Hawking changes his mind about Black Holes

[Vader]

I don't know how many people are even interested in stuff like this, but I eat it up. To bad though that what he now believes makes the movie The Black Hole complete fiction. Not that it wasn't but at least it was based on a certain theory.



http://www.boston.com/dailynews/203/world/Renowned_physicist_changes_min:.shtml
_________________
Duct tape is like the force they both have a light side and a dark side and they bind the universe together.

[Legion]

I particularly liked this line

[extro...]

I'm still waiting for an intelligible explanation of what it's all about.

[Legion.]

When he said disappear he meant that the energy disappeared as well.

[kevinatilusa]

This may or may not be right, but I think what he's changed his mind about is what happens once matter is sucked into a black hole.

At one time it was thought that black holes just sucked everything in and let nothing at all back out. Therefore once something got put in the black hole you could never find anything out about it since the black hole would never let any information about it back out.

Hawking theorized a while back that in fact black holes DID emit radiation out on rare occasions. This occurs when particle/antiparticle pairs are spontaneously produced (which happens from time to time, in theory). Normally the pairs just annihilate each other immediately, but if one particle in a pair is inside the event horizon of the black hole and the other is outside, the one inside the event horizon could be sucked into the black hole and the other one escape. Nevertheless, what he believed would escape would just be generic radiation, and we still couldn't find out anything about things which fell inside the event horizon.

Now Hawking believes that this is false, i.e. that black holes emit radiation in some way which allows us to determine information about what fell in.

[Leptonn]

That's pretty much it.
I'm looking forward to the official paper. Does anyone know which journal will be carrying it?

[One Skunk Todd]

[Chuck]

Fun Facts about Black Holes

[Leptonn]

OST, you are right. But the antiparticle still becomes a real particle. It has mass, and it's flying away from the event horizon.

[Chuck]

Then why doesn't other particle also become real and add mass to the black hole?

We can't really trust Hawking any more anyway. If he can change his mind once he can do it again. By next week he might be claiming that black holes don't exist.

[Lepton]

Chuck, you have asked the correct question.
These particle-antiparticle pairs occur because space sort of "lends" enough energy for them to exist. But the space that lends the energy doesn't always have the energy to loan. So what we see, far outside the black hole, is either an electron or an anti-electron flying away from the event horizon. The energy debt is repaid by the black hole, since that is where most of the local energy is located.

In any case, this picture is just one of many to explain how black holes may leak. If you've studied quantum mechanics, you'll know about tunnelling - the probability wave associated with a particle can actually "leak" though a barrier. One such barrier is the event horizon of a black hole.

[One Skunk Todd]

[shadyforce]

Here's my understanding about black holes:

* They are super-dense clusters of matter.
* Because of their large mass, they have a huge gravitational pull.
* Therefore all nearby asteroids and such get sucked in.
* However, what distinguishes a black hole from any old lump of matter floating about in space is that it is black (ie. You get no light from it.).
* The reason for this is that the density is so great that light itself cannot leave.
* As a natural extension to this, neither can electro-magnetic radiation of any form, and if they can't get out, everything else is pretty screwed.
* So what happens is matter keeps piling up and piling up, completely unable to escape from it, and any energy that is created inside the black hole can't get out either.
* So the problem is not that matter/energy simply disappears, but it goes to a place where detection of matter/energy is impossible, because matter/energy can't leave.

But hey, I came up with that in 10 minutes so I think we better follow the guy who spent most of his life formulating his theory on black holes.

[Leptonn]

Shadyforce, your conception of what a black hole is makes conceptual sense. Unfortunately, there are some weird effects that go on when you factor in Quantum Mechanics. QM seems to say that the black hole should be "leaking" a tiny bit of matter. Just the tiniest bit.

The matter/energy is still there - we can feel it because of the gravity it has. We can detect black holes by looking at stars and stuff circling around what seems to be empty space.

If you are interested in the subject, the best book (imho) is A Brief History of Time by Dr. Hawking himself.

[Digit Ne]

Suddenly, I don't feel so bad about my destiny of doing horribly in Physics this year. I mean, even Hawking can't keep his story straight.

Something I've been trying to keep up on - I've seen a few articles - is the possibility of dark matter and dark energy. I have some books I want to check out - The Elegant Universe, by Brian Greene, and The Fabric of the Cosmos, by same. Could dark matter and/or dark energy be contributing factors in the confusing behavior of black holes?

[Lepton]

Not in the sense of what Hawking is talking about.

Dark matter and Dark energy are observational objects that exist because the universe doesn't look the way our theories say it should. In other words, there's no theory-based reason for it to exist.

Black holes, on the other hand, are almost entirely theoretical. There's virtually no experimental or observational evidence about them yet.

[tinman]

Hawking detected waves that radiate out of black holes and there called Hawkin Waves. New thing thats waht changeg his mind. An object going into a black hole will suffer spegetification, where in all elements will line up by there atomic weight Hyd He etc this would happen long before you went into hole. So youd be a few hundread miles taller. After you enter the black hole you will reach the point called the singularity. Of which no one yet can tell what happens at that point. Reason they found the Hawkin Waves was use of new radio sensor on satalite and scopes. Black holes are the vacume cleaners of the Galaxy and only get so big do job and go away.

tinman

thanks great topic

[Guest]

According to the BBC, strictly speaking Hawking has not really changed his mind. Apparently the prior statements attributed to him were not actually his opinions. His speaker box had in fact inadvertently picked up some interference from a passing taxicab.

