In satisfaction with the laws of thermodynamics, black holes must have an increasing entropy whose increase more than compensates for the decrease in entropy carried by the object that was swallowed by the black hole. This means that even black holes do not satisfy the ideal concept of a black body. As the entropy of the black hole increases, its temperature also increases. This is because of the third law of thermodynamics, which states that entropy is temperature dependent. As the temperature increases, the black hole will emit black body radiation whose change in frequency is proportional to the change in temperature. This is also known as Hawking's radiation. It exists because of the laws of quantum mechanics, i.e. the Hisenberg's Uncertainty Principle and the Casimir Effect. It allows a very small probability for photon pairs to be created near the event horizon of the black hole and have high enough energy that allows one of the photons to escape the black hole's gravitational force. It's like the Coulomb barrier. We know that no particle can escape its strong force but due to quantum tunneling, we know they do. So, as the temperature of the black hole increases above room temperature, the frequency in the electromagnetic spectrum will approach the visible spectrum, whose wavelength is between 400nm to 700nm. The question is, why haven't we observed a black hole that can emit hawking radiation at those wavelengths? In fact, it is well hypothesized that black holes at its terminal evaporation stage will emit a gamma ray explosion as it goes through the electromagnetic spectrum. Also, the mass of the black hole decreases exponentially as energy is radiated, in accordance to the mass-energy equivalence of Albert Einstein (E=mc^2). Eventually radiation is free to radiate outwards with no gravitational resistance. According to Newtons' law of universal gravitation and Einstein's general relativity, force of gravity =(Gm1m2)/r^2. Also, the fact is that photons of energy contains no mass which theoretically makes them virtually immune to the effects of gravity (although in practice, Einstein did prove that light can bend a little due to gravitation).

I searched elsewhere on the internet on "why black holes can't be observed" and most of them either do not know the existence of hawking radiation or they just state the lame excuse that quantum mechanics breaks down under strong gravitational fields (that leads nowhere towards research). I might have to wait until the string theory is established so that my question is well answered. In the meantime, I'm going to do more linear algebra and partial differential equations with quantum mechanics.....

P.S. If you've read everything this far, you'd understand that the average Joe barely understands what a black hole is.

hmm... well I guess that the reason why we can't see / observe a black hole is because, well no light escape from it... and we see stuff by the light that is reflected off an objects... and since no light escape from a black hole... we can't see any of the light that is suppose to relfect off it, because, well it just get suck in...

Lol I don't know lol, I really hate math and science... I mean for god sake I am in Math 101 right now... and is the only Asian in that class.

Ok, I'll just repeat it here in one sentence. The Casimir effect and the Hisenberg's Uncertainty Principle of quantum mechanics allows photons of electromagnetic radiation known as hawking radiation to escape the black hole. Thus, light can theoretically escape the black hole but to date, none are in the visible spectrum. So the question is why none of the black holes have emitted visible electromagnetic spectrum of light yet.

If you ignore quantum mechanics then yes, light can't escape. But quantum mechanics is reality so it's a myth that electromagnetic radiation can't escape black holes.


Edit: I know it's strange that particles can arise from a vacuum but this is quantum mechanics. Think of it as the generation of a particle and an antiparticle. However, when these particles combine, a photon is created. A lot of physics students still have difficulty trying to understand this concept but the world of quantum physics is strange. But these laws have been proven.


Solved. This has been posted on other forums simultaneously and it turns out that it is indeed possible for black holes to emit visible light. It's just that these black holes has to fall between specific masses. Anyway, I have lost nothing by posting this here. I hope everyone can see the truth for themselves.

Hey it has been many years since I touch any of these stuffs, thus to really to do those calculations (to really "understand" it) one need a solid understanding of QFT/Particle physics/GR. There is around PhD level which is way beyond my own understanding. My understanding of QM stopped at around the Dirac equation.

Find some interesting links:

How come x-rays can escape from a black hole when visible light can not?

Black holes and Hawking radiation

Hawking Radiation not limited to BHs?, if due to gravitational tidal force

^ Thanks for the links. The first link had the answerer avoiding the black hole evaporation concept though so that's a disappointment.
Anyway, University of Colorado has something interesting to say as well:



P.S. It is this webpage that I've previously looked at which states the specific masses the black hole has to fall between to emit visible light: http://library.thinkquest.org/C007571/english/printcore.htm
So it's theoretically possible after all. We just need to find primordial black holes.

What happens to a human in a black hole?

^ Its mass gets recycled into radiated energy, calculated using E=mc^2, where m is the mass [kg] and c is the speed of light [m/s].


Actually, I'm having new thoughts that reinforces this phenomenon of black holes emitting visible light. Because of gravitational lensing that arose from Einstein's general theory of relativity and the time-dilation effects of Einstein's special theory relativity, black holes of bigger masses can still emit visible light due to the blue-shifts that occur as electromagnetic radiation escapes a black hole's event horizon.

^ What then happens to the radiated energy...

* Hey this may have nothing to do with black hole, but this is an interesting observation I just felt electricity, not a large jolt but a small one but very painful. I was charging my ipod by putting it into the ipod speaker dock, and touched my i Pod and felt a very sharpm painful but small shock. Anyone know how ths happen?

^ Static electricity, perhaps?

The radiated energy just perpetuates and expands through space. There's something called CMBR (Cosmic Microwave Background Radiation) that should interest you. Some energy are so small that they form the cosmological constant for vacuum energy. This is also known as dark energy.

^ I think that if a person enters into a black hole they either survive somehow or don't. Survive as in something weird, that happens to them and change them or soething - sounds a bit fantasy but I think they would be alive in some consciousness or something...? Maybe?

Edit 1: I don't know, but I jsut heard that the black hole can work as a worm hole or something so thats what I mean... but nevermind.

^ Ok, let's be realistic. A human in outer space without any form of protection will die instantly from the harsh gamma radiation that bombards the Earth's atmosphere each day. So, unless you're in some futuristic spaceship, you're not going to survive in outer space, in a black hole or not. Now, the wormhole theory for a black hole can only happen if it bends the fabric of space-time deep enough. This means the black hole needs a very heavy mass. Of course, wormholes is a contestant for the most theoretical piece of concept in physics.