Transcript Searching for Life in the Universe: from Microbes to Intelligence Lecture 24 Allen Telescope Array.

Searching for Life in the Universe:
from Microbes to Intelligence
Lecture 24
Allen
Telescope
Array
Announcements
• HW
• Read Ch. 24: Life in the Universe
• Homework
Mastering Astronomy: Chapter 24
Due Friday, Dec 5, at 6pm
Final Exam:
Thursday, Dec 18, 11:30-2:30
Pimentel Auditorium (Here, usual room)
• Multiple Choice
• All Chapters: 1-5, 9-14, 24 & All Lectures.
Emphasis on chapters 12, 13, 24
• Review Sessions:
Thu (Dec 11) at 5pm in Pimentel
Come with questions !
Life in the Universe
1)
2)
3)
4)
5)
6)
Life in Extreme Environments on Earth
Life in other solar systems
Search for extraterrestrial intelligence
The Drake Equation
Interstellar travel
Is Intelligent Life Common or Rare
in the universe ?
Please vote
!
Is there Life in the Milky Way Galaxy?
Beyond the Earth, in our Milky Way Galaxy, there Is:
A)
B)
C)
Neither primitive nor intelligent life.
Primitive life but not intelligent life.
Both Primitive and Intelligent life.
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Prospects
for
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Life in the Universe
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The Universe:
• > 200 BillionGalaxies
•. 13.5 Billion Years Old
.
Spiral Galaxies
Elliptical Galaxies
Each Galaxy has:
Each Galaxy:
~100 Billion Stars.
200 Billion Stars
Each star is a Sun.
20% have Earth-size planets
in the habitable zone.
Laws of Physics and Chemistry
are the same
Everywhere in the Universe
Method to Detect
Earth-size Planets
Planet passes in front of the star, blocking its light.
Kepler-10 Light Curve
11
Kepler-10 Light Curve
Period = 45.29 days
12
Multi-Planet Systems are Common
over 500 Discovered
Is there Life in the Milky Way Galaxy?
Only Known Site of Biology
In the Universe.
Need one more
example in our
Solar System
or beyond . . .
Life Began On Earth
3.8 Billion Years Ago
Earth: 4.6 Billion years old.
Life started fast here.
Does biology normally start quickly
on habitable planets?
Are there
Universal Laws of Biology ?
Is DNA the only Replicating Molecule ?
Intelligence:
An inevitable result
of evolution ?
Liquid Water:
Are there other chemical mixers ?
Estimate Number of Earths in
Milky Way Galaxy
200 billion stars
20% of all Stars have Earth-size
planets in the habitable zone.
What properties make a planet
suitable for life?
Earth-sized planets are common.
But how common are - - -
What conditions
are necessary
for life ?
One of the Least Hospitable Places on Earth:
Yellowstone National Park
• Boiling Geysers
• Freezing winter
• Sulfuric acid
Suitable for Life ?
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
Filamentous bacteria thriving in pH=2.
Yellowstone
Churning Cauldron
Boiling Temp
Yellowstone
Churning Cauldron Hot Spring
Near Boiling
Temperature
Algae
pH = 2
Corrosion
pH = 2
Bacteria &
Algae Thrive
Life Thrives at:
Temp = 0 - 75 C
&
Wide Range of Acidity
Cyanidium Calderium
Lives at Temp > 65 C
Zygogonium sp.
Extremophiles on Earth 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
Origins of Life
Are we alone?
Urey-Miller Experiment
February 5, 1996
Recipe for Microbial Life
 Planets
 Organic Molecules
 Water
 Energy - - Stars, Tidal, Geothermal
Molecular Biologists:
“Single-cell life must be
common in the universe”.
Evolution
Charles Darwin (1859) Origin of Species
Darwin’s key observations:
1) Each generation: Offspring struggle for survival
2) Traits are passed on from parents to offspring, but offspring
are not exactly like their parents
Conclusion: Individuals with traits that best allow them to survive
and reproduce will on average produce the greatest number
of surviving offspring: Natural selection.
Advantageous traits are passed on.
Is Intelligence an “advantage” ?
Is our Milky Way Teeming
with Intelligent Life ?
Our Milky Way Galaxy:
40 Billion Planetary Systems.
Half of the planets are older than Earth
What fraction of Earths
have Intelligent Life ?
Pessimist: 1 in a Million
There
mustStars
be Thousands of Civilizations
200
Billion
In the Milky Way Galaxy. . .
The Drake Equation:
NCivil: Number of Advanced Civilizations in the Galaxy
NCivil = NumStars fracHab.Pl. fracLife fracIntel frac Intel.Now
Let’s Estimate Values:
NumSTAR
fHab.Pl. =
fLife =
f
= Number of Stars in Milky Way Galaxy
=
Fraction of stars with habitable planets
200 billion
= 1/5
=
Fraction of habitable planets on which life appears
???
