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Cover image of Astronomy 141 - Life in the Universe - Autumn Quarter 2009

Astronomy 141 - Life in the Universe - Autumn Quarter 2009

Astronomy 141, Life in the Universe, is a one-quarter introduction toAstrobiology for non-science majors taught at The Ohio State University.This podcast presents audio recordings of Professor Richard Pogge'slectures from his Autumn Quarter 2009 class. All of the lectures were recorded live in 1005 Smith Laboratory on the OSU Main Campus in Columbus, Ohio.

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Lecture 41: Interstellar Travel and Colonization

If we ever detect life elsewhere, how will we go visit? This lectureconsiders the challenges of interstellar travel and colonization. Theproblem is one of basic physics (the enormous energy requirements ofstar flight) coupled with the vast, irreducible distances between thestars. I will describe various starship concepts that use reasonableextrapolations of current technologies (nuclear propulsion and solarsails), ignoring for our discussions science-fiction exotica likefaster-than-light drives and wormholes. My interest is in thescientific aspects of the problem, not an exploration of speculativefiction. I then turn to interstellar colonization, and how evena relatively modest star-flight capability might allow a determinedcivilization to colonize the entire galaxy very rapidly. This hasimplications for how we might interpret the results of Drake Equationtype arguments about the frequency of intelligent life in the Galaxy,and leads to the Fermi Paradox that will be the topic of the nextlecture. Recorded live on 2009 Nov 25 in Room 1005 Smith Laboratory onthe Columbus campus of The Ohio State University.

45mins

25 Nov 2009

Rank #1

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Lecture 2: Astronomical Numbers

An introduction and review of the basic notation and physical units we will beusing throughout this course. In particular, we will be using theMetric (SI) system for lengths, masses, times, and temperatures, andspecial astronomical units for distances (AU and Light Years) and masses(Earth Masses and Solar Masses) appropriate when discussinginterplanetary and interstellar scales. Recorded live on 2009 Sep 24 inRoom 1005 Smith Laboratory on the Columbus campus of The Ohio StateUniversity.

43mins

24 Sep 2009

Rank #2

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Lecture 3: Imagining Other Worlds

What is the cultural history of our imaginings of other worlds and their possible inhabitants? I will draw examples from history, philosophy, literature, cinema, and popular culture. In the end, our imaginings about other worlds inform us more about ourselves, ourhopes and our fears, than about extraterrestrial life. The scientificinquiry we are undertaking must therefore approach the problem from adifferent direction. Recorded live on 2009 Sep 25 in Room 1005 SmithLaboratory on the Columbus campus of The Ohio State University.

40mins

25 Sep 2009

Rank #3

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Lecture 40: SETI - The Search for Extra-Terrestrial Intelligence

Is anybody out there? This lecture reviews the ideas behind SETI, theSearch for Extra-Terrestrial Intelligence, an effort to find otherintelligent communicating civilizations by tuning in on their radio orother electromagnetic communications. I will discuss the basicapproaches being taken by various SETI efforts, and what we expect tofind. In addition to listening, we have also been broadcasting,intentionally or otherwise, messages into space, and we have sentphysical artifacts with descriptions of our home on robotic spacecraftheaded out of our solar system into interstellar space. Recorded liveon 2009 Nov 24 in Room 1005 Smith Laboratory on the Columbus campus ofThe Ohio State University.

46mins

24 Nov 2009

Rank #4

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Lecture 19: The Origin of Life on Earth

How did life arise from non-life? Frankly, we don't know, but currentexperimental work is aimed at trying to understand how it might work inbiochemical terms. This lecture sets out the problem of "abiogenesis",and describes our current thinking about the likely origins of life onEarth. We will review the classic Miller-Urey experiment, and look atits insights and limitations, discuss meteoritic sources of amino acids,and the basic requirements needed for protolife. I will then describein outline two scenarios that are active areas of origins research: theRNA World model and the Metabolism First model. Finally, I will verybriefly mention Exogenesis and Panspermia, which don't really addressthe problem of abiogenesis so much as move it elsewhere. Recorded liveon 2009 Oct 20 in Room 1005 Smith Laboratory on the Columbus campus ofThe Ohio State University.

46mins

20 Oct 2009

Rank #5

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Lecture 20: The History of Life on Earth

In this lecture we step back and look at the history of life on Earthfrom the first signs of life at start of the Archaean Eon 3.5 billionyears ago to just up to the present day. We will review the appearanceof photosynthesis and the rise of oxygen in the atmosphere in theProterozoic, the appearance of the first eukaryotes and sexualreproduction, and the Cambrian explosion of plant and animal species atthe start of the Phanerozoic Eon, and briefly review the changes in lifeto the present day from the Cambrian Explosion to the colonization ofland by plants and then animals. Most of the lecture will be where mostof the time was spent, in the early, microbiological Earth. Recordedlive on 2009 Oct 21 in Room 1005 Smith Laboratory on the Columbus campusof The Ohio State University.

