Re: ET: Scientific American article on GHZ

From: Robert J. Bradbury (
Date: Wed Oct 03 2001 - 07:31:16 MDT

Daniel wrote:

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

It isn't in decay Daniel, the metalization of the galaxy is actually
a very good thing for advanced technological civilizations. You can't
build a heck of a lot out of H/He/Li. He dislocations in frozen H
as data storage cubes or perhaps monoatomic H in frozen He as a
rocket propellant are about the best things I can think of.

One of the reasons we may still see stars is because the could
perhaps be the best breeder reactors available at this time.

> Well, it is a bacteria. Bacteria overall are much hardier than most more
> complex organisms. This doesn't utterly refute your point, but what
> applies to bacteria shouldn't be extrapolated to higher life to readily.

>From what I understand of the Deinococcus radiodurans DNA repair
strategy it isn't that hard to copy it. They are much more tolerant
of double strand breaks (allowing hundreds per cell vs. humans 2-3),
then they are polyploidal and use homologous recombination to manage
the repair of the DSB (in contrast human cells undergo apoptosis in
an anti-cancer strategy). I suspect DNA repair strategies are tuned
by each species to balance the need to survive and reproduce with
the need to allow some evolution to occur. There could be a wide
variety of molecular foundations for life that are much more radiation
tolerant than our DNA based strategy is.

Rafal wrote:

> By the way, I wonder what are the limits to the resolution and
> light-gathering capacity of space-based telescopes. [snip]
> Maybe you could read the license plates on cars in the Alpha
> Centauri system ;-)

Rafal, I've done some calculations on this for my Matrioshka Brain
work (

Using 1% of the material available in our solar system (without
star-lifting) you can build 100 billion lunar diameter telescopes.
It would fill an area out to the orbit of Jupiter (which is why
occultation astronomy is a reasonable way to search for signs of
ATC -- such a large array would cause fairly frequent occultations
of the stars behind it). You can certainly see back to the beginning
of the universe and view planets around stars in your corner of the
galaxy and perhaps even nearby galaxies. More importantly you can
probably do almost real time monitoring of all the stars in your
galaxy. Feeding their orbital information into one very large chunk
of computronium allows you to do a many-many-body calculation for
the least expensive path (in terms of mass/energy expenditure required
to alter course) through the galaxy to avoid anticipated future

The point about avoiding radiation due to impacts on the magnetosphere
and possible loss of hydrogen does seem moderately important though.
However, it looks like there may be a lot of "water worlds" out there
and so one could argue that occasional magnetosphere disruptions could
actually be a good thing since the H loss would likely eventually bring
some of the ocean floor above sea level.


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