Re: ET: Scientific American article on GHZ

From: Technotranscendence (
Date: Mon Oct 01 2001 - 23:37:23 MDT

On Monday, October 01, 2001 9:49 AM Hal wrote:
> A preprint of a technical presentation on the same topic is at
> We discussed this some time
> ago I think but I have not read it recently.

Thanks for the URL!

It has been discussed before, of course, and I think it will be again.:)

> "One of the arguments proposed to avoid that conclusion [i.e. that
> extraterrestrial life should have been here already] is that ETs may
> have no motivation to leave their home world and scatter signs of their
> presence through space. But if our ideas about the GHZ are correct,
> we live within an especially comfortable region of the Milky Way.
> Any civilization seeking a new world would, no doubt, place our solar
> system on their home-shopping list. The GHZ theory also weakens the
> argument that the galaxy is so big that interstellar explorers or
> colonizers have passed us by. The GHZ may be large, but it is just a
> part of the entire galaxy, and any galactic travelers would tend to roam
> around the annulus rather than haphazardly through the galaxy."
> The explanatory power claimed for the GHZ with respect to the Paradox
> is that it reduces the time frame in which life could have evolved.
> Until the last few billion years the galaxy was supposedly much more
> dangerous, with supernovas and an active nucleus. Plus our Sun is
> about 40 percent richer in heavy elements than most other stars formed
> in the same place and time, making it more likely to develop a variety
> of planets. This suggests that the Solar System may be near-optimal
> for the first development of complex life in the galaxy.

Very true. If they are right, then not only do we have to worry about
places suitable for complex and intelligent life to evolve have to exist,
but these might only exist for a short time.

It makes it all the more important for us not to mess things up here and
now. (Not like any of us here is trying to...)

Kind of reminds me of Olaf Stapeldon's _Star Maker_, where by the time a
supercivilization is created, the universe is already in decay.


Daniel Ust
    "Macroeconomics for the Real World" is now online at:

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