# I Conservation of Information and indeterminism?

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1. Jan 17, 2017

### AlexSH

I just recently learned about Leonard Susskind's work on conservation of information.
From what I've read and from his lectures, conservation of information and the holographic principle are based on the reversibility of physical laws. Reversibility in turn implies determinism, so if conservation of information holds, then the universe is deterministic.

But isn't the fact that the universe is not deterministic one of the big discoveries of the 20th century?

What am I missing here? How is conservation of information compatible with indeterminism? Or is it that Susskind and other's results regarding conservation of information brought back determinism and refuted indeterminism?

2. Jan 17, 2017

### phinds

The Heisenberg Uncertainty Principle rules out determinism. As for the rest, I can't bring myself to believe in the holographic principle (although I certainly do believe that Susskind knows more physics than I ever will) so I'll leave that part to others.

3. Jan 17, 2017

### mathman

We know the past, but we cannot predict the future.

4. Jan 17, 2017

### Pleonasm

No it does not. The Heisenberg Uncertainty Principle has no bearing on whether the universe is deterministic in a unfolding sense, irrespective of our observations.

5. Jan 17, 2017

### Pleonasm

No. QM predicts better than any other theory, unambigiously, how the world will evolve in the future. It's just that it predicts it by rather exact probabilities, which is a paradox because probabilities and determinism were long held to be opposites of each other.

6. Jan 17, 2017

### AlexSH

Hmm - QM gives us probabilities of the most likely outcome, but it doesn't predict the outcome itself - it's still equivalent to some throw of the dice: more than one outcome is possible. But in a deterministic universe only one outcome is possible.

7. Jan 17, 2017

### Pleonasm

That is your inference. Let's take this by way of the dice analogy. You don't know how a dice will land after being thrown, but the universe does. Information is kept from you despite being fully worked out by the laws of physics.

8. Jan 17, 2017

### Pleonasm

There are several theories to why it doesn't predict exactly what will happen but the macroworld (that is to say Newtonian Mechanics) is fully deterministic, so it would be a state of total chaos if you actually believe that the universe hasn't made up it's mind on the micro level, since the micro and macro coexist.

Last edited: Jan 17, 2017
9. Jan 17, 2017

### Staff: Mentor

I too am a Susskind fan. If you watch his lecture series on Classical Physics, you'll see him explain why things aren't reversible even in classical physics and without quantum mechanics. Here is the first lecture. (By the way, the whole course is very entertaining and worth your time).

10. Jan 18, 2017

### AlexSH

Saying that the universe knows amounts to a hidden variable theory - weren't those pretty much disproved by Aspect's and subsequent confirmation of the violation of Bell's inequalities?

11. Jan 18, 2017

### phinds

HUH ??? What do our observations have to do with it? Any how do you get determinism when you can't predict where particles are?