Life in the Universe

Astronomy 115

What is Life?

• “Life is what dies when you stomp on it” -Dave Barry

• Simple definitions all fail– Moves? Grows? Feeds? Reproduces?

• Best definitions focus on:– Self-organizing, complexity, adaptation– Information coding– Feedback (homeostasis)

DNA• Deoxyribonucleic acid• Total length of human DNA in a single cell is

about a meter• A human body contains about 20 trillion

cells• The total length of DNA in a human body is

thus 20 trillion meters, or twenty billion kilometers, the circumference of the orbit of Pluto.

Prebiotic Evolution• The basic molecules of organic chemistry are

easily made • The first self-replicating molecule was almost

certainly not DNA • DNA assembles from simpler materials all the

time • Many likely candidates• Clay minerals as templates?

Plants and Animals

• Carbon dioxide and water in the presence of an energy source can make sugars6 CO2 + 6 H2O + energy C6H12O6 (glucose) + 6 O2

• O2 is actually toxic (even to us!)

• Metabolism: Take the sugars and starches (from yourself or somebody else) combine it with the waste O2, and get the energy back to make different molecules

Planetary Habitable Zones

• Primarily in the Liquid Water Zone• Can’t be too warm

– Water Vapor in upper atmosphere broken down by solar UV and charged particles (photodissociation)

– Hydrogen escapes to space– Too hot planets will quickly lose all their water

• Freezing not so much of a problem

Reasons to be a "Carbon Chauvinist".

• Carbon is abundant in the Universe• Carbon can bond to four neighboring atoms• Carbon can bond to other carbon atoms,

sharing one, two, or three electrons• These properties make it possible to form a

vast array of organic molecules• No other element has these properties

Reasons to be a ”Water Chauvinist".• Water stays liquid over a wide range of

temperatures. • Water is very abundant in the Universe• Water is a polar or asymmetrical molecule. It

attracts ions easily, making it a good transporter of nutrients

• It does not dissolve organic molecules (so we do not dissolve in our own cell fluids)

The Role of Phosphorus

Adenosine triphosphate(ATP) is an energy transport molecule in all organisms

DNA requires phosphorus to link itself

Alternate Biologies?• Ingredients need to be abundant in Universe• Need solids to maintain structure• Need liquids or gases to transport nutrients

and wastes• Need source of energy• High temperatures destroy complex

molecules– Also solid state electronics– Why your computer has a fan

Alternate Biologies?• Silicon? Earth’s crust is 27% Si

– If silicon biology is possible, why not here?– Silicon doesn’t bond to itself well– C + O = gas, Si + O = quartz– CO2 dissolves in water, SiO2 doesn’t

• (SiH4 and SiF4 are gases, however)

• Alternatives to water?– Ammonia? Polar like water– Methane? Not polar– Hydrogen peroxide?

Alternate Biologies?• Nitrogen or Phosphorus?

– Can form complex molecules– Both are more rare in universe than carbon

• Arsenic?– Alternative to phosphorus– Even more rare in universe

• Chlorine– Alternative to oxygen?– More rare in universe than oxygen

Alternate Biologies?

• Sulfur?– Not likely as alternative to carbon– Can be alternative to oxygen – even on earth

• We cannot design a probe to look for “alternative biology” because we just don’t know what to look for.

Earth’s Alternative Biologies• Extremophiles: organisms that thrive under

extreme temperature, pressure, or chemical conditions

• Many of Earth’s simplest organisms are extremophiles

• Extremophile domain is a bigger target– We’re more likely to find planets inhabitable by

extremophiles than planets suitable for humans

Tolerance Ranges

Alternative Biology on Earth (GFAJ-1)

Mono Lake, California, a highly saline lake

Arsenic-Eating GFAJ-1• Not “arsenic based” life

– Organic structures built of carbon

• More than merely able to utilize arsenic• Can apparently replace P with As

– Up till now, P considered absolutely essential

• Seems to build As into DNA instead of P

Life on Early Earth

• Oldest minerals: 4.4 b.y.• Oldest rocks: 4.2 b.y.• Probably no life until Late Heavy

Bombardment over (3.8 b.y.)– Large impacts would sterilize Earth

• Liquid water as far back as we can see• Life by 3 b.y.

Life on Early Earth

• Faint Early Sun– Sun 4 b.y. ago was 70% as bright as today– We have liquid water throughout Earth history– Probably thick greenhouse atmosphere

• How life originated?– Cold earth: improves chemical stability– Hot earth: speeds up chemical reactions– Use minerals as templates?

