Transcript Searching for Life in the Universe: from Microbes to Intelligence Lecture 25 Allen Telescope Array.

Searching for Life in the Universe:
from Microbes to Intelligence
Lecture 25
Allen
Telescope
Array
Announcements
• HW
• Read Ch. 24: Life in the Universe
• Homework
Mastering Astronomy: Chapter 24
Due Friday, Dec 6, at 6pm
Final Exam:
Thursday, Dec 19, 11:30-2:30
RSF Field House: Main Floor Gym
• Multiple Choice
• All Chapters: 1-5, 9-14, 24 & All Lectures.
Emphasis on chapters 12, 13, 14, 24
• Review Sessions:
Tue and Thu (Dec 10 & 12) at 5-6:30
in 2040 VLSB
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 ?
.
.
.
.
.
Prospects
for
.
Life in the Universe
.
. .
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
10
Kepler-10 Light Curve
Period = 45.29 days
11
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:
Inevitable Result
of Evolution ?
Liquid Water:
Other 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 makes a planet
suitable for life?
Earth-sized planets are probably 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 ?
Yellowstone
Grand Prismatic Spring
Near Boiling:
T ~ 80 C
Each color
a different
species of
bacterium
Bacteria
Thrive
Life Thrives at:
Temp = 0 - 75 C
&
Wide Range of Acidity
Cyanidium Calderium
Lives at Temp > 65 C
Zygogonium sp.
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
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 is
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 ?
40 Billion Planetary Systems
1/2 are older than Earth
What fraction have Intelligent Life ?
Pessimist: 1 in a Million
There
mustStars
be Thousands of Civilizations
200
Billion
In the Milky Way Galaxy. . .
The Drake Equation:
Number of Advanced Civilizations in the Galaxy
N = NSTAR fHab.Pl. fLife fIntel f Intel.Now
Let’s Estimate Values:
NSTAR
= Number of Stars in Milky Way Galaxy
fHab.Pl. =
fLife =
f
=
=
Fraction of stars with habitable planets
Fraction of planets on which life appears
=
=
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
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
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.)
Earths: A Lucky Amount of Water
is Needed for Intelligent Life
Earth is 0.06% water.
Water in Other Earths:
< 0.03%: Desert World
> 0.09%: Water World.
Delivery of Water to Earth
by Asteroids and Comets
Most Rocky Planets are
Water Worlds or Deserts
No Technological Life
Does Evolution Favor Intelligence ?
Paleontology:
• Walnut-size brains
• No tools
• Bird-like brains
200 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
among current animals?
Intelligence is not strongly favored . . .
Prediction:
1000 Civilizations in 5 Billion Years
.
•
•
For contemporaneous civilizations,
• •
Their Lifetimes Must Overlap:
Need: Lifetime > 5 Million yr
•
•
•
•
What is the
Typical Lifetime
of a Civilization ?
•
•
•
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:
“ 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.”
Prediction:
1000 Civilizations in 5 Billion Years
.
•
•
For contemporaneous civilizations,
• •
Their Lifetimes Must Overlap:
Need: Lifetime > 5 Million yr
•
•
•
•
What is the
Typical Lifetime
of a Civilization ?
•
•
•
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