Onefella

Could anybody clarify what is meant by 'lost information' with Hawking's Black-hole "Information Paradox"?

I grasp that a black-hole has a massive mass taking up no space, that basically obliterates any solid, or energy, particle that gets drawn in to it.

So, how is this 'lost information', and why is it considered against the laws of physics?

tagg

yes i saw that program, i too could not understand his new therory about dimension cancelling each out ??? if one dimension has no black hole no information is lost, this sounded like a cop out

Tagg

Onefella

Was he was trying to say that an alternative dimension would have black-hole information from our universe, or exactly like our universe? Also, how would it get there if there are no black holes?

I think I'm missing a few steps.

tagg

Well what i think he was saying there was multiple dimension some with black holes and some without , so to lose imformation all dimensions needed to have black holes, but seeing that some don't he is claiming that you can't lose it , like having a break in a chain or missing link there is no consitancy. it gave me a headach trying to work it out, unless he can prove there is more then one dimension his theroy is flawed. but seeing that i am not a physicst i could be wrong


Tagg

tytower

Dreamers think up these ideas of multiple dimensions ,initially to sell Sci-Fi books .Theorists on the Quantum Phyisics ferris wheel try to scam the public to believe they are wonderous geniuses.

There are four dimensions and thats it . Length ,breadth ,height and time .
x,y,z -the where and t -when.

If I look at that bird in your avatar will she grab the bra by mistake ? I can dream and theorise and maybe even calculate the probability but the unfortunate reality is she won't.

Onefella

Oh, ok.


Good, then you don't really need to discuss it anymore then do you?

tagg

Sorry bro but you are wrong in your thinking, i am not going to tell you either, you can think about your statment

Tagg

Onefella

Back on topic, by 'information', do physicists mean stuff we can observe and measure?

If he's saying a black hole radiates heat and therefore will eventually sublime away to nothing, isn't the heat the 'information'? Matter changes state all the time, why is it 'lost' because it joined with a black hole for near-eternity?

tagg

Quote
if the material entering the black hole were a pure quantum state, the transformation of that state into the mixed state of radiation would destroy information about the original quantum state. This violates Liouville's theorem and presents a physical paradox.

More precisely, if there is an entangled pure state, and one part of the entangled system is thrown into the black hole while keeping the other part outside, the result is a mixed state after the partial trace is taken over the interior of the black hole. But since everything within the interior of the black hole will hit the singularity within a fixed time, the part which is traced over partially might "disappear", never to appear again. Of course, it is not really known what goes on at singularities once quantum effects are taken into account, which is why this theory is conjectural and controversial.

The fact that information is lost is reflected in the thermal nature of the emitted radiation. But any thermal system can be assigned an entropy via the Gibbs law dE = S dT. Thus, we can calculate the black hole entropy by dint of the fact that we can calculate the black hole temperature (by dint of the fact that the quantum radiation is thermal). This is, I think, what people are getting at when they say that black hole entropy is responsible for the information loss. I would say it the other way, that black hole information loss is responsible for black hole entropy. The simple fact of the matter is that they are the same thing in slightly different terms

As you can see Onefella your are correct

Tagg

Onefella

Thanks for that quote tagg, I don't understand all of it, but it sounds like the jury is still out on whether black holes obliterate information or not.

I'm going to research it a bit more, it's got me intrigued.

trash

Tagg's description is a good example on a quantum level.
I can probably describe it a little simpler for mere mortals.

Information as we think of it is more like a universal memory.
A person dies, but you remember details about them. Grandpa was a short man with dark hair and a good sense of humor etc.

If matter falls into a black hole, does the universe remember what that matter was ?

An electron falls into a black hole, the mass of the black hole increases... so the information of that electron, it's mass, it's energy, it's charge, it's spin are all trapped inside the black hole.

Now, if we look carefully at Hawking Radiation at the Event Horizon, a positron and electron pair spontaniously occur, the positron falls into the black hole while the electron escapes. The black hole appears to emit the oringinal electron and any difference in energy from the orignal absorbed electron is made up in emitted X-radiation from the black hole itself and the black hole looses a little mass.
In that example, the information is preserved.

