Assuming they are, you would have a hard time decomposing human activities or decisions into separate classical “worlds”, and of necessity need to consider the total picture anyway. In any case, it is more complicated than a binary experiment when you start to take the state of the measurement apparatus and experimenter and environment into account as well.
You’re claiming things without any evidence at all.
MW claims there there is no collapse as such, but there are a zillion copies of us, each of which measured the particle in one of the possible states. Copenhagen says that measurement causes collapse but it’s left unsaid what really constitutes a measurement (can a physicist in a box remain in a superposition?). Etc.
That we see ourselves as classical objects has no bearing on any of this. All of the interpretations are equally good at explaining macroscopic objects.
If you want to say that QM doesn’t apply to macroscopic objects, fine–but that’s a bitter pill to swallow for physicists since it means QM isn’t actually universal after all, and there’s some arbitrary threshold where it breaks down.
Maybe that’s true, but again there’s no evidence for it. On the contrary: we’ve never found a case where QM didn’t apply. MW accepts that QM is universal, and at least in an Occamic sense seems to have a stronger claim than interpretations that assume a breakdown.
Kind of like what you just did right there?
I decided to brush up on Many Worlds using this site:
https://plato.stanford.edu/entries/qm-manyworlds/
Now maybe it’s just my lack of understanding. But it seems to me that people here are taking what is largely interesting mathematical artifacts to describe phenomenon at the sub-atomic level and overly applying them into science fiction concepts like parallel worlds or time travel and hippy bullshit.
To answer the OP’s question, “no”. If you are the person in this “world” thinking happy thoughts, then presumably someone in one of the other worlds is thinking “jerk thoughts”. Or vice versus.
In this layperson’s understanding, it doesn’t. Last time I checked, quantum physics applied at the very small level and general relativity applied at the macroscopic level. Scientists still haven’t figured out how to unify the two.
Pretty sure this statement doesn’t actually mean anything in real scientific terms.
Well, it was a question not a statement. And I do have another:
How do you define “real scientific terms”?
Me? I believe that much, and maybe all of physics (and mathematics) is, ultimately, philosophy. So, real scientific may not be “real” or “scientific”.
What is being glossed over is the impact that tiny quantum fluctuations will have on physical atoms and, through the butterfly effect, the impact this will have on real world events.
For a simple example – imagine that some quantum process occurs in our world, but not another, and that this nudges an atom slightly, and the forces binding that atom to other atoms cause slight perturbations in entire molecules, and eventually this difference affects the macro scale in a very very tiny way, slightly slowing down an electrical signal in someone’s brain. That person happens to be in the middle of intercourse, and this tiny change causes them to shift their position before completing the act in a tiny, imperceptible way. This tiny shift leads to a different sperm reaching the egg, leading to an entirely different person being born.
Now imagine this happened 500 years ago. Even if this particular person wasn’t very important, at least some of their descendants were – or even if they weren’t, maybe this new person (who has different genes that manifest in all sorts of ways) gets the same career as their equivalent in our world, and both are shop keepers. But one is slightly faster at packaging than the other, which over the years irrevocably changes the lives of every customer at this shop, since they get home at a slightly different time, maybe one guy leaves the shop 10 seconds faster and therefore reaches a light just as it turns yellow but is able to pass where he wasn’t before, saving him 30 seconds at the next light which was now green, meaning he arrives at a third intersection a little earlier, just in time to be sideswiped and killed, ending his life and changing countless others in tiny but irrevocable ways that balloon up to huge changes.
Because even the tiniest difference can balloon to change so many different things in this way (even something as simple as deciding to have sex a few seconds later or in a slightly different position could lead to a different sperm reaching the egg changing entire lives) tiny quantum fluctuations that affect atoms in even tiny ways WILL and MUST affect the macro world in HUGE ways.
Why I mean is saying things that actually means something based on the commonly understood definitions of the words being used. Yes, human activities are “ultimately based on quantum processes” in the sense that humans are made of molecules made of atoms made of subatomic particles made of elementary particles subject to the laws of quantum mechanics. But that doesn’t mean that “quantum fluctuations” at the subatomic level has any more influence over what you choose to eat for dinner tonight than that decision has over the movement of the Earth around the sun.
And just saying “all of physics is ultimately philosophy” sounds suspiciously like “I choose to believe in whatever bullshit I feel like”, unless somehow anchored to scientific observation.