Planetary Habitable Zones

Also known as the “Goldilocks zone”

The Ultimate Long-Term Forecast

• Slow warming trend for the next billion years

• Increasing humidity• CO2 decrease leads to extinction of plants?

• Boiling and evaporation of the oceans

Surviving on a Warming Earth• Higher organisms stop reproducing around 50°C• There will be no place cool to hide• Possible evolutionary strategies

– Ultra-sturdy heat resistant molecules– Concentrated solutions to raise boiling point– Retreat underground where pressure and boiling

point higher– Pressurized cells – Ultimate limit 150-200° C?

Surviving on a Warming Earth• Plants need > 10 ppm CO2

• Animals and plants die around 50° C• Micro-organisms can tolerate 130° C +• But biology seems to like heat and we have

a billion years to experiment– Pressurized cells?– Anti-boiling fluids?– Problem is breakdown of organic molecules– 150 – 200° C (300-380° F) max?

The Oreo Model of Life History

Micro-organism Earth (0-3 billion years)Multicellular Earth (3-5 billion years)Micro-organism Earth (5-6 billion years)“The white creamy middle”

The Drake Equation

“A wonderful way to organize our ignorance”

- Jill Tarter

Life in the Universe

• What are the odds of intelligent life elsewhere in the Universe?

• How many communicating civilizations are there in the Milky Way?

• How do you guess?• How do you guess the number of

jellybeans in a jar?• Break the problem down into things

you can guess.

The Drake Equation

N = Number of communicating civilizations in our galaxy right now.

And what about the rest?

LfffnfR N cilep*

Star Formation Rate: R*

• There are 100 billion stars in the Milky Way.

• The Milky Way is 10 billion years old.

R* = 100 billion stars/10 billion years

LfffnfR N cilep*

R* = 10 */year

Fraction with Planets: fp

• What fraction of stars have planets?

• Extrasolar planet research since 1995:– 539 confirmed planets– 414 planetary suystems– 55 multi-planet systems– 1 star has six

LfffnfR N cilep*

fp = 1/20

Number of Earths: ne

• How many habitable planets are there in each of these planetary systems?

• Habitable zone: water should be a liquid• Depends on star.

– No O or B– No M– No binaries

LfffnfR N cilep*

ne = 1

fl = ?

Fraction with life: fl

• On what fraction of habitable planets does life evolve?

• Look at our Solar System.• 3 planets in habitable zone, life has

evolved on 1 (or maybe 2).

LfffnfR N cilep*

Fraction with intelligence: fi

• What fraction of life bearing planets have life evolve to intelligence?

• Is intelligence inevitable?

LfffnfR N cilep*

fi = ?

Fraction that communicate: fc

• What fraction of intelligent civilizations become technological enough that we could communicate?

• Is technology inevitable?• Desirable?

LfffnfR N cilep*

fc = ?

Lifetime: L

• How long does a civilization last?• Do we have time to communicate

with them?• For us: L = 75 years!

LfffnfR N cilep*

L = ? years

What’s the Answer?

• R* = 10 */year• fp = 1/20• ne = 1• fl = ?• fi = ?• fc = ?• L = ? year• N = _____ # of technological

civilizations in Milky Way, right now.

LfffnfR N cilep*

Let’s Put It All Together!

But space is vast

• Milky Way is a giant cylinder (disk).– Radius = 15000 pc– Thickness = 1000 pc

• Volume = (Radius)2 x Thickness• V = 7 x 1011 pc3 = 700 billion cubic

parsecs!

How far to the neighbors?• If there are 100 civilizations in 700

billion cubic parsecs, then:– 1 civilization in every 15 billion cubic

parsecs

• Imagine every civilization surrounded by a bubble in which it is alone.

• V = 15 billion cubic parsecs• R = 3 kpc• Distance between civilizations:

3 kpc = 9000 ly (optimistically)!

R

R

How Can We Know?• How can we tell if there are

extraterrestrial civilizations?• Go visit. Is this practical?• Look for visitors? Is there evidence?• Look, or listen, for signals from E.T.

SETI• Search for Extraterrestrial Intelligence• Several organized searches over the last 30

years.• Use a radio telescope to try to detect signs of

E.T.• Why?• The Earth floods space with radio waves.

– TV– Radio– Cellular phones– etc

E.T. FM• Most natural radio sources are

broadband.• Radio stations are narrowband.