A more simple real world example is take a piece of paper, write a number on it, any number. Put the piece of paper into a bag. You then place another piece of paper with another number written on it. You repeat this exercise with as many pieces of paper the bag can hold.

The numbers written on the paper represent the information, the bag represents the black hole.

Now you take the pieces of paper out of the bag. If the numbers are the same numbers that you put in, then the information is preseved.
If however the numbers coming out are different (random) to the numbers you put in, then the information is lost.

Example. You put in..... 1,2,3,3,3,9,10,10,10,10
the numbers you put out are ..... 1,1,1,1,1,1,4,6,10,15,20

Though the same total value was placed into the bag/black hole and recovered, but the actual numbers and the amount of pieces of paper has changed, the information was lost.

Onefella is also right, the jury is still out, though it is suspected that the information is lost.

tagg

Very well put Trash, i am impressed, a nice simple explanation mate.

Tagg

biggeorge

I was once told to baffle 'em with bullshit and nobody can argue with you.

Maybe hawkings theory is just that ^^.


I watched that show as well, but my conclusion at the end was that a black hole might simply just accumulate SO much energy that it ends up at a critical point where it has to release some, as something. The centre of our / a galaxy springs to mind.

That bright spot in the centre is probably a critical mass black hole, releasing it's energy.

Energy has to go somewhere. Nothing disappears or goes to another dimension. It just changes form.

Onefella

Thanks for the explanation Trash. I think I've got a handle on it now, but it is nice to see a simple explanation to reinforce what I thought.

So Hawking maintained for a long time that perhaps the information never really joined with the singularity, but possibly was 'smeared' on it's surface. Now he says there could be other universes without black holes that retain the information. But surely they would be retaining the information from their own universe, not ours. Or is the alternate dimensions supposed to be identical to ours? (with the exception of black holes)

Another thing I don't understand is why black holes are believed to be quite hot. Wouldn't the intense gravity stop all sub-atomic movement thereby making it cold? - Still a newb at this I guess.

trash

Yes... that's how I handle it too.... "I think I've got a handle on it", but I'm never quite sure and I feel like I missed something.

Hot is a funny thing. To give another example, a chuck of Uranium I have is quite hot. The radiation that it emits has a very high temperature/energy level, but the material is cold to touch.
Though each particle is very hot, quantitively, they only have a very small amount of energy in the real world.

Like a piece of metal heated red hot, then dropped into a bucket of water.
You can't handle the hot metal, but you can stick your hand into the bucket of water and retrieve the metal. The water and the metal have the same combined energy as they did before the metal cooled down.

The energy emitted by the black hole (hawking radiation) is rather a secondary radiation. There are a few similar examples of secondary radiation that I can think of. Cherenkov Radiation is one, Bremsstrahlung (braking radiation) is another.
Bremsstrahlung is probably the main reason why we can see black holes.

psycho2000

The only radiation I am feeling now is the heat radiating from my head attempting to follow all this - owie!!!! ..........

I am so behind the ball in this area as my knowledge is about 15-20 years old and I feel like the metaphysical Neanderthal man being dropped in Time Square and attempting to rationalise everything going on around him........ but I will get there one rock at a time.....

trash

Your not alone. My head hurts too. But don't feel you're being left behind.
Just because the big end of town is churning lots of numbers, it takes a little time for the bigger picture to sink down to our level.
We see E=mc^2 .... but there is lots more to it and Einstein just didn't rock up and say, hey check out this simple little equation I invented.

Seriously psycho, There is an illistrated version of "A brief history of time." and there is "A briefer history of time" by Steven Hawking.
I loaned my copy and well, somebody liked it too much and didn't return it.
It's written for the man off the street and there is very little maths in it.
Most second hand bookshops have a couple of copies of the original book for like $3 etc.

psycho2000

Ta trash!!!

Thanks for the response - will have to start hunting in the second hand book shops....

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trash

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