that level of accuracy? We know this. The local value is basically 74 kilometers per second per megaparsec.

Fraser Cain:                 Right. And so, let’s go the other end of the range because there is another group of measurements that are taken not locally.

Dr. Pamela Gay:         Right, and this is where things are squirrely. In the cosmic microwave background, we see these baryonic oscillations, these soundwaves that move through the early universe, causing slight over- and underdensities, and we can map so beautifully this distribution with our theoretical models, and by combining our understanding of, okay, the universe had this much regular matter, this much dark matter, this much – putting all of these base understandings that we come at from the theory, combining our average temperature information that we got from COBE and other missions, putting it all together, it gets us in the 60s, 68, generally.

Fraser Cain:                 But the most accurate version of this was the Planck satellite from the European Space Agency.

Dr. Pamela Gay:         Right, and this is where it’s important to note the Planck data was used to get at that distribution of baryonic oscillations, and that was used in combination with a mean temperature that they were, in a lot of the papers, referring back to COBE data. So, Planck got us, very specifically, deviations about the mean, and we just fed all the data together in the context of what’s called lambda cold dark matter.

This is a theoretical framework that says that our universe is not just expanding, but it’s accelerating as it expands, that the dark matter, the stuff that we’re not really sure what it is, that may be related to neutrinos in some way – whatever it is, it wasn’t moving extremely fast early in the universe, so that’s where the “cold” part comes in. So, we have lambda, the dark energy, and cold dark matter, two things we have very poor understanding of. When you combine those with the data, it gets you, again, roughly 60 kilometers per second per megaparsec with error bars that don’t overlap.

Fraser Cain:                 Right, and this is the key. So, you look at the local neighborhood and you get a measurement that’s in the low 70s with very tight error bars, you look at the early universe, you get 68 with very tight error bars. Both are exquisite observations, both are trying to tell you the same thing, and they disagree with one another, and this, at the heart, is the crisis in cosmology.

Dr. Pamela Gay:         Correct.

Fraser Cain:                 So, this is the crisis in cosmology, so what’s the answer?

Dr. Pamela Gay:         Well, this is where I personally am a bit excited, and I don’t know how many people are with me on this one because I wasn’t at the meeting, but at the American Astronomical Society meeting, there was a lot of discussion about how JWST images of gravitationally lensed early galaxies appear to be showing from two different studies that have both made it through peer review that there were already well-formed galaxies 350 million years after the Big Bang, and that’s early.

There is other work that is being done that is still going through peer review that is showing there may have already been galaxies – massive ones – at 200 million years after the Big Bang. So, with galaxies forming this early in the history of the universe, it tells us that that model we have, lambda cold dark matter, is off somewhere because while we thought there would be a couple, a few massive galaxies early on, those baryonic oscillations didn’t lead us to believe there would be as many as we are now finding.

And so, we have to figure out a new way to get from mostly smooth universe with the cosmic microwave background to galaxies forming in bigger and probably larger numbers than we anticipated to our present structure, and folks are putting out ideas like maybe there was a bit of leftover inflation, maybe the value of dark energy hasn’t been constant, and all of these different ideas – I don’t think we can really throw anything out yet, and I am the first person to want to throw out ideas.

Fraser Cain:                 Right. So, the challenge here is that you’ve got – the most obvious possibility is that one or both measurements is incorrect –

Dr. Pamela Gay:         Yes.

Fraser Cain:                 – which is what would be everybody’s first instinct, that someone’s wrong, that one of these measurements is incorrect. But, because of this dichotomy, both measurements have been scrutinized and scrutinized, and teams have gone back, and all they’re doing is narrowing the error bars. They’re not finding a large discrepancy. So, that’s the one that is most likely, and yet, that seems to be less and less of the case, and so, you’re left with the universe –

Dr. Pamela Gay:         New physics.

Fraser Cain:                 New physics, right, that our understanding of Einstein, our understanding of what those acoustic oscillations should be in the cosmic microwave background, is wrong.

Dr. Pamela Gay:         And this is where I’m not gonna lay blame on anybody. Relativity seems to work so far, it doesn’t seem to be the problem, but our understanding of the distribution of kinds of matter, the way different forces interplayed, whatever the heck inflation might be – we have no idea what inflation might be – it is somewhere in this physics of how we get from the Big Bang to now that we are missing something, and it’s kind of awesome.

We don’t get a whole lot of surprises anymore, it feels like, some days. We’ve found all the particles in a standard model. We didn’t find any of the particles from supersymmetry. This gives us something new to chase, and the fact that even the folks using gravitational waves to measure distances – they’re still getting the same local universe numbers.

Fraser Cain:                 And that’s harder to get wrong.

Dr. Pamela Gay:         Yeah!

Fraser Cain:                 I know I’ve talked to some people working in gravitational wave observatories, and I’ve had this conversation, and effectively, the more precise, the more powerful these gravitational wave observatories get, the farther they’re able to see out into the universe. You can rely on their measurements, so it’s another layer of observation, but one that’s very trustworthy, and it only goes so far. It doesn’t take you all the way up to the end of the universe, but maybe some future observation will.

So then, new physics – so, maybe we don’t understand how the early cosmic microwave background worked, maybe we don’t understand how Cepheid variables work, maybe we don’t understand all these different pieces, but there have been a few hints. Maybe Type 1A supernovae aren’t the standard candles that we thought they were.

Dr. Pamela Gay:         And this is where there are so many different things that are getting us that local 73-ish that, yeah, I’m happy saying there are discrepancies from one Type 1A supernova to another in weirdo special cases. We’ve got to talk about some of those. If the white dwarf ends up inside of another star, that explosion’s gonna be a bit different, and that happens, but it really seems like there is something about how you get from there – cosmic microwave background – to here – gravitational waves, Cepheids, planetary nebulae, supernovae, all these other mechanisms. There’s something in the science that we have yet to uncover.

Fraser Cain:                 And then, another possibility is if the rate of expansion of the universe changed. So, perhaps there was a – the model that I’ve heard is this idea of late inflation.

Dr. Pamela Gay:         Yeah, that’s the one I was looking at as well, where whatever it was that caused us to initially blow up, there’s a little bit of that left over that caused another kick, but we don’t understand what’s going on there.

Fraser Cain:                 Right, right. And so, if you had an expansion rate of 74 early on – or, sorry, 68 early on, and then it slowed down, you could get the one that’s today, and that’s even taking into account dark energy. I’m sure people are like, “What about dark energy?” That’s layered on top of this. That’s accounted for. And so, you would have this almost – instead of the universe smoothly applying the accelerator on the gas, it was like putting the accelerator a little harder, and then pulling the foot off the pedal a little bit, and then putting it on harder again, and who knows what kind of shenanigans it got up to in the intervening period? So, what is the way forward at this point? What is the way out of the crisis in cosmology?

Dr. Pamela Gay:         We need to basically do a survey of just what was the distribution of galaxies and galaxy clusters in the early universe. We have done a beautiful job, first with the Sloan Digital Sky Survey, doing a volume around our galaxy. Then, with the Dark Energy Survey, we have pushed out even farther in some areas of the sky. With JWST, we’re going to be able to continue pushing the survey of structure size further and further out, watching how the universe goes from being Swiss cheese with giant holes in it to being Swiss cheese with smaller and smaller holes in it –

Fraser Cain:                 Right.

Dr. Pamela Gay:         – and by measuring how that large-scale structure changes over time, that will start to put a different form of constraint on our models. We need to be out there, counting early galaxies.

Fraser Cain:                 Right, and so, you’ve got this structure of the cosmic microwave background radiation, and the hot spots and cold spots should map to equivalent clusters and distributions of galaxies, and so, you’ll know that this transition from the farthest that you can see to more recent is smooth –

Dr. Pamela Gay:         Yes.

Fraser Cain:                 – and then, that will tell you, and you can keep moving forward at that point, but that’s a much harder observation. Weird as it sounds, the galaxies are much dimmer and harder to spot and map out than the cosmic microwave background radiation, which is everywhere in all directions.

Dr. Pamela Gay:         Yeah. More telescopes.

Fraser Cain:                 Yeah. And then, the other side of that is going farther with gravitational waves, and hopefully, you’ll get to this point where the two overlap, where the gravitational waves reach the cosmic microwave background, or shortly after.

Dr. Pamela Gay:         That is technology that someone maybe someday will fund, and we’re at that frustrating point where the next big discovery beyond what we can do with the new, massive radio telescopes that have started to catch star formation at earlier periods, and what we can do with JWST – it’s gonna take multiple nations getting together to build these 30-, 80-, however-many-meter telescopes that are being discussed to be able to look back.

Fraser Cain:                 All right, place your bets. It’s the close observations are wrong, the CMB observations are wrong, or there’s new physics.

Dr. Pamela Gay:         New physics.

Fraser Cain:                 Really? That’s the most exciting outcome possibility, is new physics, so if that’s true, that would be wonderful.

