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Hermes
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Frederick R. Liss DTN 237-3649
Oct 22, 1985, 12:34:00 PM10/22/85
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I posted this the other day. I don't think it got through the
gateway so I'll give it one more try.
************************************************************
I've heard on the radio this morning that back in the 1930s an
asteroid, by the name of Hermes, almost collided with the
Earth. It only missed us by 500,000 miles, which in
astronomical terms is fairly small. The asteroid was large
enough to do considerable damage to the Earth. Can anyone
supply more information?
Fred
---
Frederick R. Liss UUCP ...decvax!decwrl!dec-rhea!dec-gramps!liss
Digital Equipment Corp. ARPA liss%gramp...@decwrl.ARPA
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Don Barry
Oct 24, 1985, 7:44:38 PM10/24/85
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In article <9...@decwrl.UUCP>, li...@gramps.DEC (Frederick R. Liss DTN 237-3649) writes:
> ....asteroid, by the name of Hermes, almost collided with the
not very unusual, either. Comet Lexell in the 1700's approached within
0.03 a.u. of the earth, and comets IRAS-Araki-Alcock and Sugano-Saigusa-Fujikawa
in 1983 approached at 0.033 and 0.06 a.u. respectively. Comet Biela in the
1800's, and Tempel-Tuttle, have approached within 2 million miles in the past,
as has Halley's comet several times in the past 2 millenia. Consider it this
way, however, and it doesn't seem so peculiar - define an cross section for
collision as the square area subtended by the earth to an oncoming projectile.
If you consider the cross section of a 500,000 mile disk, you'll find that
of random objects moving through this disk, only about one in 15,000 will
hit the earth. So 500,000 is a very comfortable distance. It can be
naively argued that the earth's gravitational attraction makes the chances of
collision much greater, but conservation of angular momentum offsets the
"vacuum cleaner" effect, and causes only a slightly modification to the
envelope figure of probabilities.
> ....asteroid, by the name of Hermes, almost collided with the
> Earth. It only missed us by 500,000 miles, which in
> astronomical terms is fairly small. The asteroid was large
> enough to do considerable damage to the Earth. Can anyone
> supply more information?
Actually, close approaches of this kind, while not terribly common, are> astronomical terms is fairly small. The asteroid was large
> enough to do considerable damage to the Earth. Can anyone
> supply more information?
not very unusual, either. Comet Lexell in the 1700's approached within
0.03 a.u. of the earth, and comets IRAS-Araki-Alcock and Sugano-Saigusa-Fujikawa
in 1983 approached at 0.033 and 0.06 a.u. respectively. Comet Biela in the
1800's, and Tempel-Tuttle, have approached within 2 million miles in the past,
as has Halley's comet several times in the past 2 millenia. Consider it this
way, however, and it doesn't seem so peculiar - define an cross section for
collision as the square area subtended by the earth to an oncoming projectile.
If you consider the cross section of a 500,000 mile disk, you'll find that
of random objects moving through this disk, only about one in 15,000 will
hit the earth. So 500,000 is a very comfortable distance. It can be
naively argued that the earth's gravitational attraction makes the chances of
collision much greater, but conservation of angular momentum offsets the
"vacuum cleaner" effect, and causes only a slightly modification to the
envelope figure of probabilities.
--
Don Barry (Chemistry Dept) CSnet: cmpbsdb%gitpyr...@gatech.CSNET
Georgia Institute of Technology BITNET: CMPBSDB @ GITVM1
Atlanta, GA 30332 ARPA: cmpbsdb%gitpyr.GTNET%gatech...@csnet-relay.ARPA
UUCP: ...!{akgua,allegra,amd,hplabs,ihnp4,seismo,ut-ngp}!gatech!gitpyr!cmpbsdb
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