That’s the point, though. Your math doesn’t “explain” anything, either. John Von Neumann’s collapse postulate can be used to calculate the probabilities of different outcomes, but doesn’t explain how or why collapse takes place. Thus quantum theory has always seemed incomplete and inconsistent. So there’s been concerted efforts made on multiple fronts to provide an explanatory interpretation of the axioms of quantum theory. David Bohm’s “hidden variables” interpretation was one such attempt. Hugh Everett’s “many worlds” was another, and while physicists were initially dismissive, it has been gaining broader mainstream acceptance. Understanding and explanation is as much a valuable part of science as math.
It wasn’t my idea, it came from the OP. But in my response, I took it to mean that quantum collapse creates new universes to accommodate every possible probabilistic state. This is not how “many worlds” was originally proposed nor how it’s regarded today. As Deutsch said, “our Universe is only a tiny facet of a larger multiverse, a highly structured object that contains many universes". They’re already all there, and this is why, in his view, the entangled qubits in a quantum computer can exploit their counterparts in the multiverse to harness a seemingly impossible amount of computing power. Verging on sci-fi fantasy for sure, but David Deutsch is a respected if unconventional theoretical physicist at Oxford.
I have a question about how all those universes are identical
( and my question originated from a joke:)
I saw the comedian John Oliver interview Stephen Hawking. He asked Hawking if somewhere there exists another universe, in which he (Oliver) is
as smart as Hawking.
Hawking answered:
“Yes.
And there is also a universe where you are funny.”
okay, it’s a good joke, and it was funny to see Oliver suddenly surprised and unable to come back with a snappy answer. But it made me think of a serious question, basically the same as the OP:
When a person is born and grows up to be a comedian, or a scientist in a wheel chair–how does that happen in ALL of the multiverses?. LSLguy says above that it’s just a re-arrangement of the already existing matter, not a new universe suddenly popping to being. But at the moment of conception, neither of those two sperm cells that became Oliver and Hawing were either funny or smart. Gradually, they became that way. But where?
It seems that I misunderstood: this is not a question about the Big Bang or baryogenesis. The answer to the question, if I apply a measurement, where does the new matter for the new state come from is absolutely that there is no new matter; it’s already there.
Well, he must be trying to sell some popular books, because “exploiting their counterparts in the multiverse” seems like a sci-fi phrase one would only use in a pop-sci book. In fact, it is, or appears to be, a false statement since a qubit is already a quantum-mechanical object and does not need any “counterparts” to hold quantum information.
Again, there is no need to clear out some real estate for extra possibilities since they exist in a superposition, on top of each other as it were.
Some of this is my own sloppy wording and shouldn’t be blamed on David Deutsch. See the end of my post #12 for a direct quote expressing Deutsch’s thoughts on the matter.
However, that last sentence seems like rather a circular argument since the whole point of “many worlds” is to explain precisely this quantum-mechanical behaviour; specifically, the phenomena of superposition and wavefunction collapse.
I am not saying this is not interesting to think about or that there may not be an important question there, but some of his phrasing seems deliberately hyperbolic or irrelevant, like mentioning 10500 (and that there are 1080 atoms in the visible universe) in the context of factoring a 500-digit number whereas Shor’s algorithm only needs on the order of let’s say 1000 “atoms”. 10500 might be relevant if you needed to enumerate all 500-digit numbers, but of course you do not.
The discussion here is of course extremely interesting and edifying, but per current thinking isn’t there “stuff” popping in and out of existence in the quantum foam all the time many worlds multiverse or not?
Once again, analogies are incomplete and fail sometimes, but virtual particles can be thought of a fluctuations in the fields, or fluctuations in the fields can be thought of as virtual particles.
The math says that something is there that has to be accounted for in order to get the experimental results that we get, but it’s not something that could ever be detected directly.
Ahh, yes. But consider also certain professional media blowhards who shall remain nameless here in FQ.
Being understandable and being persuasive doesn’t mean you’re even close to being right. I can spin a good yarn. Unlike some blowhards I’m not trying to deceive. But I might be doing so unwittingly.
