[meteorite-list] Space.com's Top 5 Cosmic Myths - #4

From: Robert Verish <bolidechaser_at_meteoritecentral.com>
Date: Thu Apr 22 09:53:34 2004
Message-ID: <20021213212233.21249.qmail_at_web80302.mail.yahoo.com>

>From a Space.com article earlier this year:

<http://www.space.com/scienceastronomy/top5_myths_020903-4.html>

Top 5 Cosmic Myths (cont.)

Myth #4 - Meteors are heated by friction as they pass
through the atmosphere . . .


This one makes sense, which is why it's so pernicious.
But it's STILL WRONG.

Meteoroids are tiny bits of dust, rock, ice or metal
that have the unfortunate luck of having their orbits
intersect the Earth's. When they pass through our
atmosphere, they are heated so ferociously that they
glow (and at this point are called meteors), and are
visible for hundreds of miles.

However, it is not friction that heats them. Think of
it this way: a space shuttle's tiles are extremely
delicate; they crumble easily in your hand. If they
were heated by friction as the shuttle de-orbits and
enters the atmosphere at Mach 25, the tiles would
disintegrate. That's not a very good design
characteristic.

In reality, it isn't friction, but ram pressure that
heats the meteoroid. When a gas is compressed it gets
hot, like when a bicycle pump is vigorously used to
inflate a tire. A meteoroid, moving at 33,500 mph (15
kilometers a second) or more compresses the air in
front of it violently. The air itself gets very hot,
which is what heats the meteoroid. That's the fact,
not friction.

See Next Message for Myth #5: More on this Hot Topic



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Received on Fri 13 Dec 2002 04:22:33 PM PST