Dr. Pamela Gay:         Or at least a new understanding of that cold dark matter temperature.

Fraser Cain:                 It would be huge thing, like there was a revision to relativity that nobody saw coming.

Dr. Pamela Gay:         So, again, I’m not sure saying a revision to relativity is the right way to say it because I think that what we’re looking at is something coming out of the realm of particle physics, and particle physics and relatively do not talk to one another, and I really think it’s going to be something about how particles interact in different regimes, and whatever the heck this dark energy is that’s gonna be what gets us to the solution to this discrepancy.

Fraser Cain:                 I think this “crisis” makes it sound like a bad thing, but you talk to astronomers, and they couldn’t be more excited. They’re so happy to not understand something, what was considered to be this bedrock idea, because the problem is bedrock is you get this ossification. Suddenly, you have this space that has opened up, where the solution is in there somewhere, and a lot of interesting ideas and theories, and a lot of brainstorming, and a lot of intellectual power gets to be put onto this problem, and they love it. They love it. So, I feel said that the term “crisis” – because you get a lot of pseudoscientists sort of rolling their eyes at scientists at this thing.

Dr. Pamela Gay:         I like “the Hubble Tension.”

Fraser Cain:                 “Hubble Tension” – yeah, but “Crisis in Cosmology” is a better name, so I’d rather reel them in with “the Crisis in Cosmology,” and then help people understand that, in fact, astronomers couldn’t be more excited and happy to have this opportunity. All right, Pamela, thank you so much.

Dr. Pamela Gay:         Thank you, Fraser, and thank you to everyone out there who makes this show possible through your patronage at Patreon.com/AstronomyCast. This week, I would like to thank Camy Raissian, Gabriel Gauffin, Benjamin Davies, Steven Coffey, john öiseth, Arcticfox, Dean, Corinne Dmitruk, Bart Flaherty, The Lonely Sand Person, John Drake, Nate Detwiler, Lew Zealand, Brian Kilby, Naila, The Air Major, Ron Thorrsen, Arthur Latz-Hall, Leigh Harborne, Jason Kardokus, Robert Hundl, Kim Barron, Paul Esposito, Ruben McCarthy, Bob Zatzke, Jordan Turner, Timelord Iroh, Daniel Donaldson, Frank Stuart, Ian Abdilla, and Geoff MacDonald. Thank you all so much for making everything we do possible.

Fraser Cain:                 Thanks, everyone, we’ll see you next week.

Dr. Pamela Gay:         Bye-bye.

Voiceover:                   AstronomyCast is a joint product of Universe Today and the Planetary Science Institute. AstronomyCast is released under a Creative Commons attribution license, so love it, share it, and remix it, but please credit it to our hosts, Fraser Cain and Dr. Pamela Gay. You can get more information on today’s show topic on our website, AstronomyCast.com.

This episode was brought to you thanks to our generous patrons on Patreon. If you want to help keep this show going, please consider joining our community at Patreon.com/AstronomyCast. Not only do you help us pay our producers a fair wage, you will also get special access to content right in your inbox and invites to online events. We are so grateful to all of you who have joined our Patreon community already. Anyways, keep looking up. This has been AstronomyCast.

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Knowledge moves forward, and so, we must move with it. Today we’ll give you an update on some of the most fascinating, and fast-changing topics in astronomy, astrophysics and cosmology.

Download MP3 | Show Notes | Transcript

PODCAST: Ep. 4: The Search for Dark Matter (Astronomy Cast)

PODCAST: Ep 487: Dark Matter: 2018 Edition (Astronomy Cast)

Planck (ESA)

Max Planck (The Nobel Prize)

Mystery of the Universe’s Expansion Rate Widens With New Hubble Data (NASA)

Hubble’s Exciting Universe: Measuring the Universe’s Expansion Rate (NASA)

Cosmologists Debate How Fast the Universe Is Expanding (Quanta Magazine)

Planck and the cosmic microwave background (ESA)

The “Crisis in Cosmology” Might not be a Crisis After all (Universe Today)

How a Dispute over a Single Number Became a Cosmological Crisis (Scientific American)

In a Numerical Coincidence, Some See Evidence for String Theory (Quanta Magazine)

PODCAST: Ep. 598: How You Could Overturn Cosmology (Astronomy Cast)

WEBINAR: “The Hubble Constant Controversy” with Adam Riess (Johns Hopkins University, USA) (International Space Science Institute)

Supernova Cosmology Project (Lawrence Berkeley National Lab)

What are Cepheid Variables? (Universe Today)

Gaia (ESA)

Hubble Space Telescope

Type Ia Supernova (Swinburne University)

Quasar (Swinburne University)

Timing a sextuple quasar (Phys.org)

What Is Gravitational Lensing? (Hubblesite)

Large-scale Structure (Swinburne University)

What is the Inflation Theory? (NASA)

Dark Energy (Swinburne University)

Nancy Grace Roman Space Telescope (NASA Goddard)

Rubin Observatory

JWST (NASA)

Sloan Digital Sky Survey (SDSS)

The universe is expanding faster than it should be (National Geographic)

What is “early dark energy” and can it save the expanding Universe? (Big Think)

No Release for the Hubble Tension (Sky & Telescope)

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Transcriptions provided by GMR Transcription Services

Fraser:                         Astronomy Cast Episode 639: Updates to Dark Matter, Dark Energy, and the Hubble Constant. Welcome to Astronomy Cast, our weekly facts-based journey through the cosmos, where we help you understand not only what we know but how we know what we know. My name is Fraser Cain. I’m the publisher of Universe Today. I’ve been a space and astronomy journalist for over 20 years. With me is Dr. Pamela Gay, a senior scientist for the Planetary Science Institute and the director of CosmoQuest. Hey, Pamela. How are you doing?

Dr. Gay:                      I am doing well. And I do need to congratulate you on the anniversary of Universe Today, which is old enough to drink in the United States, I believe.

Fraser:                         Oh, it’s been doing that for two years. It’s 23 years – is Universe Today now. So, yeah.

Dr. Gay:                      Excellent. Excellent. So, congratulations.

Fraser:                         Yeah, it’s been –

Dr. Gay:                      It’s awesome.

Fraser:                         Apparently, you just keep showing up every day and keep doing the same job and eventually you’ve done it for a long time. And I’ve found my life’s purpose, so I have no plans to change. I’ll do this for another 23 years.

Dr. Gay:                      You know, I am happy to keep doing this with you for another 23 years.

Fraser:                         There you go.

Dr. Gay:                      We are going to be dodder and gray-haired old people. So, one of my favorite things to do early in my career was to ask the oldest astronomers I encountered, “What was the biggest discovery of your life?” And I was shocked when I realized they consistently said galaxies. What do you think we’ll be saying?

Fraser:                         Oh, interesting. Photos from the surface of Titan.

Dr. Gay:                      Really?

Fraser:                         Ah, I don’t know. That’s gonna be cool, though, having a helicopter flying around Titan.

Dr. Gay:                      I was gonna go with dark energy, which is kinda related to the theme of our show today.

Fraser:                         Well, speaking of, let’s get into it. Knowledge moves forward and so we must move with it. Today, we’ll give you an update on some of the most fascinating and fast-changing topics in astronomy, astrophysics, and cosmology. So, this is gonna be just like a catchall of some interesting news that is pushing our knowledge of these topics forward. So, where do you wanna start?

Dr. Gay:                      Let’s start with why we made an episode like this.

Fraser:                         Okay, right. Wait, are you saying like the early episode that we did that says, “Dark Matter” and just call it a day? That’s not enough?

Dr. Gay:                      No. No, sadly it’s not. It’s not. Back when we started this show, we thought, naïve summer children that we were, that with improved observations from Planck, from – continuing to look at supernovae, that we would see our understanding of the universe converge on a single value that explained the modern of expansion rate of the universe in the context of the creation of the cosmic microwave background radiation and everything that has happened in between.

And what we have instead seen is the two values had the error bars getting smaller and smaller and smaller. And they no longer overlap and the difference between them is statistically significant. And what we have actually learned is there is something fundamentally wrong, either with our understanding of the universe or our ability to observe things in many different ways.

Fraser:                         And this term – this is the crisis in cosmology, which gives it – it gives it this really negative sounding name. But you talk any astronomer about this and they’re gitty. They’re so excited that things are weird and they don’t understand and they don’t know why this is the way it is, and they can’t wait to figure this out. And it means a genuine puzzle that they can finally sink their teeth into because all it means is better measurements at different times to get – to understand is it a measuring problem or is it a physics as we don’t understand it problem? And they love it. So, I wish there was a better term than the crisis in cosmology. But, anyway, that’s the term we’re stuck with.

Dr. Gay:                      So, the thing is, for people who are even at the more senior levels and not retired and shouldn’t be retired in astronomy – we still have people in their 90s not retired. I’m excluding them from this conversation. For all of those of us who are below a standard retirement age, when we were learnings astronomy, all the really cool stuff was done before World War II. You had the mapping out of the atom, where it went from the plum pudding model to our model today with the nucleus and the cloud.

