Transcript . . . . . Prospecting for . Life in the Universe . . . Universe: Hundreds of Billions of Galaxies 13.5 Billion Years Old . .

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Prospecting
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Life in the Universe
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Universe:
Hundreds of Billions of Galaxies
13.5
Billion Years Old
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Final Exam
- Comprehensive
May 20 @ 8am: 237 Hearst Gym
- Bring pencils or pens.
No Calculator or book needed.
Final Exam:
Closed Book
• Comprehensive:
Emphasis on last 5 weeks:
Chapters 12, 13, 14, 24
– Asteroids, Comets, Kuiper Belt, Pluto
– Extrasolar planets
– Sun
– Life on Earth & in Universe (today’s lecture)
Bring two pencils or pens.
Review Session
Monday, May 19, 5-7 pm,
in 145 McCone
Come with Questions.
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Prospects
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Life in the Universe
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The Universe:
• > 200 BillionGalaxies
•. 13.5 Billion Years Old
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Spiral Galaxies
Elliptical Galaxies
Each Galaxy has:
Each Galaxy:
~100 Billion Stars.
200 Billion Stars
Each Star is a Sun.
Most Stars have planets.
Laws of Physics and Chemistry
are the same
Everywhere in the Universe
Universal Laws of Biology ?
DNA:
Only Replicating Molecule ?
Intelligence:
Inevitable Result
of Evolution ?
QuickTime™ and a
Liquid Water:
Other mixers ?
QuickTime™
and a decompressor
TIFF (Uncompressed)
TIFF (Uncompressed)
decompressor
are needed
to see this picture.
are needed to see this picture.
Only Known Site of Biology
In the Universe.
Need one more
example in our
Solar System
or beyond . . .
Last Week:
Life Began On Earth
3.8 Billion Years Ago
Earth: 4.6 Billion years old.
Life started fast here.
Would it start elsewhere?
Is Biology a
Cosmic Imperative?
Earth is our only example.
Three Weeks Ago . . .
Discovery of New Worlds
Around Other Stars
Now . . .
Prospects for Life in the Universe
Keck Observatory
Big Island, Hawaii
Now Exiting our Solar System to …
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The Milky Way
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Galaxy
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16 Cygni: Planet & Moon
Life on Gas Giant Planets ?
Earth-Like Moon
Floaters
Upsilon Andromedae
Three Planets Orbiting Gliese 876
7 1/2 Earth-masses
More Low-Mass
Planets
Planet Mass
Milky Way Galaxy
200 billion stars
~10% of all Stars
have detected planets.
Detected so far:
• Jupiter-mass
• Saturn-mass
• Neptune-mass
~ Earth-Mass ?
Earth-Sized planets are probably common. But how common are
What conditions
are necessary
for life ?
Many of the new planets are too
hot or too cold to support life.
Too hot!
(too close to star)
Just right!
Too cold!
(too far)
``Search for habitable worlds . . .’’
Habitable Zone
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Region around star
where Liquid water
can exist at the
surface.
. . . Temp = 0 - 100 C
Only Known Abode of Life
Conclusion: Many Earth-mass Planets
But are they
Habitable ?
Must Environments
Be “Just Right”
For Life ?
One of the Least Hospitable Places on Earth:
Yellowstone National Park :
Suitable for Life ?
• Boiling Geysers
• Freezing winter
• Sulfuric acid.
Yellowstone
Pinwheel Geyser
Near Boiling:
T ~ 80 C
Each color
a different
species of
bacterium
Bacteria
Thrive
Water: Acidic
as battery acid
Yellowstone
Grand Prismatic Spring
Near Boiling:
T ~ 80 C
Each color
a different
species of
bacterium
Bacteria
Thrive
Yellowstone
Life at High Temperature
and High Acidity
Temp = 65 C
pH = 2
Yellowstone
Churning Cauldron
Boiling Temp
Yellowstone
Churning Cauldron
Boiling Temp,
pH = 2
Algae
Corrosion
pH = 2
Bacteria &
Algae
Thrive
Life Thrives
0 - 75 C
&
Wide Range of Acidity
Cyanidium Calderium
Lives Temp > 65 C
Extremophiles Show that Life
• Tolerates heat or cold
• Thrives in acidic or alkaline environments
• Takes food from a variety of sources
• Copes with Intense Solar Radiation - - or none!
Liquid Water
Life
Primitive Life: Common in the Universe
Is our Milky Way Teeming
with Intelligent Life ?
