Determinism re-explored

[PKJ]

If a super computer had the position and movement of every particle in the world (and infinite processing power), could it predict the future and trace back the past?

 

[Patzak]

Yeah, I wanted to ask the same question a while ago when reading the free will thread. If we discount random quantum effects (let's just say they do depend on a deterministic hidden variable, although this is by no means certain) I'm tempted to say yes.

However, there's a factor to its predictions which I find very problematic. If the supercomputer is to be a part of our universe, it would also have to include itself in its computations - the positions and movements of all particles involved in the computation of these same positions and movements.

I would try asking a somewhat analogous question that I think is a bit easier to imagine: if I could see the future and saw that I'm going to die in a certain car accident, what would I do? I'd do everything I could to avoid being there at the time it's supposed to happen, falsifying my own prediction. Any prediction about my own future would have had to include the effects of my knowledge of the prediction itself. I'm not sure this would neccessarily lead to the impossibility of predicting the future (I guess one could imagine a string of events that takes account of my knowledge and still unfolds exactly as predicted) - but it would surely narrow down the selection of possible futures. Any thoughts on this?

 

[David Gould]

Ignoring QM, I can see no reason why not.

Of course, if this universe was affected by things 'external' (whatever that might mean) to it then prediction would be a bit of a hit and miss affair.

 

[z3ro]

I would try asking a somewhat analogous question that I think is a bit easier to imagine: if I could see the future and saw that I'm going to die in a certain car accident, what would I do? I'd do everything I could to avoid being there at the time it's supposed to happen, falsifying my own prediction. Any prediction about my own future would have had to include the effects of my knowledge of the prediction itself. I'm not sure this would neccessarily lead to the impossibility of predicting the future (I guess one could imagine a string of events that takes account of my knowledge and still unfolds exactly as predicted) - but it would surely narrow down the selection of possible futures. Any thoughts on this?

But the knowledge could lead to the chain of events; like the movie minority report.

 

[Patzak]

But the knowledge could lead to the chain of events; like the movie minority report.

It could, of course. All the easier if your knowledge of the future is vague, like in Minority Report (all he knew was that he would kill the guy) or Oedipus or any other story of prophecy. But can you imagine perfect knowledge of the future that would lead to the future unfolding exactly in the way predicted? I'm not saying it's impossible, I think it is, I'm just having a really hard time coming up with even a very simple scenario.

 

[z3ro]

It could, of course. All the easier if your knowledge of the future is vague, like in Minority Report (all he knew was that he would kill the guy) or Oedipus or any other story of prophecy. But can you imagine perfect knowledge of the future that would lead to the future unfolding exactly in the way predicted? I'm not saying it's impossible, I think it is, I'm just having a really hard time coming up with even a very simple scenario.

This is why an omniscent scenario is unworkable; given the OP, even if a supercomputer could plot the position of all the particles in the universe, how would that knowledge lead to predictions? I don't think it could.

But to the question at hand; if you had perfect fore-knowledge, how would this affect the future. Like the more vague scenario, I think perfect fore-knowledge would take into account that you had the fore-knowledge.

 

[TeddyKGB]

Such a supercomputer could not exist in the same universe with Heisenberg.

 

[marvmax]

Ignoring QM, I can see no reason why not.

Of course, if this universe was affected by things 'external' (whatever that might mean) to it then prediction would be a bit of a hit and miss affair.

I think QM can be safely ignored in the macro-world we live in.

I don't think this is really determinism re-explored, as much as re-hashed. It really comes down to is do humans have true free will, or are their actions determined. If the computer can determine humans reactions then a computer can do what you are asking, if it can't, then it can't predict the future.

 

[Patzak]

Such a supercomputer could not exist in the same universe with Heisenberg.

It couldn't exist inside any universe it were simulating anyway, because the universe should be the smallest possible computation of itself.