I didn’t purchase the article. I always understood (I’m probably wrong) that a vacuum-fluctuation universe occurs when a universe experiences accelerated expansion. Eventually you have some random point where spacetime is expanding away from it faster than light. Then some quantum fluctuation occurs. Bang, you have a new universe.
This has been a very informative thread. My thanks to all who contributed.
The matter was already there, as were the alternate universes. @wolfpup, does that mean there is some uncountable number of universes already in existence that can accommodate every superposition that will ever occur?
You’ve answered my question, but now the smoke emanating from my ears is the result of this new question. Is there some number of universes, a number that somehow anticipates all the possibilities in all the eventual superpositions?
I’m considering this as some type of design challenge, as if some programmer need to develop specs that covered everything, and I suspect that’s the wrong way to think about it.
Hmm. I have to noodle on this and let it settle in my pea brain. Again, grateful for the responses.
Anything beyond the math is pure philosophical speculation. The math says that the universe evolves in a certain way, and our everyday perceptions say that it can’t do that. We have to find a way to square what the math says against what our perception says.
I used to be against many worlds, but Sean Carroll changed my mind on that. It’s the model that makes the fewest assumptions.
But empirically, we can’t prove one or the other, and it’s likely that we never will be able to.
Isn’t Hawking Radiation theorized to be caused by virtual particle-antiparticle pairs that try to materialize and disappear, but do so across a black hole’s event horizon, and thus get separated? That would, again theoretically, be measurable, although taking a measurement would take a very long time.
Basically, yes, and the apparently illogical aspect of it arises from the fact that “infinity” – or anything close to it – is not intuitively comprehensible. The idea of “many worlds” is that there already exists a universe in which any possible state of a wavefunction collapse already exists. Which also means that any imaginable version of any macro object – such as ourselves – also exists.
You still would not be detecting the virtual particle, but rather, the real particle that emerges from that interaction.
We know they exist, either as fields or as virtual particles, as they influence particle interactions, but more or less by definition, they cannot be directly detected.
Many Worlds is emphatically not a theory. It’s an interpretation. It’s taken seriously to the extent that, like dozens of other interpretations of quantum mechanics, it has been shown to be consistent with quantum mechanics and with all of the other interpretations. No interpretation can be proven or disproven, because they all make the exact same predictions.
One might say that the various interpretations of quantum mechanics “explain” things, where the bare theory by itself doesn’t. But what is an “explanation”, and why is it necessary? When we say that we “explain” something, usually what we mean is that we’ve related it to things that we’re familiar with (note: not things that we understand, just un-understood things that we take for granted). But quantum mechanics isn’t something we’re familiar with. It may even be that it’s something that we can’t be familiar with. But that’s a limitation of our brains, not of reality, and really, why should brains evolved to be able to tell which fruit is ripe be able to “understand” the fundamental processes of the Universe?
You could say that, but we should more simply emphasize that a central tenet of “many worlds” is that there is no wave function collapse. There certainly exists a universe (or multiverse, whatever you want to call it in this context) where any possible subsequent state already exists, namely, the same universe there was before the measurement or time evolution or whatever.
Yes, I was throwing the word “theory” around in the casual layman meaning, not the scientific sense. As I alluded to earlier, Everett’s “many worlds” an explanatory hypothesis.
Now this I disagree with. It appears to be a pessimistic and cynical approach to the philosophy of science that underestimates our capacity for having at least a tenuous and imperfect grasp of even its most esoteric aspects, a goal that is fundamental to the basic curiosity that drives all of science. The journal Nature, perhaps the most respected journal in all of science, published a special issue (as I mentioned earlier) back in 2007 to celebrate the 50th anniversary of Hugh Everett’s first publication of “many worlds”. That issue featured apparently whimsical but well-considered cover art depicting what was clearly a science-fiction motif, making this particular issue of this venerable journal look like an issue of Astounding Stories. This was a deliberate attempt to illustrate the fact that good science fiction embodies an important aspect of real science, which is pushing the boundaries of human imagination.
Correct, and again I apologize for my sloppy language. Indeed, the whole point of “many worlds” is that wavefunction collapse doesn’t actually happen, and is only an artifact of our perception.
Very glad I started this thread and very appreciative of the knowledgeable participation. I am certain my intelligence has increased by some quantum measurement, no small feat.