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25 Cards in this Set
- Front
- Back
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What are we looking for in the search for life?
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1) Non-intelligent Life
-impact of life on environment (atmosphere) -raw resources we feel are required for life (water) 2) Intelligent Life -detection of products of technology -direct communication (SETI) |
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What types of questions might we able to answer about life in the universe based on the example of our own Earth?
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-what are raw resources, conditions required for life?
-how quickly can life develop on a suitable planet? -how likely is intelligent life |
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What are the properties of life?
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-reproduction
-growth and development -order -energy utilization (the fad of polywater) -response to environment -evolution and adaptation (biology views this as fundamental) |
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Why are sedimentary rock deposits good fossil record indicators?
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layers of sedimentary deposits from sea show early life records with stuff at the bottom being the oldest records
ex. grand canyon |
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When did life arise on Earth? What evidence do we have for this?
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3.5-3.85 billion years ago (immediately after BB)
-oldest stramatolites - microbial life that exist in sheets on tops of oceans are incorporated into rocks - fossil evidence -Carbon isotopes -living things have preference for C12 over C13 (we show a greater ratio than fossilized things) -found in greenland rocks with this characteristic ratio 3.85 billion years ago |
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How did life arise on Earth? How was this tested?
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Miler-Urey Experiment
-subjected chemicals in a sealed flask thought to be present in early Earth's atmosphere to electric discharges (lightening) -used = water, methane, ammonia, and H -produced amino acids & DNA bases |
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All current life is based on DNA/RNA...how did this complex molecules arise?
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Unknown
-possibly clays acted as catalysts for short RNA strands -may have been genetic takeover from DNA now and something else was the "Scaffolding" in the past |
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What is the role of evolution in the development of intelligent life? What is Darwin's theory of evolution?
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-All life on Earth is closely related
-Darwin: 1) Overproduction and competition for suvival 2) Individual variation 3) Unequal reproductive success |
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What is Hoyle's Junkyard Tornado?
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Hoyle remarked that the odds of cellular life evolving was 1 in 10^40,000 (so zero)
-he profoundly misunderstood evolution -thought that evolution is comparable to a tornado passing through a junkyard and assembling a Boeing 747 |
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What are the misconceptions of evolution?
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1) evolution is directed toward higher forms life
-intelligence is not a necessary outcome of evolution -there's no end goal to evolution (evolution is trying to tailor organisms to their LOCAL environment) |
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What are the main candidates in our solar system for life (obvs besides Earth)?
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Europa (galillean moon) and Mars
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What kind of tests have been done on Mars to test for life? Can we currently live on Mars?
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Viking probe has directly tested the soil for metabolic activity and organic material
-unsuccessful Mars is very inhospitable to live on currently -no liquid water (low atmospheric pressure) -harmful UV light from Sun and solar wind (absence of magnetic field and atmosphere) |
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What was the notion behind Martian Meteors? What were the criticisms behind these meteors?
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A small number of meteors recovered on Earth are known to come from Mars
-one meteor was claimed to harbor fossilized life Problem: -the proposed microbes are too small (100x's smaller than a typical living cell (life is dilute chemistry - can't just jam everything into a tiny volume) |
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What about life on Europa? What are the criticisms about having life on Europa?
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See lots of cracks on Europa - may have been from liquid ocean cracking the ice surface by an impact crater
Problem: -Europa is about the same size of the moon -moon lost its heat very quickly and is geologically dead... WELL - europa is being constantly stretched and relaxed b/c of moons elliptical orbit around Jupter preventing its bulge from being pointed directly at Jupiter - TIDAL BULGE HEATING due to difference in gravity between near and far side |
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What are the requirements for surface life?
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1) Planet must be within the habitable zone of its parent star (temperature range has to allow for liquid water)
2) Planet must be large enough to maintain its internal heat long enough so that: -volcanism can help create an out-gassed atmosphere -plate tectonics/CO2 cycle, climate stability -global magnetic field to help maintain atmosphere and shield surface |
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What is the theory that life on Earth may be due to the moon?
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The Stability of Earth's 23.5 degree tilt creates climate stability
-tilt is important for our seasons -if we take away the moon, our axis tilt would range greater, and our climates would be unstable |
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What is the Drake Equation?
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a simple way to estimate the number of civilizations in the MW at the present time capable of interstellar communication
Number = N(hp) x f(life) x f(civ) x f(now) N(hp) - number of habitable planets in MW f(life) - fraction of habitable planets in MW with life f(civ) -fraction with advanced civilizations f(now) - fraction that exist now **last two are very unknown though |
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What is the problem with the f(now) factor?
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We know we are spatially isolated in the galaxy...but we may also be temporally isolated in time
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What is SETI? What are the three major problems for SETI?
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SETI
-long program radio telescope searches fro specific targets looking for repeating, artificial signals 3 Problems: 1) what targets are we looking for? 2) which frequency should we be looking at them with? 3) what is a non-natural signal? |
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What frequency to SETI searches typically focus on?
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Microwave searches - looking for narrow band signals
-microwaves can pass through the atmosphere and noise from galactic sources is minimized -lower frequency - would get more background noise from galaxy -higher frequency - would get more molecules absorbed by Earth's atmosphere |
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What counts as a non-natural signal? What did the signal contain?
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we sent a binary (on/off) signal to a globular cluster M13
- sent using 1679 pulses (can only be factored one way 23 x73) The image contained: -DNA helix -a picture of a person -solar system -radio telescope -number 1-10 |
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To date SETI has not found a repeatable narrow-band transmission that cannot be naturally explained...why might this be?
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1) wrong time?
2) wrong frequency? 3) data not analyzed by other life? |
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What is the Fermi Paradox?
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We have ZERO evidence for extraterrestrial civilizations - where is everyone?
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What was the Von Neumann probe idea?
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-Proposed the idea of a self-replicating robotic spacecraft
-would be able to travel to nearest stars, locate raw resources, build an identical copy of themselves, and ready for a new mission - so then why hasn't a civilization tried to do this? |
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What are the possible answers to the Fermi Paradox?
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1) Such self-replicating probes (Von Neumann) are impossible - nah probes and interstellar travel are possible
2) Extraterrestrials would chose not to visit us 3) Extraterrestrials/artifacts are already here but we don't recognize them 4) There are no extraterrestrial civilizations |
