Open Questions: Extraterrestrial Intelligence

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Introduction

Where are they?

What are they?

Can we talk?

Search for extraterrestrial intelligence

Recommended references: Web sites

Recommended references: Magazine/journal articles

Recommended references: Books

Introduction

Life exists on Earth. We're pretty sure of that. Whether there is intelligent life on this planet is still an open question.

But let's assume, for the sake of discussion, that there are intelligent life forms on Earth. Once such life forms come to realize that the home planet is not unique and that there are at least some, and possibly very numerous other planets and possible habitats for life, then it's natural for them to ask three questions:

Does life exist elsewhere?
If so, does intelligent life exist elsewhere?
If there is intelligent life elsewhere, can we communicate with it?

What is "intelligent" life, anyway? As a working definition we might take it to mean a form of life that is capable of asking those questions. On this definition, then, there is "intelligent" life on Earth.

Another definition, however, would require of intelligent life the ability to communicate with other intelligent life. In this more restrictive sense (at least) the question of the existence of intelligent life on Earth is still open.

Naturally, then, most of the focus has been on the question of the existence of extraterrestrial intelligent life.

Now we come to an interesting paradox. On one hand, life in some form or other, however primitive, is a prerequisite for intelligent life. And intelligent life is probably a whole lot scarcer than life in any form. But on the other hand, with the current state of our technology, it might be easier to find signs of intelligent life before we find signs of any other (except perhaps within our own solar system). The reason, obviously, is that we would expect "intelligent" life to have sufficient technology, at least as advanced as ours, to be able to send out signals (deliberately or otherwise) that indicate it exists. Most likely, such signals would use a part of the electromagnetic spectrum, especially at what we call "radio" frequencies. But other parts of the spectrum, such as what we call "optical" might also, or instead, be used. Or perhaps even more exotic techniques, such as neutrino signals.

Where are they?

Let's not forget that our first question was whether any life at all exists elsewhere. It's easy to lose sight of that, because it may be easier to answer the following question as to whether intelligent life exists elsewhere. This is because, except for planets (and some of their satellites) in our own Solar System, it could be a rather long time before we are able to detect the existence of rudimentary life forms elsewhere. But intelligent life should be much easier to detect even at interstellar distances, even if we can't actually "communicate" with it.

Site indexes

Open Directory Project: Extraterrestrial Life: Categorized and annotated links. A version of this list is at Google, with entries sorted in "page rank" order. May also be found at Netscape.
Galaxy: SETI: Categorized site directory. Entries usually include descriptive annotations. More listings here.
SETI SuperStar Award Winning Websites: List of SETI Web sites that have been selected monthly since May 1999 for special merit by the SETI League.

Sites with general resources

Yahoo News Full Coverage: Search for Extraterrestrial Life: Links to recent news stories from various sources. Also includes links to sites dealing with the search for extraterrestrial life.
SETI Institute: "The SETI Institute serves as an institutional home for scientific and educational projects relevant to the nature, distribution, and prevalence of life in the universe." Site contents include news, bibliography, and general SETI information.
SETI@home: Cooperative distributed computing project to assist in the search for extraterrestrial intelligence.
Sky and Telescope's SETI Section: Contains news and background articles on SETI by varions contributors.
SETI Central: Articles and news related to SETI from a variety of sources. A WebSeed site.
The Planetary Society: SETI Page: General news and information on SETI, with emphasis on projects sponsored by The Planetary Society. Has good history and overview articles. There is also information on the Society's SETI Optical Telescope.
Jodrell Bank Observatory SETI Research: Pages that describe the Observatory's SETI research. They include a history of SETI, common questions and answers, and an explanation of the Drake equation.
The SETI League: Web site of an "international grass-roots organization dedicated to privatizing the electromagnetic Search for Extra-Terrestrial Intelligence." The site includes general information on the organization and SETI. There is an archive of publications, such as newsletters, journals, press releases, and photos. The organization also selects other SETI sites for a special award.
Princeton Optical SETI Project: "The Optical SETI (OSETI) project at Princeton University, working in collaboration with Harvard University, searches nearby stars in an effort to detect brief, high-powered laser pulses that might signify the existence of extraterrestrial life in other solar systems."

Surveys, overviews, tutorials

SETI: Article from Wikipedia. See also Drake equation, Fermi paradox.
SETI Institute/Space.com articles: A series of articles about SETI and (sometimes distantly) related subjects, published weekly since Nopvember 2000 by the SETI Institute and Space.com. The most relevant articles provide excellent information on astrobiology and SETI..
Astronomy - SETI: Explanation of Drake's equation.
Are We Alone?: Special feature story from ABC News.
The Search for Extraterrestrial Life: Part of the SEDS site. Contains overview information and external links.
The search for astroengineers: April 2008 article from Physics World, by Bruce Dorminey. "Having so far failed to find evidence for extraterrestrial civilizations by searching for their radio transmissions, some physicists think it is worth scouring the sky for signs of their astronomical construction work."
The Search for Extraterrestrial Intelligence: Extensive January 1997 article from Scientific American online, by Carl Sagan and Frank Drake. "There can be little doubt that civilizations more advanced than the earth's exist elsewhere in the universe. The probabilities involved in locating one of them call for a substantial effort."

Recommended references: Magazine/journal articles

Using Lasers to Detect E. T.
Steve Nadis
Astronomy, September 2002, pp. 44-49: There's no good reason an advanced extraterrestrial civilization would use radio frequencies to signal its presence instead of infrared or visible light. Within just the last few years searches have begun for such signals -- which might be generated by laser pulses that could be (briefly) a million times brighter than a star.
Where Are They?
Ian Crawford
Scientific American, July 2000, pp. 38-43: If advanced civilizations exist elsewhere in the galaxy, they should develop the ability so spread throughout the galaxy in only a few million years. As Enrico Fermi first noted, this means we should have seen more evidence of such civilizations than we have.
Is There Life Elsewhere in the Universe?
Jill C. Tarter; Christopher F. Chyba
Scientific American, December 1999, pp. 118-123: The dedicated search for signs of extraterrestrial life and intelligence has barely begun. But the search, by a variety of means, is due for rapid acceleration.
Are We Alone?
David J. Eicher
Astronomy, November 1999, pp. 60-63: Several researchers who have studied the issues involved in SETI discuss opinions, both optimistic and pessimistic, on the likelihood of discovering extraterrestrial intelligence.
Who's Out There?
Jeff Greenwald
Discover, April 1999, pp. 64-70: New techniques and technology continue to be deployed in the search for extraterrestial intelligence. One of the latest involves using home computers to process data.

Recommended references: Books

Stephen Webb – Where Is Everybody? Fifty Solutions to the Fermi Paradox and the Problem of Extraterrestrial Life
Copernicus Books, 2002: The title alludes to Fermi's question – if intelligent extraterrestrial life exists in our galaxy, why haven't they shown up yet in an obvious way? Webb considers 50 possible answers in three different categories. Along the way, he explains a lot of exobiology. Just so you know what you're getting with this book, Webb's own conclusion is that the conditions for life on Earth are so special that there are no intelligent extraterrestrials.

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