Gear.0

Nothing gets "jumbled around in time". For instance, have you heard of the "twin paradox"? Basically it is a situation in which (leaving out details) 1 twin travels near the speed of light for some time and returns, the outcome depends on the details but let's say the first twin claims to only have been gone for 5 years, but twin 2 who stayed on Earth claims that twin 1 was gone for 30 years. So the two twins who were born on the same day could now have an age difference of 25 years. However, they both still exist in the present, they are not jumbled around at different time coordinates or anything. I don't think I understand what you are asking in your second question. But if it helps, all we really know is what we perceive. Also, there are some things in nature that have a sort of "clock", like the half-lives of radioactive elements. In order for us to perceive relativity working properly it must also apply to such things.

The answer you are looking for really depends on why you are asking. If this is a conceptual highschool level homework question, then probably you would want to say they have no effect because they are electrically neutral. However, the more detailed answer is that out of the 4 fundamental forces, 2 of them act between neutrons. They are the gravitational interaction, and the strong interaction. Gravity acts because they have masses, however make sure that you understand this effect is extremely tiny. It is negligible and is almost always considered to not be present. So the only interaction that matters is the strong nuclear interaction. Neutrons and protons are actually composite particles, meaning they are made up of smaller fundamental particles called "quarks". The strong force acts between these quarks and is the strongest of the 4 interactions, therefore it easily overcomes any electrical repulsion.

Some theories are widely accepted, almost as if you can take them as fact. The many worlds theory, as far as I know, is definitely not one of them. It's just one possibility, and as long as we have some, no matter how small, reason to think it is a valid possibility then it would be foolish to dismiss it. But, as you say, if all realities happened all at once but were independent of each other, then as I have already shown there is no need for that.. Why can't there just be one? What I was showing in my previous post is that there is actually a logical progression of thought that leads to the many worlds theory as a solution to something, and the many worlds are not independent of each other, so if the theory is right, then it plays a direct role in our reality. The idea you are trying to use, where all realities exist simultaneously should have no effect on our reality whatsoever whether it is right or wrong, and as such it is probably impossible for us to ever know, which is why it is not really a useful theory.

But if there were already an infinite number of universes that sort of defeats the purpose of the many worlds theory. I don't think the idea of many worlds came about simply because there are so many possibilities that we think there has to be a universe for all of them... that doesn't really make any logical sense. The reason for the idea I think, is to correct an obvious paradox that arises from the Copenhagen interpretation of the wavefunction collapse. If we are observing a particles spin, say, up or down. It has a 50% chance of being either. Now, say I measure spin up, then the wavefunction has collapsed and the particle is now in a definite state of spin up. However, if you are completely isolated from me and are unaware of my measurement, then the particle should still be in a superposition of 50%-50% spin up and spin down... But how can this be? I know for certain that when you measure the particle you will find it to be spin up because I know it is spin up, but the wavefunction is still a superposition to you. So in order to preserve the notion that the system really is undetermined until you measure it requires that there can be different realities. In this hypothetical scenario you and I are completely isolated from each other, so even if you do measure spin down, then you will be in the world in which I measured spin down at the beginning, and if you measure spin up then you will be in the world in which I measured spin up. Also I think that is how the idea is introduced, as a branching set of worlds that continually grows.