Re: Comet impact in the Eastern United States - Feasibility of Evacuation

In article
<606fddac-d790-45bb-aed8-76aa6aae7404@[EMAIL PROTECTED]
>,
Matt Browne SFW  <matt.h.browne@[EMAIL PROTECTED]
> wrote:
>
>There is only one natural disaster that has the potential to destroy
>all life on Earth: a direct hit by a comet.

	Pft. The interval between impact caused sterilization events 
at this point in the solar system's history is much larger (by a factor
about two hundred) than the Sun's remaining time on the main sequence.
It is very unlikely that the Earth will be struck by a large enough
object in the next five billion years.

	In fact, even if we move the goal posts to mere mass extinctions, 
there's only one mass extinction that is thought to have been caused by
an impact and lots of large craters that are not associated with
extinctions 
at all. Your garden variety flood basalt seems to be worse for the 
environment and any cooling event that leads to a snowball or slushball
Earth would also be very bad. 

	Sterilization events that any half-way competent SF writer 
should know about include the Sun's progressive brightening, something
that should kick the Earth over into runaway greenhouse in the next
billion years or so, and gamma ray bursters, which in theory could
have much the same effect on the Earth as putting it in a (very large)
microwave oven. 
-- 
http://www.livejournal.com/users/james_nicoll
http://www.cafepress.com/jdnicoll
(For all your "The problem with
defending the English language [...]" T-****rt, cup and tote-bag needs)