Well, I didn't mean rewind time in person, but lets say that the very same "random moment" happens in a/several parallel universe(s). If the same result keeps happening wouldn't that imply that fate exists and that random actually is determined?

given the same placement and velocities of particles, whether 10 of them or a googleplex of them, the exact same thing will happen every time.

Yeah, I was just breaking it down for him ;)


About the poll: Surprised to see one third (currently) believes that there's fate. I was expecting something like 20% or less...

Fate real!? NO! I'm my own master! No one can make me blead my own blood, I created my self!! AArhg!

This statement is perfect as an example of how common sense is invalid for science. In this case, scientific knowledge also provides insight into philosophical arguments.

You can never know the exact position and velocity of a very small object at the same time. This is called Heisenberg's Principle, and it's one of the fundamental principles of quantum theory. Thus, there is no way that you can have the same placement and velocity of the particles, that is fundamentally impossible. You can come up with good approximations, sure, and the bigger a particle is, the much more likely that the approximation is correct.

Another thing is that a chaotic system is deterministic by definition, but it's almost impossible to predict what will happen because of the nature of the system. Therefore, in the theoretical rewinding of time, a chaotic system (note this is not necessarily the real world) will give the same result every single time. However, chaos doesn't explain very small objects accurately.

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I've finished the small science sermon. Now I'd like to put it into application. The cells that make decisions in our body (brain, spine, etc.) do so by sending information to other cells. This information is carried by electrons. Electrons behave probabilistically. Therefore, free will is not an illusion in the sense of which you speak of it, however it doesn't exactly mean one can do as one pleases, as one will probably do as the neurons tell one to do. If a human can't overcome the immediate desires of the body (being happy, eating, cheating to get ahead, etc. all for their own well-being), then a human isn't really free in my opinion; though I think I'm deviating too much now.

I'll use a quote to say my feelings on this,
"You cannot change your fate; however, you can rise to meet it."

Depends on how you define 'fate'. I believe the universe is completely deterministic even though we may not be able to measure it accurately. I do know that quantum mechanics involves lots of randomness but I also believe it's not because the universe is random but because we just can't measure it accurately enough. That said, I have practically no faith in 'fate' in religional/supernatural/whatever sense.

Yeah, I don't define fate as something religional either. I was just making the question more simple.

only one thing can happen in any instance. so you might as well consider that event as an unavoidable fact since nothing else can happen at that time.

What you say makes sense, except that quantum mechanics doesn't say that. It says that it's fundamentally probabilistic. Nobody inside the universe can measure all properties with exact accuracy, no matter how advanced the technology they use to measure.

Just as a thought though, what if one is outside the universe? Does this hold true then? Of course there's no way to scientifically arrive at conclusions on this, but see what you think.