You had the resolution of quantum mechanics. You had all of this cool electromagnetism and quantum mechanics and gravity, and it didn’t really speak together real well. But other than gravity not behaving, all the big stuff we thought had been figured out. And let’s face it most of us are just like, “Okay, gravity, we have a problem.” And it was really hard when most of us didn’t want to be embroiled in because string theory is ugly. But, now, we have an approachable problem that even observers like me can get in on and have opinions and thoughts and debates and –

Fraser:                         Yeah, why don’t we try this. What if –

Dr. Gay:                      – it is awesome.

Fraser:                         – we just do that. Yeah.

Dr. Gay:                      Yeah.

Fraser:                         So, I guess, what’s the update because we’ve done an episode on the crisis in cosmology. So, what is the update?

Dr. Gay:                      So, the update is that the folks who are using supernovae, this is Adam Reiss’s team out of Johns Hopkins and the Space Telescope Science Institute, the more and more supernovae they look at, it is still converging at a higher value. And they have gone through and they have compared their data with cepheids and nearby galaxies with supernovae in nearby galaxies with cepheids in our galaxy, and Gaia data is allowing us to understand those cepheids as we have never understood them before.  

And Adam’s team has has figured out how to use the Hubble Telescope in ways that it really was designed for but works to make sure that they understand the photometry they’re taking like it’s never been understood before. And so, observationally, there’s nothing wrong with what he’s doing to think cepheids to supernovae – well, geometry to cepheids to supernovae and work our way out. All right. One day at a set.

Fraser:                         And so, just to clarify this, right, these are observations of type 1a supernovae, which in theory give off a set amount of radiation when they detonate. So, they act as standard candles. This is the most comprehensive survey of these supernovae to date. And it is –

Dr. Gay:                      And of the cepheids.

Fraser:                         And of the cepheids, right, at the same time, and is narrowing the error bars on both of them and they are still not overlapping.

Dr. Gay:                      No, no.

Fraser:                         They are more accurately disagreeing with each other.

Dr. Gay:                      Yes. So, then, we also have the folks that are looking at quasar timing and gravitationally lensed systems. So, if you have a large cluster of galaxies and then you have something behind that large cluster of galaxies, light that meant to go up here some where can get bent by the gravity to come down and reach us. And then light that meant to go down here can get bent up to reach us. And those paths that the light takes can cause the light to travel different distances, and it can also cause it to have multiple operations of the same distant object.

And, if that object happens to be a quasar or a quasi-stellar object with an active galactic nuclei, a black hole that is eating stuff, it can fluctuate in brightness over time. And we can use geometry to figure out the two path differences. And, then, we can use timing to see what’s going on. And, when you start using gravitational lensing of background quasars to figure out the expansion rate of the universe, it’s matching up with Reiss’s team on the supernovae. So, that data matches. Yay.

Fraser:                         Right. So, when last we saw our heroes, the supernovae timing had been refined to the quasars had been measured and their timings had been refined close to and matching essentially what the supernovae are telling us. The cepheids had also been refined and they were completely disagreeing with the supernovae and the quasars. So, what does this mean then? Is this removing or really reducing the possibility that the measurements are wrong and that there’s something more fundamental going on here?

Dr. Gay:                      It is looking more and more like there is something fundamentally wrong with how we’re interpreting the Planck data of the cosmological background radiation.

Fraser:                         Right. And that’s the measurement done by Planck to – incredibly precise measurement that gives us a different number than the cepheid supernovae quasars. And you think about it, cepheids are close. Supernovae are in between. Gravitational lens quasars are really far. That gives you a giant chunk of time. That gives you what, 10-plus billion years. And that’s all on one side. And, then, you’ve got the cosmic microwave background radiation, which is the first few hundred thousand years after the big bang. And it’s those two numbers that disagree with each other.

Dr. Gay:                      So, this is where it gets interesting because we are directly measuring the expansion rate by looking at supernovae, by looking at quasars, by looking at cepheids that are distributed through space-time. With the understanding of the cosmic microwave background, what we’re doing is we’re looking at the point – I believe it’s .003 difference in temperature, which reflects density in the CMB and the size of those differences. And these differences arise from acoustic waves moving through the early universe.

And the way they interacted led to a what we call spectrum of spots, where you see a bunch of spots of one size, bunch of spots of another size, and so on through the spectrum. And the spectrum in our models and the spectrum we see beautifully match. Then you take this measurement of the hotspots, and you’re like, “Okay, that’s dense.” Those are going to become galaxies and clusters of different distributions. And you look at the coldspots and you say, “These are going to become emptiness.” And you project your model forward and you measure right now what is the distribution of the large-scale structure of the universe, in the walls and voids that we see.

You have two measurements. You assume from making other measurements what the geometry of space-time is. We believe the geometry is flat. And that’s backed up by multiple sets of evidence. And, when you run from cosmic microwave background at T=400,000ish to modern-day universe and you figure out how the expansion rate has evolved to get from that to this, you end up with just a slightly slower expansion rate.

But to do that there is a whole lot of assumptions in the physics going on. And we know that the physics is weird because within the first few minutes of the universe, there was a epic of massive inflation that blew our universe up from super tiny to solar system size. We know weird stuff happens. And there is this new idea that there was early dark energy. This is a terrible name, terrible, terrible name. There was early in the universe some factor that rushed the expansion and then stopped.

Fraser:                         But this is post-inflation.

Dr. Gay:                      Yeah.

Fraser:                         This is after the cosmic microwave background radiation was released but before the first quasars, the first really massive galaxies could form. There was this weird speed up and then slow down. Could it have been that just inflation carried on at an ever-decreasing rate until it stopped inflating the universe even after the cosmic microwave background?

Dr. Gay:                      So, saying slowdown is kind of – this is calculus.

Fraser:                         It’s less acceleration.

Dr. Gay:                      Yes. So, it’s a second derivative issue. So, it’s like you put your foot on the accelerator. You go from 30 to 50. You pull back on the accelerator, and, in the same amount of time, you go from 50 to 60. So, you’re still accelerating, but your acceleration is slowing down.

Fraser:                         Right. So, what I’m saying, though, is in the beginning of the universe, that expansion due to inflation is ludacris. The universe was something like the size of a volleyball, and then it was bigger by a factor of – I forget what it is.

Dr. Gay:                      Whatever the size of the solar system is.

Fraser:                         Yeah. Some enormous version of that. And that expansion happened in a fraction of a second. It happened in an incredibly short period of time. I’m gonna use all these very generic terms because I don’t have them in my head right now. But then it was still growing, but, now, it wasn’t growing as quickly –

Dr. Gay:                      Yes.

Fraser:                         – as it was in the beginning. Okay, right.

Dr. Gay:                      And, then, it was during this period that we can’t see because of the cosmic microwave background is opaque, that it’s thought that early dark energy played a role so that the universe wasn’t the size we thought it was when we’re looking at the cosmic microwave background.

Fraser:                         So, Pamela.

Dr. Gay:                      Yes.

Fraser:                         What does this mean?

Dr. Gay:                      It means that there are good folks running interesting models that are finding that cold, dark matter with dark energy doesn’t match the expansion rate of the universe as well as a model that adds early dark energy to the mix. And, as I wrote one of my friends this morning when she asked how I was, I think we know less about cosmology now than we thought when I did my dissertation, and I’m glad I graduated when I did.

Fraser:                         Wow, this is exciting then. This is good news.

Dr. Gay:                      It is. It is.

Fraser:                         It’s always better to know less. It’s awesome.

Dr. Gay:                      Yeah, yeah.

Fraser:                         There’s an analogy. When you work on a large project, you go with this naïve enthusiasm for the project. And you get into it. And there becomes this moment of clarity when you’re like, “Oh, now I know what I didn’t know before, which is how much I don’t know yet.” But you didn’t even know that in the beginning, and you get to the point where – and that – it feels to me like that’s the halfway point. And, then, the sort of the 90 percent point is when you now know all the stuff that’s left, and now you just have to do the work. But it still takes half of the time.  

So, the halfway project is when you finally understand what’s left to do. And we’re at the point now, where at least we know what we don’t know what we don’t know, which is exciting, as opposed to not knowing it. I’m sure none of that’s making any sense. But how will we get an answer to this then? How will we sort this out?

Dr. Gay:                      That is always the question. We need simultaneously both improvements in our understanding of the cosmic microwave background distribution, which we need for a variety of other reasons. If we can get high enough detailed observations, we can start to rule out certain geometries of space-time because we either will or won’t see the same features mirrored on opposite parts of the sky, which means light is going all the way around. We’re seeing in from the front and the back.

Fraser:                         But, if I understand this correctly, we pretty much can’t make a more accurate measurement of the cosmic microwave background. We’re literally – we can measure other factors in it like the polarization of the light, but you can’t just measure those temperature changes more precisely.  

