Asteroid impacts (was August 27, 2003 - Mars)

[How did this thread come to involve asteroid impacts? Never mind.]

In article ,
(Paul Schlyter) writes:
In addition, there are much greater dangers to our lives: the risk of
dying for some other reason is vastly larger than the risk of dying
from an impacting asteroid.

There's some information in the FAQ at
http://sciastro.astronomy.net/sci.astro.5.FAQ
but it is a little thin on collision frequency for different size
impactors. The standard comparison has been that your personal
chance of dying due to asteroid impact is about the same as your
chance of dying in a plane crash. As Paul wrote, this is a vastly
smaller risk than many other things, but society is still willing to
spend modest amounts of money to improve aircraft safety.

There have been some recent results that imply somewhat lower
asteroid impact frequencies than previously thought, but I don't know
how well accepted they are or what they imply for the overall risk.
Anybody care to research the facts and write a new section for the
FAQ?

Whenever there's an accurate prediction of an actual asteroid impact
several years or more into the future, I think it will be done.

This is my view, too. The FAQ has some references to possible
prevention methods.

It's like if you build a house in the US
midwest -- would you build it as a bunker so it could endure a tornado?

Houses in the midwest generally have tornado shelters to protect the
occupants, although it's true that few houses are built to withstand
tornadoes without damage. This contrasts with hurricane areas, where
many houses are built to withstand hurricanes with at most limited
damage. Likewise, new housing construction in earthquake zones in
the US takes seismic standards into account. As Paul says, it's a
matter of trading off frequency of occurrence and potential damage
against cost of countermeasures. Lead time is important too. When a
hurricane is predicted, people near the expected landfall rush out to
buy plywood, but they don't usually stockpile plywood beforehand.

With a modest search effort, we can expect several years to decades
warning before a significant asteroid impact. There is, however, no
guarantee. Even if a very thorough (and expensive) search is done,
there will still be non-zero risk from long-period comets.

--
Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA
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In article ,
Jonathan Silverlight wrote:

For most people the risk of dying in a plane crash is zero.

:-) ....no! The risk may be extremely small, but it's still larger
than zero for almost everyone on this planet: even if you never ever
ride an airplane in your whole life, you may still die from an
airplane crashing into your house (or wherever you may happen to be).
Yes, the risk is very small (almost all airplane crash victims are
passengers or crew of the crashed plane; apart from the terrorist
attacks on 11 Sept 2001 there have been few airplane crash victims on
the ground) but it's still slightly larger than zero.

Thus, to ensure that your risk of dying in an airplane crash really
is zero, you must, besides never riding an airplane, also settle down
somewhere above where airplanes never fly - today and in the future.
And you must also never travel to places above which airplanes do
fly. Few people live a life like that.

--
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