Tuning the Dial

• Nearly all searches have been looking for extremely narrow radio signals.– But there are millions and billions of

frequencies to listen to.– And millions and billions of stars

• Concentrate on nearby sun-like stars.– No luck.

• Point in the sky randomly.– No luck yet. But you can help.

SETI@Home

• Receiver piggybacks on Arecibo telescope.

• Constantly searches as telescope observes.

• Millions of channels (frequencies).• Thousands of hours.• Lots of data.• Needs lots of computer power.• Your power; http://setiathome.ssl.berkeley.edu/

SETI@Home

“Is there anybody out there?”

We have made three attempts to communicate.

1. The Arecibo broadcast to Hercules Cluster.

The Voyager Record ClubVoyagers 1 and 2 contain a plaque and

a record.

Voyagers 1 and 2

• Greetings 55 languages• 115 images• Music

Sumerian"May all be well." Arabic"Greetings to our friends in the stars. We

wish that we will meet you someday." Urdu"Peace on you. We the inhabitants of this

earth send our greetings to you." Italian"Many greetings and wishes." Ila (Zambia)"We wish all of you well."

So Where Are They?• Populations expand exponentially• It would take an exponentially-growing

civilization only a few million years to fill the Galaxy, even at sub-light speeds

• 2 to the 40th power is over a trillion• If it takes 10,000 years for a colony to

achieve interstellar travel, 40 doubling times is only 400,000 years.

• So why aren’t they all around us?

Is There A Problem?

• Alien psychology? We barely understand humans!

• Why did it take us so long to develop technology?

• Maybe we’re first?• Maybe we’re unique?

The Ming Dynasty (15th Century)

1405-1435 Chinese vessels sailed through Indian Ocean.Under Admiral Zheng He, the Chinese established tributary and trade relations throughout the region.

Why? We do not know. Rise of the land-oriented bureaucracy?Rise of expensive internal canal projects?Rise of inward-looking neo-Confucianism?

After the 7th grand expedition in 1435, the Chinese abandoned sea trade and exploration. Junks were broken down and left to rot, and it became a crime to build a vessel with more than two masts.

Search the Solar System for Alien Artifacts (for instance, 2001, A Space Odyssey)

Look for spacecraft and/or Von Neumann Machines (self-replicating probes) in Earth orbit, the Moon, the Asteroid Belt, etc. Nothing so far.

Search Biological Systems for "Messages"

A stable, "non-functioning" section of our DNA could carry a coded message. After all, coded information is precisely what DNA is all about. The Human Genome Mapping Project is COMPLETED. To my knowledge, there has been no such message detected.

Eyewitness Accounts & Memory

What we “see” is often not really there (Lowell’s “canals”)

People can be convinced during questioning to “remember” things that did not happen (many recent sexual abuse allegations)

People lie

People like to play tricks

People tend to “want to believe”

People don’t like to change their minds

People don’t like to admit when they are wrong

People make up things when they do not understand*

PEOPLE ARE HUMAN

Some claim to see UFOs in artwork

Flying Saucer or a common motif ??

Want to learn more?

Aliens in Spacecraft?

Actually depict the Sun & Moon

Lenticular clouds

Unidentified Flying Objects (UFOs)

Most people equate UFO with alien craft

The term “unidentified” actually means unidentified

Reports of UFOs go back centuries

Prior to invention of airplanes, UFOs tended to look like zeppelins

“Flying Disks” reported by Kenneth Arnold in 1945 while flying airplane near Mt. Rainier - this is where the “modern era” began - aliens now operate flying saucers, not flying cigars!

What aliens “looked like” also varies from culture to culture and one era to another.

Global mass communication has changed this….The “Greys” (Close Encounters of the 3rd Kind)

RoswellObject crashes in June 1947 on

Brazel’s ranch

Debris collected & brought to nearby Army Air Corps Base

Base press officer releases report of “crashed discs”

Legend grows of alien bodies set to Wright Field in Dayton

Recently, at the request of Congressman H. Shiff (R-NM), the US General Accounting Office released all records relating to Roswell. They indicate:1. no evidence for a cover-up2. no evidence for a UFO3. no evidence for alien bodies

Crash debris identified by Columbia & NYU as theirs - part of Project Mogul (now declassified) - balloon-borne microphones to listen for Soviet nuclear tests.

