[Paleopsych] SW: On Communication with Extraterrestrials

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Astrobiology: On Communication with Extraterrestrials

    The following points are made by Woodruff T. Sullivan III (Nature 2004
    1) Although the Search for Extraterrestrial Intelligence (SETI) has
    yet to detect a signal, the efforts continue because so little of the
    possible parameter space has been searched so far. These projects have
    almost all followed the dominant paradigm --launched 45 years ago by
    Cocconi and Morrison(1) -- of using radio telescopes to look for signs
    of extraterrestrial life. This focus on electromagnetic waves
    (primarily at radio wavelengths, but also at optical ones) was based
    on various arguments for their efficiency as a means of interstellar
    communication. However, Rose and Wright(2) have made the case that if
    speedy delivery is not required, long messages are in fact more
    efficiently sent in the form of material objects -- effectively
    messages in a bottle. Although the suggestion itself is not new(3,4),
    it had never before been backed up by quantitative analysis.
    2) A fundamental problem in searching for extraterrestrial
    intelligence is to guess the communications set-up of the
    extraterrestrials who might be trying to contact us. In which
    direction should we look for their transmitter? At which frequencies?
    How might the message be coded? How often is it broadcast? (For this
    discussion I am assuming that the signals are intentional, setting
    aside the a priori equally likely possibility that the first signal
    found could be merely leakage arising from their normal activities.)
    Conventional wisdom holds that they would set up a beam of
    electromagnetic waves, just as we could do with, for example, the
    305-meter Arecibo radio telescope in Puerto Rico, Earth's most
    powerful radio transmitter, or a pulsed laser on the 10-meter Keck
    optical telescope in Hawaii. Rose and Wright(2) conclude, however,
    that the better choice would be to send packages laced with
    3) Unless the messages are short or the extraterrestrials are nearby,
    this "write" strategy requires less energy per bit of transmitted
    information than the "radiate" strategy does. Cone-shaped beams of
    radiation necessarily grow in size as they travel outwards, meaning
    that the great majority of the energy is wasted, even if some of it
    hits the intended target. A package, on the other hand, is not
    "diluted" as it travels across space, presuming that it's correctly
    aimed at its desired destination. For short messages, however,
    electromagnetic waves win out because of the overheads involved in
    launching, shielding and then decelerating a package, no matter how
    small it is. For a two-way conversation with extraterrestrials, the
    light-speed of electromagnetic waves is far superior.
    4) As an example of a large message, consider all of the written and
    electronic information now existing on Earth: it's estimated(5) to
    amount to about one exabyte (10^(18) bytes). Rose and Wright(2)
    calculate that, using scanning tunnelling microscopy, these bits could
    be inscribed (in nanometer squares) within one gram of material! But
    this precious package would still require a cocoon of 10,000 kilograms
    to accelerate it from our planet to a speed of 0.1% of the speed of
    light, protect it from radiation damage along a 10,000-light-year
    route, and then decelerate it upon arrival.
    1. Cocconi, G. & Morrison, P. Nature 184, 844-846 (1959)
    2. Rose, C. & Wright, G. Nature 431, 47-49 (2004)
    3. Bracewell, R. Nature 187, 670-671 (1960)
    4. Papagiannis, M. Q. J. R. Astron. Soc. 19, 277-281 (1978)
    5. Murphy, C. Atlantic 277, No. 5, 20-22 (1996)
    Nature http://www.nature.com/nature
    Related Material:
    The following points are made by J. Cohen and I. Stewart ((Nature 22
    Feb 01 409:1119):
    1) The authors point out that it is possible to imagine the existence
    of forms of life very different from those found on Earth, occupying
    habitats that are unsuitable for our kind of life. Some of those
    aliens might be technological, because technology is an autocatalytic
    process, and it follows that some aliens might possess technology well
    in advance of our own, including interstellar transportation. So much
    is clear, but this train of logic begs the obvious question of where
    these intelligent non-humanoid aliens might be.
    2) The authors point out that the subject area of this discussion is
    often called "astrobiology", although in science fiction circles
    (where the topic has arguably been thought through more carefully than
    it has been in academic circles) the term "xenobiology" is favored.
    The authors suggest the difference is significant: Astrobiology is a
    mixture of astronomy and biology, and the tendency is to assume that
    the field must be assembled from contemporary astronomy and biology;
    in contrast, xenobiology is the biology of the strange, and the name
    inevitably involves the idea of extending contemporary biology into
    new and alien realms.
    3) The authors ask: Upon what science should xenobiology be based? The
    authors suggest that the history of science indicates that any
    discussion of alien life will be misleading if it is based on the
    presumption that contemporary science is the ultimate in human
