Are We Alone?

Objective

1: The process of cosmic evolution as it is currently understood.

2: Evaluate the chances of finding life in the solar system.

3: The various probabilities used to estimate the number of advanced civilizations that might exist in our Galaxy.

4: Some of the techniques we might use to search for extraterrestrials and to communicate with them.

Cosmic Evolution

The collection of the seven major phases of the history of the universe, namely:

1: Particulate 2: Galactic 3: Stellar 4: Planetary 5: Chemical 6: Biological 7: Cultural, And Future Evolution

Characterization Of Living Organisms

1: Their ability to react to their environment

2: To grow by taking in nutrition from their surroundings.

3: To reproduce, passing along some of their own

characteristics to their offspring.

4: To evolve in response to a changing environment.

What do we need for life?• Water?

• Stable planetary orbits?

• Temperate conditions (not too hot or cold)?

• Not to be too near the center of the galaxy?

• Not to be too far out?

• A “Shield” like Jupiter?

• An iron core?

Assumption of Mediocrity

1: Life on earth depends on just a few basic molecules.

2: These basics molecules are common to all stars.

3: The law of science must apply to entire universe so, life must exist in other part of universe.

Miller-Urey Experiment(1953)

Miller-Urey Experiment(1953)

In this experiment they tried from (primordial soup) of water, methane, carbon dioxide, and ammonia by passing electrical discharge after few days they made Amino acid.

Amino Acids: Organic molecules which form the basis for building the proteins that direct metabolism in living creatures.

Drake Equation:Factoring the Unknown

Probability someone will eat a Big Mac for Lunch =

chance they will go to McDonalds

x

chance they will order a Big Mac

x

chance they will eat what they ordered

N = R* fp ne fl fi fe L

R* = rate at which solar type stars form (stars/year)

fp = fraction of stars which have planets

ne = fraction of planets per solar system suitable for life

fl = fraction of those planets upon which life arises

fi = fraction of those life forms which evolve intelligence

fe = fraction of those species which develop the technology to send signals into space

L = the average lifetime of those species

Searching for Intelligent Life

• Most likely extra-solar• If technologically intelligent life existed in our

solar system, we’d probably know it by now.

• Communication• We can’t visit, but maybe we can “phone”

• Talking to ETs takes a long time• 4 light years to Alpha Centuri• 8 years to get a reply• And that is the closest star

If they are talking, what do we look for?

Types of signals:

continuum(like blackbody)

Line (atomic transitions)

Narrow band (not found in nature)

At Which Wavelengths?

Other stars are in the plane of our galaxy

you are herethey are there

Use Radio wavelengths to penetrate galactic dust clouds

Aricebo

What can you do?

• Search for extraterrestrial life at home

• http://setiathome.ss1.berkeley.edu

• distributed computing

• Screensaver searches for alien signals