David Deutsch initially conceived of quantum computers precisely as a way of demonstrating the practical reality of the many-worlds interpretation. His particular view on the matter was stated thus: “When Shor’s algorithm has factorized a number, using 10[sup]500[/sup] or so times the computational resources than can be seen to be present, where was the number factorized? There are only about 10[sup]80[/sup] atoms in the entire visible universe, an utterly minuscule number compared with 10[sup]500[/sup]. So if the visible universe were the extent of physical reality, physical reality would not even remotely contain the resources required to factorize such a large number. Who did factorize it, then? How, and where, was the computation performed?” As Riemann said earlier, Deutsch was a strong believer in MWI, which has become much more accepted in mainstream physics than when Hugh Everett first proposed it in the 1950s. Indeed Nature ran a couple of feature articles on it on the 50th anniversary of Everett’s first thesis on the subject.
However, I don’t find Deutsch’s argument all that persuasive. If such a quantum computer existed, it would only show that quantum computers are incredibly more efficient at executing certain algorithms than classical computers, and not proof nor even strong evidence that they are “borrowing” resources from another world. Quantum particles and their entanglements are so weird that it seems implausible to count them as discrete classical objects.
As for ethics, it’s not relevant. MWI just says that for every wave function collapse that we observe, there must exist at least one universe in which it collapsed into a different state.
It will (assuming its a normal number) produce every number. Somewhere in pi is the binary for all nine movies of the star wars saga on blue ray but with the directors commentary replaced with the sound or your play in first grade.
Similarly if the many worlds is correct there is a world that is just like this one but the particles that previously made up your computer screen are actually in the locations that match that of an over ripe avocado. If that isn’t all possibilities than I don’t know what is.
You are correct that “an infinite number of possibilities doesn’t mean all possibilities,” which is what iiandyiiii’s wording seems to imply. But if I understand it correctly, “many worlds” does mean all possibilities. That is, everything that is possible to happen will happen in (at least) one of the many parallel universes.
I’m not even sure what “multiple universes” even means in any real sense. Sure, it’s an interesting plot device in TV and movies where a character can open a door to a world just like ours except the Brooklyn Bridge is blue or the Nazis won World War II. But where would such a universe exist, relative to ours (or what we understand the universe to be)? It’s very hand-wavy to just say there are “multiple universes”.
This is not correct for the many-worlds interpretation.
As several people have said, the many-worlds apply to quantum wave function collapses, not human activities. No matter how many times this happens, the result is always finite, not infinite. All we are talking about is 2 to a very large number. A totally different thing, mathematically, existentially, and philosophically.
The other universe exists in its own universe. The “hand-wavy” part is the non-physicist making statements about some of the most advanced physics we know of.
Yes, I should have specified that “everything that is possible to happen” has to be interpreted in the specific quantum-mechanical sense of every way a quantum wave function (or set thereof) could collapse.
If there is no “collapse”, then the state of the universe decomposes as the sum of many “worlds”. What does that look like? You are in all of them simultaneously (whether alive, dead, etc.) It is maybe worth analysing philosophically, but at the end of the day it is still just another way of describing your usual experience.
I recommend against getting any bright ideas involving Russian roulette, lottery tickets, cats, or hot cups of tea.
Still, there’s only so many places a particle can be, and so many quantum states, so pretty much any fiction you can imagine is probably happening somewhere in a parallel universe. Even exceedingly unlikely things like croissants appearing out of the air after someone casts a spell.
I believe that this “QI” model is quite plausible, as perhaps did Hugh Everett himself:
Some refuse to accept it, for example, Jacques Mallah, Ph.D. Frankly these “refutations” of the Quantum Immortality model seem to me to miss the whole point.
I don’t base my life on QI, but it sometimes intrudes a little on my memories. There were a few instances where I barely avoided disastrous automobile accident. Sometimes I wonder if there are other worlds where the near-accident had a different outcome and my loved ones suffered much grief.
You may wonder about stuff like that or about croissants appearing, as long as you understand this is pure fantasy. Intriguing theoretical questions about the the nature of the “multiverse”, anthropic principle, etc., notwithstanding since none of those are necessarily relevant in a simple quantum-mechanical situation like this many-worlds picture.
This is the worst thing imaginable, it means that the end point is ultimate lonliness in an empty universe devoid of anything except your conciousness, like a Boltzmann brain.
I always understood the many worlds hypothesis, when applied to human decision making, is the theory that when a choice is made, one fork makes one choice and the other makes the other. This implies two things:
No matter which choice you make the same two branches are created, so any further branches you create are unaffected in any way by your choice: the same web of branches and varied outcomes is created regardless.
If you made one choice, the other you that forked away made the other.
Which means that if you are concerned about how your decisions effect alternate “yous”, then you should always make the worst choice you can imagine, to push the alternate-universe clones you are creating in the better direction. Of course this doesn’t increase or decrease the actual set of outcomes or overall level of suffering; what’s really happening is you are volunteering to lay claim to the worst possible path to spare the other “yous” from going down it.
Wouldn’t this be a rejection of causality? I mean, one “possible world” would be the one where the entire world turns to jello right now. And there’s nothing saying that that possibility won’t come to pass. In fact any random event could occur at any time, and the many worlds theory as you appear to imagine it would imply it should. That the universe isn’t continually erupting into random nonsense is sheer chance - it’s like a coin that has constantly come up heads for the last hundred billion trillion flips despite being a fair coin.
I mean, yes, if you dissociate quantum stuff from decision making and ascribe decision making purely to deterministic physical behavior then there’s no connection, but I’ve actually heard quantum mechanics and the like used as a mechanism to justify free will. If somebody does that then it ties directly in.
You seem to be claiming that quantum mechanics does not apply to macroscopic objects. This may be the case, but it’s not evidently the case. And it goes directly against the normal formulation of MW.
It’s difficult to say whether some specific thought or action will have a non-zero probability of appearing in a slice of the multiverse. But it’s not at all hard to arrange a situation where it’s true for specific actions: just say “if particle X decays before time T, I’ll do action A; otherwise B”. If MW is true, then there should be some slices where you did A and others with B. And it would lead to very different future histories for your different selves.
The interesting flaw in QM is that no one can tell where the line between classical and quantum objects lies or why or if there is one at all.
Yet humans proceed through their lives as if they are classical objects, even to physicists. As such, we are not subject to wave function collapses. If you want to say we are, show me the math. Make the case that you can fit a left turn instead of a right turn into the equations. That something unspecified about humans is quantum somewhere in the depths is not that case, however.