จำนวน 6 ความเห็น, หน้า่ | -1-

ความเห็นเพิ่มเติมที่ 1 10 มิ.ย. 2550 (23:29)
How do black holes evaporate?
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This is a tough one. Back in the 1970's, Stephen Hawking came up with theoretical arguments showing that black holes are not really entirely black: due to quantum-mechanical effects, they emit radiation. The energy that produces the radiation comes from the mass of the black hole. Consequently, the black hole gradually shrinks. It turns out that the rate of radiation increases as the mass decreases, so the black hole continues to radiate more and more intensely and to shrink more and more rapidly until it presumably vanishes entirely.

Actually, nobody is really sure what happens at the last stages of black hole evaporation: some researchers think that a tiny, stable remnant is left behind. Our current theories simply aren't good enough to let us tell for sure one way or the other. As long as I'm disclaiming, let me add that the entire subject of black hole evaporation is extremely speculative. It involves figuring out how to perform quantum-mechanical (or rather quantum-field-theoretic) calculations in curved spacetime, which is a very difficult task, and which gives results that are essentially impossible to test with experiments. Physicists *think* that we have the correct theories to make predictions about black hole evaporation, but without experimental tests it's impossible to be sure.

Now why do black holes evaporate? Here's one way to look at it, which is only moderately inaccurate. (I don't think it's possible to do much better than this, unless you want to spend a few years learning about quantum field theory in curved space.) One of the consequences of the uncertainty principle of quantum mechanics is that it's possible for the law of energy conservation to be violated, but only for very short durations. The Universe is able to produce mass and energy out of nowhere, but only if that mass and energy disappear again very quickly. One particular way in which this strange phenomenon manifests itself goes by the name of vacuum fluctuations. Pairs consisting of a particle and antiparticle can appear out of nowhere, exist for a very short time, and then annihilate each other. Energy conservation is violated when the particles are created, but all of that energy is restored when they annihilate again. As weird as all of this sounds, we have actually confirmed experimentally that these vacuum fluctuations are real.

Now, suppose one of these vacuum fluctuations happens near the horizon of a black hole. It may happen that one of the two particles falls across the horizon, while the other one escapes. The one that escapes carries energy away from the black hole and may be detected by some observer far away. To that observer, it will look like the black hole has just emitted a particle. This process happens repeatedly, and the observer sees a continuous stream of radiation from the black hole.

Resource: http : // cosmology . berkeley . edu / Education / BHfaq . html.

It is really disturbing when I typed in a link to a certain website to make a reference. Vcharkarn system was just too aware as if I was spamming and symply didnt let my reply posted. Can anyone help me get out of this stupid problem?

One more thing, I really can't type in Thai. So, please translate this text if you are able to.

ความเห็นเพิ่มเติมที่ 2 23 มิ.ย. 2550 (02:00)
ดาวนิวตรอน ,bigbang ,เอกภพจักรวาล,แกลแลตคซี่,หลุมดำ วนรอบละ 80,000 ล้านปี

ความเห็นเพิ่มเติมที่ 3 23 มิ.ย. 2550 (02:05)
ไดโนครองโลก 200 ล้านปี พึ่งมีมนุษย์แบบลิงๆ 5ล้านปี แบบคนๆ 100000ปี พึงฉลองเครื่องบิน100ปี

ความเห็นเพิ่มเติมที่ 4 23 มิ.ย. 2550 (21:59)
จุดจบน่าจะเป็นการยุบลงไปด้วยแรงโน้มถ่วงของมันเองด้วยแรงมหาศาล (คาดการณ์)

ความเห็นเพิ่มเติมที่ 5 18 มี.ค. 2551 (20:53)
Nice site!

ความเห็นเพิ่มเติมที่ 6 20 พ.ค. 2551 (21:18)
55+