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Use a stamp “X” to select the most abundant element in the universe.
neon nitrogen hydrogen oxygen
helium carbon sodium iron
Axis of rotation
Approx. 1 light yearAxis of rotation
Rotation retardscollapse in thisdirection
Slowly spinninginterstellar cloud
Gravity makes cloudshrink. As it shrinks it spinscaster and flattens into adisk with central bulge.
Approx.100 AU
Big Questions in Science
• Where did we come from?
• Are we alone?
Questions about origins:
Other astrobiology questions:
1. How did life on Earth form?
2. Should we expect life on many other worlds?
3. Is life on other worlds like life on Earth?
4. How can we detect life elsewhere?
Put a stamp on the most abundant element in life on Earth.
neon nitrogen hydrogen oxygen
helium carbon sodium iron
The Most Abundant Chemical Elements in the Universe and in Life
• H• He• O• C• N
In the Universe In Life
• H• • O• C• N
• Life on Earth is carbon-based.• Life on Earth requires liquid water• The amino acids in life are easily
formed.
A few facts about
Life on Earth
Signs of Life (not yet possible to detect with current technology)
• Seasonal changes
• Unusual abundances of gases
• Gases produced by life
• Unusual patterns of electromagnetic radiation (e.g., radio or TV broadcasts, the nighttime glow of cities)
Records of Life on Earth
Life elsewhere could be similar to any of
These stages, or entirely different.
Amino Acids: building blocks of life.
Some of these were produced in the lab by Harold Urey out
of primeval gases like methane, ammonia, carbon dioxide--by zapping them with electricity (lightning). (1950s)
Human DNA
Nobody has produced this
artificially or even hopes
to. Too complicated.
50,000 genes.
However, the total makeup
Of a human being requires
More information.
The distance between civilizations in the Milky Way
N=no.
of civilizations.
R=radius of
spherical galaxy
r = average
separation.
4 pi (r/2)2 N
= 4 pi R3/3
implies
r = 2R/N1/3.
The Drake Equation• N = N* fp ne fl fi fc fL• N* represents the number of stars in the Milky Way
Galaxy • Question: How many stars are in the Milky Way
Galaxy? • Answer: Current estimates are 100 billion. • fp is the fraction of stars that have planets around them • Question: What percentage of stars have planetary
systems? • Answer: Current estimates range from 20% to 50%. • ne is the number of planets per star that are capable of
sustaining life • Question: For each star that does have a planetary
system, how many planets are capable of sustaining life?
• Answer: Current estimates range from 1 to 5.
The Drake Eqn. continued• N = N* fp ne fl fi fc fL• fl is the fraction of planets in ne where life evolves • Question: On what percentage of the planets that are capable of
sustaining life does life actually evolve? • Answer: Current estimates range from 100% (where life can evolve
it will) down to close to 0%. • fi is the fraction of fl where intelligent life evolves • Question: On the planets where life does evolve, what percentage
evolves intelligent life? • Answer: Estimates range from 100% (intelligence is such a survival
advantage that it will certainly evolve) down to near 0%. • fc is the fraction of fi that communicate • Question: What percentage of intelligent races have the means and
the desire to communicate? • Answer: 10% to 20%
The Drake Eqn. continued• N = N* fp ne fl fi fc fL• fL is fraction of the planet's life during which the
communicating civilizations live • Question: For each civilization that does communicate,
for what fraction of the planet's life does the civilization survive?
• Answer: This is the toughest of the questions. If we take Earth as an example, the expected lifetime of our Sun and the Earth is roughly 10 billion years. So far we've been communicating with radio waves for less than 100 years. How long will our civilization survive? Will we destroy ourselves in a few years like some predict or will we overcome our problems and survive for millennia? If we were destroyed tomorrow the answer to this question would be 1/100,000,000th. If we survive for 10,000 years the answer will be 1/1,000,000th.
• N, the number of communicating civilizations in the galaxy.
SETI—Search for Extraterrestrial Intelligence
Over 30 messages
suspiciously intelligent.
They are using home
computers to scan for
messages.
Summary
• We have learned an enormous amount about the origins of stars and planets.
• We are just starting to learn about life in the universe.
• These explorations require a team effort involving scientists from many disciplines.
• There is still much more to explore. Students will be able to make discoveries and help us learn even more!
NASA’s Navigator Missions: http://planetquest.jpl.nasa.gov/
Origins Education Forum: http://origins.stsci.edu/