If you’re driving while listening to this, please think of your vehicle not as a mere car or SUV, but as a starship cruiser!

Here’s why: the iron it’s made of came from the heart of a distant star.

Stars begin their lives as giant balls of gas, mostly hydrogen, the first element on the periodic table, with one proton.

Under the force of the proto-star’s enormous gravity, hydrogen atoms fuse together to produce helium, with two protons.

This nuclear fusion releases a huge surge of energy, and the star is born.

Hydrogen continues to fuse into helium, releasing more and more energy.

Helium atoms then fuse into carbon atoms, which fuse into silicon atoms, with each subsequent element being heavier.

All this nuclear fusion releases more energy than it takes to fuse the atoms together. And so, the process continues, for millions of years…until the elements fuse into iron.

At that point, it would take more energy to fuse iron into something else than the resulting reaction would produce.

So fusion stops, and the star begins to die.

Soon, the gravity of its iron core becomes so strong that the star collapses on itself, then explodes outward in a supernova, scattering iron across the universe…which eventually forms planets like ours. And our cars.

We talked about how a fungal network connects plants underground. But did you know it allows them to communicate?

Specifically, they exchange sugars, and chemical and electrical signals, with each other.

The largest trees are now known to “mother” the surrounding forest. They give their sugars back to the entire soil community, to support neighboring plants and trees.

They’ve even been shown to preferentially identify young trees within their own species, and send them a larger serving of sugars via the fungal network.

And, plants and trees have learned to communicate through the air.

Many studies have shown that, when attacked by insects or disease, they release distress hormones to other plants, as well as defensive compounds.

Pine trees, for instance, when preyed on by caterpillars, send out pheromones that attract wasps to the forest, which prey on the caterpillars.

Acacia trees, when eaten by grazing giraffes, release ethylene gas, which prompts other acacias to flood their leaves with bitter tannins. Giraffes have learned to graze downwind...

Traditional lumber practices have removed large trees, with the idea that it allows other trees to access their sunlight. This new research may require rethinking how we maintain healthy forests.

This isn’t to say that trees can think—at least not in the way that humans define sentience.

But they certainly have a type of language that has allowed them to thrive for millions of years. We’re only now learning to understand it.

Leonardo da Vinci once said: “We know more about the movement of celestial bodies than about the soil underfoot.”

He was right 500 years ago, and he’s still right today.

That’s partly because the study of space is mysterious and cool, and there really wasn’t much interest in studying dirt. Until recently...

We now know that about 90 percent of all land-based species live in the soil, not on it. Most of these are microscopic, but they’re incredibly plentiful: there are more microbes in a handful of dirt than people on the planet.

And they’re also incredibly important: without soil microbes, plants might not exist.

Plants require nitrogen and other trace elements, and it’s soil bacteria, and the single-celled organisms that eat them, that process these elements into forms that the plants can use.

With this knowledge, agricultural researchers are reintroducing bacteria into depleted soils to increase the health and nutrition of crops.

Most plants also depend on soil fungi, and this relationship is symbiotic.

The fungi penetrate or encase the roots of plants to draw out what they can’t make themselves: sugars from photosynthesis.

In exchange, the fungus filaments stretch deep into the soil, gathering water and nutrients from a volume 100 times greater than the roots could reach on their own.

This fungal network can even join plants together beneath the soil, which allows amazing things to happen—and we’ll talk more about that on another EarthDate.

Volcanic eruptions can affect global warming—or cooling. And one of the ways we measure their impact is by looking at a lunar eclipse.

To understand this strange connection, we need to know a bit about Earth’s atmosphere.

The lowest part, the troposphere, extends from the surface up 4 to 12 miles. It’s where Earth’s weather happens.

The stratosphere, above that, is dry and less active.

Dust and ash particles carried into the troposphere by volcanoes, fires, or other sources will quickly fall or be rained out.