=
Intel = Fraction of planets with life where Intelligence emerges
???
=
f Intel.Now =
=
fraction Surviving Today = Life
Civ
Life Civ = Lifetime of typical civilizations
/LifeStar
???
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Non-Detections of
Intelligent Life in the Galaxy:
• Moon: No Alien Spacecraft, Crash Debris, Obelisk
• Mars: No sign of past visitors or colonies
• Earth: Lovely Planet for 4 Billion Years . . .
Yet, no Alien Settlement.
• 100’s of Telescopes: No Alien spacecraft spotted
• Night Sky: No Exotic Rocket Exhaust-gamma rays
• No Robotic Probes orbiting Solar System
• SETI: No Radio Signals in 40 years.
Where
Is
Everybody?
Did We Overestimate the Probability
of Intelligent Life in the Galaxy?
Aliens should already have wandered
here
If only by chance!
( Even ants eventually find your Kitchen.)
Where
Is
Everybody?
How Might Intelligent Life
Be Rare in the Galaxy?
Aliens should already have wandered
here
If only by chance!
( Even ants eventually find your Kitchen.)
Earth: A Lucky Amount of Water
Earth is 0.06% water.
Lucky Delivery of Water
by Asteroids and Comets
0.03%: Desert World
Other Earths:
Most Rocky Planets are
Desert or Water Worlds
No Technological Life
0.09%: Water
World.
Does Evolution Favor Intelligence ?
Test: Dinosaur brain evolution
Paleontology:
• Walnut-size brains
• No tools
• Bird-like brains
150 Million Years of Dinosaur Evolution: A No-Brainer
Dinosaur Brain Mass:
150 Million Years of Evolution
Dinosaur brain mass:
Similar to birds and reptiles.
Smartest was the Troodon:
with Ostrich-size brains
Does Evolution Favor Intelligence?
Is Intelligence strongly favored? .
Does Evolution Favor Intelligence
among current animals?
Intelligence is not strongly favored . . .
Prediction:
1000 Civilizations in 5 Billion Years
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For contemporaneous civilizations,
• •
Their Lifetimes Must Overlap:
Need: Lifetime > 5 Million yr
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What is the
Typical Lifetime
of a Civilization ?
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You Are Here:
Earth’s Orbit
The Sun
Saturn
o
Uranus
o.
Neptune
o
Jupiter
.
o
G
How Far is the Nearest Star,
Alpha Centauri ?
d = 4 light years
= 4 x 1016 m
4 light years
scales to:
4000 km
(= 3000 mi)
Grapefruit-sized
Sun in Berkeley
Nearest Grapefruit:
Alpha Centauri
In Washington D.C.
G
How Far is the Nearest Star,
Alpha Centauri ?
d = 4 light years
= 4 x 1016 m
G
How Far is the Nearest Star,
Alpha Centauri ?
d = 4 light years
= 4 x 1016 m
G
How Far is the Nearest Star,
Alpha Centauri ?
d = 4 light years
= 4 x 1016 m
Grapefruit-sized
Sun in Berkeley
Nearest Grapefruit:
Alpha Centauri
In Washington D.C.
G
How Far is the Nearest Star,
Alpha Centauri ?
d = 4 light years
= 4 x 1016 m
Speed of Modern Spacecraft : 0.0001 c
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
Grapefruit-sized
Sun in Berkeley
Nearest Grapefruit:
Alpha Centauri
In Washington D.C.
Interstellar Travel
Long Travel Times
Speed of Light 300,000 km/sec
Light travels a distance of 1 “Light Year” in 1 Year
100,000 Light Years
Andromeda Galaxy: Near Twin of our Milky Way
Jon Stewart:
“ 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.”
SETI
Search for Extraterrestrial Intelligence
Where do you point your
Radio Telescopes ?
Habitable,Earth-Like Planets:
- Stare for weeks.
New:
Allen Radio Telescope Array:
Search for radio
transmissions.
Under construction at Mount
Lassen
Please vote
!
Is there Life in the Milky Way Galaxy?
Beyond the Earth, in our Milky Way Galaxy, there Is:
A)
B)
C)
Neither primitive nor intelligent life.
Primitive life but not intelligent life.
Both Primitive and Intelligent life.
Lecture 25
Summary: Life in the Universe
• Planets are Common in the Universe
• Life Survives in Extreme Environments (but needs water)
• Detection of first Earth-Like Planets: Coming Soon.
• Interstellar Travel: Takes over 100,000 years and enormous energy
• Primitive Life: Probably Common
Still Only One Precious Example of Life.
G. Chin (GSFC)
• Technological Life: Possibly Rare