SETI: The Search for Extra-Terrestrial Intelligence

SETI, or the Search for Extraterrestrial Intelligence, is a scientific effort aiming to determine if there is intelligent life out in the universe.  There are many methods that SETI scientific teams use to search for extraterrestrial intelligence. Many of these search billions of radio frequencies that flood the universe, looking for another civilization that might be transmitting a radio signal. Other SETI teams search by looking for signals in pulses of light emanating from the stars.

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Enrico Fermi

Fermi's Paradox: Extra-Terrestrials - Where Are They?

The galaxy contains roughly a hundred billion stars. If even a very small fraction of these have planets which develop technological civilizations, there must be a very large number of such civilizations. If any of these civilizations produce cultures which colonize over interstellar distances, even at a small fraction of the speed of light, the galaxy should have been completely colonized in no more than a few million years [1]. Since the galaxy is billions of years old, Earth should have been visited and colonized long ago. The absence of any evidence for such visits is the Fermi paradox.

> Extra-Terrestrials: Where Are They? (Scientific American, July 2000)
> The Fermi Paradox: An Approach Based on Percolation Theory
> So Where Are They?
> SETI and the Fermi Paradox: Why our search for extraterrestrial intelligence has failed
> The Possibilities of FTL:Or Fermi's Paradox Reconsidered
> The Fermi Paradox - by Nick Bostrom
> The Fermi Paradox - by Chris Boyce
> An Overview of Proposed Solutions to the Fermi Paradox

Frank Drake

The Drake Equation

How can we estimate the number of technological civilizations that might exist among the stars? While working as a radio astronomer at the National Radio Astronomy Observatory in Green Bank, West Virginia, Dr. Frank Drake (now Chairman of the Board of Trustees of the SETI Institute) conceived an approach to bound the terms involved in estimating the number of technological civilizations that may exist in our galaxy. The Drake Equation, as it has come to be known, was first presented by Drake in 1961 and identifies specific factors thought to play a role in the development of such civilizations. Although there is no unique solution to this equation, it is a generally accepted tool used by the scientific community to examine these factors.

> The Drake Equation
> Science - Drake Equation Background Information
> The Drake Equation

The Chance of Finding Aliens
by Govert Schilling and Alan M. MacRobert

In 1961 the Drake Equation put the search for alien civilizations on a scientific footing and launched the modern SETI movement. How do its numbers look today? What is the chance of finding aliens? 

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The Drake Equation

N = R * · f p · n e · f l · f i · f c · L

Where,

N = The number of civilizations in The Milky Way Galaxy whose radio emissions are detectable.
R_* = The rate of formation of stars suitable for the development of intelligent life.
f _p = The fraction of those stars with planetary systems.
n _e = The number of planets, per solar system, with an environment suitable for life.
f_l = The fraction of suitable planets on which life actually appears.
f _i = The fraction of life bearing planets on which intelligent life emerges.
f _c = The fraction of civilizations that develop a technology that releases detectable signs of their existence into space.
L = The length of time such civilizations release detectable signals into space

Microbe Life on Mars

NASA has made a startling discovery that points to the possibility that a primitive form of microscopic life may have existed on Mars more than three billion years ago. The research is based on a sophisticated examination of an ancient Martian meteorite that landed on Earth some 13,000 years ago. The evidence is exciting, even compelling, but not conclusive. It is a discovery that demands further scientific investigation. NASA is ready to assist the process of rigorous scientific investigation and lively scientific debate that will follow this discovery. I want everyone to understand that we are not talking about 'little green men.' These are extremely small, single- cell structures that somewhat resemble bacteria on Earth. There is no evidence or suggestion that any higher life form ever existed on Mars.  -- Daniel Goldin, Administrator, NASA, 1996

> Life on Mars

Extra-Solar Planets

Alien worlds are a staple of science fiction but until just a few months ago, they had no place in science fact. Despite decades of earnest searches, astronomers had no direct evidence that planets circle other stars. Then last October, Michel Mayor and Didier Queloz of Geneva Observatory detected a planet circling the star 51 Pegasi--and the floodgates opened.

> Extrasolar Visions
> Scientific American - A Parade of New Planets

Space & Astronomy

Hubble Heritage Project
Images from the Hubble Space Telescope

The Hubble Space Telescope (HST) is a research tool dedicated to scientific studies of nature. Enroute to illuminating the forces shaping our cosmos, HST has accumulated a cosmic zoo. The Hubble Heritage Project sees this instrument also as a tool for extending human vision, one that is capable of building a bridge between the endeavors of scientists and the public. By emphasizing compelling HST images distilled from scientific data, we hope to pique curiosity about our astrophysical understanding of the universe we all inhabit.

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> Hubble Heritage Project Home Page

Interstellar Travel