Astronomy 141 - Life in the Universe - Autumn Quarter 2009

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.

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.

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).

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.

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.