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What is N?
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The # of advanced intelligent civilizations which are communicating in the galaxy RIGHT NOW
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How can we determine the value of N?
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Active search, passive search, and estimation through statistics
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What is an active search?
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visit every star/planet and look for intelligence
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What is negative about active search?
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Too far, too long and not enough technology
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What is a passive search?
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Stay here & listen for signals from outer space
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What is negative about passive search?
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missed signals, too weak of a signal, are we listening to the proper channel?
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What is negative about statistical estimations?
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accuracy is limited by accuracy of statistics
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What is the drake equation?
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N= N* fs Np fe fl fi (LC/LMW)
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What is N*?
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# of stars in galaxy
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How do we calculate N*?
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use our sun's motion around Galactic center
M= a^3/ p^2
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What is the effect of N* and what is it equal to?
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more stars -> more chances for life
N* = 200 billion
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What is fs?
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Fraction of stars that are sunlike?
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What are the constraints for fs?
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age, mass, lifetime, single star, location, metal contents, large circular jovian orbit
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What is the value of fs?
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10% or lower
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what is N*fs?
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# of sunlike stars in galaxy
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What is Np?
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Average # of planets per sunlike star
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What is the value and implication of Np?
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more planets -> more that have a chance for life
using POM -> Np = 10
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What is N* fs Np?
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# of planets in Galaxy (orbit sunlike stars)
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What is fe?
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Fraction of planets which are potentially habitable
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What are the constraints for fe?
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HZ (sunlight), significant mass, organic compounds, liquid H20, rotation speed, maybe large moon
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What is the value and implication of Np fe?
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# of habitable planets per star
-conservative optomism: 1
-negative: less than 1
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What is N* fs Np fe?
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# of habitable planets in galaxy
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What is fl?
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Fraction of potentially habitable planets where life actually develops
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What is the problem with fl?
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-We havent found life elsewhere
-WE dont fully understand how life formed on EARTH
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What is the vlaue of fl?
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Optomistic - if it can it will 100%
Pessimistic - 1%
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What N* fs Np fe fl?
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# of places in Galaxy with life
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What is fi?
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fraction of planets with life where intelligence develops
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What are the views of fi?
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Optomistic - natural course of evolution
pessimistic - only 1 species got on Earth - is that a reare quality?
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What is N* fs Np fe fl fi?
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# places in Galaxy with intelligence at some point
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What is LMW?
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Age of Galaxy = 10 Billion Years
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What is Lc?
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Lifetime of a communicative civilization
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What does Lc assume?
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Present technology and desire to communicate
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What can influence Lc?
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-Self Destruction
-Staying Motivated
-lifetime of the star
-asteroid/comet/geological catastrophic event
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How does Lc effect N?
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-Shorter the time that they are online ->very few if any will be "online" at the same time -> N decreases
-Longer Lc -> more likely to overlap with more civ. -> N increases
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What are Chauvinisms?
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Energy Source, Location of Life (Distance from star), Location of Life, Organic based element, & Chemical medium for life
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What is the chauvinism for enery sources?
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Starlight
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What are alternative for energy sources?
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Tidal forces from a large Jovian, Gravitational contraction, geothermal vents on ocean floor
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What is the chauvinism for location of life?
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Habitable Zone but it is not required as viewed on Europa
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What is the chauvinism for Location of life?
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Planet/Surface (ocean)
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What are alternative for location of life?
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Jovian moon; icy crsut of arctic ocean; Earth atmosphere has life; Carbon compounds; liquid H20; panspermia vs. life evolution on Earth
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What is the chauvinism for organic based elements?
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DNA -> carbon "carbon based life"
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What are the requirements for an element to be basis of life?
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a)naturally occuring
b)must create chemical bonds (no noble gases)
c)Must be able to create bonds to several other atoms
d)must be able to create bonds to several other atoms
e)must be able to create multiple bonds with other elements
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What are the only 2 possibilites for organic elements?
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Carbon and Silicon
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Why cant Si based life work on Earth?
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a) SI is not usually as plentifull as Carbon (but here it is)
b) double bonds dont form well with Si
c) b.c outer shell is so far from nucleus, the bonds it forms are very weak
d) "common molecules"
-CO2 is a gas
-SiO2 is a rock
e) C: chains millions of atoms long
Si: at room temp - longest chain is 30-40 atoms
But at T < -300F Si can make molecules millions of atomes long
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What is the chauvinism for Chemical medium for life?
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H20 as liquid that transports nutrients/waste in/out of cells
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What is range of liquid for H20?
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0-100 degrees C
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What is range of liquid for NH3?
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-78-(-33) Amonia
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What is range of liquid for CH4?
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-182-(-164) Methane
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What is range of liquid for C2H6?
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-183-(-89) Ethane
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What is the typical range for a HZ for NH3 & Ch4?
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Very Narrow
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