I was just watching a new video by Sabine Hossenfelder about the many worlds interpretation of quantum mechanics, and I had an idea for an argument against Many Worlds. This argument is based on my flimsy understanding of physics, so take it with a grain of salt.
The many worlds interpretation is based on the idea that the wave function of a particle is real, and it never collapses. The wave function describes the movement of subatomic particles (like electrons) over time, and it gives you a probability distribution of where you should expect to find the particle if you were to try to measure it. You can observe the wave-like nature of particles using the double slit experiment. If you shoot a laser of photons or a beam of electrons through a double slit, it produces an interference pattern on the other side, which is what you would expect if there were a wave.
But the individual photons or electrons hit the wall in one particular spot. In the Copenhagen interpretation, this is understood to mean that the wave of probability collapsed to one particular result. Whereas the probability of where an electron might hit the wall is described by the wave function, it actually only hits in that one spot.
In the many worlds interpretation, though, the wave function doesn't collapse. Instead, the electron actually does hit the wall in each spot where it's possible it could have hit. This is possible because for each possibility, there is a branching universe in which it happens. We observe it hitting the wall in one spot because we're only in one of those branches at a time.
Since there's an interference pattern on the wall, that means there will be more branching universes in which the electron hits within the peaks of the probability distribution than in the valleys.
Since there is a branching universe with every possible outcome of every subatomic particle (including photons) in the universe, there are an unfathomable number of universes being generated each moment. For every possible scenario that could happen, given the laws of quantum mechanics, there is a branching universe in which it does happen.
If you take the many worlds interpetation seriously, you can have a lot of fun thinking about the other branching worlds that exist. In some of them, you are wildly successful because you made all the right decisions. In others, you've already been eaten by a bear. In several of them, you are Batman.
It's crazier than that, though. It also means that what we might usually think of as a miracle could happen purely by natural means. If the subatomic particles of a dead person could take a path resulting in them being rearranged in such a way as to cause the person to be alive, then a person could rise from the dead purely by natural means. It wouldn't be a miracle, but it would look like a miracle. It would be a wildly unlikely scenario, but since the location of each particle necessary to make the person alive exists somewhere in the probability distribution, and the wave function never collapses, then there are definitely worlds in which dead people come to life. Maybe this is one of them.
Now, let me get to the argument I came up with. If the wave function never collapses, and there's a different world for every possible outcome of every particle in the universe, then we should expect there to be a lot more universes in which the subatomic particles all randomly move in such a way as to kill us. I mean if my body kind of disintegrates because every particle went the wrong way, I would die. It seems more likely that given all the possibilities, there are more possibilities in which I die than in which I continue to live. Since I'm still alive, does this cast doubt on many worlds?
One response might be to invoke an observer selection effect. I can only observe worlds in which I live, so the fact that I'm not dead doesn't tell me anything. I would have to be in one of the rare worlds in which I live to be thinking about this.
But what about everybody else? Granted, I must be alive in a world in which I'm thinking about this, the same thing doesn't apply to everybody else. Shouldn't I observe a world in which I'm alive, but people are dropping like flies all around me? The fact that they aren't suggests that many worlds is probably not true.
As I was watching Sabine's video, I saw what might be the clue to a flaw in this argument. She made a distinction between a path integral and a measurement. She said the many worlds interpretation is about measurement outcomes, not path integrals. My argument kind of assumes the path integrals are spread out along a probability distribution.
But it seems to me that path integrals and measurement outcomes are related. If an electron hits the wall at a specific location, doesn't that tell you something about its path integral? It had to travel along some path to get there.
I don't know. I suspect there's something wrong with my argument, but I'm not sure what it is. Maybe the problem is in misunderstanding what a measurement even means. I take measurement to refer to causal interaction. When an electron hits the wall, that's essentially a measurement because it collapses to one specific result. So if the subatomic particles in our bodies are interacting with each other, they should be collapsing to specific locations all the time.
But I don't know. Electrons in orbitals seem to fill the orbitals. The whole reason they occupy spread out space, rather than specific points, is because they have wave functions. As I mentioned in a different post, the size of an electron is defined by its Compton wavelength. If they are waves, they can only exist in specific energy levels, just like how a guitar string can vibrate in different specific harmonics, but not just any-ole-where. An electron can only exist in specific orbitals, but not between them any-ole-where. So if electrons are in their wave-like states around all the atoms in my body, rather than some specific location, that seems to suggest that their wave functions are not collapsing, and they are not being "measured." If so, that would undermine my whole argument. Maybe that's why I'm wrong. I don't know, though.
Anywho, check out Sabine's video, but don't read the comment section. There's a lot of nonsense going on there. And yes, I do see the irony in that statement.
Edit (11/5/2023): I have decided this argument is completely flawed. If what I argued here were true, you wouldn't even need there to be a multiverse before you should expect people to be dropping like flies all around you. On the many worlds interpretation, many worlds exist, but you only observe one. The one you observe is every bit as random as the many others you might have observed. So even without all those worlds actually existing, people should be dropping like flies all around you because your path through life takes you through many random outcomes. If the mere randomness of the outcomes is enough to put our lives into jeopardy, then your life would be just as much in jeopardy under the Copenhagen interpretation. If we have nothing to fear from random quantum events on the Copenhagen interpretation, then we should have nothing to fear from the randomness of which world you happen to live in under the many worlds interpretation.
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