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Comment by ploxiln | Hacker News Reader

Well, the only one of the many-worlds that actually matters is this particular one, right here. What can we say/predict about this exact one. The others don't matter to me in the slightest...

EDIT: well that's not a great explanation of why I dislike the many-worlds hypothesis, let me try again. Like some other ideas, including the existence of God, it's not (yet?) falsifiable. Which doesn't make it false, of course. But it's a really extraordinary idea. It's not just many worlds, it's a fuck-ton. And what can we do with all of them? Are they for nothing? Does nothing that happens matter because it happened differently in a separate but equally real "world"?

I guess, I can believe that "god plays dice with the universe", but I can not believe that "god makes infinite copies of the whole universe and tries all possible quantum outcomes".

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The interpretation we use does not have any effect on our ability to make predictions; the equations are the same.

EDIT: response to parent edit

Almost by definition interpretations are not falsifiable. The many world interpenetration is literally equivalent to the other interpretations, because they all describe how we understand the meaning of the same mathematical model; and it is that model that is making predictions.

In my opinion (as a mathematician, not a physicist), the many worlds interpretation is the more natural way to read quantum theory. That is to say, if I were tasked to design a universe given quantum physics as the specification, my naive implementation would correspond to the many worlds interpretation.

An equally valid interpretation is that we are a computer simulation, and quantum physics describes the rounding behavior of said simulation. As far as I am concerned the only point of having an interpretation is to help build an intuition for the models.

But it's a really extraordinary idea. It's not just many worlds, it's a fuck-ton.

Another way of looking at it is that there's only one "world": the amplitude distribution over quantum configuration space. https://www.quora.com/How-does-observation-collapse-probabil... has a decent explanation/argument.

> "god makes infinite copies of the whole universe and tries all possible quantum outcomes".

MWI says that probability is conserved across the multiverse (unitarity of the global wavefunction)! The only reason we can "create universes" is because we're in the low-entropy time near the Big Bang. As we start getting closer to the heat death of the multiverse, then less "universes" are being created, because there's no room for them. In fact, given enough time, eventually some of the "universes" will actually join back together! If the multiverse is finite and closed (we don't know this), then sooner or later (like e^2^120 years later, according to a back-of-envelope calculation I saw) all of the universes will be lucky enough to join back up (Poincare recurrence), and we'll end up where we started.

I like looking at MWI not as the creation of universes, but as the creation of perspectives on one universe. In any case, it obeys conservation laws.

> it's a fuck-ton

Or zero. (But it's definitely not one.) Personally I find the zero-worlds view to be the most intuitively satisfying:

http://www.flownet.com/ron/QM.pdf (Or the movie version: https://www.youtube.com/watch?v=dEaecUuEqfc)

David Mermin's Ithaca interpretation is essentially the same thing:

http://arxiv.org/abs/quant-ph/9609013

The slogan is that "we are correlations without correlata".

A usual reply is that physicists don't or shouldn't care about metrics of the size of the universe but rather the simplicity and symmetry of physics. After all, the universe might well be infinite without many worlds, and why do even we care about amounts of stuff? The library of Babel doesn't contain more information than any single book in it. Similarly, pointing to specific areas in a large universe may require adding details.

Do you believe god exists and has a psychology? I'm trying to understand if you have trouble believing because you don't think god would create such a universe, or if you have trouble believing because such a universe is innately unbelievable.

If the latter, then I would ask, "Do you believe the ocean is deep, even though you can only see the surface?"

The latter.

I don't really understand the ocean metaphor, since humans have seen below the surface, quite a distance with remote-controlled submersibles.

Perhaps a better analogy would be, do you believe that matter exists beyond the observable universe?

Because of the expansion of the universe, it is theoretically possible for me to get in a space ship and travel away from you at such a high speed that we would never be able to meet again, even if at some point we both decided to head back toward each other as fast as possible, and even if we were both immortal. Our light cones would no longer intersect.

Probably you would assume that I continue to exist, despite that for all intents and purposes I cannot affect your life in anyway and therefore "don't" exist.

Similarly if I crossed the event horizon of a black hole.

I believe that a qubit is in superposition (i.e. exists in multiple miniature "universes"), because that theory produces results that are consistent with experiment. When the qubit's universes de-cohere with mine, such that for all intents and purposes I can now only ever observe the qubit in one particular state, why should I assume that the other universes have ceased to exist? Decoherence is a continuous process, just like traveling outside of a light cone, so why treat them any differently. It's rather arbitrary to say that increased distance in space preserves existence, while increased distance in phase space does not.

Why not?

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