Comments on: Understanding Black Holes http://www.environmentalgraffiti.com/sciencetech/understanding-black-holes-universe/6800 for environmentalists who don't take themselves too seriously Tue, 24 Nov 2009 17:42:29 +0000 http://wordpress.org/?v=2.8.4 hourly 1 By: Burt Jordaan http://www.environmentalgraffiti.com/sciencetech/understanding-black-holes-universe/6800/comment-page-1#comment-177004 Burt Jordaan Thu, 12 Mar 2009 04:36:22 +0000 http://www.environmentalgraffiti.com/?p=6800#comment-177004 Bennet wrote: "Black Holes are often said to be ‘powered’ by the dust and gas in their accretion disk. As this material crosses the event horizon and is drawn into the black hole, the immense gravitational field breaks matter down to elementary particles and atomic fragments. The search for black holes is often a search for the radiation emitted by this violent activity at the accretion disk boundary and event horizon." The article is very well interesting and written, but the fragment quoted above is a little misleading. Quasars are ‘powered’ by the dust and gas in their accretion disks, but not by "material [that] crosses the event horizon and is drawn into the black hole" and also not quite by breaking matter down to elementary particles and atomic fragments. The source of the immense radiation is more mundane: simple compression and friction between molecules in the accretion disk heat them to extreme temperatures where they emit high-energy radiation. This also robs the material from mechanical orbital energy, causing them to spiral into the hole. The visible radiation happens before the material crosses the event horizon; otherwise none of it can escape for us to observe. Bennet wrote: “Black Holes are often said to be ‘powered’ by the dust and gas in their accretion disk. As this material crosses the event horizon and is drawn into the black hole, the immense gravitational field breaks matter down to elementary particles and atomic fragments. The search for black holes is often a search for the radiation emitted by this violent activity at the accretion disk boundary and event horizon.”

The article is very well interesting and written, but the fragment quoted above is a little misleading. Quasars are ‘powered’ by the dust and gas in their accretion disks, but not by “material [that] crosses the event horizon and is drawn into the black hole” and also not quite by breaking matter down to elementary particles and atomic fragments. The source of the immense radiation is more mundane: simple compression and friction between molecules in the accretion disk heat them to extreme temperatures where they emit high-energy radiation. This also robs the material from mechanical orbital energy, causing them to spiral into the hole. The visible radiation happens before the material crosses the event horizon; otherwise none of it can escape for us to observe.

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