I don’t quite understand this topic, but maybe this could be useful:
The problem with “converging / mangled worlds” is statistical. To make two worlds interact (and become the same world, or erase each other, depending on mutual orientation of their amplitudes), those worlds must have all their particles in the same position. In usual circumstances, this seems unlikely. Imagine the experiment with the cat, where in one world the cat is dead, and in other world the cat happily walks away. How likely is it that at some moment in the future, both universes will have all particles in the same positions?
So, in usual circumstances two worlds interact only if a moment ago they were the same world, and the only difference was one particle going two different paths. (Yes, there are also all the other particles in the universe, also splitting all the time. But this happens the same way in both branches, so it cancels out.)
It still seems mysterious to me how the single photon state turns into two distinct L and R.
My intuition is that this “single state” was never literally one point, but always a small interval (wave? hump?). An interval can break into two parts, and those can travel in different directions. There is no such thing as a single point in quantum physics.
(Disclaimer: I don’t really understand quantum physics; I am just interpreting the impression I got from looking at Eliezer’s drawings. If you have better knowledge, feel free to ignore this.)
What forces the worlds to be same in order to interact? You could also have merely adjacent worlds where the “collisions angle” could compensate for small differences. It is just a little harder to imagine how worlds of unrelated state would interact. Maybe dark energy is the sum total of gravity from other worlds?
It’s also that two worlds won’t long stay singular, but branch all the time into subworlds. The probability of some of the pairwise worlds being close enough is higher.
edit: Also there are settings where splitting doesn’t mean lack of structure. For example in the mirror experiements the two paths will systematically intersect and this is a pretty stable result of the mirror positionings.
It’s also that two worlds won’t long stay singular, but branch all the time into subworlds. The probability of some of the pairwise worlds being close enough is higher.
If something branches in a limited space, soon the branches will touch each other. The question is, how soon is “soon”. If we imagine a real 3D tree in a 3D world, the branches will touch before dozen splits. But if the tree would be extremely large (a few kilometers) and the branches extremely tiny (a few milimeters), there could be more splits.
If we imagine the history of the whole universe as a branching tree in a many-dimensional world, we have to realize there are many dimension (I guess approximately six dimensions for each particle: position and momentum), and compared with the size of the dimension, the branches are really tiny (take two random particles in the whole universe, what is their probability of hitting each other). So there is a lot of time for the tree to grow.
Eventually, the branches will run out of space and start hitting each other all the time. But I think this will happen at the “heat death” of the universe. Then the branches will hit each other so much that the whole concept of time or even reality may become meaningless. But I think this is not happening now, yet. There is still a lot of space for the universe to grow without intersecting with other branches.
What forces the worlds to be same in order to interact? … Maybe dark energy is the sum total of gravity from other worlds?
This seems to me like a new hypothesis, outside of the quantum physics as we know it yet, not supported by experimental results. Maybe it is so; maybe it isn’t. Without good evidence for it the prior probability seem small (there are many possible new hypotheses we could make to explain dark energy, this is just one of them, why should it be preferred to the alternatives).
I don’t quite understand this topic, but maybe this could be useful:
The problem with “converging / mangled worlds” is statistical. To make two worlds interact (and become the same world, or erase each other, depending on mutual orientation of their amplitudes), those worlds must have all their particles in the same position. In usual circumstances, this seems unlikely. Imagine the experiment with the cat, where in one world the cat is dead, and in other world the cat happily walks away. How likely is it that at some moment in the future, both universes will have all particles in the same positions?
So, in usual circumstances two worlds interact only if a moment ago they were the same world, and the only difference was one particle going two different paths. (Yes, there are also all the other particles in the universe, also splitting all the time. But this happens the same way in both branches, so it cancels out.)
My intuition is that this “single state” was never literally one point, but always a small interval (wave? hump?). An interval can break into two parts, and those can travel in different directions. There is no such thing as a single point in quantum physics.
(Disclaimer: I don’t really understand quantum physics; I am just interpreting the impression I got from looking at Eliezer’s drawings. If you have better knowledge, feel free to ignore this.)
What forces the worlds to be same in order to interact? You could also have merely adjacent worlds where the “collisions angle” could compensate for small differences. It is just a little harder to imagine how worlds of unrelated state would interact. Maybe dark energy is the sum total of gravity from other worlds?
It’s also that two worlds won’t long stay singular, but branch all the time into subworlds. The probability of some of the pairwise worlds being close enough is higher.
edit: Also there are settings where splitting doesn’t mean lack of structure. For example in the mirror experiements the two paths will systematically intersect and this is a pretty stable result of the mirror positionings.
If something branches in a limited space, soon the branches will touch each other. The question is, how soon is “soon”. If we imagine a real 3D tree in a 3D world, the branches will touch before dozen splits. But if the tree would be extremely large (a few kilometers) and the branches extremely tiny (a few milimeters), there could be more splits.
If we imagine the history of the whole universe as a branching tree in a many-dimensional world, we have to realize there are many dimension (I guess approximately six dimensions for each particle: position and momentum), and compared with the size of the dimension, the branches are really tiny (take two random particles in the whole universe, what is their probability of hitting each other). So there is a lot of time for the tree to grow.
Eventually, the branches will run out of space and start hitting each other all the time. But I think this will happen at the “heat death” of the universe. Then the branches will hit each other so much that the whole concept of time or even reality may become meaningless. But I think this is not happening now, yet. There is still a lot of space for the universe to grow without intersecting with other branches.
This seems to me like a new hypothesis, outside of the quantum physics as we know it yet, not supported by experimental results. Maybe it is so; maybe it isn’t. Without good evidence for it the prior probability seem small (there are many possible new hypotheses we could make to explain dark energy, this is just one of them, why should it be preferred to the alternatives).