Do physicists really believe in true randomness?
askamathematician.com
askamathematician.com
Consequently, if local determinism is not plausible (Bell) and randomness is not plausible (Kolmogorov et al), that leaves non-local determinism as the most sensible assumption. It does lend some credence to the idea that we perceive a low dimensionality projection of a higher dimensionality space.
It separates out the notions of "random" events like coin flips, which we know will go heads with p=.5 and tails with p=.5, from truly unpredictable events, where we can't say even in principle what the probabilities of the outcomes might be. These latter events are where he finds some wiggle room for free will.
1) Person faced with ethical decision
2) Random events somewhere in the brain
3) _____________
4) Unpredictable autonomous decision!
Or something like that.
Edit: moyix's is a much better response than mine
Something random can be seen as an event that has no causual expanation (and thus cannot be predicted by studying the previous state of the system). But there still must be an agent, bringing the random outcome into the universe. In the same manner, free will too can be thought of as a event that has no causual explanation.
In this case, the difficult question is how a "free will" based decision relates to the person making it (if it's a product of his memories then it's deterministic, and thus not free).
One way to solve this might be to think of the persons' decision making process as a "random number generator". So, the output is deterministic (the same for the same state of memories, like with a programmatic RNG), but with a unique seed for this person (the state of memories itself), and a unique RNG algorithm (the wiring of his brain).
In this case, unlike calculating a dice result given dimensions, weight, power of throw, wind conditions, etc, nothing can produce the same output as the free will person without going through the whole process (a total simulation).
This is a popular statement but I've never thought that to be the case. Imagine you're creating a movie. You can pick the actors, the characters, the plot, etc. When you play the movie, the playback is completely deterministic. But that doesn't mean free will didn't design the film.
I could see something similar applying to reality. Your actions may be predetermined, but that doesn't specify exactly how they were determined.
Not according to compatabilism.
I think people mean they make decisions. Doesn't that mean randomness robs you of free will? The you (whatever that is) isn't making decisions, chance is.
If it's you making decisions, wouldn't those decisions have to depend on you and the situation, which means it's entirely deterministic? If I know you and I know the situation, I could predict your decision?
Any rookie in philosophy 101 can tell you that tons of philosophers have been in favor of EVERYBODY participating in philosophical discussions, and that leaving philosophy to the "experts" is mostly an idea of academic philosophers (that is, people with very little contribution to the history of philosophy, and a whole lot of secondary and derived output of annotating the historically important --and usually "amateur"-- philosophers).
Suppose we lived in a deterministic universe (e.g. one that actually ran on Newtonian mechanics and classic electromagnetism).
If you're of a mildly Bayesian persuasion, you 'believe' in randomness - even in a deterministic universe - because probability represents your knowledge. Sure, all the rules for the universe's evolution over time are deterministic, but you don't know the initial conditions, so you consider some probability distribution over initial conditions. Thus, the results of future events are 'random.'
The counterargument might go something along the lines of "that's not really random the way quantum mechanics is, because Bell's inequality demands violating either hidden-variables or locality and violating locality is worse. Without local variables, you can't meaningfully talk about having a 'underlying' deterministic universe."
Except you (sort of can). Bell's inequality implies that we can't have a theory with local laws of physics for single universe. But we can have a theory with local laws of physics for a multiverse which is the approach many-worlds takes.
It is effectively a hidden variable theory consistent with quantum mechanics.
So at least some physicists do not believe in true randomness.
Isn't true randomness unverifiable? In other words, it seems (to me) that there is no body of evidence that would verify that a particular event was "caused" by (i.e. was the result of) true randomness (as opposed to the result of hidden events/variables)
There's a great (and pedagogical enough) discussion of this at the back of Griffith's Introduction to Quantum Mechanics
That isn't what the post you linked to, or the links it gives, says. Bell's inequality is violated. The book is closed on that. (Technically, there are a few holdouts who won't be convinced unless we do the experiments with 100% accurate detectors, but they've been done with detectors that are better than 90% accurate and the inequality is violated.)
The argument seems to assume that the experiment is perfectly controlled, and given that we're still figuring out quantum effects, this seems to be in impossible task (Make sure no outside effects can change the experiment, without knowing all the outside effects). So, to me, all the experiment proves is we don't understand what's going on.
My belief: There is no such thing as true randomness or chaos. Only order we don't understand.
So if you want to claim that there is no such thing as true randomness, then you are essentially calling for another revolution of physics on a similar scale as the quantum revolution at the start of the last century. It is entirely possible that this happens, but it contradicts the most fundamental theories of physics we have.
[1] Actually three, it is not obvious what optimal strategies have to do with either of the definitions above.
I know you asked for a better explanation, but it's rather long so I won't give one. But the general idea is that you can show that no system of hidden variables can simultaneously satisfy all the experimental results we see.
I feel like the expirement is saying "we generate random numbers then prove random exists". Ok and a horse is a horse.
It may be the case that there really is a hidden variable, but it would need to communicate it's value nonlocally, which I'd argue is stranger than the universe just being somewhat random.
Basically, you have two entangled photons that travel in opposite directions. Let's say one heads toward New York and the other heads toward California. The particles arrive at their destination at the same time.
Each experimenter has a little filter (called a polarizer) that he can rotate, and each experimenter rotates his filter to whatever angle he wants the instant before the photon strikes it. Each experimenter then measures whether the photon passed through his filter or got absorbed.
Because each experimenter rotates his filter at the last possible instant before the photon strikes it, there's no way that the guy in New York could know what angle the guy in California chose, because to know this would require that information to travel faster than the speed of light.
Now let's ask the question: what is the probability that both photons had the same measurement? (That is, what is the probability that either both photons passed through the filter or both photons were absorbed). From looking at data from multiple runs of this experiment, it turns out this probability is a function of both filter angles.
But since nothing can travel faster than light, how is it possible that the probability is a function of two independently chosen angles? Well the simplest way this can happen is something like P = f(θ1)g(θ2). You can see here that the total probability is a separable function. In other words, the total probability can be computed using functions of two separate angles. It would be like computing the probability that two separate baseball players both hit the ball; you don't need any faster than light information transfer to figure this out.
However, in actual experiments, it turns out that P = f(θ1, θ2), and this function is not separable. What this means is the total probability is a function of both angles together -- you can't compute independent probabilities and combine them.
What does this mean? It means that somehow each filter "knew" the angle the other filter was rotated to, instantly. So reality is "non-local". BUT there's another option if you don't like that: the universe "knew" in advance what angles the experimenters would choose, and let each photon know this before they separated. This would give the correct experimental results, and you wouldn't have to give up locality. This is called superdeterminism, and it hasn't been ruled out yet, but let's be honest: is the universe really working that hard to conspire against us? (At least one Nobel-prize holding physicist thinks so).
EDIT: Also, why did this article instantly drop like 40 spots on HN? Is it because I shouldn't post comments on articles I submit? (I didn't write the original article by the way.) It's kind of annoying to spend twenty minutes writing a comment that nobody's going to see.
I love it!