47mins

21 Oct 2009

Rank #6

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Lecture 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 withquasi-quantitative estimates is the Drake Equation, first introduced byradio astronomy Frank Drake in the 1960s. I will use the Drake equationas an illustration of the issues related to the question ofextraterrestrial intelligence, and to set the stage for future lectureson the likelihood of finding other intelligences in our Universe.Recorded live on 2009 Nov 23 in Room 1005 Smith Laboratory on theColumbus campus of The Ohio State University.

45mins

23 Nov 2009

Rank #7

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Lecture 8: The Cosmological Revolution - The Depths of Space and Time

Cosmology is the study of the entire Universe as a physical system. Thepast century has witnessed a revolution in cosmological thought that has revealed the vastness of space and the depths of cosmic time, a revolutionthat is still playing out in the present day. The lecture will review the Earth's place in the Universe, the age of the Universe as reckoned by the timesince the Big Bang, and the origin of the elements. We will return tomany of these topics later in the course, but this presents the bigpicture. Recorded live on 2009 Oct 2 in Room 1005 Smith Laboratory onthe Columbus campus of The Ohio State University.

46mins

2 Oct 2009

Rank #8

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Lecture 18: The First Living Things on Earth

What are the first recognizable forms of life that we find in thegeological record? How far back can we go in geological time and stillfind life? This lecture reviews three lines of evidence that haveemerged in recent years to suggest that life may have emerged very earlyon the young Earth, perhaps within a few hundred million years of theend of the epoch of heavy bombardment. I will describe fossilstromatolites, microfossils, and carbon isotope data that are used toexplore these questions. Recorded live on 2009 Oct 19 in Room 1005Smith Laboratory on the Columbus campus of The Ohio State University.

46mins

19 Oct 2009

Rank #9

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Lecture 21: Impacts and Extinction

We end our exploration of life on the Earth with a look at death in thefossil record. This lecture looks at the role asteroidal impacts haveplayed in the history of the Earth, and their possible role in massextinction events in the fossil record. We will discuss near-earthasteroids, historical impacts, and the K-T event in which a massiveasteroid impact caused a mass extinction of species that included allnon-avian dinosaurs among its victims, opening up the biosphere to thedominance of mammals. We'll look at other mass extinctions during thepast 500Myr, and talk about whether extinction-class impacts are in ourfuture. Recorded live on 2009 Oct 22 in Room 1005 Smith Laboratory onthe Columbus campus of The Ohio State University.

46mins

22 Oct 2009

Rank #10

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Lecture 4: The Copernican Revolution

Modern science was borne of an effort over many centuries to understandthe motions of celestial bodies. The Copernican Revolution of the 16thand 17th centuries was the crucial moment in history when we finallyunderstood the nature of celestial motions, and opened the door to themodern world. This lecture reviews the problem of celestial motions,the two competing models for explaining them, and the final revolutionin thought starting with Copernicus and ending with Newton. Mid-lecturemy classroom AV system lost power, and the recovery slowed things down abit. These are recorded live, after all. This lecture was conducted on2009 Sep 28 in Room 1005 Smith Laboratory on the Columbus campus of TheOhio State University.

43mins

28 Sep 2009

Rank #11

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Lecture 6: The Geological Revolution - Deep Time and the Age of the Earth

The geological revolution revealed that the Earth is of great antiquityand yet has a history we can read in the land. We will discuss ideas of cyclic and linear time, historical versus physical age estimates, the discovery of geological time, andradiometric dating methods that give us our present estimate of4.54+/-0.05 Gyr for the age of the Earth. Recorded live on 2009 Sep 30in Room 1005 Smith Laboratory on the Columbus campus of The Ohio StateUniversity.

46mins

30 Sep 2009

Rank #12

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Lecture 5: The Chemical Revolution and the Nature of Matter

What is the nature of matter, and how did we come to understand thechemical elements and atomic structure? This lecture is a brief andselective overview of the history of our understanding of the nature ofmatter and chemistry. We will also introduce spectroscopy andradioactivity, two very powerful tools that came out of the chemicalrevolution that are crucial for the inquiry in this class into thequestion of life on other worlds. Recorded live on 2009 Sep 29 in Room1005 Smith Laboratory on the Columbus campus of The Ohio StateUniversity.

