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Meteor velocities

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Author:  frank@sneezy.sri.com (Victor Frank) at smtp-fhu 
Date:    8/15/96 7:39 PM

     The question was asked, how fast is a meteor going (relative to the
earth) before it forms a trail, and (if it sufficiently massive) when it 
strikes the earth.

     The answer for the latter is almost the same as the former.
Unfortunately, sufficiently massive might result on extinguishing most
life on earth.

     If I've done my math correctly, a particle started off with no
orbital motion from the Oort belt would reach 42 km/sec by the time it
had reached the earth's orbit (and 618 km/sec by the time it had
reached the sun's surface).  The earth moves around the sun at about
29.85 km/sec.  In comparison to these, the radial velocity of a spot
on the surface of the earth relative to the center of 0.463 km/sec can
be neglected.

     The vector sum of 42 km/sec and 29.85 km/sec (at right angles) is
about 51.5 km/sec, which is probably a tad high for real solar system
particles which are orbiting the sun in the same counter-clockwise
direction (looking down from the north).  Thus most meteors will
probably approach at under 30 km/sec.

     Be thankful that most are completely ablated.  Their constituent
atoms may be kept aloft for a time, and while in the E-region may be
reponsible for some Sporadic-E; but eventually these atoms will settle
on the earth's surface.

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