Project Blue Book - 1965

Because some UFOs might actually be aircraft belonging to hostile countries (read: USSR), the US Air Force launched a study to try to identify all such

sightings as best as they could. The breakdown:

Identification Number of Sightings Percentage of Total

Astronomical events (Venus) 245 26.7%Aircraft 210 23.7%Satellites 152 17.1%Hoaxes, Imagination, etc. 126 14.2%Insufficient Data 85 9.6%Weather Balloons 36 4.1%(still being processed) 17 1.9%UNIDENTIFIED 16 1.8%

The 16 unidentified cases are just that - unidentified

The Alien Autopsy Film

First aired by Fox as a true documentary in 1995. But:

1. Autopsy not carried out using methods of the profession

2. Examiner does not handle instruments properly

3. Anticontamination suits are bogus

4. Injuries inconsistent with crash

5. Warning signs used did not exist until 20 years later (OSHA)

6. Organs have no connective tissue!! Etc.

Kent Jeffrey, co-founder of the International Roswell Initiative, along with many other UFO supporters, claim that the film is a hoax.

1998 - Fox “reveals” the film as a hoax in subsequent airing!

Crop Circles

These patterns of crushed grass began to appear in England in the 1980's. Since then, they have been seen on other places, and the patterns have become more complex. Explanations given:

•Alien landing sites - it was 'impossible" for any human to do this•Wind vortices (totally absurd for the complex patterns seen)•Hoaxes

In 1991 David Bower and Dave Chorley claimed responsibility for starting the crop circle craze. They demonstrated live on BBC TV exactly how they did it. Since then, others have been caught in the act.

Apparently aliens have force fields & invisibility (i.e. the motion picture Signs), travel interstellar distances and/or cross “dimensions” but have to navigate by making drawings in corn fields??

For more visit this site.

Crop circles have become a form of art…

Also http://www.circlemakers.org/

The “Face” on Mars

Viking vs. MGS

Richard C. Hoagland The monuments of Mars: A City on the Edge of Forever (1987) claims the feature is artificial

“Happy Face” on Mars!

Other Stuff For the Drake Equation

• Jupiter Stabilizes Solar System?• Jupiter lessens impact bombardment• Moon stabilizes Earth’s axial tilt• Earth’s magnetic field deflects cosmic rays• Liquid Water Zone is narrow and changes with

time as stars brighten• Center of the Galaxy Deadly?

Galactic Habitable Zone?

Civilizations: Type + • Type I+

– Able to restructure planets

• Type II+– Able to restructure solar systems

• Type III+– Able to restructure galaxies

• Type +– Able to restructure Universe

Dyson Sphere -A sphere with a radius of 1 AU will have a temperature of approximately 300K, and radiate strongly near 12 m wavelength.

Other Things We Might DoDetection of Massive Engineering Projects- Astroengineering

Freeman Dyson

IRAS

An examination of sources detected in the infrared survey of the sky made by the IRAS satellite yielded no sources that could be definitively labeled as coming from such a structure.

Civilizations: Type • Type I-

– Able to manipulate objects on their scale

• Type II-– Able to manipulate genes, transplant and replace parts of

themselves

• Type III-– Able to manipulate molecules, create new materials

• Type IV-– Able to manipulate atoms, create nanotechnologies and

artificial life

Civilizations: Type – (contd.) • Type V-

– Able to manipulate atomic nuclei

• Type VI-– Able to manipulate elementary particles of

matter and create new states of matter

• Type -– Able to manipulate space and time

Which Path Shall Our Species Take?

• Rat Race Strategy (RRS)– Short Term Gain– Self Interest– Competition

• Evolutionarily Stable Strategy (ESS)– Cooperation– Great Foresight– Great Altruism– Longevity

Which path should we take ?

What if we succeed?Some Features of Culture Shock

• Loss of Faith in Beliefs and Institutions• Xenophobia• Over-Dependence, Copying• Nihilism

Models for Alien Encounters

• Star Trek?– We’re OK, they’re OK (Klingons sort of, Romulans

not so much)

• War of the Worlds? (Also, the Borg)– We’re food (or raw materials)

• Watership Down?– We’re irrelevant

Why Would Aliens Want Earth?• If they can freely travel in space:

– Water from icy bodies and comets– Hydrocarbons and organic molecules from gas

giants and frozen methane– Oxygen from silicates and water– Metals from asteroids– Unlimited size solar collectors close to Sun for

Energy• We are not likely to be

– A threat– A source of anything useful

Why Would Aliens Want Earth?

• A Planet to Live On• Convenient working conditions• Lithophile Elements• Hydrothermal ores• Organic materials• It probably won’t be about us

– Not that it will make it any easier

“Wonderful, just

wonderful. So much for

instilling them with a sense

of awe.”