[tinman]

Good post

Should probaly be studying additional data.....
Tinman

Thanks

[Leptonn]

I'm not sure what you are refering to, tinman. Gravity waves *should* exist, and haven't yet been detected absolutely-for-sure (although many are trying). Hawking radiation is thermodynamic radiation from a black hole that is characteristic of a black body.

[tinman]

[Lepton*]

Sorry, tinman, I would reply to your post but it looks like spam. If you'd repost, I will try to explain Hawking's calculation about the information non-loss of a black hole. I will also try to explain some other issues that are arising from your post.

[Bicho the Inhaler]

I don't know what tinman is on about, but I would sure love to hear more about this subject.

[raekuul]

Actually, the fact that Q.P. allows for such radiation to escape, which as I understand travels at the speed of light, means two things to me.

1) Light is only the fastest thing we can percieve.

2) Q.P. only works on a quantum level.

(Ah, but then again, I am the Daedalian Idiot)

[Lepton*]

tinman, since I haven't heard from you, I won't bother wasting deprecatory remarks on you. raekuul, you are in water which you cannot tread. Bicho, you are a smart guy, consider reading the paper (it's on the arXiv -> arxiv.org): no details of his calculations, but it seems that he did it in the context of some highly-theoretical assumptions.

[Bicho the Inhaler]

Here's the paper: http://arxiv.org/pdf/hep-th/0507171

I didn't understand most of the details, despite its brevity, so the following is probably substantially wrong; in any case, this is what I got from it.

Here's the problem: say some matter gets together and makes a black hole, and the black hole then radiates away completely, as discussed earlier in this thread. If the radiation from the black hole was completely random (i. e., independent of what went into it), then the information about what went in is now completely lost, gone from the universe. This is a problem for quantum theory, since the quantum-mechanical evolution of wave functions is theoretically reversible. So we should never be able to end up in a state (a. k. a. wave function) from which we can't tell where we started (unless the wave function collapses; I'm unsure of this, but can we just assume the wave functions don't collapse in the middle of our experiment?).

What Hawking is saying is that we can't know that the black hole ever existed (from afar), so the wave function at the end has contributions from the histories where the black hole was never formed. When you figure this into the calculation, apparently you find that information is preserved at the other end.

[raekuul]

My perception of what happens in a black hole is this.

1) non-tachyonic matter passes the event horizon (For my purposes, light is non-tachyonic matter) in one direction- towards the singularity.

2) The density of the singularity allows for gravitational acceleration that exceeds the speed of light, compressing the matter to the point of nonfunctonality, while the actual matter is preserved in the form that I am calling "Ultra-dark".

2a) Because of the natures of the event horizon and the singularity, nothing sent into the "Black Hole" can be retrieved unless it can surpass the speed of light and still have enough inertia to escape the event horizon. ^{Thus, the only way to discover what falls in is to fall in yourself, and that dosen't do anyone else any good.}

3) This superdense matter, according to S. Hawking's origional assumption (which was based on Quantum Physics), leaks a kind of radiation that, assuming statements 2 and 2a are correct, would have to be travelling above the speed of light and thus is undetectable outside of theory in order to be able to escape the gravitational pull of the "Black Hole".

3a)

[Bicho the Inhaler]

In my understanding, the radiation from a black hole doesn't travel faster than the speed of light, since it isn't escaping the gravity well of the black hole due to its speed. You can interpret it as "tunneling" through the event horizon of the black hole (in the same sense that a particle can tunnel through any apparent barrier in quantum mechanics), or alternatively, as a particle-antiparticle pair coming into existence near the event horizon of the black hole with one particle being sucked in and the other escaping.

[raekuul]

Okay, I have a couple of semi-related questions.

1) Relativity relies almost entirely on the "fact" that Light is the fastest thing in the universe, no if ands or buts end of story. But, what if Light is only the fastest thing we can see?

2) Quantum mechanics and "regular" physics differ, as I understand, because one is used for subatomic particles and the other is not. So why are we using quantum mechanics to explain the possible death of something so massive that light itself cannot escape it's pull?

also, see 2a of my previous post. I never assumed that the tachyonic matter retained enough inertia to keep going above light speed, I just said that it had the ability to surpass it.

[Lepton*]

raekuul:

[raekuul]

I have, but you'd still need to have a massive amount of acceleration initially in order to avoid being pulled back into the event horizon. Is this not fundamentally correct?

[Lepton*]

The photon that is escaping by getting a short-lived boost above the speed of light has to be near the event horizon already, since this boost will be very small. The acceleration doesn't have to be very large at all.

[raekuul]

[Jack_Ian]

[raekuul]

[ctrlaltdel*]

so qm says black holes must leak at least tiniest bit of something. particles. i guess. therefore information.

how do we know about black holes? its because they leak information. THEY want US to know them!

[CzarJ]

[Lepton*]

We know about black holes the same way that one usually knows about a car crash. Sirens, emergency vehicles, a big crowd... but usually never the actual car that crashed. Well, with black holes you technically *can't* see the car.

[raekuul]

Ehh, that's true.

But wait a second! We discover black holed by looking for grav distortions, not for Hawking Radiation.

[Jack_Ian]

I thought searching for X-Rays was the usual way.
X-Rays are the scream that matter makes as they are torn apart while being pulled into a black hole.