Re: >H Re: The Great Filter

Michael Lorrey (
Tue, 18 Mar 1997 18:07:39 -0500 wrote:
> (Michael Lorrey) writes:
> > wrote:
> >> I would think that if such events are truly as common as this, the
> prognosis
> >> for long-term space colonization is poor. It would be very hard for a
> >> space-based civilization to sustain hundreds of years of hard radiation at
> >> such intensity that an atmosphere is insufficient shield. Even planetary
> >> based nanotech using civilizations would be very strained by such events.
> >That technicium levels in molybdenum deposits indicate the existence of
> >such gamma ray bursters in our own geological past (supposedly the late
> >cretaceous), or that our sun was once eight times as bright as it is now
> That's fascinating. Do you have a reference I could look at? Were there any
> other such events?
> >Once we've
> >expanded past the limit of possible extinction, then any such
> >catastrophe thereafter is simply a stumble in our march across the
> >skies.
> Depends on how fast we can expand, which isn't yet clear.

If the threat radius is 1000 light years on average, then the most
likely location for one that will threaten us is somewhere 870 light
years away. Given this, then its all a function of rate of expansion
versus time till dooms day. If the probability is once every 200 million
years, and the last one was 100 million years ago, then there's a 0.50%
chance of it being sometime in the next million years. Assuming this is
the case, then we could expand at a rate of 0.50% of light speed in all
directions (.005 C) and still have the ability to allow 50% of all of
humanity to escape destruction, assuming they are still human in a
million years. At faster rates of expansion, obviously, the percent of
humanity surviving goes up.
> >Besides this, I expect that technology will allow
> >the development of sheilding sufficient to protect any "Noah's Ark" type
> >preserves, possibly in the cores of asteroids or dead moons like our
> >own. Several hundred miles of solid rock in every direction should be
> >enough sheilding against anything two neutron stars can cook up from
> >several hundred light years away.
> Noah's Ark is a myth, remember.

Of course, simply a metaphor.

You can survive in a "Noah's Ark", but a
> civilization can't (nor an ecology). Complex civilizations need very large
> numbers of people to support them. And imagine the chaos created if a solar
> system-wide civilization discovered 99.9% of the population was going to die
> in the near future? I'd expect the fighting to destroy the Arks.

Given the vastness of space, it will hardly be like the evactuation of a
city. Even using salt mines would suffice for planetary protection,
while with space, there are plenty of comets to go around in the Kuiper
belts of most stars. Even at a slow rate of huma expansion, the
population density will still be less than one person per cubic AU or
even small fractions of that.


Michael Lorrey ------------------------------------------------------------ President Northstar Technologies Agent Inventor of the Lorrey Drive

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