We’re at Max – and Planck sort of closed the book on that portion of it, so now the polarization is gonna matter and all other – which will tell us essentially which way these blobs were turning in the early universe, which is very interesting and give us a sense of their interactions and give us a sense of whether there was gravitational waves and primordial gravitational waves and so on and so forth. But we’re gonna have to measure that in-between time, right? We really need that time from between 0 and about 10 billion years ago.

Dr. Gay:                      And this is where folks have hope for what was previously called the WFIRST and is now called the –

Fraser:                         The Nancy Grace Roman.

Dr. Gay:                      Thank you. I wanted to say Vera Rubin because I am in love with that telescope.

Fraser:                         Well, Vera Rubin will also help, so –

Dr. Gay:                      It will also help but not as much, not as much. The Nancy Grace Roman Telescope is really our next great hope for understanding dark energy. And, of course, there is the JWST always lingering in the background as Schrödinger’s telescope that either will or won’t solve all of our problems for us.

Fraser:                         Yeah, but it only does it – it’ll solve specific problems. James Webb is when you need to call – when you got something you need fixed, you bring in James Webb to take a good, close look at it. But Nancy Grace Roman is also in the infrared –

Dr. Gay:                      It’s a workhorse.

Fraser:                         – but it’s gonna be observing vast swaths of the sky, huge chunks. As with Vera Rubin, it is gonna be able to see big pieces of the sky. So, how will – and, ahh, I’m trapped in Pamela’s paradox now. We can’t talk about the Nancy Grace Roman Telescope because it hasn’t launched yet.

Dr. Gay:                      Exactly.

Fraser:                         And yet, in theory, it would be really interesting to know how it’s supposed to work. But how can we do that? Anyway –

Dr. Gay:                      Yeah, but there’s W bosons launch to discuss and we haven’t got there yet.

Fraser:                         Yeah. Well, that’s gonna have to be a whole other show because we’re running out of time for this one.

Dr. Gay:                      All right.

Fraser:                         Yeah. But the point being, all of these concepts, the Hubble constant, dark energy, dark matter, their interactions, their proportion of the universe, they’re all tied up together in this job of measuring the expansion rate of the universe at different times. And there is a giant gap that is about to get filled thanks to Nancy Grace Roman. But let’s imagine – okay, so fine – so, let’s imagine that you wanted to launch a Hubble-scale telescope. So, how does it, like – is it like the same size as the Hubble Space Telescope but it was all –

Dr. Gay:                      Like WFIRST.

Fraser:                         But was it infrared? But WFIRST doesn’t exist because it hasn’t launched yet. But I’m sort of envisioning a hypothetical space telescope that has infrared capability. And let’s say you launch it in say about 2026 or so that could do these surveys. How would it help in this project?

Dr. Gay:                      It’s going to give us a larger perspective on all the little things that we’re looking for, the discovering the supernova, the measuring the gravitationally lensed quasars, the looking for – Wendy Freedman is also out observing massive red stars that flare. And it’s going to give us this systematic understanding of also the distribution of the large-scale structure. So, that thing that we’re building on from the Planck observations of the CMB to our modern understanding of the structure of the universe, we’re gonna be able to get a much better understanding of how that structure has evolved over time. We started to get there with SDSS. Nancy Grace Roman is going to take us further than the Sloan Digital Sky Survey, and its amazingness that Apache Point could ever do from the surface of our planet, so –

Fraser:                         And in infrared, which –

Dr. Gay:                      Yeah, puts us further back in time.

Fraser:                         – SDSS can’t do because it’s visible light. And so –

Dr. Gay:                      It’s on the Earth.

Fraser:                         Right. And so, Nancy Grace Roman, because it’s viewing infrared, like James Webb, we’ll be able to see the stuff that is farther and older, which is that missing point in time. And, then, if it turns up any really interesting objects, cool, early gravitationally lensed quasars, then James Webb can step in and give us a better look and measure the redshift to these specific objects with precision.

Dr. Gay:                      And just to be clear, it’s not seeking supernovae. It is surveying the sky. And, if there happen to be supernovae in there, cool, cool. It will have the capacity to uncover these duplicate quasars that can get followed up, but it’s out there measuring the large-scale structure of the universe. And that’s a pretty awesome job.

Fraser:                         Mm-hmm. Mm-hmm. Well, that was good. It’s hard to kind of wrap together what this was, what we just talked about. But there is this crisis in cosmology.

Dr. Gay:                      It is awesome.

Fraser:                         It’s awesome. As astronomers have gotten better at measuring, it has resolved itself. What were thought to be error bars that would resolve themselves have actually turned into a giant gap in our understanding of how the universe worked at the earliest times, but we don’t have an answer. But at least we finally have a question, and, I think, that is enough to keep us busy and excited for years to come. Thanks, Pamela.

Dr. Gay:                      Thank you Fraser. And, yeah, we’ve got a lot of work to do. And we can keep bringing it to you here on Astronomy Cast thanks to all of you out there on Patreon, who support us week after week and allow us to pay all of the people that keep us organized. I’m talking about Nancy, Rich, Ally. There are names I’m sure I’m forgetting – Beth. Why do I always forget Beth’s name? I am sorry Beth.

Anyways, this week I would like to thank Scott Bieber, Matthias Heyden, Nial Bruce, Disasterina, Daniel Loosli, The Lonely Sand Person, Justin Proctor, Jim Schooler, Gregory Singleton, Paul L Hayden, Jeff Wilson, Cooper, Eran Segev, Paul D Disney, Kenneth Ryan, Nate Detwiler, Allan Mohn, Steven Shewalter, Omar Del Rivero, Tim McMackin, Alex Raine, Benjamin Müller, Don Mundis, NinjaNick, Micheal Regan, Dean McDaniel, Scott Briggs, Matt Rucker, Janelle Duncan, J. AlexAnderson, Father Prax, Philip Grand, Benjamin Carryer, Mark Heather, Widick, Frode Tennebø, Anitusar, Dwight Illk, Mark Steven Rasnake, Abraham Cottrill, schercm, Bruce Amazeen, Gabriel Gauffin, Dustin A Ruoff, Brent Kreinop, Jim McGihon, Gfour184, Kimberly Rieck, Glenn McDavid, Steven Coffey, john öiseth.

And if you would like to join us and have the potential of me either pronouncing or not pronouncing your name correctly, join us over at patreon.com/astronomycast. And feel free to add pronunciation instructions to your name.

Fraser:                         Or don’t

Dr. Gay:                      I love all of you.

Fraser:                         Or don’t if you want to laugh. Thanks, Pamela. We’ll see you next week.

Dr. Gay:                      Thank you, Fraser.  

Voiceover:                  Astronomy Cast is a joint product of Universe Today and the Planetary Science Institute. Astronomy Cast is released under a Creative Commons attribution license. So, love it, share it, and remix it, but please credit it to our hosts, Fraser Cain and Dr. Pamela Gay. You can get more information on today’s show topic on our website astronomycast.com.

This episode was brought to you thanks to our generous patrons on Patreon. If you want to help keep this show going, please consider joining our community at patreon.com/astronomycast. Not only do you help us pay our producers a fair wage, you will also get special access to content right in your inbox and invites to online events. We are so grateful to all of you who have joined our Patreon community already. Anyways, keep looking up. This has been Astronomy Cast.

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We think of space as a vacuum, but there are regions of different density. There are winds blowing from stars and other objects that clear out vast bubbles in space, and look absolutely fantastic in pictures. And might have been critical for Earth to even exist in the first place.

Download MP3 | Show Notes | Transcript

Bubble Nebula (NGC 7635) (Hubblesite)

The Horsehead Nebula (NASA)

The Pillars of Creation (NASA)

HII Region (Swinburne University)

Solar Wind (NOAA)

Voyager (NASA)

Magnetospheres (NASA)

V838 Monocerotis (Hubblesite)

Hubble Space Telescope (NASA)

Planetary Nebula (ESA Hubble)

NGC 2392 (Hubblesite)

Supernova 1987A (AAVSO)

Molecular Cloud (Swinburne University)

What is a quasar? (EarthSky)

Active Galaxies (NASA)

Galaxy Clusters (Harvard | Smithsonian CfA)

Dynamo Effect (University of Oregon)

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Transcriptions provided by GMR Transcription Services

Fraser:                         Astronomy Cast, episode 636, Blowing bubbles in space. Welcome to Astronomy Cast, your weekly facts-based journey through the cosmos where we help you understand not only what we know, but how we know what we know. I’m Fraser Cain, publisher of Universe Today. With me as always is Dr. Pamela Gay, a senior scientist for the Planetary Science Institute and the director of CosmoQuest. Hey, Pamela, how are you doing?

Pamela:                       I am doing as good as one can do when spring is in high pollination. I’m having fantasies of being out in one of these vacuous bubbles in space.

