A Mathematical Answer To the Parallel Universe Question 566
diewlasing writes to mention that Oxford scientists have proffered a mathematical answer to the parallel universe question that is gaining some support in the scientific community. "According to quantum mechanics, unobserved particles are described by 'wave functions' representing a set of multiple 'probable' states. When an observer makes a measurement, the particle then settles down into one of these multiple options. The Oxford team, led by Dr. David Deutsch, showed mathematically that the bush-like branching structure created by the universe splitting into parallel versions of itself can explain the probabilistic nature of quantum outcomes."
One question... (Score:4, Interesting)
From my perspective, even if this mathematical "proof" is true, it is only true in the ontological sense, i.e. that these branches can happen and maybe do happen, but not in reality. Then again, I believe the entire basis for the universe is ultimately ontological but that's a different matter.
My point is that these alternate "universes" may only exist in infinitesimally-small times (possibly below the Planck time threshold) and then simply cease to exist again as compared with our reality in the next moment, moment after moment.
Re:Parallel Universes conflict with Mind-Body Prob (Score:3, Interesting)
Fixed!
Where is the paper? (Score:4, Interesting)
By the way, Deutsch is a well known physicist, not some crackpot. One of the first problems discovered to be theoretically sped up by a quantum computer is named after him (link [wikipedia.org]).
Re:Occam's razor (Score:3, Interesting)
Re:Occam's razor (Score:5, Interesting)
(1) Shit happens.
(2) Shit happens. Parallel universes are created.
(1) (Copenhagen) The act of "observing" a particle at some point between the particle, the measuring apparatus, and your mind, somehow magically causes the particle to collapse from a wave state to a fixed one, without any other action on your part. Nobody has ever explained exactly what an observation is (we are, after all, made of particles too) nor when this happens.
(2) (Multiple worlds) Reality consists of particles in quantum waves of superimposed states. Period. When we observe a particles state, it's state becomes entangled with the state of the particles in our mind, and hence we observe the particle as collapsing to a single state "in each world".
I don't know about everybody else, but the fact that all states can exist, yet I can only perceive them separately, is no stranger to me than that all moments of time exist, yet I can only perceive each one separately.
Re:Raises the question (Score:3, Interesting)
My theory is that we actually ARE experiencing parallel universes. But the pressures of biological evolution have driven us toward brain structures which hide this fact. Maybe we actually ARE spread out across many different possibilities, but our conscious view of reality is as a single whole. Why? Because it made survival easier, perhaps. Or maybe, individuals with parallel awareness inevitably go insane and die out. Who knows.
Sometimes this parallelism "leaks through," in the form of quantum strangeness. But it's not the universe which is strange, it's actually us. Our brains contradict reality by trying to condense everything and the result is "weird" physics. Is the electron here, or there? Maybe it's both, but our brains decide to interpret it as a concrete one-way-or-the-other, because doing otherwise would require us to be consciously aware of all of reality, something which is probably impossible.
Re:Raises the question (Score:5, Interesting)
Briefly, the theory shows (rigorously) how pseudo-classical states are the only ones that are robust against decoherence. Hence, those are the states that tend to persists for measurable periods of time. And those pseudo-classical states are the ones that give rise to other pseudo-classical states.
Moreover the main developer of these ideas (Wojciech Zurek [wikipedia.org]) describes in his papers how what we typically term "memories" are inherently classical states (it's either "a" or "b"--not a superposition of both). He explains how macroscopic states will tend to be pseudo-classical, so of course any biological (macroscopic) creature will evolve to assume that reality is classical (it's an adaptive advantage and a good approximation of reality).
The point is that these larger-scale superpositions do indeed exist, but that local observers (e.g. instruments, or ants, or humans) can inherently only record/remember classical states, not quantum ones. So, our perception of reality (and memory of reality) is inherently a classical one.
