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Comment by xlm1717 | Hacker News Reader

Replace non-locality with infinite universes, which is more troubling? The article does touch on this question.

Additionally, the article's aim was to demonstrate that the ESSW does not contradict pilot-wave theory, not to show that pilot-wave theory explains the results better than alternative theories, and it demonstrated this by showing that there is no contradiction if you take in account nonlocality.

The title is not misleading because the experiment described in the article does provide experimental support to the theory, support which ESSW aimed to take away. Importantly, it is not an experiment designed to show pilot-wave theory describes the results better than other theories.

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If the experiment does nothing to advance this theory over any competitor, or vice versa, how can you say that it provides experimental support to the theory?

ESSW demonstrated that pilot-wave theory requires a weird form of non-locality. These experiments confirm that experiment requires the exact form of non-locality that ESSW required. Whether non-locality bothers you depends on your philosophical position, and is not affected by this experiment.

> If the experiment does nothing to advance this theory over any competitor, or vice versa, how can you say that it provides experimental support to the theory?

Non-contradiction of existing theories can be seen as a prerequisite for support. As a restricted affirmation of non-wrongness perhaps.

>restricted affirmation of non-wrongness

I think this is a really good way to put it, and an important criteria given the timescale over which these theories develop.

You seem to suggest that support for a theory is meaningless unless it is absolutely conclusive. If that was the case, I'm pretty sure most of quantum physics would have been abandoned long ago.

Until we know everything, is anything in theoretical physics really a zero-sum game?

I think the problem is in the thinking quantum physicists must possess in order to believe in such a theory in the first place. I mean, the idea of, "if we don't know where it came from, it couldn't possibly be hidden information; it must therefor be 'random'" is absurdly egotistic in the first place.

I have no idea how you get from my words to, "...support for a theory is meaningless unless it is absolutely conclusive."

What I said is that if the outcome of an experiment is predicted by two different theories, getting the expected result does nothing to help you decide between them. It happens to be the case that ANY experiment that is in accord with quantum mechanics is equally well explained by EVERY interpretation of quantum mechanics. The result is that most working physicists so not consider wondering about the right interpretation to be a useful scientific endeavor. Indeed most will gladly affirm that they belong to the "shut up and calculate" school of physics in practice.

There are plenty of detailed questions within quantum mechanics which can be asked and answered by experiment. That is what scientists tend to do instead of debating interpretations.

>> Replace non-locality with infinite universes, which is more troubling

It's a question to the philosophers, not the scientists. There is no objective measurement for what "troubling" is.

And if we don't start with any preconceived notions of how things _should_ work, then discovering that they work differently is not particularly troubling.

> It's a question to the philosophers, not the scientists.

As discussed upthread, this is all philosophy. The popular interpretations of quantum mechanics are all experimentally equivalent, so we need to use elegance, intuitiveness, troubling-ness, etc to choose between them (and these can be highly personal).

EDIT: After re-reading your comment I think I'm agreeing with you here.

You can also use the `operational non-interpretation', and just use the math to calculate without worrying about what it `means'.

(That's pretty close to the spirit of the Copenhagen interpretation, though.)

> Replace non-locality with infinite universes, which is more troubling?

The nature of the multiple universes is deply misunderstood. If you just think of the universe as a very large N-bit quantum computer, then the "multiple universes" are simply the superpositioned state of the computer itself. Nothing magical or non-physical about it.

And since we are almost certainly living in a simulation [1]... ;-)

[1] http://www.simulation-argument.com/simulation.html

The problem is that you wouldn't just need a superposition over a finite number of state, but for the theory to make sense the universe should be some superposition over all possible physical states.

There are simply just too many possible states to meaningfully describe something like a distribution over them, which is what a superposition would be. Mathematics simply gives up when you try to integrate over an infinite number of dimensions.

I don't know where you are seeing a relevant infinity. At any given time, there are a finite number of particles each with a finite number of observables. It's a large number, but finite.

How do you know? All we can see is the visible universe, and the horizon is receding faster than the speed of light. Where do you get that there are finitely many particles?

There was (to the best of our knowledge) a single big bang, since when energy is conserved. That gives us a total energy for the universe, which is large but finite, which puts an upper bound on the number of particles at any given time.

The big bang is just a theory that is obtained by extrapolating the current movement backwards. For all you know, the multiverse is infinite. And in fact so could the universe be -- the big bang could have happened much earlier and the universe could be much bigger. And when you say that there was only one big bang and there was a finite amount of energy, you are making too many asssumptions.

> it demonstrated this by showing that there is no contradiction if you take in account nonlocality

The article suggests pilot-wave theory "apparently" contradicts special relativity. We know the other interpretations "only" have a problem uniting with general relativity.

Perhaps the core issue is Steinberg's quote in the last paragraph: “The universe seems to like talking to itself faster than the speed of light. I could understand a universe where nothing can go faster than light, but a universe where the internal workings operate faster than light, and yet we’re forbidden from ever making use of that at the macroscopic level — it’s very hard to understand.”

The problem with general relativity is that general relativity can't be quantized. We have produced quite a few theories of gravity that can be quantized...then subjected them to experiment and they all failed.

These days theorists are trying to create theories out of which both QM and GR could arise in the limit. An unbelievable amount of energy has gone into things like string theory and loop quantum gravity. True believers believe that a theory will be found..but they haven't succeeded yet.

Back to pilot-wave theory. In special relativity, no inertial reference frame is privileged over the others. In pilot-wave theory one must be..but no experiment can reveal which one is. This is aesthetically ugly, but not actually a contradiction.

> In pilot-wave theory one must be..

Would this be the reference frame of the center of gravity of the universe? If so, and if some parts of the universe are unreachable due to inflation, would that be the center of gravity of everything within the light cone of a system? Sorry if I'm being imprecise, I only dabble in this stuff.

> Would this be the reference frame of the center of gravity of the universe?

This is a little confused, I'm afraid. The centre of gravity of any system doesn't define a reference frame, it defines a location. For the universe, it doesn't even do that, since 'the observable universe' is a function of the observer: anyone anywhere can look around and observe some universe for 50 odd light years in each direction. Assuming homogeneity, the 'centre of gravity of the observable universe' is just a clumsy way of saying 'my current position'.

The universe does sortof define a reference frame, and it's the frame in which the CMB (cosmic microwave background) is isotropic. In other words: if the CMB looks warmer to your left than your right, that means you're travelling left relative to the CMB frame.

But it would be very surprising if the laws of physics depended on that. (Indeed, special relativity assumes the laws of physics are the same in every frame, and so far we have no evidence to contradict that).

> In pilot-wave theory one must be [preferred]..but no experiment can reveal which one is.

Interestingly has this in common with tangherlini relativity... which, iirc, also has nonlocal effects (haven't done the math; am not sure)

No one has combined bohm + tangherlini

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