Fraser:                         Right, where there’s no pollen?

Pamela:                       Where there are no trees. Yeah, yeah.

Fraser:                         No pollen, yeah. Yeah, again, every year, it gets a little worse for me. Every year, as allergy season arrives, I have to remind myself that I have… that I do suffer from seasonal allergies, because I didn’t when I was younger, and now I do. And to just take my Claritin and move on. So, yeah, but I definitely am a little gurgly right now.

Pamela:                       We apologize for any sniffles that make it through to the final recording.

Fraser:                         Yeah.

Pamela:                       We’re sorry, folks.

Fraser:                         We’re counting on our editors to clean up the final audio. So, hopefully, it’ll be better. All right, we think of space as a vacuum. But there are regions of different density. There are winds blowing from stars and other objects that clear out vast bubbles in space and look absolutely fantastic in pictures. And they might have been critical for earth to even exist in the first place. So, we’re recording the show right now. And I’ve set one of these bubbles. I think it’s the Bubble Nebula, but one of these incredible bubbles in space, and many of them had been seen before.

And so hopefully, people are sort of remembering these cool photographs, and like the Hubble space telescope that really looks like a bubble, like someone has blown a soap bubble in middle of space. What is it?

Pamela:                       So, they are a variety of different things, the one that is behind you, the one that I’m currently showing up on the screen, these are what are called H II regions. That means there are areas where hydrogen has been ionized, that a little electron has been heated up and blown away. And these regions are created by extremely hot stars giving off ultraviolet ionizing light that over the distance where that light is intense enough to ionize the hydrogen, you get these amazing spheres of glowing gas. And the reason they look like bubbles is these spheres we see the thickest amount of the sphere around the edges. So, that’s where, well, we see these cool red areas.

Fraser:                         So, I just sort of imagined that you had like the solar winds and the radiation was pushing material away from the stars. But you’re saying that the intense radiation from the star itself is ionizing the hydrogen in this area and causing it to glow in a way that’s different from the I guess the background nebula?

Pamela:                       So, it’s a little bit of all of the above. And looking at regions like the Helix Nebula which is formed from a variety of different hot stars where you can start to see the structures, what you have is the winds from the hot stars are pushing material out. The ultraviolet light from the hot stars is creating that ionizing radiation that is creating glowing spheres around the stars. So, you have regions that are glowing brightly due to the ionizing radiation, and you have these filamentary structures that are created by the winds from the stars.

Fraser:                         And I guess what are the implications? Like you’ve got a young hot star that is blowing out this intense radiation, what happens to this region around it beyond it looking pretty in our telescopes? Does it stop star formation? Does it cause extra star formation? What does it do?

Pamela:                       So, the awesome thing about this is really big blobs of material collapse the fastest, form hot stars that create all of this amazing structure as the first thing that gets created in a star-forming region. Once these hot stars are out there doing their bubble-blowing thing blasting out the material around them, they can shock other clouds of material to collapse and form additional solar systems. So, this is part of a chain reaction of star formation that just starts with something knocking on the side of a giant molecular cloud getting that biggest thing forming, and it just all collapses down from there.

Fraser:                         So, you’ve got these stars, they’re blowing up these winds, they’re causing overdense regions out at the limits around them, and those overdense regions are still I guess, cold hydrogen, and so they can start collapsing –

Pamela:                       Yes.

Fraser:                         Into new stars. And eventually, you’re going to get overlapping stars blowing their bubbles and you’re going to run out of material that is capable of collapsing.

Pamela:                       Exactly. And when we look out at regions like the Horsehead Nebula, the Pillars of Creation, those not bubble-shaped areas are the remnants of material that got knocked around into the shape they are through the combination of massive stars pushing out, and then the gravity of what’s inside of them pulling in.

Fraser:                         Like when you look at the Pillars of Creation, and you see those tentacles, like a tentacle hand reaching up. And you can see other examples of these same kinds of nodules, it looks very familiar, very similar to what we talked about these other Bubble Nebula, but the things are kind of enshrouded in gas and dust and we can’t really see what’s going on inside of them.

Pamela:                       Those are just protostars. So, when they’re still enshrouded like that, those are either proplyds, protostars, it all depends on what stage in their evolution they’re in. And they haven’t fully ignited, their nuclear reactions haven’t fully turned on yet. And so they don’t have that light pressure to push everything out from around them. Over time, those pillars are going to get eaten away by the light of the stars forming inside of them. They are literally going to cannibalize themselves to form new stars.

Fraser:                         And then we would see the bubble?

Pamela:                       Well, it depends on how much material is left around and what the shape of the material is. So, I have to admit, I’ve picked and choose which H II regions to show to you because these happen to look like bubbles. What’s amazing about the H II regions is as you get different pockets of star formation, you can end up with these incredible filamentary structures of the pockets colliding together to blow a series of bubbles that you get more of a froth in that kind of a situation.

Fraser:                         It’s amazing to me that all of this is essentially driven by gravity. That –

Pamela:                       Yes.

Fraser:                         That gravity is what triggers the star formation in the first place, that the gravity pulls in these stars into denser and denser regions, pulls the gas and dust into denser regions, which turns them into stars. And then the stars because of their gravity ignite with their fusion and then are pushing out with the radiation and their own stellar winds that are causing gravity to make other parts collapse down and continue this cycle. And this isn’t necessarily what has to do with today’s episode, but literally, gravity just is just writing the rules of the whole universe.

Pamela:                       But light is the other side of this, and that’s the thing that always gets me is our universe is a balance between gravity pulling things together and light pushing things apart. Stars support themselves in light. Our Solar System is largely protected from the interstellar medium by the bubble that our own Sun has cleared out around us. It’s light versus gravity.

Fraser:                         Right, so that actually transitions into the next part of this conversation that I wanted to have. So, you were starting to go into this idea, and I had sort of mentally wanted to cover this, as well as that when we look at these beautiful bubbles, nebulae, they’re young stars, they’re hot stars.

Pamela:                       Yeah.

Fraser:                         But we’ve got spacecraft out there examining the bubble, that the solar system, that our own Sun four and a half billion years old, is continuing to blow.

Pamela:                       Yes. And, so here, it’s our solar wind is the driving process. And it is thin enough, and at a temperature where it’s not really something that we can go out and just look at. But as the Voyager probes have gone on their escape trajectory out of our solar system, they’ve been able to see the kinds of particles that they’re experiencing, the kinds of fields that they’re experiencing, are varying on their journey outwards so that now they’re starting to see more and more and more interstellar medium as they leave that protective bubble.

Fraser:                         And I mean, I guess every star has one of these bubbles, and you call it protective, what is this protecting us against?

Pamela:                       There’s a lot of high-energy particles out there that get somewhat deflected. And radiation is really just not a good thing for the human body. So, I think it is safe to say that less cosmic rays is always a good thing.

Fraser:                         More better.

Pamela:                       Yes.

Fraser:                         So it’s like the Earth has a magnetosphere and then the solar system has a magnetosphere.

Pamela:                       Exactly. And there’s beyond the magnetosphere, literally, the solar wind is pushing out and moving the material around us. And while we don’t get to see this with our own solar system, it’s the kind of thing that we’ve had the opportunity to see in other systems. V838 Mon is my favorite example. This star for unknown reasons led off two different flashes of light, and a flash of light has a width to it. And as these expanding bubbles of light with width move away from the surface of the star, they are illuminating the structure of the material around the star allowing us to see that bubble that has been cleared out by the stars’ solar winds in the past and perhaps even enhanced through mass loss of that star.

Fraser:                         That’s crazy. Yeah, it’s one of these dramatic images, and especially because it’s a sequence that Hubble has been observing this star for decades now we can actually see the light echoes moving through this region, we can see how the shape of the bubbles that it has blown out or changing over time. It’s unbelievable that you sort of imagined things to work at astronomical amounts of time. And yet every now and then there are these things that are unfolding in front of us in vastly faster time periods.

Pamela:                       Yes, the speed of light, literally the speed of light.

Fraser:                         The speed of light. Now we’ve talked about young stars creating bubbles, but as stars die, they can as well.

Pamela:                       Yeah, and this is where on the low energy side of death we get to the planetary nebula. This is the ultimate fate of our own star. And it’s how a lot of stars out there are going to, well, eventually end their lives. What happens is the outer layers of the star during its red giant phase and beyond get let go as the star expands, and the material goes past the point that gravity can hold on to it.

We don’t fully understand the pulsation mechanism of these massive stars but stars like Mira can breathe in and out over the period of roughly a year in a rather irregular manner. And on the way back in they always bring everything with them.

Fraser:                         I’m sort of imagining you’ve got this star that’s pulsing and like the mere variables, the scale to which they pulse is mind-blowing that they can change on their brightness and their size, like at one point, they’re way out beyond the orbit of, say Jupiter. And then the next moment, or weeks later they’re now down –

Pamela:                       Several months down.

