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re: (meteorobs) Zenith Attraction Quuestion

Steve queried:
>I suppose that the mass of the meteroid also has something to do with its
>zenithal attraction..or have I forgotten my basic basic-physics stuff 
>already?

ACtually you did :-> It's one of those concepts that argues againts the 
common sense of life here on earth, but if you recall, the acceleration due 
to gravity is 32 ft/sec/sec (~11km/s/s). There is no mass term! This was 
demonsrated by Galileo (allegedly) in his dropping of balls from the 
leaning tower of Pisa, and even more emphatically by the Astronauts on the 
moon, who without all that nasty air actually dropped a feather, and 
something else (I forget what), which proceeded to fall at the same speed. 
So mass is not relevant until it hits the air; for all intents and purposes 
by the time a meteoroid hits air it's life is already over!
	From the IMO handbook, here are some #'s:(reprinted with hopeful 
permission of the IMO)

Vel of  Shwr    30     40     60   kps

Rad elev  20   2.5d   1.6d    0.7d
          30   2.1d   1.3d    0.6d
          40   1.7d   1.0d    0.4d
          60   1.0d   0.6d    0.3d

As you can see, the radiant's elevation is also a factor since, a radiant 
at the zenith can't have it's meteors attracted closer to the zenith. So 
the effect is greater at lower elevations. For those of us up north here, 
with a shower like the alpha-Capricornids (Vel 25 kps) and a consistantly 
low elevation, it might be more than 3 degrees. Sorry, I don't have the 
time now to do the calcs, but anyhow, you get the idea I hope.	
	I am not sure whether or not this factor is included in the radiant 
positions that the IMO gives; I suspect it is since they have tried to base 
them on "observed" locations by various means. The "theoretical" locations 
calculated from pure geocentric velocities would be different.
	And if you think it's hard to believe that physics can be right, when 
your common sense tells you otherwise, just stand next to a 747 and imagine 
that physics is what tells you that this huge heavy hunk of metal the size 
of a hotel is going to fly. Yeah, right....tell me another one :-)
	Hope you had fun twisting your brain up like I did trying to explain 
it !!! :->
	
	Wayne, who's going for an Aspirin now.....