Granted, physics, particularly quantum physics and even plain old relativity does describe some pretty weird phenomenon that we know to be true. The Big Bang. Black holes. Time dilation. Dark matter. Dark energy. Infinity. So on and so forth. So it might simply be that I can’t conceptualize many worlds as anything besides abstract mathematical equations and science fiction plots.
So here are some questions. Let’s say I flip a coin and that creates a “quantum event” of two worlds (one Heads, one Tails):
-Where does the other world actually exist? Like do the two realities sit on top of each other and just exist at separate “frequencies” where they can’t interact?
-Is it possible for these worlds to interact with each other and if not, do the other worlds even matter? Or even “exist” in any meaningful way?
-Why do I perceive this current world and not the other one?
-Or maybe it actually is a more philosophical construct? i.e. when I toss that coin in the air, I can imagine both a a world of Heads and a world of Tails. Both are as real and as possible as the other until the coin lands. But then only one becomes reality.
Flipping a real coin is not a “quantum event”, at least not moreso than every event is a quantum event. A simple “event”, i.e., “collapse”, can be performed by preparing, e.g., an electron in a linear combination of two observable states, say with spin component pointing up as well as down along a certain axis, then measuring the spin, which changes it to a definite state— changes something, anyway, as a result of the interaction.
So, all of the “worlds” exist superimposed atop each other at the same time and place; the discussion is not about a physically separate universe, and no, the different “worlds” cannot interact in any way, at least as far as I understand what “world” means in this context. They do matter, though, because to describe the behavior of even a single electron you may need to take into account in your calculation multiple “worlds”, that is, a superposition, as quantities may not have definite values at all.
What you perceive is the sum of all the possible worlds. Granted, I am not sure how to shove you through a special diffraction grating or an ideal Schrödinger’s box to see what it’s like to do two opposite things at once (as it were); in some sense it isn’t really possible due to quantum decoherence. Better to try to start with experiments involving a small or medium number of atoms. See examples of cat states, GHZ states, and so on for simple, yet very non-classical, examples
(real behavior, not just thought experiments).
There is a separate philosophical question of what it means to think about a world where you zigged instead of zagged, but such considerations do not necessarily need counterfactual worlds to be real, and in any case that is not what the many-worlds interpretation is about. It is merely supposed to be an interpretation of quantum mechanics and is not supposed to make obvious (non-quantum) intuitive sense.
Basically no one thinks that QM actually stops working for macroscopic objects. It’s too arbitrary. All the work on unifying QM and GR are searches for some form of quantum gravity–not figuring out a way for QM to somehow stop working at large scales.
And we do know that some parts of QM work macroscopically. The behavior of superfluids can’t be explained classically; it’s a quantum behavior. There’s also this recent article where researchers demonstrate positional uncertainty with a cluster of 10[sup]8[/sup] atoms.
Now, it still may well be that there’s a cutoff. In fact you can prove that at least one of these things is false:
- QM is universal (it applies everywhere, no matter what the size or other characteristics)
- QM is consistent (different observers will always make the same predictions for the same system)
- QM is definite (a thing can’t be both true and false, heads and tails, etc.)
MW violates the last one: it says that you get universes with the coin on heads and ones with the coin on tails. But none of the three are easy to give up and maybe giving up universality is the right answer.
My point is just that we can’t say right now. The apparent fact that we don’t see feline superposition isn’t evidence that QM isn’t universal, because what we observe is still consistent with MW and other universal interpretations. We’ll need better experiments.
You can speed this up quite a bit by going to the ANU Quantum Random Numbers Server. Now you don’t have to wait for the quantum bits to propagate and percolate to macroscopic levels.
Fun trick, use that to pick your lottery numbers, and in one out of 300 million universes, you are a winner.
Now, as far as the philosophical or scientific parts of many worlds, that starts getting deep into areas where science cannot answer, because the questions are not defined enough to do so.
That said, the Many Worlds theory is the only form of conceptualizing quantum mechanics that doesn’t require an interpretation, but only following the math. The math says that particle went both ways, that we don’t interpret it that way is a failure of our perceptions, not of physics. The other interpretations all rely on “collapse of the wave function” something that doesn’t actually have a rigorous definition. No one has ever pointed to where and how this wave function collapses, and it is unlikely that that question will ever be answered outside of a philosophical context.