Fraser:                         Yeah, months later, now they’re down vastly smaller. And then they do this again at a very regular rate. And I guess each time as they are expanding outward, they’re accelerating this material away from the star, and then the star stops and pulls back in but a lot of that material is still coasting away from the star on an escape velocity. And so you get these just shells of dead star sloughed off into space, around the star.

Pamela:                       And exactly how they get sloughed off is going to be determined through a combination of what stuff is inside that solar system that can block the expansion of that material. So, you can end up with systems that have areas that clearly have less material or more material within them. Planetary nebulae are something we’re still working very, very hard to figure out because they come in detail where the more and more and more resolution we get on our telescopes, the more crazy structures are revealed in these planetary nebulae.

These structures are that combination of a star getting puffed out by light pressure, coming back in as best it can, and just letting go of the light eventually, as the core just stops producing more energy, collapses down to become a white dwarf. Now, the star that was expanding and contracting is doing this in an irregular matter. It’s doing it while gravitationally interacting with perhaps a binary star, perhaps planets within the system. It’s doing it while having whatever interstellar media is surrounding it.

And to understand the structure, we have to understand what was there in the first place? What influences might have changed the symmetry of the stellar wind, and everything inside that might have been adding that little extra kick is perhaps a massive planet went past.

Fraser:                         Right. It seems like the magnetic field of the sun, perhaps the interactions of the planets, these all play a part of the mix to create the planetary nebula. And it’s still like, we don’t even know if the sun is going to turn into a planet. Maybe the sun doesn’t have the right, raw ingredients to create a planetary nebula like we see out there. Or maybe it does. It’s funny that it used to be assumed but now it’s a bit up in the air.

Pamela:                       I still remain firmly in the camp of it’s going to be a planetary nebula.

Fraser:                         You just want one?

Pamela:                       Yeah, I do. It may not last very long. They don’t all last the same amount of time. But –

Fraser:                         Yeah. All right, we’re gonna talk about this some more in a second, but it’s time for a break.

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Fraser:                         And we’re back. All right, so what happens if we need a bubble and we need it fast?

Pamela:                       The best way to do that is to just explode a giant star, just explode it. Yeah, it’s going to release a massive kick of energy that is going to include remaindary bits of the former star and also collide with violence into any surrounding material and shock it into doing its own glowing kind of thing.

Fraser:                         I think my favorite example of this is the Supernova 1987 A, which was really the closest supernova that has been recorded in modern history while we had really good telescopes, and you can see this debris cloud again, year after year expanding outward with blobs of fiery material.

Pamela:                       And it’s a figure eight.

Fraser:                         Yeah, yeah.

Pamela:                       There’s a central bit, and then these two expanding rings that there’s literally a dumbbell of Shockwave out there.

Fraser:                         And this ties back to the first part of the show when we were talking about how you’ve got some triggering event that causes the collapse of star formation in a nebula in the first place. And it’s often these supernovae, these bubbles are the ones that actually get the whole process rolling.

Pamela:                       And they can be amazingly energetic events that are giving off gamma rays, X rays, ultraviolet light, they are heating the area around them, they are shocking them and compressing the gas around them. And if one of these goes off near a giant molecular cloud, it can be just enough force to set that giant molecular cloud out of balance between gravity in and just gas pressure out. So, the nudge of a supernova is thought to be part of what triggers this entire process in the first place.

Fraser:                         And that’s interesting, when you sort of imagine that you’ve got like the supernova first is just a big shock to the system that begins the process, but then afterwards this more gentle, roiling star formation continues the process until all of the fuel in the solar nebula has been used up. It’s absolutely fascinating to think about.

Pamela:                       And it’s really this bubble-blowing process that seems to be at the core of moving a whole lot of things around. So, at the very center of our galaxy, our supermassive black hole appears to periodically blow bubbles as well. And these are also shockers that, well, have radio bands, and these bubbles giving off high energy light, it looks currently like there are two different sets of bubbles. Again, we have that figure-eight structure where something fell to its doom in the center of the Milky Way galaxy and the high energy light that was given off while the thing was being destroyed blew out bubbles in the interstellar medium above and below that black hole. And that too can trigger star formation.

Fraser:                         And so this is where I was going to take this next as we talked about just stars themselves and fairly small phenomena, but these can exist at this much greater scale. These bubbles blowing out of the supermassive black hole are tens of thousands of light-years long. They’re enormous.

Pamela:                       Yes.

Fraser:                         And yet, it’s weird, or isn’t it interesting that they kind of fall, they’re perpendicular to the spin of this supermassive black hole that has something to do with the way this magnetic field is wrapped up around and the way it’s rotating. This material is falling in, and then it’s being thrown out in both directions. And it happened a long time ago. It happened tens of thousands, millions of years ago, and we’re still seeing the repercussions. Is it a time when the supermassive black hole might have been a quasar, might have been very bright?

Pamela:                       I think going all the way to quasar is a few steps too far.

Fraser:                         Right.

Pamela:                       But it definitely was active at that point. And we see, essentially, they appear to expand as the shockwave moves through space. This is at a much more energetic level, similar to when an explosion goes off, and the sound waves propagate through the air creating this wind that pushes things out, and the light goes far faster. But then that shock follows behind. And there are some really cool concerts and stuff where you can see the sound propagating through the crowd as they react.

Fraser:                         Wow.

Pamela:                       And here what we’re seeing is the energy propagating well through the galactic region as it travels through space.

Fraser:                         Can we scale this up one more notch? Do we see bubbles at the galaxy cluster scale?

Pamela:                       I am reluctant to say the word bubble. What we do see in galaxy clusters is the region in the center of the galaxy is extremely hot, it’s giving off X-ray radiation. It’s that level of hot. But this is gravity pulling everything together and heating it up. Not some central Dynamo heating it up. We do have jets in the centers of a lot of these systems. But that’s different physics that we talked about last week.

Fraser:                         Right, right, right. So, you can definitely get wins at a galactic scale, coming from these collisions and interactions and so on, but not necessarily these nice, clean bubbles blowing in all directions in the same way. Well, it’s absolutely fascinating and they’re wonderful to look at. And now when you see one of those pictures, maybe you’ll know a little more about what’s going on. Thanks, Pamela.

Pamela:                       Thank you so much, Fraser. And thank you so much to everyone out there who makes this show possible week after week. This week I want to say thank you to a group of our Patreon over on patreon.com/astronomy cast. Thank you to Ninja Nick, Janelle Duncan, Michelle Cullen, Mark H. Widick, J. Alex Anderson, Benjamin Carryer, Frode Tennebø, Matt Rucker, and Anitusar, Schercm, Moose and Deer, Abraham Cottrill, Father Prax, Kimberly Rieck, Philip Grand, Mark Steven Rasnake, Jim McGihon, Dwight Illk, Bruce Amazeen, Jen Greenwald, Andrew Stephenson, Brent Kreinop, Dustin A Ruoff, Planetar, Gfour184, Kseniya Panfilenko, Gabriel Gauffin, Cemanski, The Mysterious Mark, Rachel Fry, Steven Coffey, Peter, Sean Martz, Joe Wilkinson, Glen McDavid, John Öiseth, The Air Major, and Benjamin Davies. Thank you all so very much.

Fraser:                         Thanks, everyone. And we’ll see you next week.

Pamela:                       Bye-bye.

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As astronomers look out across the Universe, they see various objects spewing jets of material light years into space. What causes these jets, and what impact do they have on the Universe.

Download MP3 | Show Notes | Transcript

PDF: The Role of Magnetic Fields on Astrophysical Jets (arxiv)

What is the Interstellar Medium? (University of New Hampshire)

Angular Momentum (Swinburne University)

Ideal Gas Law (Hyperphysics)

How to Make an Engine from a Battery, Wire and a Magnet (WikiHow)

How Rail Guns Work (How Stuff Works)

Binary Star (Swinburne University)

Einstein’s theory of general relativity (Space.com)

Frame-dragging (Einstein Online)

T Tauri Stars (Swinburne University)

Herbig-Haro Object (Swinburne University)

What is a neutron star? (EarthSky)

What Is a Black Hole? (NASA)

IMAGE: A cosmic searchlight (ESA)

Stanford astrophysicists report first detection of light from behind a black hole (Stanford University)

Gamma Ray Burst (Swinburne University)

Quasar (Swinburne University)

A stellar vampire mimics a black hole (Physics Today)

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Transcriptions provided by GMR Transcription Services

Fraser:                         Astronomy Cast, episode 635: Astronomical Jets. Welcome to Astronomy Cast, your weekly facts-based journey through the cosmos where we help you understand not only what we know but how we know what we know. I’m Fraser Cain, publisher of Universe Today. With me, as always, is Dr. Pamela Gay, a senior scientist for the Planetary Science Institute and the director of CosmoQuest. Hey, Pamela. How you doing?

Dr. Gay:                      I am doing well. How are you doing?

