Are We Alone?
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Transcript of Are We Alone?
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Are We Alone?
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Objective
1: The process of cosmic evolution as it is currently understood.
2: Evaluate the chances of finding life in the solar system.
3: The various probabilities used to estimate the number of advanced civilizations that might exist in our Galaxy.
4: Some of the techniques we might use to search for extraterrestrials and to communicate with them.
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Cosmic Evolution
The collection of the seven major phases of the history of the universe, namely:
1: Particulate 2: Galactic 3: Stellar 4: Planetary 5: Chemical 6: Biological 7: Cultural, And Future Evolution
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Characterization Of Living Organisms
1: Their ability to react to their environment
2: To grow by taking in nutrition from their surroundings.
3: To reproduce, passing along some of their own
characteristics to their offspring.
4: To evolve in response to a changing environment.
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What do we need for life?• Water?
• Stable planetary orbits?
• Temperate conditions (not too hot or cold)?
• Not to be too near the center of the galaxy?
• Not to be too far out?
• A “Shield” like Jupiter?
• An iron core?
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Assumption of Mediocrity
1: Life on earth depends on just a few basic molecules.
2: These basics molecules are common to all stars.
3: The law of science must apply to entire universe so, life must exist in other part of universe.
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Miller-Urey Experiment(1953)
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Miller-Urey Experiment(1953)
In this experiment they tried from (primordial soup) of water, methane, carbon dioxide, and ammonia by passing electrical discharge after few days they made Amino acid.
Amino Acids: Organic molecules which form the basis for building the proteins that direct metabolism in living creatures.
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Drake Equation:Factoring the Unknown
Probability someone will eat a Big Mac for Lunch =
chance they will go to McDonalds
x
chance they will order a Big Mac
x
chance they will eat what they ordered
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N = R* fp ne fl fi fe L
R* = rate at which solar type stars form (stars/year)
fp = fraction of stars which have planets
ne = fraction of planets per solar system suitable for life
fl = fraction of those planets upon which life arises
fi = fraction of those life forms which evolve intelligence
fe = fraction of those species which develop the technology to send signals into space
L = the average lifetime of those species
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Searching for Intelligent Life
• Most likely extra-solar• If technologically intelligent life existed in our
solar system, we’d probably know it by now.
• Communication• We can’t visit, but maybe we can “phone”
• Talking to ETs takes a long time• 4 light years to Alpha Centuri• 8 years to get a reply• And that is the closest star
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If they are talking, what do we look for?
Types of signals:
continuum(like blackbody)
Line (atomic transitions)
Narrow band (not found in nature)
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At Which Wavelengths?
Other stars are in the plane of our galaxy
you are herethey are there
Use Radio wavelengths to penetrate galactic dust clouds
Aricebo
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What can you do?
• Search for extraterrestrial life at home
• http://setiathome.ss1.berkeley.edu
• distributed computing
• Screensaver searches for alien signals