    understanding. Consider the position of science a century ago. We
    believed then that we inhabited a newtonian clockwork Universe with
    absolute space and absolute time; that time was independent of space;
    that both were of infinite extent; and that the Universe had always
    existed, always would exist, and was essentially static. We knew about
    the biological cell, but we had a strong feeling that life possessed
    properties that could not be reduced to conventional physics; we had
    barely begun to appreciate the role of natural selection in evolution;
    and we had no idea about genetics beyond mendelian numerical patterns.
    Our technology was equally primitive: cars were inferior to the horse,
    and there was no radio, television, computers, biotechnology or mobile
    phones. Space travel was the stuff of fantasy. If the past is any
    guide, then almost everything we now think we know will be
    substantially qualified or proven wrong within the next 25 years, let
    alone another century. Biology, in particular, will not persist in its
    current primitive form. At present, biology is at a stage roughly
    analogous to physics when Newton (1642-1727) discovered his law of
    gravity. "There is an awfully long way to go."
    4) The authors point out that evolution on Earth has been in progress
    for at least 3.8 billion years. "This is deep time --too deep for
    scenarios expressed in human terms to make much sense. A hundred years
    is the blink of an eye compared with the time that humans have existed
    on Earth. The lifespan of the human race is similarly short when
    compared with the time that life has existed on Earth. It is
    ridiculous to imagine that somehow, in a single century of human
    development, we have suddenly worked out the truth about life. After
    all, we do not really understand how a light switch works at a
    fundamental level, let alone a mitochondrion."
    Nature http://www.nature.com/nature
    Related Material:
    Notes by ScienceWeek:
    The conjured image is poignant: intelligent life sprinkled throughout
    our Galaxy, each sprinkle separated from the others by 1000 light
    years, each sprinkle searching for the others with radio transmitters
    and receivers, small robotic spacecraft sent beeping into empty space
    between the stars, the beeping like a faint bleating in the dark as
    the sprinkles search for each other. Of course, the conjured image may
    be wrong: there may be intelligent life dense in the Galaxy; or we may
    be alone. It does not matter. For the human species on this planet
    Earth, the quest is part of our destiny, part of what we do as a
    species, and it will go on as long as we remain civilized.
    J.C. Tarter and C.F. Chyba (SETI Institute, US) present a review of
    current and future efforts in the search for extraterrestrial
    intelligence, the authors making the following points:
    1) During the past 40 years, researchers have conducted searches for
    radio signals from an extraterrestrial technology, sent spacecraft to
    all but one of the planets in our Solar System, and expanded our
    knowledge of the conditions in which living systems can survive. The
    public perception is that we have looked extensively for signs of life
    elsewhere. But in reality, we have hardly begun to search. Assuming
    our current, comparatively robust space program continues, by 2050 we
    may finally know whether there is, or ever was, life elsewhere in our
    Solar System. At a minimum, we will have thoroughly explored the most
    likely candidates, a task not yet accomplished. We will have
    discovered whether life exists on Jupiter's moon Europa, or on Mars.
    And we will have undertaken the systematic exobiological exploration
    of planetary systems around other stars, seeking traces of life in the
    spectra of planetary atmospheres. These surveys will be complemented
    by expanded searches for intelligent signals.
    2) The authors point out that although the current language is that of
    a "search for extraterrestrial intelligence" (SETI), what is being
    sought is evidence of extraterrestrial technologies. Until now,
    researchers have concentrated on only one specific technology -- radio
    transmissions at wavelengths with weak natural backgrounds and little
    absorption. No verified evidence of a distant technology has been
    found, but the null result may have more to do with limitations in
    range and sensitivity than with actual lack of civilization. The most
    distant star probed directly is still less than 1 percent of the
    distance across our Galaxy.
    3) The authors conclude: "If by 2050 we have found no evidence of an
    extraterrestrial technology, it may be because technical intelligence
    almost never evolves, or because technical civilizations rapidly bring
    about their own destruction, or because we have not yet conducted an
    adequate search using the right strategy. If humankind is still here
    in 2050 and still capable of doing SETI searches, it will mean that
    our technology has not yet been our own undoing -- a hopeful sign for
    life generally. By then we may begin considering the active
    transmission of a signal for someone else to find, at which point we
    will have to tackle the difficult questions of who will speak for
    Earth and what they will say."
    Scientific American 1999 December

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