Astronomy 141 - Life in the Universe - Autumn Quarter 2009 episodes:

• December 04, 2009Lecture 46: This View of Life (Course Finale)

  Course finale and summary. We look back over where we've been the last

  eleven weeks, and bring together all of the main themes of this course

  on Life in the Universe. Recorded live on 2009 Dec 4 in Room 1005 Smith

  Laboratory on the Columbus campus of The Ohio State University.

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• December 03, 2009Lecture 45: The Future of Life in the Universe

  How will life, the Universe, and everything end? This lecture looks at

  the evolution of our expanding Universe to project the prospects for

  life into the distant cosmological future. Recent observations show

  that we live in an infinite, accelerating universe. I will trace the

  evolution of the universe from the current age of stars into the future.

  The final state of the Universe will be cold, dark, and disordered, and

  ultimately inhospitable to life as we understand it or perhaps can

  imagine it. Recorded live on 2009 Dec 3 in Room 1005 Smith Laboratory

  on the Columbus campus of The Ohio State University.

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• December 02, 2009Lecture 44: The Future of Life in the Solar System

  What is the future of life on Earth and in our Solar System? The Sun is

  the source of energy for life on the Earth, but it will not shine

  forever. This lecture looks at the impact of the various stages of the

  evolution of the Sun on the habitability of the Solar System, with

  particular emphasis on the continued habitability of the Earth. I will

  refer to state-of-the-art computer models of the Sun to get is

  properties at various stages in its past and future life. NOTE: Due to

  a recorder malfunction this lecture was re-recorded later in the day on

  2009 Dec 2, rather than being live from the class room in Smith

  Laboratory. As such, it is about 10 minutes longer than usual (my

  pacing is off when not in front of class).

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• December 01, 2009Lecture 43: Extraterrestrial Life

  What does extraterrestrial life look like? This lecture explores

  current thinking about what extraterrestrial life might be like not by

  guessing their appearances, but instead applying lessons learned from

  our growing understanding of how evolution and biochemistry work on

  Earth. I will discuss Universal versus Parochial characteristics,

  Convergent Evolution, Radical Diversity, and other ideas from

  evolutionary biology that might inform how life might emerge on other

  worlds. We will then look at alternatives to carbon biochemistry,

  specifically the possibility of silicon-based life, and alternatives to

  liquid water as a solvent medium for biochemistry, specifically the

  possible role of Ammonia. Finally I will give one example of a highly

  speculative idea about life without chemistry. In the end, the outcome

  of such studies may not be to tell us much about extraterrestrials as to

  help focus questions on how we ourselves arose. Recorded live on 2009

  Dec 1 in Room 1005 Smith Laboratory on the Columbus campus of The Ohio

  State University.

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• November 30, 2009Lecture 42: The Fermi Paradox

  So, Where is Everybody? Interstellar colonization, in principle, is an

  exponential growth process that would fill the galaxy in a few million

  years even with a very modest star flight capability. This is a small

  fraction of the lifetime of the Milky Way Galaxy, so the Galaxy should

  be teaming with life. But, we so far have no compelling evidence of

  extraterrestrial visitations, alien artifacts, or any other evidences

  that the Galaxy is populated. Physicist and Nobel Laureate Enrico

  Fermi's apparent paradox and some of the proposed resolutions are the

  topic of this lecture. I will review the Fermi Paradox and describe the

  most common possible resolutions. The Fermi Paradox is useful in

  helping to frame the question of extraterrestrial life, even if we so

  far have no answers. At the end I only touch on the Rare Earth

  Hypothesis, but this is a very nuanced question which requires a whole

  other lecture to explore that I have not had time to fully prepare for

  during this busy quarter. Recorded live on 2009 Nov 30 in Room 1005

  Smith Laboratory on the Columbus campus of The Ohio State University.