“’Take me to your stove?’

You idiot, give me that book back!”

Arthur C. Clarke’s Laws• The only way to test the limits of the possible is

by going beyond them into the impossible• When an elderly but distinguished scientist says

something is possible, he is probably right. When he says something is impossible, he is very likely wrong

• Any sufficiently advanced technology is indistinguishable from magic

No Point in Hiding• At Radio Frequencies, Earth is brighter than

the Sun• Our Radio signals are now 70+ light years

out• From our signals, aliens could determine:

– Length of our day and year– Size of Earth, Distance from Sun– Probable mass and gravity– Draw a crude map of Developed World

Mapping Earth by Radio

Our Views of Aliens• Post World-War II

– “Savior Model”– “Hostile Aliens” - Eat or Enslave

• Science Source of Fascination and Fear– Winning World War II– Nuclear War

• Similarity with Westerns– We’re the Good Guys– Fighting off Hostile Threats

Our Views of Aliens Evolve• 1960’s: “Hostile Alien” films and Westerns

both decline• We’re Not Always the Good Guys

– Historical Revision of Frontier – “Spaghetti Westerns”-Dark and satirical– Civil Rights Movement– Vietnam

• Star Trek, 1967– Enlightened, Optimistic Future

Variations• Humans as Helpers: E.T.• Encounter as Wonder: Close Encounters of

the Third Kind• Encounter as Dreary: Contact• Swashbuckling: Star Wars• Satire: Men In Black• Return to Hostile Aliens

– Star Trek Spinoffs (The Borg, the Dominion)– Independence Day

Back Door to Area 51

What Really Happened to the Aliens

Going to the Stars

Visiting Other Star Systems

• Time problem– @ 10%c, 43 years to Alpha Centauri– @ 90%c, 4.8 years to Alpha Centauri– Missions need to be ultra reliable– Missions need to be totally autonomous

• Energy problem– @ 10%c, a 10-ton probe needs 1000 Mt– @ 90%c, a 10-ton probe needs 250,000 Mt

How Do We Get There?• Problem with rockets is just moving all that fuel• Solar Sail

– Very low acceleration using sunlight– Speed up using laser or microwave beams

• Orion Design– “How I learned to stop worrying and love The

Bomb”– Used in movie Deep Impact– Only known technology capable of accelerating

large masses to high speeds

Looking A Little Further Ahead

• Bussard Ramjet– Use large collector or magnetic fields to scoop

particles out of interstellar space– Use nuclear reactor to accelerate particles and

generate thrust– If we master fusion, we could use the particles

(mostly hydrogen) as fuel

Going There In Person

• Low speed = Low Energy = One-Way Trip• High speed = High Energy = Return Trip

(Nearby Stars Only)• Life Support

– Static Life Support Practical Only For Small Crew, Short Trip

– Hibernation or Suspended Animation?– Long Voyages Will Need To Be Self-Sustaining

Answer to Population Growth?• In 50 years we have sent less than 500

people into space (A few thousand counting multiple trips)

• In 50 years we have established zero extraterrestrial colonies

• Earth’s Population Growing at 250,000/day• That’s Madison today, Louisville tomorrow,

then Newark, Orlando, Tacoma…• …Just to keep up.

Time Dilation

• Requires speeds >50% c to be important• Makes a difference only to those on the trip• Might be useful in terms of making trips

within a human lifetime• Irrelevant to Earth

Life Support and Star Travel• Radiation Shielding

– Becomes critical at high speeds

• Food, Oxygen, Water– Recycle biologically– Biosphere II Experience– Not as Easy as Often Envisioned– Inevitable Losses– Needs to be almost perfect

• Energy

The Psychological Factor

• Humans are Very Adaptable• How Big Does Crew Need to Be?• Intellectual Stimulation, Variety• How to Maintain Commitment?

OK, We’re Here. Now What?• Exploration versus Colonization• Exploration

– Can use Lander and Living Module– Medical and Biochemical Issues

• Colonization– Will Need Functional Shuttle System– Will Need Broad Range of Expertise– Will Need To Be Able to Make or Repair High

Technology

Terraforming• Eliminate Dangerous Organisms• Introduce Earth Organisms• Domesticate Local Organisms• Alter Biochemistry• Increase Water Supply• Increase Oxygen Supply• Eliminate Toxic Chemicals• Modify Greenhouse Effect• Moral Issues