Re:Why is this news? (Score:1, Interesting)
Re:Occam's razor (Score:1, Interesting)
In any case, your comment about the CI doesn't apply. Nothing in QM makes people some special class of observers. In fact the idea of 'collapse' and 'observer' don't really precisely make sense. Given that an observer has another quantum wave function of its own how can you even say the observer observed anything? Its location at the point necessary to make the observation is ITSELF subject to localizing its own wave function. Beyond that consider the case of Schroedinger's Cat. Is the cat dead or alive? Well, if you're INSIDE the box, you can answer that question (IE the wave function has collapsed). If you're OUTSIDE the box, it hasn't. Thus the very notion of 'collapse of a quantum wave function' is meaningless in the general sense.
In fact if you think about it the GENERAL case of the 'many worlds' interpretation is therefore also meaningless. There can be said to be many LOCAL "branches" of the universe, but the differences between them are all localized to one area of spacetime. One cannot say that 'the universe forks', one can only say that 2 versions of some localized portion of the spacetime continuum exist, and at whatever point they become indistinguishable they cease to have distinct existence.
Both 'interpretations' are in all particulars indistinguishable.
Re:Ummm . . . (Score:2, Interesting)
I mean, practically speaking, we are unlikely to ever go to some other distant galaxy and to verify physics there. But there is nothing in the laws of science that prevent us from doing that. It is "practically" impossible to falsify the axiom, but not theoretically impossible.
The many universes theory, is, on the other hand, impossible to falsify in every way (theoretically and practically). The universes are disjoint. We could never travel to them. We could never exchange information between two disjoint universes such to communicate the truth or falseness of the axiom of physical law.
This I think is the real definition of non-falsifiable, and for this reason, I think that theories like the many universes theories are science fiction and not even remotely scientific. Also they're a ridiculous waste of time; I didn't read the comments to this Slashdot article because I think that many universes is an interesting theory, I just wanted to be amused by how the misinformed attempt to justify it.
Don't take that the wrong way - your post was informative and interesting. But people who really believe in stuff like multiple universes and time travel and think it's all very scientific just really make me laugh out loud.
Re:idiotic circular logic (Score:3, Interesting)
Unless, of course, God(s)(ess)(esses) constructed the universe deterministically, to compute something. I suspect it is to create the question to which 42 is the answer.
Re:Ummm . . . (Score:3, Interesting)
Another poster asked [slashdot.org] "Why am I experiencing this universe?" To which a poster replied [slashdot.org], "Because you are in this one. If you were in a different one you would wonder the same thing. That's the anthropic principle."
So then, if the anthropic principle holds multi-versally, then each observer is trapped in a universe of singular experience. But logically, if anything can change in a forked universe, including the laws of physics, we might imagine a universe where the inhabitants could traverse one or more universes. They might ask, "Why do I experience these universes?" Furthermore, there might be a universe where the laws of physics are such that inhabitants can traverse *any* universe -- a universal universe, so to speak. They wouldn't wonder why they were having a singular experience -- their universe would contain *all* universes. They would be experiencing everything! "Why do I experience everything?"
So what really is different between all the forking universes? They must have some commonality, at least in the laws of physics. If not, then there is the possibility of a universe where you can traverse universes. Am I off base here? Can the laws of physics be different in another universe, even if it is descendant of a universe with laws like ours?
Re:idiotic circular logic (Score:4, Interesting)
Re:More links (Score:1, Interesting)
It's a judgement call, is the bottom line. If all the kinks are worked out of the MWI for good, then out comes Occam's Razor. There will be interminable arguments between scientists over which one they consider "simpler," and therefore better. Is it better to postulate an invisible pair of dice in the sky, or an endless infinity of universes we can never observe? As I understand your post, you've chosen your side in that debate, for the present; that's fine. But nothing in your post, or the article from what I've seen, settles the debate. In fact, unless one or the other eventually leads to a deeper theory of physics that can't exist without a multiverse (or can't exist with it) and is experimentally testable, it can be argued that this debate lies outside the ability of science to settle.
Re:Occam's razor (Score:4, Interesting)
Many people mix those up. Our "mind" doesn't have anything to do with it.
The wave function collapses when a particle interacts with a macrosystem. When two macrosystems are separate from each other, we have to assume the other macrosystem is not coherent with us until contact.
And remember contact *includes* photons reflected off the other macrosystem, so if we see it, otherwise put "observe" it, we're already in contact.
This is why "observation" causes collapse. Not because we're smart.