[meteorite-list] Asteroid warning, future impact, and panic
From: Sterling K. Webb <kelly_at_meteoritecentral.com>
Date: Thu Apr 22 10:31:29 2004
What you've got to remember is that even the most sophisticated computer modeling is, at heart, just highly refined
guesswork! Not only do we not have actual experience with impacts, if one actually happened tomorrow, there would be
nobody on hand to observe it scientifically, take measurements of pressure waves, etc.
We guess by scaling up from observed nuclear events and scaling down from inferences drawn from the remains of great
impacts of the past. Another data deficiency is a fortunate one: our atmosphere screens us from the smaller objects. By
smaller, I mean up to big H-bomb size. The Defense Department detects a number of Hiroshima-sized events in the atmosphere
and every few years an H-bomb-sized event, all of which our atmosphere prevents us from observing more closely!
Volcanoes like Krakatoa and Tamboru provide models for the effect of dust in the atmosphere, but they are not a
perfect match for impact debris, which is finer grained and boosted into the atmosphere more energetically than volcanic
ash and dust.
So it's all ballparking, matching the scales of various effects.
If you're going to be practical about the danger of impacts, you have to acknowledge that smallish and medium impacts
are statistically much more likely to happen than large and very large ones. Moreover, there's lots we can do to deal with
medium ones and very little we can do about large ones.
True, the big ones make better movies (sometimes) and more entertaining novels, but the 100 megaton event is ten times
more likely than the 1000 megaton event, and the 1000 megaton event is ten times more likely than the 10,000 megaton
As for warning us ordinary folk about potential impacts, a friend of mine to whom I told the story of the warning
dilemma that has been discussed here on the List, replied, "Sure glad we slept thru armageddon again. Nothing would annoy
me more than to have my last nite's sleep on earth disturbed by a bunch of sirens and [censored]heads running around!"
I regard the "panic" rationale that has become a cliché since the invention of nuclear weapons and the start of the
Cold War as a totally unsubstantiated assumption, prized by the U. S. government and widely promoted by media. I think
it's ridiculous that the government believes in the notion that when the populace is confronted by a serious event, they
respond by squawking like chickens and throwing themselves off tall buildings.
It was the belief in "panic" in the population that led the U. S. government to bury a small-city-sized bomb shelter
in the Virginia hills so that bureaucrats from the IRS, the post office, and other government departments could survive
total nuclear war and then return to the surface of the Earth in their grey suits to collect taxes from, and deliver mail
to, the scarred, starving, and mutated survivors.
The notion of "panic" as the most likely public response to trouble can be traced to the 1938 "War Of The Worlds"
broadcast, of course, and the notion has been popular with U. S. authorities ever since, as always desirous of protecting
us from ourselves. Strange, then, that the U. S. populace has managed to deal with everything from World War II to 9-11
without a lot of panic.
In all probability, it is the government's fear of causing "panic" that forces the Office of Homeland Security to
present itself to the public in a manner that has most people regarding it more as a Clown Bureau than anything to be
taken seriously (unless, of course, they really are just clowns).
So, until the Martians land in New Jersey with their Heat Rays, let's not worry first about "panic" amongst the
Sterling K. Webb
> Arbitrarily, obvious math, estimated, little difference, safe to assume, I suspect, I think, etc. Thats enough please.
> Bill Kieskowski
> > 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.
Received on Sat 28 Feb 2004 04:42:10 AM PST