Fraser:                         Also well. Sort of dealing with the trials and tribulations of getting our house completed. We’re in the final stretch now and it’s all the little details that need to be done perfectly and each one can hold up the thing. But we’re getting there. We’re getting there. As astronomers look out across the universe, they see various objects spewing jets of material light years into space. What causes these jets and what impact do they have on the universe? All right, jets. Now, we’re not talking about aircraft jets. We’re talking about space jets. But they’re not aircraft jets in space. What is a jet?

Dr. Gay:                      So, at the most simplistic level, a jet is anytime you have something that sends out materials at high velocities. So, when we call an airplane a jet, what we’re actually referring to is its engines that are spewing material out at high velocities instead of just having a propeller at the front.

Fraser:                         And throwing an airplane in the opposite direction.

Dr. Gay:                      Exactly. Exactly.

Fraser:                         Right.  

Dr. Gay:                      Now, in astrophysical situations, we are talking about situations where you have some sort of an object that has a entire environment around it that is leading up to it sitting at the center of normally bipolar, going-out-in-two-different-direction jets that have been built up most typically by a magnetic field.

Fraser:                         So, I guess, think of a fountain throwing water high up in the air. The distance that the fountain goes is limited by the force of gravity, so it reaches sort of a maximum height. It’s running into the air, and so you’re getting both the jet getting a little bit slowed down but also sort of broken apart a little bit as well as other spray and material going off in all directions; except with the astronomical ones, they go in two directions, so you’ll get jets, as you say, in polar directions.

Dr. Gay:                      And the gravity of the object can, if it doesn’t make it very far away, cause the material to flow back at you. But most of the time, as the material’s getting kicked out at such high velocities, you don’t really see this – we refer to it as collimated – getting focused into a tight beam. We don’t see that focused beam start to diffuse out into a cloud of material like at the top of a fountain until it hits that interstellar media, until it hits all the stuff that is just filling space between galaxies or between stars.

Fraser:                         Right, right. I guess there’s not that much to run into.

Dr. Gay:                      Depends on the system.

Fraser:                         So, what can generate these jets? What is their cause?

Dr. Gay:                      The bulk of the time it is extremely complex physics where the correct is, we don’t entirely know.

Fraser:                         You can’t just say “extremely complex”. “The answer’s “extremely complex physics”.” That is unsatisfying to me.

Dr. Gay:                      I know. I know, and this is why in introductory textbooks, magazine articles, all that complicated physics gets hidden behind the phrase magnetic fields.

Fraser:                         Perfect. Now, we’re talking. It’s magnets.

Dr. Gay:                      And the truth is there are magnetic fields that are involved, where you have this compact object that has materials spiraling around it and it’s often getting either stolen off of another object or it’s flowing in the center of a galaxy. And as it comes in, it is getting denser and denser and denser because the material has to shed angular momentum in order to get in towards the center. So, it backs up while it’s going through this process of shedding angular momentum, and this built-up material gets denser and it gets hotter due to that PV nRT equation that we learned in high school. Chemistry, pressure, density, temperature, all related things.

                                    And if it gets hot enough, it can even start having nuclear reactions. So, hot gas, it’s gonna eventually become, hot ionized gas. And hot, ionized gas means that you have atoms that have shed electrons away and these are now charged objects. Charged objects orbiting are charged objects going in a circle. Moving charged objects create magnetic fields. Moving charged objects going in a circle create basically electromagnetic fields like a battery and some wire can do, and you’ve now built a very small railgun that can fling things out of the magnetic field along these polar axes.

Fraser:                         All right, so you’ve got matter moving at high speed crushed together, heated up to enormous temperatures, starting to undergo more exotic processes like fusion. But ionization of these particles, they’re moving in circles around whatever object they’re orbiting. This is generating electricity, magnetic fields, and complex physics, that soup of madness, is now creating this, as you call it, a Gauss gun, a railgun, a magnetic accelerator that has been taking this raw material and hurling it away from the accretion disk.  Right.

Dr. Gay:                      And what I love is, at the most simplistic level, this is something you could do with a sixth grader: wire batteries and a tiny magnet. So, go figure this out for yourselves, people.

Fraser:                         And feeding material from a binary companion star or generating nuclear fusion. Any sixth grader can do this. All right, so we got a sense of what the underlying complex physics, or at least the ingredients of the mess, that is happening. And I think you said it perfectly. Astronomers still don’t know. Some of the finest minds in nuclear physics, in particle physics, in magnetic field, in fluid dynamics, in all of these fields working together are still arguing and discussing.

Dr. Gay:                      Lemme give you one example.

Fraser:                         Also, relativity has effect as well.

Dr. Gay:                      Frame-dragging.

Fraser:                         Frame-dragging.

Dr. Gay:                      Frame-dragging is a thing. And to give you one example of why this is confusing. If you go back to your sixth-grader model. Literally you can do this. Go grab some wire that isn’t insulated the way this is, wrap it in a circle, attach both ends of the wire to a battery and now you have charge flowing and you can use this to fling small objects. It’s fun. If you get big and fancy, car battery, PVC wrapped in wire. Now, you have a small railgun. Now, when you build your small railgun, it is always going to fling magnets in the same orientation. With galaxies, you have electrons being thrown both directions out of this, and so you have to build up a system that allows symmetrical flinging of materials in both ways.

                                    Now, electrons have both north and south magnetic orientations. There’s ways to get there, but just understanding it is flinging things in a symmetric manner. It’s kind of –

Fraser:                         Right.  

Dr. Gay:                      – where you get at the “This is hard”.

Fraser:                         But it’s perpendicular to the axis of –

Dr. Gay:                      Right.

Fraser:                         – rotation of the object. So, if the galaxy is –

Dr. Gay:                      Right-hand rule.

Fraser:                         – rotating, right-hand rule. You’re gonna see material blasting up out of the center of the galaxy and also down out of the center of the galaxy in completely opposite directions of the galaxy. All right. Again, I guess I say, “We know why this happening.” We don’t know why this is happening. All we know is that, in that mess of complicated physics this is happening. What kinds of objects are capable of generating these jets?

Dr. Gay:                      Okay, at the most pathetic level, we have very young stars called T Tauri stars. The bulk of a T Tauri star’s jets are due to outflows of just it’s not eating the material fast enough as it flows down onto the star and things escape. But, also, its magnetic fields will bloop out material in pockets now and then, so you have ineffective bloopy jets coming from T Tauri stars. Then, skip through most of the stars in between that are happily doing their main sequence and beyond life of nuclear fusion and their core, and then we get to the neutron stars.

                                    So, as soon as you get to something as dense as a neutron star, these objects become capable of gravitationally pulling stuff off a companion and getting it going fast enough around the neutron star because it has enough gravity and it’s tiny enough and you need both, that you can start getting that jet that has the magnetic field again. So, for individual objects that have long-term lasting jets, you have T Tauri stars, Herbig-Haro objects at the very beginning; things forming stars. Stars are happy, stars are happy, stars are happy, stars die. And for dead stars, you have neutron stars and bigger. And when I say “and bigger” I mean, all black holes all the way up to super black holes are capable of having jets. So, you can have a full fledge galaxy that has the exact same, not-entirely-well-understood physics as the neutron star.

Fraser:                         It’s just a matter of scale?

Dr. Gay:                      Yes.

Fraser:                         Right. All right, so let’s talk about scale then. We talked about how a neutron star will generate some level of jets, and super massive black holes, the most massive objects in the universe, will generate these jets. What is the scale? How far out can these jets go from their source?

Dr. Gay:                      Light years and light years and light years and light years, by which we’re talking thousands and thousands and thousands of light years from the center of a galaxy. And the image of those of you who happen to be watching on YouTube or live while we’re recording on Twitch, there is a tiny speck that, on my particular monitor is the size of my pinky fingernail, that represents where the galaxy is. And about 6 inches away in this image is where the jet ends, and the jet is actually pointed a bit at us, so that’s hiding some of the full length of this jet. In the radio sky, galaxies are a very different size than they are in the optical sky because of how big these jets are.

Fraser:                         So, for a neutron star, we’re talking like dozens of light years?

Dr. Gay:                      It can be. Now, the neat thing about neutron stars and stuff is they exist in much more complicated parts of our galaxy, so their size is going to be beautifully dependent on how much stuff is around them. And so, we can end up with, they go out and now they’re pushing their way out, blowing a bubble around them. And it’s this blowing a bubble around them that, at a certain degree, allows us to figure out how long they’ve been doing things in some cases.

Fraser:                         Because you know how fast the material’s moving and then that lets you figure out when it started this process? Okay.

Dr. Gay:                      Yeah. And so, you’re looking at different kinds of environments, but what is particularly fascinating is when we look back at the center of our galaxy, even from what we are, in the correct wavelengths of light we see all these bubbles all over the place. Some of them are spherical bubbles that are created by supernova explosions. But in other cases, what we’re seeing is the material pushed out by jets.

