[meteorite-list] Large (future) impact

From: stan . <laser_maniac_at_meteoritecentral.com>
Date: Thu Apr 22 10:31:29 2004
Message-ID: <Law10-F5exx9CctGMPP0002d63a_at_hotmail.com>

While I agree that my number of '1000 years' was picked arbitrarily, to be
realistic, if we can not prepair hardened food production facilities within
the warning time avalible, it would matter little if the 'nuclear winter'
lasted for 1000 years or only a few years, as both numbers are well over the
elngth of time a human can go without food, even your average overweight
american! :)

Also, with regards to an impact that would cause long term effects in
comparison to prompt killoffs, keep in mind that the blast radius of an
explosion scales at the cube of the energy released, whereas the amount of
dust that gets kicked up into the air scales pretty linearly. So to point
out the obvious math, when you compare 2 impacts, one that causes a prompt
damage of radius 'x' to one that causes prompt damage of radius 2x, the
latter will eject 8 times as much material into the air. 3x you are at 27
times as much material, and so on. (this rule of thumb applies to nuclear
weapons and other 'conventional' explosions, as impact events liberate
energy during their entire trip through the atmosphere, the numbers may be a
little diffrent, but I'd say they are close enough for the purpose at hand).
To put that in perspective, an impact event that liberates 1000 times as
much energy (and hence dust into the atmosphere) as krakatoa would only have
a damage radius of about 250 miles (defined as the point where buildings,
trees, ect are knocked over) and a thermal burn radius of about 1000 miles,
but I suspect that number is a bit off, as the curvature of the earth would
come into play by then. Obviously there are many places where such an impact
could occur without killing any signifigant number of people (in the global
sense)


I think that it's safe to assume there are a large number of areas on the
planet where an impact could occur that would cause orders of magnitude more
climate altering dust to go into the atmosphere, than say krakatoa, without
killing off a large portion of the life on this planet.


>On the subject of the aftermath of a large impact -- specifically the
>duration of
>"nuclear winter", Stan wrote:
>
> > "In the event of a large impact, we would need to build an enclosure
>that
> > protects food crops from the environment, and provides an alternate
>source
> > of energy to the crops. Rice isn't going to grow if the sun is blacked
>out
>for
> > 1000 years because of a comet induced nuclear winter."
>
>An impact that doesn't kill everyone and everything within hours should not
>have effects lasting anywhere near that long. Months to a few years, I
>would
>guess, depending on the size and velocity of the impactor. It's a very
>difficult
>thing to estimate since the only contemporary, large energy releasing
>events
>we have to compare to are many orders of magnitude smaller in energy.
>Krakatoa's four explosions on August 27, 1883, for instance, are estimated
>to have released the energy equivalent of around 200 megatons of TNT. They
>gave us red sunsets for more than a year and lowered global temperatures as
>much as 1.2 C.

_________________________________________________________________
Stay informed on Election 2004 and the race to Super Tuesday.
http://special.msn.com/msn/election2004.armx
Received on Fri 27 Feb 2004 07:31:37 PM PST