From: Billy Brown (bbrown@conemsco.com)
Date: Thu Mar 11 1999 - 08:07:02 MST
David Blenkinsop wrote:
> I'll refer you here to http://www.kepler.arc.nasa.gov/nature.html, and
> the comment at the end of that page related to stellar flaring and the
need
> for life-promoting stars to be more massive than M-class on that account.
Well, since they don't cite any details its hard to know what their concern
is. I will say that NASA tends to be very conservative about that kind of
estimate - i.e. their criteria is closer to "would we want to live there"
than "could life exist". We really don't know much about how much radiation
resistance is possible in large organisms.
A solar flare would blanket the facing hemisphere of the planet with intense
radiation, which would kill most types of land life. You are correct in
assuming that a denser atmosphere provides better shielding, and would thus
allow land life to evolve under a more variable star than would otherwise be
the case. However, a few yards of water will provide better shielding than
even the densest atmosphere, so it is very hard for such events to kill off
sea life.
> These are the very points that interest me about a planetary situation
that
> would be much tougher to launch out of than our own. Right at the outset,
it
> would appear that regular bulk scale chemical rocket technology simply
could
> not do the trick of launching satellites to twice the orbital speed that
we
> require. Because of this, the ET's in that situation would miss out on the
> "dawn of the Space Age" as we've experienced it.
Ah, no. They would be limited to much smaller payloads (in proportion to
rocket size), which would mean you'd need 1980s technology to put up
Sputnik. Communication satellites would become practical with technology
only slightly more advanced than what we have now. From there the
progression would continue on in the same way - their launch costs remain
about an order of magnitude greater than ours, so their use of space at any
given time is much more limited than ours. When our launch costs fall to
$1,000/lb, theirs are $10,000/lb. When advanced technologies like laser
launch or nanotech construction give us $100/lb launch costs, they get
$1,000/lb. They aren't barred from space, they just need better technology
for any particular use.
> At the same time, if they take awhile developing nanotech and any related
> technologies that might be helpful, it's difficult to say for certain what
> other problems might come about as a result of missing that early
> opportunity. For instance, suppose that some of the ET's make use of
> technology to boost their own reproductive capacity....
So, if "A" goes wrong, then "B" might go wrong, which could lead to a purely
speculative problem "C", which under some conditions could combine with
problems "D" and "E", perhaps leading to problem "F"....
This is a long chain of speculative problems, most of which are suspect in
the first place. That's a fatal flaw for any attempt to explain the Great
Filter. If we say each of your steps happens in 99.99% of all cases (which
is far to generous), we still end up with a fairly modest number of races
actually being trapped this way.
It seems to me that you don't really appreciate the magnitude of the numbers
involved in this problem. That, or you implicitly assume that the most
advanced technology that anyone can ever invent is only slightly better than
what we currently have. Putting some numbers in, what you're suggesting is
that:
1) Virtually all advanced life (99.99999% or so) evolves on heavy worlds
orbiting dim stars. Earth is a freak of nature that can never occur under
any reasonable conditions.
2) No possible technology can ever make space launches from such a world
even reasonably cost effective.
3) If space launches are expensive, a technological civilization will never,
ever expand beyond its home planet. Not even over the course of hundreds of
millions of years. No matter what kind of social structure they have. No
matter what psychological drives they may have.
All three of these propositions seem extremely implausible to me.
Billy Brown, MCSE+I
bbrown@conemsco.com
This archive was generated by hypermail 2.1.5 : Fri Nov 01 2002 - 15:03:18 MST