Talk:Hawking radiation

Removed pending confirmation:

Recent observation of Black Holes has confirmed that they do emit radiation, for example a recent example showed that one Black Hole was emitting sound at 47 octaves below middle C.

I don't think so... I think this person is getting Hawking radiation confused with gravitational radiation -- Tim Starling 06:45, Sep 10, 2003 (UTC)

Let's see. Middle C is 278 hertz I think, so the 'sound' frequency would be 278/2⁴⁷ Hz, corresponding to a period of 16000 years. Nah...
—Herbee 14:04, 2004 Feb 25 (UTC)

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The area of a sphere is normally 4πr², but space near a black hole is curved so this probably needs a correction. What is the expression for the surface area of a Schwarzschild black hole's event horizon? This has bearing on my calculation of the power emitted in Hawking radiation.
—Herbee 22:13, 2004 Feb 24 (UTC)

It is 4πr² because the blackholes metric is spherically symmetric, and thus on the surface of the sphere we can treat it as though it were imbedded in euclidean geometry(so long as we do not refer to anything off the surface).

JeffBobFrank 04:31, 25 Feb 2004 (UTC)

I'm not buying that. A circle drawn on a sphere is also symmetric, but its circumference is certainly not 2πr.

—Herbee 13:52, 2004 Feb 25 (UTC)

The metric tensor of the sphere is not equivalent to that of a plane, even when we limit ourselves to the circle, and discard the components that lead out of the circle, whereas in this case distances are the same as long as the time component and the radial component(the only ones that changed from what it would be without the black hole) are 0. Since the sphere being considered is at constant time and distance from the black hole it does have the same surface area.

JeffBobFrank 19:49, 26 Feb 2004 (UTC)

Isn't the radial coordinate *defined* to be such that the area of a sphere at radius r is 4πr²?? -Lethe | Talk 10:37, May 4, 2005 (UTC)

Contents

1 Hawking cracks black hole paradox 1 Information paradox 2 Confirmed by observation? 3 First equation unclear

Hawking cracks black hole paradox

See http://www.newscientist.com/news/news.jsp?id=ns99996151

After nearly 30 years of arguing that a black hole destroys everything that falls into it, Stephen Hawking is saying he was wrong. It seems that black holes may after all allow information within them to escape.

Sombody who knows about this stuff can put it in the article. Walter 09:51, 16 Jul 2004 (UTC)

Information paradox

I've added a note to this article and Hawking's article explaining that the vaporization of particles at the event horizon has been called incorrect by Hawking. I've also noted that he will present new findings at the 17th International Conference on General Relativity and Gravitation in Dublin, Ireland in July 2004.

I'll try to update the article once Hawking has presented his findings.

Hawkings talk in Dublin was not to disprove Hawking radiation, but rather Information loss in evaporating black holes. Since information loss is not mentioned in this article (although it should be), nothing in this article was disprove by Hawking's Dublin talk, therefore I am removing your notice. -Lethe | Talk 21:46, Sep 17, 2004 (UTC)

Confirmed by observation?

One thing I think this article could use (I can't add it because I don't know anything about the subject) is to what extent this phenomenon has been confirmed by astronomers' observations, as opposed to being a theoretical prediction. The article kind of makes it sound like a theoretical prediction...?

First equation unclear

Could someone please consider cleaning up the following, which is totally unclear without following the link to Plank units:

"Tsub(h) = κ/2π,

... where G, c, ħ and k are all equal to 1..."

There are no G, c, ħ or k in the equation!

It is frustratingly unclear to have to follow the Natural Units link to understand the explanation for the equation

It's only frustratingly unclear if you have some perverse engineer's insistence on particular units. In natural units, all those constants are 1, which is why they do not appear in the equation. Many people (including me) think that this makes the equation more clear, not less clear. Here is what the equation says in words: the temperature is proportional to the surface gravity. The constant of proportionality is whatever combination of G, c and h it takes to turn temperature units into acceleration units (plus an additional 2π). What is that combination? Who cares!? Not I.

It is true that natural units can be somewhat confusing if you're not too familiar with them. But then again, so can a lot of things in physics. Maybe the equation would be easier for dilletantes if equations in theoretical physics were written in SI units. But this is tedious and does not conform to the actual practices of physicists. -Lethe | Talk 10:06, May 4, 2005 (UTC)