RE: Doomsday vs Diaspora

From: Robert J. Bradbury (bradbury@aeiveos.com)
Date: Fri Apr 25 2003 - 13:58:15 MDT

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    On Fri, 25 Apr 2003, Greg Jordan wrote:

    > Or, it could be that life is more common in the universe than dangerous
    > life, which could explain a biosphere being ignored for millions of
    > years.

    Our biosphere is pretty uninteresting to species that can construct
    anything constructable. Is an intelligent species developing around
    a star that happens to have a hot-giant in close orbit around their
    sun (if such species can develop in such a solar system) going to
    focus its attention on communicating with us or focus their attention
    on dismantling the gas giant?

    > Dangerous civilizations in our vicinity may be reactive rather
    > than proactive or predatory, waiting until threats appear or become
    > obvious to deal with them.

    There aren't any "threats" to a distributed replicated intelligence
    (like a Matrioshka Brain) except perhaps a black hole. The only
    weapon they would care about would be intertial weapons -- someone
    throwing a *lot* of matter at them. But it requires one *huge*
    amount of matter to deal with something that masses 10^25 to 10^27 kg
    and is distributed over a volume of space from 30 AU to 3 light years
    in diameter.

    Just like Angel -- you can't kill it.

    > Ah, worse than to be hated is to be ignored...

    They have better things to do. I just read Egan's "The Plank Dive"
    last night. Didn't understand much of the black hole stuff but
    thought the transmission of a human "entity" in an exabyte of
    information was great.

    Previously I had thought this would be impossible. An exabyte
    is 10^18 bytes which is a zettabit (10^21 bits). To even begin
    thinking about this one has to learn how to modulate a carrier
    of X-rays (10^18 Hz) to Gamma-rays (10^20 Hz) to carry a zettabit.
    That did not look like an easy task to do in a short period
    of time (SciFi authors get to ignore some of these more complicated
    details with a little hand-waving).

    But, if one used digital encoding of femtosecond (10^-15 sec) laser
    pulses (~10fs is about the best we can do now) *and* used an array
    of such lasers to send the pulses accurately synchronized with
    each other (because the setup takes much longer than the pulse),
    then it does appear that you could transmit an zettabit in less
    than a month -- using current technology it could take anywhere
    from 6-12 months.

    So if ETI are communicating they are likely doing it at high pulse
    rates (which almost all detectors we now use are unlikely to
    detect for say OSETI). In addition it seems possible, if not probable,
    that the frequencies may be high (UV to gamma) where we aren't
    currently listening. Finally, they aren't going to be sending
    these data streams at us -- all we will see is the spread of
    the lasers if we happen to be along the line of sight between
    them and someone they are sending the data to.

    Robert



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