liss@gramps.DEC (Frederick R. Liss DTN 237-3649) (10/22/85)
I posted this the other day. I don't think it got through the
gateway so I'll give it one more try.
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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
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Frederick R. Liss UUCP ...decvax!decwrl!dec-rhea!dec-gramps!liss
Digital Equipment Corp. ARPA liss%gramps.DEC@decwrl.ARPA
333 South St. Shrewsbury MA, 01545 Mail Stop SHR1-4/D21cmpbsdb@gitpyr.UUCP (Don Barry) (10/25/85)
In article <968@decwrl.UUCP>, liss@gramps.DEC (Frederick R. Liss DTN 237-3649) writes: > ....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 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.GTNET@gatech.CSNET Georgia Institute of Technology BITNET: CMPBSDB @ GITVM1 Atlanta, GA 30332 ARPA: cmpbsdb%gitpyr.GTNET%gatech.CSNET@csnet-relay.ARPA UUCP: ...!{akgua,allegra,amd,hplabs,ihnp4,seismo,ut-ngp}!gatech!gitpyr!cmpbsdb