Most of the time, the many worlds will all describe pretty much the same world. QM calculations and experiments come out to a bell curve. While it is possible that that electron went through the Andromeda Galaxy between the emitter and the receiver, it’s not all that likely. Same with many worlds. If you are not a jerk in this world, then you are probably on the bell curve of not being a jerk in most. The universes that you are a jerk would be few in number, as that is an outlier of possibility.
QM is how the world works, and classical physics, including relativity is a simplification of that that we can interpret and understand with our senses and perceptions. The “fight” between relativity and QM is not really a debate, both are correct in what they describe. Relativity breaks down in some instances, mostly in black holes and other extreme cosmic phenomena, and QM doesn’t have a way to describe gravity. Within their bailiwicks, however, they predict the results of experiments to at least the accuracy of our experiments.
As far as quantum immortality goes, I came across this concept back in the early 2000’s. It’s interesting, and it doesn’t really defy any rules. It is technically falsifiable, but only the experimentalist gets the results, and is prevented from sharing them with others. I do sometimes have some sort of close call, and wonder how many universes I just died in. You could put yourself into a Schrodinger’s box, with the kill conditions that the lottery ticket that you got in the second paragraph being a loser, and now you are guaranteed to survive in a world in which you won the lottery (assuming of course, that your setup is accurate and robust enough that it doesn’t have false positives or negatives of a similar order as the lotto odds).
I agree with this. As soon as people hear about many-worlds they leap to grab the sparkly bits, which plunges then right over the edge.
If you want your brain bent, just read Wikipedia’s compendium of Interpretations of quantum mechanics, especially the Comparison chart.
Everything else lies in the fetid marsh between pop science and pop philosophy. It’s not a good place to hang out.
My very, very, very limited understanding of quantum physics and Everett’s “many world’s” theory has been more or less described by some of the posts already. As I understand it, Everett’s work expressed in mathematical terms that different outcomes within our “world” could exist simultaneously and that they might be “real” but that we might not be aware of this reality. If I’m getting it right, he wasn’t referring to a physical universe outside our own per se; he’s saying that these outcomes, these “worlds” exist all around us in this universe.
There are those who believe in other forms of multiverses, as in actual universes outside of our own, but the field of physics generally doesn’t go there because those multiverse theories (e.g. “simulation”) cannot be observed and evaluated by scientific method. By contrast, Everett’s work at least has math behind it, or stated more accurately, Everett made mathematical arguments that haven’t (AFAIK) been completely debunked.
As a follow up, I don’t think there are any ethical concerns in Everett’s world (worlds). What goes on in those worlds has no impact on you or anyone else in this world.
Right, but somehow people interpret quantum mechanics to mean that a ball sitting on the table has a non-zero probability of appearing in the Andromeda galaxy or spontaneously turning into a chicken.
If a particle can tunnel out of a nucleus, do you doubt it could tunnel further (albeit with lower probability of doing so)?
As an aside, and in a similar (but non quantum) vein, do you also doubt there is a non-zero probability that an ink drop dissolved in water may momentarily re-form?
I doubt that macroscopic objects could spontaneously “tunnel” across the room. That is to say, while it might work for a particle, It is so statistically unlikely for it to happen to EVERY particle in a single object that the universe would burn out a trillion times before it could happen.
I would say it would be about the same probability of taking a broken glass, putting it in a box and having it reform by shaking the box. That is to say “zero” because of the Second Law of Thermodynamics.
Interesting link on “multiple universes”.
Your “trillion” there is probably woefully short. I think the number would be one of those numbers that puts the number of particles in our universe to shame.
Entropy is all about statistics. If you have 2 coins, the probability that they both come up heads is not all that small. If you have 4, it’s quite a bit smaller. If you have 10[sup]23[/sup](the order of Avogadro’s Number), then the chances of all of them coming up heads is close enough to zero that it is better described by zero than by “small”.
A broken glass has quite a number of Avogadro’s Number of particles, and you are asking them to come up with a much more specific outcome than simple heads or tails.
We are part of the universe. If your version of the many-worlds thing is true, there is just a parallel universe in which the other you did not choose to drive carefully; did not refrain from thoughts about murder, etc - we are just as much effect as we are cause.