45mins

29 Sep 2009

Rank #13

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Lecture 11: The History of the Earth

How have we pieced together the geological history of the Earth?This lecture reviews the different types of rocks and the cycleof transformation between them, with particular emphasis on stratigraphy. I will outline the 4 major Eons in Earth's history, and focus on theearliest Hadean Eon which proceeded from the formation of the Earth to the end of the epoch of Heavy Bombardment. The Hadean Eon saw the formationof the primordial atmosphere of the Earth and the formation of the Oceans. Recorded live on 2009 Oct 7 in Room 1005 Smith Laboratory on the Columbus campus of The Ohio State University.

42mins

7 Oct 2009

Rank #14

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Lecture 35: The Solar Neighborhood

What stars are near the Sun? Now that we have some idea of what we arelooking for - rocky planets in the habitable zones of low-massmain-sequence stars - what are the prospects near the Sun? This lectureexamines the hunting ground for planets, the nearby stars that make upthe Solar Neighborhood. I will describe our nearest neighbor, theProxima Centauri/Alpha Centauri triple system, and then look at theproperties of our nearest stellar neighbors. What we will find is thatG-type stars like the Sun are uncommon, only about 7% of all nearbymain-sequence stars. Red dwarfs, on the other hand, are very common,about 75%. To find Sun-like main sequence stars, we will have to extendour search to larger distances into our Milky Way galaxy proper.Recorded live on 2009 Nov 16 in Room 1005 Smith Laboratory on theColumbus campus of The Ohio State University.

46mins

16 Nov 2009

Rank #15

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Lecture 37: Strange New Worlds

What are the properties of the 400+ exoplanets we have discovered sofar? This lecture reviews the properties of exoplanets, and finds acouple of surprises: Jupiter-mass planets orbiting close to their parentstars, and Jupiter-mass planets in very elliptical orbits. Both seem torequire some mechanism for migration: strong gravitational interactionswith either the protoplanetary disk or other giant planets to cause theplanets to move inward from their birth places beyond the "Ice Line".We will then briefly discuss why we are seeing systems very differentfrom our own, mostly we think a selection effect due to our searchmethods to date. Microlensing, however, is more sensitive to systemslike ours, and is starting to find them. Earths, however, remainelusive so far, but the hunt is on. Recorded live on 2009 Nov 18 inRoom 1005 Smith Laboratory on the Columbus campus of The Ohio StateUniversity.

46mins

18 Nov 2009

Rank #16

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Lecture 33: The Deaths of Stars

What happens to a star when it runs out of hydrogen in its core? Thislecture describes the post main-sequence evolution of stars. Whathappens depends on the star's mass. Low mass stars swell up into RedGiants, and eventually shed their envelopes and end their lives as whitedwarf stars. High mass stars become Red Supergiants, and if largeenough, end their lives in a spectacular supernova explosion that leavesbehind a neutron star or black hole. The explosion itself createsmassive quantities of heavy elements, which then seed interstellar spacewith metals to be incorporated into subsequent generations of stars.Recorded live on 2009 Nov 12 in Room 1005 Smith Laboratory on theColumbus campus of The Ohio State University.

47mins

12 Nov 2009

Rank #17

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Lecture 38: The Pale Blue Dot - Seeking Other Earths

Are there other Earths out there? Do they have life on them? Thislecture looks at the search for ExoEarths - Earth-sized planets in thehabitable zones of their parent stars, and what we might learn frommeasuring them. The ultimate goal of all planet searches is to findother Earth's, what the late Carl Sagan so poetically calledthe "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.

44mins

19 Nov 2009

Rank #18

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Lecture 32: The Lives of Stars

Why do stars shine? How long do they shine? This lecture describes thephysics of stars on the main sequence, describes the mass-luminosityrelation of main sequence stars, introduces nuclear fusion power and thenuclear fusion lifetimes of stars. From this we gain an importantinsight into one of the criteria we might apply to the search for lifearound other stars: we want planets around low-mass main sequence starsthat can shine more or less steadily for more that 500 Myr to 1 billionyears - maybe longer if our goal is to find intelligent life. Recordedlive on 2009 Nov 10 in Room 1005 Smith Laboratory on the Columbus campusof The Ohio State University.

46mins

10 Nov 2009

Rank #19

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Lecture 27: Is There Life on Mars?

Is there life on Mars? We begin with a brief historical survey of the idea of inhabitable Mars, from Herschel to Lowell, and look at how the idea of Mars and Martians is deeply embedded in the popular culture. We then turn to spacecraft explorations of Mars, and how they have changed our view of the Red planet. We will discuss the on-going search of Martian life, past and present, particularly the Viking 1 and 2 experiments, the Allan Hills Meteorite controversy, Mars Methane, and recent important results from the Phoenix lander. We'll end by briefly noting future directions in Mars exploration. Recorded live on 2009 Nov 2 in Room 1005 SmithLaboratory on the Columbus campus of The Ohio State University.

47mins

2 Nov 2009

Rank #20