Conservation of information law

[Kedas]

How to prove or disprove this 'law' if you can't calculate/determin the amount of information?

[timo]

I´m not sure what this law would be, actually. How do you define "information"? Is a particle decaying into two particles a gain of information?

[swansont]

How to prove or disprove this 'law' if you can't calculate/determin the amount of information?

 

There is no such law in physics. Even in information theory, I don't think there is such a law.

 

 

edit to add: In physics, all conservation laws stem from a symmetry (and vice-versa), by Noether's Theorems. What symmetry is present for conservation of information?

[timo]

Even in information theory, I don't think there is such a law.

I computer sciences, there is this thing called "Shannon entrophy" which gives a measure on the amount of information say in a file.

But it´s a few years since I last encountered this so I don´t know many details about it anymore.

[Kedas]

some articles about it

http://arxiv.org/PS_cache/gr-qc/pdf/0108/0108010.pdf

http://www.sciencenews.org/articles/20040925/bob9.asp

Drop a book through a black hole's outer edge, known as the event horizon, and, according to Einstein's theory of gravitation, it never gets out. The law of information conservation, however, would still hold. Although inaccessible, the information would be preserved.

Found some other but the fact that a lot of them contain 'intelligent design' isn't really a good sign that it's physics.

[swansont]

I computer sciences' date=' there is this thing called "Shannon entrophy" which gives a measure on the amount of information say in a file.

But it´s a few years since I last encountered this so I don´t know many details about it anymore.[/quote']

 

I think Shannon Entropy assumes that you have a bit that's either 0 or 1, and it needs to have a value to be information i.e. you stored data there, and if the bit changes, that information is lost.

 

Hoever, I think that's different from some configuration of an atom or molecule. I don't think you can inherently assume that a different configuration represents less information, just different information. "Information," of course, not having been well-defined, makes a lot of this moot. I think the bit about the black hole was "information about the matter," like what state it was in or something like that.

[MattC]

Perhaps I am misunderstanding your idea of conservation of information (as that could be interpreted a number of ways), but here's my two cents:

 

matter has a direction, velocity, mass, etc - various properties which can be considered "information." In normal space, this information is conserved - for instance, a baseball flying through the atmosphere contains "information" about where it came from, it's initial velocity, etc, down to the spin directions of all the electrons. Granted, we may not be able to access most of this information, due to the uncertainty principle, but it's there.

 

Some people have argued that when matter is sucked into a black hole, it is converted to some sort of informationless sludge, and since all matter presumably (or at least some matter) will end up in a black hole, information will be lost.

Steven Hawking recently suggested or decided (I don't recall the exact details, but if you're really interested a quick google will fill in the gaps) that information sucked into a black hole actually does retain the information, and perhaps that information is actually emitted by black holes (in the form of the matter or antimatter that escapes from the border of the event horizon, or in the form of the entire black hole, which may eventually evaporate completely as it leaches matter via the matter-antimatter processes on the edge of the (potentially shrinking?) event horizon.

 

If that is the case, then indeed all information is preserved, from the moment of "creation," however we define that, to the "end," if there is such a thing.

 

My understanding of this stuff is only in the abstract, and I have to take the word of experts like Hawking, and who knows how much of this I truly understand - it's one thing to read a book and maybe even be able to regurgitate some of it in a meaningful way, and it's another thing entirely to be able to grasp the mechanics of processes that occur on such vast or minute scales. If the human mind is even able to grasp these things at all, there is the question of whether or not I read it all right. I'm just an environmental scientist, after all, not a physicist. But I hope this helps to answer your question, or at least lead you down a path that might lead you to an answer.