Date: Tue, 1 Jul 2008 02:29:11 -0400 (EDT)
From: dicconf <dicconf at radix.net>
To: WSFA members <WSFAlist at KeithLynch.net>
Subject: [WSFA] Re: Tunguska event centennial today
Reply-To: WSFA members <WSFAlist at KeithLynch.net>

On Tue, 1 Jul 2008, ronkean at juno.com wrote:
> -- <lees103 at verizon.net> wrote:
> *
>   Ron stated "something more or less like that happens on Earth with a
> frequency of about once per hundred years or so, on average."  Declassified
> Department of Defense satellite data shows that Earth takes a one megaton
> meteor strike in the upper atmosphere on the average of once every eight
> months.
> *
>
> Yes, I was aware of that when I wrote my reply, and I thought about
> mentioning it.  The Tunguska event was orders of magnitude larger than
> one megaton, according to what I have read, which is why it is said to
> be something that happens every hundred years or so, on average.  That,
> and the fact that the Tunguska object apparently exploded at just the
> right height to have a large effect over a large area.  If a rocky
> object of the same mass and velocity had simply slammed into the ground
> there, without exploding in the atmosphere, it would have been much less
> dramatic.
>
> At the other end of the size scale, hundreds of small objects must be
> hitting the Earth or its atmosphere every day, most of them too small
> to be noticed unless they happen to hit where and when someone is
> watching and/or nearby.

One experiment I've seen recommended for kids is to lay out a fresh
sheet of newsprint at night (dry and weighted down) and check what
has landed on it in the morning; a few will be meteorites. They
tell me that many thousands of very tiny meteorites reach the
earth every day.

=Tamar