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75 Cards in this Set

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  • Back
What is N?
The # of advanced intelligent civilizations which are communicating in the galaxy RIGHT NOW
How can we determine the value of N?
Active search, passive search, and estimation through statistics
What is an active search?
visit every star/planet and look for intelligence
What is negative about active search?
Too far, too long and not enough technology
What is a passive search?
Stay here & listen for signals from outer space
What is negative about passive search?
missed signals, too weak of a signal, are we listening to the proper channel?
What is negative about statistical estimations?
accuracy is limited by accuracy of statistics
What is the drake equation?
N= N* fs Np fe fl fi (LC/LMW)
What is N*?
# of stars in galaxy
How do we calculate N*?
use our sun's motion around Galactic center

M= a^3/ p^2
What is the effect of N* and what is it equal to?
more stars -> more chances for life

N* = 200 billion
What is fs?
Fraction of stars that are sunlike?
What are the constraints for fs?
age, mass, lifetime, single star, location, metal contents, large circular jovian orbit
What is the value of fs?
10% or lower
what is N*fs?
# of sunlike stars in galaxy
What is Np?
Average # of planets per sunlike star
What is the value and implication of Np?
more planets -> more that have a chance for life

using POM -> Np = 10
What is N* fs Np?
# of planets in Galaxy (orbit sunlike stars)
What is fe?
Fraction of planets which are potentially habitable
What are the constraints for fe?
HZ (sunlight), significant mass, organic compounds, liquid H20, rotation speed, maybe large moon
What is the value and implication of Np fe?
# of habitable planets per star

-conservative optomism: 1
-negative: less than 1
What is N* fs Np fe?
# of habitable planets in galaxy
What is fl?
Fraction of potentially habitable planets where life actually develops
What is the problem with fl?
-We havent found life elsewhere
-WE dont fully understand how life formed on EARTH
What is the vlaue of fl?
Optomistic - if it can it will 100%
Pessimistic - 1%
What N* fs Np fe fl?
# of places in Galaxy with life
What is fi?
fraction of planets with life where intelligence develops
What are the views of fi?
Optomistic - natural course of evolution
pessimistic - only 1 species got on Earth - is that a reare quality?
What is N* fs Np fe fl fi?
# places in Galaxy with intelligence at some point
What is LMW?
Age of Galaxy = 10 Billion Years
What is Lc?
Lifetime of a communicative civilization
What does Lc assume?
Present technology and desire to communicate
What can influence Lc?
-Self Destruction
-Staying Motivated
-lifetime of the star
-asteroid/comet/geological catastrophic event
How does Lc effect N?
-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
What are Chauvinisms?
Energy Source, Location of Life (Distance from star), Location of Life, Organic based element, & Chemical medium for life
What is the chauvinism for enery sources?
What are alternative for energy sources?
Tidal forces from a large Jovian, Gravitational contraction, geothermal vents on ocean floor
What is the chauvinism for location of life?
Habitable Zone but it is not required as viewed on Europa
What is the chauvinism for Location of life?
Planet/Surface (ocean)
What are alternative for location of life?
Jovian moon; icy crsut of arctic ocean; Earth atmosphere has life; Carbon compounds; liquid H20; panspermia vs. life evolution on Earth
What is the chauvinism for organic based elements?
DNA -> carbon "carbon based life"
What are the requirements for an element to be basis of life?
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
What are the only 2 possibilites for organic elements?
Carbon and Silicon
Why cant Si based life work on Earth?
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
What is the chauvinism for Chemical medium for life?
H20 as liquid that transports nutrients/waste in/out of cells
What is range of liquid for H20?
0-100 degrees C
What is range of liquid for NH3?
-78-(-33) Amonia
What is range of liquid for CH4?
-182-(-164) Methane
What is range of liquid for C2H6?
-183-(-89) Ethane
What is the typical range for a HZ for NH3 & Ch4?
Very Narrow
What is the typical range for a HZ for NH3 & Ch4 and C2H6 for planet sun distance?
Much further from sun
On What object in our solar system could there be Si based life?
What are the effects of colder chemical mediums?
Slower that chemical reactions take place
What is the effect of lowering the temp by 10 degrees C?
Takes twice as long
What frquencies should/do we send out in our search for ET?
easier and cheaper to produce/send low energy signals, like radio waves
What is the advantage of radio waves?
They can penetrate interstellar dust
What are some examples of galactic noise being too loud?
-Freq. <1000 MHz: galactic noise is loud
-Freq. >1000 MHz: atm. interference
What is advantages being between 1000 - 3000 MHz?
a)galactic noise is relatively low
b)low energy -> low cost to produce
c)Long wavelength penetrates the dust
What is at 1420 MHz?
the spectral line of OH (Hyroxyl)
What is b/w 1420-1721 Mhz?
What telescopes would be used to search for ET?
Since radio waves are weak large telescopes gather photons so you can "hear the signal"
At what sensitivity do we search for ET?
A single bandwidth provides a range of freq. for an EM singal
What is the problem with artificial signals?
They have very narrow signal bandwdth
What search bandwidth do you use?
Use a tiny search bandwidth to acheive better success but it takes a very long time
What is Project OZMA?
From April to July 1960, for six hours a day, Project Ozma's 85-foot NRAO radio telescope was tuned to the 21-centimeter emission (1420 MHz) coming from cold hydrogen gas in interstellar space. A single 100 Hz channel receiver scanned 400 kHz of bandwidth. The astronomers scanned the tapes for a repeated series of uniformly patterned pulses that would indicate an intelligent message or a series of prime numbers such as 1, 2, 3, 5 or 7.
what is Project Phoenix?
Project Phoenix was the world's most sensitive and comprehensive search for extraterrestrial intelligence.
It was an effort to detect extraterrestrial civilizations by listening for radio signals that were either being deliberately beamed our way, or were inadvertently transmitted from another planet.
Project Phoenix is sustained entirely through private funding.
What is Project Serendip?
The UC Berkeley SETI Program, SERENDIP (Search for Extraterrestrial Radio Emissions from Nearby Developed Intelligent Populations) is an ongoing scientific research effort aimed at detecting radio signals from extraterrestrial civilizations. The project is the world's only "piggyback" SETI system, operating alongside simultaneously conducted conventional radio astronomy observations.
What is the idea of a Positive Signal?
It is a narrow signal bandwidth
And reproduced again, again, and again
How long will it take for voyager satellites to get to closest stars?
70,000 ys.
What is the foundation for the Fermi Paradox?
What if N >1?
if N is large they may be close to us
and if they chose to colonize a galaxy time to colonize would be small
What are the possible answers for the Fermi Paradox?
1. they came and went
2. they chose not to travel or communicate
3. they're calling but we dont hear them
4. they're aware of us but we are not ready yet
5. active search is not possible
6. They are here and watching us
7. We are them
8. They chose not to visit our part of the galaxy
9. N = 1
What if N=1? What are some possible explanations?
1. life is a fluke
2. we are alone right now
3. all intelligent civ. chose not to communicate
4. we got to intelligence 1st
Review POM?
A. our sun is one of billions of similar stars
B. Our mily way is 1 of millions of galaxies
C. Planets for around other stars
D. Spectroscopy: chemicals found on Earth are found everywhere
E. Laws of Physics/Chemistry are universal
F. Biological Implication - if life exists here, why not elsewhere?
Review Lawki?
Life as we know it
1. Significatn energy source: sun
2. organic Compounds - carbon
3. Chemical Medium for life - liquid water
Review HZ
Region where temp is that H2O is liquid
sunlight is energy source
Effecting HZ
-distance to sun
-amount of greenhouse