Black holes.

[Agamemnus]

Sci-fi? :-?

I've modified the post above.

[marzecTM]

I've read some about "Hawking Radiation", which is supposedly the solution to this mess, but I have yet to see a real explanation as to how this radiation happens. All the explanations I've read indicate some hocus-pocus method that just "happens" to solve the contradiction, i.e. a "virtual pair":

so virtual particle pairs are hocus pocus but quantum tunneling which our entire modern technology is based on is no hocus pocus? i'd say physics in general are hocus pocus, used hocus pocus, but still hocus pocus.

see kids that's what happens if you read stephan's book...

[Agamemnus]

From what I understand of the virtual particle solution to the black hole entropy question, it's like saying that rain falls because there's some "thing" that causes rain in the atmosphere. Doesn't explain anything at all.

[marzecTM]

to my limited understand the theory goes like: vacuum is not vacuum but fluctuating field of different forces ( 4 general forces ). due to heisenberg uncertainty principle you can't have a field to have clearly defined properties ( normaly people are told that you can not determine the velocity and position of a particle at the same time without falsifying one of them, the same applies to fields which have other properties ). thus there have to be "quantum fluctuations" which can be thought of as matter anti matter pairs aka virtual particle pairs which are created out of nothing and anihilate again, their lifespan is very short of course. given the gravitational pull of a blackhole there's a possibility to split that pair up. one of the particles falls into the black hole, the other one continues to exist due to not having a partner to anihilate with. thus it looks as if the black hole radiates, also the particle is no longer virtual ( meaning not really existing but only a mathematical imbalance to guarantee that the heisenberg uncertainty principle is also valid in "vacuum" ) and becomes real thus adding mass/energy to the universe and by this increasing it's entropy. case solved move on...

i still don't understand why this is hocus pocus but stuff like quantum tunneling ( which basically results from the fact that a particle can be anywhere, really anywhere just that the probability is very low that it is "there" but it can still happen ) is not.

[Sterling Christensen]

Incorrect. The second law states that the entropy of an isolated system must increase over time. Black holes aren't isolated, as they keep on receiving matter and energy.

You don't know what you are talking about.

Yes, he does.

You can't take a black hole, call it an isolated system, and then say that some other new matter magically pops into the system and falls into the black hole. That's not an isolated system. An isolated system consists of whatever it's defined to contains and nothing else - just an empty universe around it. I.e. nothing else around the black hole to fall in.

For it to work, the matter/energy that's going to fall in has to be counted as part of the system all along. You can't discount it's contribution to the system's entropy before it has fallen in.

You didn't exactly make yourself clear, so I'm not sure if this is what you're doing, but Radical Raccoon made a valid point.

[Agamemnus]

When I refer to two objects, the black hole and the light beam, you cannot assume that something new falls in. When/if it does, that new system does not automatically cancel out what happened before it!

[Radical Raccoon]

When I refer to two objects, the black hole and the light beam, you cannot assume that something new falls in. When/if it does, that new system does not automatically cancel out what happened before it!

We can assume, because you didn't specify that it was only the beam of light and a black hole in an isolated system.

However, I still don't see how you come to the conclusion that it breaks the second law. Why must something exit? If light enters a black hole, then it just enters the black hole and gets trapped in there for all eternity not able to perform anymore work, therefore increasing the entropy of the isolated system. End of story. Right?

[Agamemnus]

Yes I did mention that... I said it in the second paragraph. :-\

As for your second objection, you could possibly consider the gravitational attraction of the black hole as "work"...

[Radical Raccoon]

Yes I did mention that... I said it in the second paragraph. :-\

Sorry about that. There were a couple of us who didn't catch that.

As for your second objection, you could possibly consider the gravitational attraction of the black hole as "work"...

I'm starting to see what you mean now...I think. So if a black hole has a constant size all the time, then it always performs the same amount of work which never increases the entropy?

[Agamemnus]

So if a black hole has a constant size all the time, then it always performs the same amount of work which never increases the entropy?

Yeah, well I guess this is why Hawking Radiation and black hole evaporation exists, which I realized after I posted the first post. It's just very very typical of how things work. When I actually read & watched (about) both these things and it seemed just hocus pocus to me because the reason for these effects was never actually mentioned.

On the same line of thinking I can accept that these things (Hawking Radiation and/or black hole decay) exist, but I now need to figure out the reasoning behind it existing the way people (esp. Hawking) describe it. In my example, one particle either goes straight through or back out, but it just seems that the basic assumptions of this accepted reality is almost never questioned.

It seems to me that all of physics is just a bunch of assumptions that people work off of and almost never properly explain. When they do explain, it becomes something like Einstein's theory of general relativity...

Edit: For instance, take Maxwell's demon. I heard about it a lot but today I read about it in detail. This character Maxwell described something that breaks the second law of entropy, but in his description of the "thing" that breaks it he neglected to figure out how this thing/demon actually functioned.

In other words, Maxwell imagines two containers, A and B, filled with the same gas at equal temperatures, placed next to each other. A little "demon" guards a trapdoor between the two containers, observing the molecules on both sides. When a faster-than-average molecule from A flies towards the trapdoor, the demon opens it, and the molecule will fly from A to B. Thus, the average speed of the molecules in B will have increased, while the molecules in A will have slowed down on average. However, since average molecular speed corresponds to temperature, the temperature in A will have decreased and in B will have increased; this is contrary to the second law of thermodynamics.

http://en.wikipedia.org/wiki/Maxwell%27s_demon