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Organic Chemistry |
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By definition, involves H,C,N,O |
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Most common elements (produced by most stars) |
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Well dispersed and available |
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Occurs even in interstellar space |
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Many organic compounds found in ISM, comets,
meteors (despite extremely harsh conditions) |
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Easily delivered to early Earth, or produced
locally |
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Biochemistry |
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Requires liquid water? |
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Arises naturally when basic conditions met? |
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What is “life”? |
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System out of chemical equilibrium which
extracts energy from its environment to maintain itself |
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Energy source could be heat, light, chemical,
other? |
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Reliably reproduces, with opportunity for
evolution |
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Able to store and decode information for this |
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0.0-0.5 Gyr Formation and intense bombardment |
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surface is uninhabitable |
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0.5-1.0 Gyr Surface stabilizes, simple life
starts |
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RNA, DNA; thermophilic progenitor (chemical
energy) |
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1.0-2.0 Gyr Anerobic prokaryotes,
stromatolite beds |
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single-celled, no nuclei; oldest fossils formed |
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2.0-2.5 Gyr Photosynthesis invented, free
oxygen |
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surface life; use of sunlight; oxygen crisis |
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2.5-3.0 Gyr Aerobic bacteria, eukaryotes |
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exploit available oxygen (more energy), cell
nucleus |
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3.0-3.5 Gyr bacteria diversify |
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Keep changing the mix, experiment |
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3.5-4.0 Gyr Sexual reproduction invented |
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Evolve, baby! |
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4.0-4.5 Gyr complex organisms appear |
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Let’s get together! Let’s get it together! |
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Our only real hope of detecting ET (unless they
come to us) is by listening to the radio |
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Radio travels at the speed of light, over the
whole Galaxy |
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Radio is a low energy way to send a message |
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We already have the ability |
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to send and receive across the Galaxy |
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Where should we listen? |
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Not the currently known extrasolar systems! |
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Solar-type stars? Milky Way? |
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How should we listen? |
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Frequencies that are relatively quiet. |
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How narrow-band?The “water hole”? |
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What should we listen for? |
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A regular carrier pattern. Complexity. |
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What are the odds we will hear |
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something? |
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The Drake equation |
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Notes