Fraser:                         That’s really fascinating. That you look at the universe in these different wavelengths, and now you see this historical record of the events. You see bubbles blown out from ancient supernovae. You see the wakes of jets released by neutron stars while they were actively feeding on some companion star or black holes while they were feeding on some companion star. And I’m guessing we see something similar for galaxies with active nuclei that we can see how things have changed over time with them.

Dr. Gay:                      I’m not sure we’ve actually seen something like that, but it could be I’ve missed it in the literature.

Fraser:                         There was a paper that I recall where they were seeing the material falling back in or they were seeing light echoes from the jet.

Dr. Gay:                      So, light echoes we see.

Fraser:                         They were seeing light echoes from the jet that was allowed them to figure out when it was an active galaxy. And it’s not an active galaxy right now.

Dr. Gay:                      Light echoes are fairly common-ish in the grand scheme of, we’ve seen more than three now. I’ve been in astronomy long enough that, anytime you see more than three, that’s awesome; but in terms of just seeing a galaxy clear out the world around it and no longer be doing that, that’s what I’m not sure we’ve seen. So –

Fraser:                         Right, right.

Dr. Gay:                      – we’ve seen a light echoing, but what’s awesome to me, and what I can’t wait for us to see the relics of is supernova explosions in just the right format, specifically gamma ray bursts. They have the shockwave going out in a sphere that may be interrupted by planetary disks and things, but generally going on in a sphere or bipolar outflows that is caused by the star itself exploding. But what we’re now starting to think is, in some cases where you have a nearby companion, the material that’s getting shot off can quickly spin up in a disk as it gets the companion creating this gamma ray burst. That’s only one of several explanations of a gamma ray burst. It’s the one I like the best.

Fraser:                         Right.

Dr. Gay:                      Whatever the source of these gamma ray bursts is, you end up with tremendous high-energy jets that last very briefly and are capable, we think, of destroying planets several hundred light years away.

Fraser:                         Several tens of thousands. It will cause damage.

Dr. Gay:                      Is it 7,000 or 700? It will cause damage.

Fraser:                         It will cause damage. If it’s a few hundred light years away, it will destroy planets –

Dr. Gay:                      You’ll have roasted rock left behind.

Fraser:                         – right. But even if you’re halfway across the galaxy –

Dr. Gay:                      Ionizing radiation.

Fraser:                         – the ionizing radiation will blast away your ozone layer and everybody will get cancer and die.

Dr. Gay:                      But the planet will recover. We believe we have experienced –

Fraser:                         Right.

Dr. Gay:                      – that in our past, the world is still here. Within a few hundred, you basically have Mercury left behind.

Fraser:                         And good news, there are no stars capable of going gamma ray burst in our vicinity that we know of. All right, so you talk about like one impact of a gamma ray burst with jets, but what influence, what effect do these jets have on their galaxies and the areas surrounding them.

Dr. Gay:                      You clearly don’t wanna get into one of them because they’re a source of ionizing radiation. They are giving off loud radio signals. So, communications near them is certainly going to be difficult, but in general it’s that disk that is generating them that I’d be afraid of because that is giving off a truly amazing amount of light in the center of a galaxy. The jet is going out of the galaxy, so you can sit there and go, “Oh, beautiful”. But that accretion disk in the galaxy you’re living in that is generating this disk, for super massive black hole ones, there’s another word for that disk. That’s a quasi-stellar object.

Fraser:                         Quasar.

Dr. Gay:                      And so, the light from that has the potential to be dangerous to fairly large distances within the galaxy it’s in.

Fraser:                         So, I did research into this. If the super massive black hole at the middle of the Milky Way turned into a quasar, you wouldn’t see it with the unaided eye. You would need a very powerful telescope to even detect it. Because you wouldn’t staring down the throat of it the way that we were with –

Dr. Gay:                      Right.

Fraser:                         – a lot of other ones, right? To see it from the side, it actually wouldn’t be significantly brighter. But I guess what I’m getting at is you’ve got this jet of material that’s flying out kind of like a fountain, like that original analogy, and then this material is falling back down into the galaxy in some cases. What influence does that have on the galaxy?

Dr. Gay:                      So, the material coming back, just like anytime you get a shockwave, it can trigger nice, happy, sitting around molecular clouds to collapse down and possibly form stars. And I just wanna go back to what you said. With your eye, all the dust in our Milky Way’s gonna hide that accretion disk from us. The trickstery bit gets to be, there are other wavelengths of light that you’re gonna have blinding light for other instruments coming out and –

Fraser:                         Right.  

Dr. Gay:                      – this is where the sky again is so different radio versus optical.

Fraser:                         And there was another piece of research that I saw, and I don’t know if you had seen this one, that a galaxy had gotten hit with the jet of another nearby galaxy?

Dr. Gay:                      No.

Fraser:                         And they think that it might in some cases maybe cause an increase in star formation, but maybe even quenching star formation, which was quite fascinating.

Dr. Gay:                      If you blast apart areas that are forming dust, then you’ve added enough energy in that, instead of the material collapsing, the material’s gonna dissipate in the face of this wind.

Fraser:                         Oh.

Dr. Gay:                      You shouldn’t smoke, people. You should not smoke.

Fraser:                         Right.  

Dr. Gay:                      But if you imagine exhaling smoke, you have a nice little cloud here, but on a windy day, you never get the cloud of smoke.

Fraser:                         Right.

Dr. Gay:                      Let’s go with a cold day. You exhale your breath. If there’s no wind you can see your breath, if there’s a lot of wind you have no chance to see your breath.

Fraser:                         And you need a nice, cold cloud of gas to form a star.         

Dr. Gay:                      Exactly.

Fraser:                         If energy is getting pumped into it and it’s heating up –

Dr. Gay:                      It can’t collapse.

Fraser:                         – then it can’t collapse. You may have the otherproblem. But the other thing that’s interesting as well is that because you’ve got fusion going on in some of the cases of these, you’ve got heavier elements that are actually being generated and thrown out into space. And so, it might actually be another source for heavier –

Dr. Gay:                      Hemorrhage.

Fraser:                         – elements that could contribute and enrich to some of these solar nebulae. So, it’s a field that is really wide open for discovery, both their underlying cause as well as their influence and their effect. It could be everywhere from no effect to life might not exist without these jets. So, more research is needed.

Dr. Gay:                      And just you can track the history of stellar vampirism. So, while we may not have vampires on our planet, there are vampires among the stars. And if they aren’t continually sucking at their neighbors, they will have puffy jets. So, I’m just gonna leave you with that thought, that there are puffy jets of non-continuous feeders out there.

Fraser:                         Very cool. All right. Thanks, Pamela.

Dr. Gay:                      Okay, thank you, Fraser. And it’s time for me to do that thing where we thank all the amazing humans out there that make this possible. Every time I say, “I’m sorry, Rich. You’re gonna have to edit,” well, it’s because of these people that we can pay Rich and Ally and Beth and the whole team of people. Oh my goodness, Nancy, thank you for keeping us lined up.

                                    This week, I wanna thank Jeremy Kerwin, Rob Cuffe, Harald Bardenhagen, Alex Cohen, Rando, David Gates, marco iarossi, Nicky Lynch, Daniel Loosli, Phillip Walker, Scott Bieber, Brian P. Cox, David, Matthew Horstman, Matthias Heyden, Justin Proctor, Disasterina, Gregory Singleton, Nial Bruce, The Lonely Sand Person, Jim Schooler, Jeff Willson, Tim McMackin, Paul Hayden, Cooper, Nate Detwiler, Eran Segev, Allan Mohn, Benjamin Müller, Steven Shewalter, Omar Del Rivero, Kenneth Ryan, Karthik Venkatraman, Alex Raine, Paul D. Disney, Micheal Regan, Don Mundis and Dean McDaniel.

                                    And Rob Cuffe, thank you for giving me a pronunciation guide for your name. And thank you so much to all of you. If you too wish to have me vaguely pronounce your name correctly in one of our episodes – I’m so sorry – please join us on Patreon. If you would like your name pronounced correctly, add a pronunciation guide.

Fraser:                         Wonderful.

Dr. Gay:                      Thank you.

Fraser:                         All right. Thanks, Pamela. We’ll see you next week.

Dr. Gay:                      Buh-bye. Astronomy Cast is a joint product of Universe Today and the Planetary Science Institute. Astronomy Cast is released under a Creative Commons Attribution’s License. So, love it, share it, and remix it, but please credit it to our hosts, Fraser Cain and Dr. Pamela Gay. You can get more information on today’s show topic on our website, astronomycast.com. This episode was brought to you thanks to our generous patrons on Patreon. If you want to help keep this show going, please consider joining our community at patreon.com/astronomycast. Not only do you help us pay our producers a fair wage, you will also get special access to content right in your inbox and invites to online events. We’re so grateful to all of you who have joined our Patreon community already. Anyways, keep looking up. This has been Astronomy Cast.

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