• 20 Billion
Planetary Systems:
1/2 are older than Earth
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What fraction have
Intelligent Life?
• Pessimist: 1 in a Million
There must be Thousands of Civilizations
In the Milky Way Galaxy. . .
The Drake Equation:
Number of Advanced Civilizations in the Galaxy
N = NSTAR fHab.Pl. fLife fIntel f Intel.Now
NSTAR
Let’s Estimate Values:
= Number of Stars in Milky Way Galaxy
fHab.Pl. =
fLife =
f
=
=
Fraction of stars with habitable planets
Fraction of planets on which life appears
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=
Intel = Fraction of planets with life where Intelligence emerges
=
f Intel.Now =
fraction Surviving Today = L=Civ
L Civ = Lifetime of typical civilizations
/LStar
=
/5 billion years
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Where is Everybody?
Why Didn’t They Come Here?
• Moon: No Alien Spacecraft, Crash Debris, Obelisk
• Mars: Same Story
• Earth: Lovely Planet for 4 Billion Years . . .
Yet, no Alien Settlement.
• 100’s of Telescopes: No Alien Ships spotted
• Night Sky: No Exotic Rocket Exhaust
• No Robotic Probes Visit Solar System
• SETI: No Radio Signals in 40 years.
Where
Is
Everybody?
• Hypothesis: - Thousands of Civilizations in Galaxy
- Head Start of Billions of years.
They should be Near!
• Migration Throughout Galaxy: Easy with robotic spacecraft
=================================================
• Observation: No Aliens Detected, and no Traces.
• Conclusion: Hypothesis possibly flawed.
( Ants eventually find your Kitchen)
Water-Delivery to Earth-Like Planets
By Asteroids &Comets
How much water
is typically delivered?
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Technological Life Requires:
- Some water on surface
- Not 100% coverage.
Are partial veneers of ocean
Common or Rare?
Need ~10-4 of water by mass
Interstellar Travel
Long Travel Times
Speed of Light 300,000 km/sec
Light travels a distance of 1 “Light Year” in 1 Year
Speed of Modern Spacecraft : 10 - 4 Speed of Light
v = 10 - 4 Light-year/year
Nearest Star: Alpha Centauri d = 4 Light years
Travel Time to Alpha Centauri = . . .
t = d/v = 4 / 10-4
= 40,000 years
100,000 Light Years
Andromeda Galaxy: Near Twin of our Milky Way
Jon Stewart:
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
“ Only 35 light years away. That’s
close enough that we could pop over
to borrow a cup of sugar
assuming we didn’t need the sugar
for 700,000 years.”
If Intelligence enhances survival ,
species would become smarter.
Flies would employ Algebra
Cats would play Jazz
Is Intelligence a Rare Outcome of Evolution ?
Expect:
1000 Civilizations in 5 Billion Years
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Contemporanious Civil. requires :
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Lifetimes Must Overlap:
Lifetime > 5 Million yr
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Typical Lifetime ?
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Suppose chance of survival = 0.9999 each century:
Probability of surviving 5 million years = 0.007
February 5, 1996
Recipe for
Microbial Life
 Planets
 Organic Molecules
 Water
 Energy - - Stars, Tidal, Geothermal
Molecular Biologists:
Single-cell life is
common in the universe.
SETI
Search for Extraterrestrial Intelligence
Where do you point the
Radio Telescopes ?
Stare for Days at
Habitable Earth-Like Planets
Berkeley & SETI Institute:
Radio Telescope Array:
Under construction
at Mount Lassen
Life in our Milky Way Galaxy:
Primitive Life: Common
Technological: Rare ?
. . . ET Non-Detection & Rare Earths ?
..
Searching for Intelligent Life
Kent Cullers
Jill Tarter
Contact : The Movie
Exploring The Galaxy
for Intelligent Life
ATA
Tiny volume explored:
Tiny Fraction
of Galaxy so far
Life in our Milky Way Galaxy:
Primitive Life: Common
Intelligence: Rare ?
Semi-Intelligent Life forms
..
Intelligence
Key Topics
• Size scale of Solar System, Galaxy, Universe
• Sizes and relative orbital sizes of planets
and comets and asteroids
• Moon phases, Seasons
• Gravity, Tides
• Light: wavelengths, colors, Doppler shift
• Formation of Solar System: Origin of planets
• Geology of Earth: Layers, Age, Composition
• Atmosphere of Earth and rocky planets
• Giant Planets: Structure, Rings, Moons
• Last 4 chapters . . . 12, 13, 14, 24