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• November 25, 2009Lecture 41: Interstellar Travel and Colonization

  If we ever detect life elsewhere, how will we go visit? This lecture

  considers the challenges of interstellar travel and colonization. The

  problem is one of basic physics (the enormous energy requirements of

  star flight) coupled with the vast, irreducible distances between the

  stars. I will describe various starship concepts that use reasonable

  extrapolations of current technologies (nuclear propulsion and solar

  sails), ignoring for our discussions science-fiction exotica like

  faster-than-light drives and wormholes. My interest is in the

  scientific aspects of the problem, not an exploration of speculative

  fiction. I then turn to interstellar colonization, and how even

  a relatively modest star-flight capability might allow a determined

  civilization to colonize the entire galaxy very rapidly. This has

  implications for how we might interpret the results of Drake Equation

  type arguments about the frequency of intelligent life in the Galaxy,

  and leads to the Fermi Paradox that will be the topic of the next

  lecture. Recorded live on 2009 Nov 25 in Room 1005 Smith Laboratory on

  the Columbus campus of The Ohio State University.

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• November 24, 2009Lecture 40: SETI - The Search for Extra-Terrestrial Intelligence

  Is anybody out there? This lecture reviews the ideas behind SETI, the

  Search for Extra-Terrestrial Intelligence, an effort to find other

  intelligent communicating civilizations by tuning in on their radio or

  other electromagnetic communications. I will discuss the basic

  approaches being taken by various SETI efforts, and what we expect to

  find. In addition to listening, we have also been broadcasting,

  intentionally or otherwise, messages into space, and we have sent

  physical artifacts with descriptions of our home on robotic spacecraft

  headed out of our solar system into interstellar space. Recorded live

  on 2009 Nov 24 in Room 1005 Smith Laboratory on the Columbus campus of

  The Ohio State University.

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• November 23, 2009Lecture 39: The Drake Equation

  How many intelligent, communicating civilizations live in our Galaxy?

  We have no idea. One way to approach the question and come up with

  quasi-quantitative estimates is the Drake Equation, first introduced by

  radio astronomy Frank Drake in the 1960s. I will use the Drake equation

  as an illustration of the issues related to the question of

  extraterrestrial intelligence, and to set the stage for future lectures

  on the likelihood of finding other intelligences in our Universe.

  Recorded live on 2009 Nov 23 in Room 1005 Smith Laboratory on the

  Columbus campus of The Ohio State University.

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• November 19, 2009Lecture 38: The Pale Blue Dot - Seeking Other Earths

  Are there other Earths out there? Do they have life on them? This

  lecture looks at the search for ExoEarths - Earth-sized planets in the

  habitable zones of their parent stars, and what we might learn from

  measuring them. The ultimate goal of all planet searches is to find

  other Earth's, what the late Carl Sagan so poetically called

  the "pale blue dot" as seen from the depths of space. This lecture

  discusses what we might learn about such planets from studies of our own

  Earth, spectroscopic biomarkers that might reveal life, and variability

  studies that might give us insight into surface features (continents

  and oceans) and weather (clouds and even climate). Recorded live on

  2009 Nov 19 in Room 1005 Smith Laboratory on the Columbus campus of

  The Ohio State University.

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• November 18, 2009Lecture 37: Strange New Worlds

  What are the properties of the 400+ exoplanets we have discovered so

  far? This lecture reviews the properties of exoplanets, and finds a

  couple of surprises: Jupiter-mass planets orbiting close to their parent

  stars, and Jupiter-mass planets in very elliptical orbits. Both seem to

  require some mechanism for migration: strong gravitational interactions

  with either the protoplanetary disk or other giant planets to cause the

  planets to move inward from their birth places beyond the "Ice Line".

  We will then briefly discuss why we are seeing systems very different

  from our own, mostly we think a selection effect due to our search

  methods to date. Microlensing, however, is more sensitive to systems

  like ours, and is starting to find them. Earths, however, remain

  elusive so far, but the hunt is on. Recorded live on 2009 Nov 18 in

  Room 1005 Smith Laboratory on the Columbus campus of The Ohio State

  University.

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