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| AST 309L · Search for Extraterrestrial Life |
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At one level, the subject of extraterrestrial life can be discussed in terms having to do with the physical and biological sciences.
For example, the question of which stars are most likely to have planets bearing life will involve discussions of the origin of planetary
systems, current searches for planets around other stars, and theories and evidence related to the origin of life on earth.
Questions concerning how we should "listen" for alien signals involve consideration of light propagation, spectral lines [just barely: don't
let this frighten you], and sources of interference.
Whether or not you think creatures even remotely like us will develop elsewhere
depends on your view of terrestrial biological evolution, so we will discuss current points of view on that subject. As we proceed into
the course, the subject matter will gradually shift away from the physical sciences as we inquire into the nature of biological evolution,
"intelligence", language, culture, cognition, and how they might differ (or not exist, or be replaced by alternative concepts) in
extraterrestrial life forms. The possibility of machine intelligence and its future, and recent theories about the nature of consciousness,
may also be reviewed critically if time permits.
However most of the course will be devoted to the areas of the study of extraterrestrial planets and theories and experiments concerning the
origin and evolution of life here and elsewhere. That is most of the subject of "astrobiology" or "exobiology." This subject has experienced
a huge resurgence of scientific interest in the past several years due to several factors. These factors include the discovery of a large
number of planets around other stars, the realization that we may be able to detect Earth-like planets in the near-future, the possible
evidence for biological traces in the "Martian meteorites," and the advent of space missions that will directly explore possible life abodes
in our solar system (e.g. a Europa probe). Astrobiology has finally become a legitimate field of science, with its own institutes, funding
programs, and even universities that offer advanced degrees in the subject. Other aspects of the problem, like "listening" for signals or
signs of extraterrestrial technological civilizations ("SETI" programs) and even potential designs for star travel vehicles are also under study,
so we will devote a significant fraction of time to these topics.
The material will almost entirely be non-mathematical, concentrating on a number of key ideas that can be understood without math.
There is also a fairly large vocabulary of terminology with which you should become comfortable - this should help a lot in studying for
and taking exams.
SCHEDULE OF TOPICS, READINGS, AND EXAM DATES
I will list topics according to the organization of the textbook (e.g. 5.2 means section 5.2 in Bennet et al.'s book).
Although I like the clarity and production of our textbook, I have decided to alter the order in which we read its
various sections. That makes it very important for you to make a copy of this reading list and keep it handy.
I will divide the course into five sections, with an exam after each section. The exam dates are only a little tentative,
and time constraints may cause one or more of them to shift by one class day. I will give you plenty of advance warning if such
a change is coming, and will try to avoid it.
I. Habitable planets
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11.1 Overview in terms of the "Drake equation" (11.1)
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Ch. 1 Review of astronomy, origin of elements, planet formation (covered in much more detail in class).
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Ch. 2 You are only required to read 41-48.
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Ch. 10 The Search for Habitable Worlds
10.1 Brief intro, 10.2 Stellar habitability, 10.3 Methods and discoveries of extrasolar planets
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Ch. 9 (Evolution and) Habitability
9.1 Habitable zone, 9.2 Venus as example, 9.3 Surface habitability, 9.4
Sun's habitable zone, 9.5 Future of life on Earth
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10.4 Signatures of habitable planets
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10.5 Earth-like planets - rare or common?
Outside reading: A galactic habitable zone?
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.....Our first exam will occur here (Monday, Sept. 22).....
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II. Origin of life by chemical evolution
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Ch. 3 The nature of life on earth - characteristics of life, cells, metabolism, genomes, extremophiles. Topics I will cover
in more depth in class are:
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Elementary background on molecular bonds, chemical reactions and cell biology.
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Why carbon? Why water? Alternative biochemistries.
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Molecular basis of life - prebiotic organic molecules; amino acids, nucleotides, proteins, nucleic acids.
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Ch. 5 Origin and Evolution of Life on Earth - We will only cover the "Origin" part of this chapter here, which means only
subsections 5.1 and 5.2, especially 5.2. I will fill in more detail in class, especially concerning origin of life scenarios and
problems.
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Alternate biochemistries again; strange life forms, artificial (digital) life.
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Panspermia (esp. from Mars) revisited.
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.....Second exam here (Friday, Oct. 10).....
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III. Life in the Solar System?
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Chapters 6 through 8
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Ch. 6 Searching for life in our solar system
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Ch. 7 Mars
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Ch. 8 Jovian moons
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.....Third exam here (Friday, Oct. 24).....
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IV. Terrestrial biological evolution and intelligence; extraterrestrial intelligence?
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Ch. 4 Geological history of the earth - ages from radiometric dating, formation of Earth and Moon, Hadean Earth, climate change.
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Outside reading: Snowball earth episodes?
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Evolution - class lectures on the standard view of mutation, diversity, and natural selection; more recent developments; concept
and importance of evolutionary convergence. We are mostly trying to understand the most important developments in evolution, and whether
they would occur elsewhere, leading to "intelligence," at least as we know it.
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Back to Ch. 5 (sections on evolution):
5.3 Early evolution and rise of oxygen ("oxygen catastrophe")
5.4 Development of eukaryotes
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Class lecture: significance of photosynthesis, meiosis, ...
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Outside reading on "Cambrian explosion"
5.5 Impacts and extinctions
5.6 Human evolution (discussion of human uniqueness and problems)
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11.2 intelligence - This will be supplemented with outside readings from cognitive science, cross-cultural
and animal studies, artificial intelligence research. We will discuss in detail in class lectures. This is crucially important
in designing strategies for signal detection (see below).
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If time: Postbiological evolution?; artificial intelligence.
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.....Fourth exam here (Friday, Nov. 14).....
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IV. Modes of contact
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Ch. 11 The search for extraterrestrial intelligence (SETI) - listening strategies
11.1 Drake equation (again). Emphasis on importance of lifetime of a technological civilization - how could L be large enough
to allow contact?
11.3 SETI experiments (proposed encoding and signaling techniques, "magic frequencies," ongoing
SETI programs)
11.4 SETI today
If time: The nature of language and its possible alternatives
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Ch. 12 Interstellar Travel -- limiting factors, proposed designs. Possiblity of exotic physics
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Ch. 13 The Fermi Paradox -- Galactic colonization and the "Where are they?" conundrum.
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Ch. 14 Contact - Implications of search and discovery
In class lecture (time permitting):
UFO's, artifacts, abduction
phenomena,...
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.....Fifth (last) exam here, on last class day (Friday, Dec. 5).
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There is no comprehensive final.
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