in case you weren't terrified yet today . . .

[Alan Jackson]

On Wed, 10 Mar 2004 09:52:10 -0500
dep <dep at linuxandmain.com> wrote:

> quoth Kurt Wall:
> | In a 0.4K blaze of typing glory, dep wrote:
> | > http://www.techcentralstation.com/031004C.html
> |
> | Gah! It's always comforting to be proven wrong. :-)
> 
> there are some public policy questions here that the scifi movies never 
> get into, such as when/whether evacuations should be ordered -- if all 
> you know is that it's northern hemisphere, for instance, it makes good 
> sense to evacuate coastal areas, but woe be to the official that sends 
> the residents of new york city inland to the place where the asteroid 
> ends up hitting -- and how to deal with the inevitable false alarms. i 
> mean, in this case there was a body of evidence suggesting that an 
> asteroid would hit the earth within *days.* if anything was to be done, 
> it would have needed to be done almost instantly; fortunately, it 
> turned out the asteroid wasn't headed for us after all. despite our 
> nifty back-of-the-mind suppositions, we do not have megaton hydrogen 
> bombs sitting on saturn v rockets waiting to go change the course of an 
> approaching asteroid. (i actually discussed all this with no less a 
> person than edward teller about 15 years ago. he thought that any 
> defense system ought to include some way of pushing approaching rocks 
> out of the way. he was right. practically no one listened.)

I'm not sure a nuke would deflect a good-sized asteroid much. I haven't
put a pencil to it, but if you think about conservation of momentum...
astreoid moving at 25,000 mph, few hundred tons of mass (I know that 
isn't actually mass)... to deflect with a nuke you have to impart momentum
which means push mass in the opposite direction (the equal and opposite
reaction stuff). The mass the nuke accelerates is small, so the V has
to be really big... add the danger of fracturing the thing into dozens
of still dangerous asteroidettes... it needs *lots* of research. To even
begin to understand how to divert an asteroid, we need to land on one,
drill some coreholes, run some seismic. Are they solid? Are they fractured?
How hard could you push against one without it shattering? Would that be
a bad or a good thing?
(I was an astrophysicist in a previous life, now a geophysicist)


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