But when a large volcano erupts, it blasts ash and gas through the troposphere into the stratosphere.

There, sulfur gas forms microscopic droplets of sulfuric acid. These “sulfate aerosols” can remain suspended for years.

One way scientists measure them is by looking at lunar eclipses. If they’re murky and dim, the stratosphere is clouded with aerosols. If they’re bright and defined, the stratosphere is clear.

Large volcanoes in the past have put up enough aerosols to reflect the sun’s heat and cool the surface of Earth by as much as 1°F.

But in the last two decades, the stratosphere has been remarkably clear, which has allowed more solar energy to reach Earth.

Some scientists estimate this has caused half the global temperature increase seen during this period.

Another example of how Earth’s processes are linked in surprising and complex ways.

Though our electricity system is highly complex, its basic principle is simple: 99 percent of our electricity comes from turning a generator.

We do that mostly by burning a resource like coal or natural gas to boil water, which makes steam, which turns a turbine, connected to a generator.

Heat from a nuclear reaction or a geothermal well are other ways to make steam and turn a generator.

Water held behind a dam, then released to flow through turbines, turns generators without having to produce steam.

All these generation systems produce emissions—like water vapor, CO2 or other gases, particulates, or a small amount of nuclear waste.

And all of them are available on demand, which is very important, because we can’t store electricity very well at scale. So it must be made when we need it.

Wind, too, turns a generator. It makes up about 1 percent of global power generation.

Solar, the only one to produce electricity without a generator, makes up another 1 percent.

Wind and solar produce no emissions. But they have other environmental impacts, in mining materials, manufacturing, the large amounts of land they occupy, and eventual disposal.

And because they make electricity only when the sun shines or the wind blows, we have to back them up with other power sources.

The modern world depends on our electricity system, and it’s something we’ll talk more about.

Whales and dolphins are spectacular creatures.

Their ancestors climbed out of the ocean 360 million years ago, developed lungs and legs, and evolved into mammals. Then, 50 million years ago, they walked back into the sea.

To survive there, they developed specialized behaviors, which require even more special biology.

Perhaps most famous is echolocation. They move air between sinus cavities to emit sound. When it bounces back to them, they don’t hear it with their ears, but feel it in a fatty fluid in their lower jaw.

Only toothed whales, like sperm whales, orcas, and dolphins, can echolocate—a skill we think they developed to hunt prey, especially squid, in the darkness of the deep ocean.

Baleen whales focused on other prey, floating shrimplike creatures, and for this they developed comblike plates in place of teeth.

They can’t echolocate but are known for their elaborate songs. We think they use these for communication. But we’re not sure how they produce them, since they don’t have vocal chords.

Both types of whales can hold their breath for 45 minutes or longer. To do this, they reduce their heart rate and cut blood flow to some organs, like the stomach, while providing it to others, like the brain.

Even their blood is specialized. It can carry far more oxygen than land-dwelling mammals, and they have much more of it.

Whales are an amazing example of what evolution can do, given enough time.

You may remember the film Close Encounters of the Third Kind, when Richard Dreyfuss fills his living room with dirt and garbage to sculpt a replica of Devils Tower. Later in the movie, the tower becomes the landing platform for alien spaceships.

But it had otherworldly connections centuries before that.

Many Plains Indian tribes gave the tower mystical significance. Most of their stories revolve around children being chased by a giant bear.

They climb atop a rock, and to save the children, the gods make the rock rise from the prairie. The angry bear scratches its claws on the tower, creating its signature fluted sides.

This legend gave rise to the Crow, Arapahoe, and Cheyenne name for the tower: Bear Lodge.

Geologists tell a different story:

The tower began as a shaft of hot magma that formed in sedimentary layers near the surface. The magma slowly cooled underground around 40 million years ago, forming the columns on its outer surface. Eventually the sediments around it eroded away, exposing the tower, which rises more than 800 ft above the plains!

