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re: (meteorobs) Zenith Attraction Quuestion
GWG,
In simple terms (good for me :->) it is the tendency for the
meteoroids path (and hence the meteor) to be affected by the earth's
gravity. Since the force of gravity is toward the center of the earth (@
appx 11 kps), the path will be shifted in that direction. For fast meteors
(remember max is about 72 kps), the effect is nearly negligable, since it
is overwhelmed by the velocity of the stream relative to the earth. However
for slower meteors, it becomes more signifigant, since the meteoroid's
original speed is comparable to gravity. So with the path becoming more
vertical relative to the earth's surface, it appears closer to the radiant.
That's the simple version.
If you'd like to go a little deeper, let me know, and I can give a few
more details to anyone who is interestd. There's a nice explanation in the
IMO Handbook.
Wayne