Today, the tower’s long cracks and columns make it one of the world’s foremost rock-climbing sites—except during the month of June, when climbers respect Native American traditions and leave the tower to their ceremonies.

One October long ago, I tried climbing it myself. We got within a hundred feet of the top before snow turned us back. Perhaps the sacred bear didn’t want us in his lodge that day.

Scientists studying the jet stream over Europe discovered that it has contributed to the extreme weather seen across the continent in the last 50 years.

Jet streams are rivers of wind, 5 to 9 miles up, in the high atmosphere. They’re caused by solar radiation heating rising air, which is then deflected sideways by Earth’s rotation.

They can move up to 275 miles an hour and are strong enough to push weather around and carry moisture, dust, or volcanic ash across oceans.

There are four jet streams on Earth: a polar and subtropical jet in both the Northern and Southern Hemispheres. And their paths can fluctuate.

When they drift toward the pole, they pull warmer air with them, causing hot summers and droughts in the middle of continents and rain in the subtropics.

When they drift toward the equator, they pull cold air from the pole, causing harsher winters in the midcontinent.

Scientists in Europe studied tree rings in the UK and the Mediterranean to analyze patterns of temperature and rain.

They found that, since 1960, the northern polar jet had drifted more frequently than in any period in the last 300 years, bringing droughts to the south and floods to the west in some years, and the opposite the next.

Climatologists theorize that a generally warming planet may be influencing the path of the jet stream. But most scientists agree that we really don’t know the cause.

It’s one more of those big mysteries blowing around, right here on Earth.

What exactly is fossil water? And why have we consumed so much of it?

No, it’s not a new brand of bottled water, imported from the days of dinosaurs.

Fossil water came from melting ice sheets, ancient lake systems, and a generally wetter climate tens to hundreds of thousands of years ago.

It percolated into porous rocks, which were then buried under deep layers of sediment, where it was sealed off from the surface, and there it stayed.

Until farmers discovered it. And in the second half of the 20th century, they started drilling wells into fossil aquifers and pumping like mad, turning sunny dry places into acres and acres of green farmland.

Crop supplies boomed. Food became cheaper and more plentiful, grown in formerly parched places like California and Kansas and shipped around the world for people like you and me to eat, ingesting fossil water with it.

The trouble is, fossil water is a finite resource, and new studies suggest that many fossil aquifers may become depleted this century, so that we won’t be able to rely on them any longer.

This could mean that the crops that depend on them could become less plentiful and more expensive again.

All the while, population will likely increase. The climate will likely warm. Our demand for water will continue to climb.

Which means we’ll have to adapt to the lack of fossil water just as we adapted to its discovery. This time with more efficient crops and farming methods—and more efficient use.

One June, a man climbed into the Ötzal Alps, on today’s Austrian–Italian border.

Dressed in leather and fur, he was mid-40s and extremely fit. He carried a wooden bow, flint-tipped arrows, and a copper axe.

He had no way of knowing that in an hour he’d be dead.

5,300 years later, some hikers discovered his body, melting out of a glacier.

Local police called in forensic experts, and so began a 30-year investigation into the best-preserved mummy from pre-modern history.

They traced the minerals in his teeth to a nearby groundwater source, to determine where he lived.

They looked at food and pollen in his gut to re-create his last day of meals and where he ate them.

Ötzi the Iceman, as they called him, had walked from his mountain home to the valley floor. That night, judging from a telltale slash on his hand, he got into a knife fight.

The wound had begun to heal by the time he died, suggesting he won it.

What had not healed were a fatal arrow wound to his back and a cracked skull. Someone had tracked him into the mountains and ambushed him.

His valuable copper axe was not taken, suggesting a revenge killing. Perhaps the killers buried him in snow, beginning his mummification.

Today, Ötzi rests in a museum freezer near where he was discovered. A model of him in life stands in the same building, while 3D printings of his body are studied around the world.