I've written about these things in this blog before, but now I'd like to summarize my thoughts about how I understand the quantum mechanics and how I see the nature of the universe in general. It seems nobody understood my previous post, and probably nobody will understand this one either, but that's OK, I'm writing these primarily for myself, to gather and organize my thoughts.

In the standard interpretation of quantum mechanics, there is a thing called "wave function collapse", which doesn't make any sense in my opinion. It's supposed to happen "instantaneously", but what does that even mean? In Special Relativity there is no such thing as things happening in different places at the same time, because "at the same time" has no well defined meaning, it depends on the observer. There are situations where for one observer event A happens before event B, and for another observer event A happens after event B. For example, when, according to the wave function, a particle can be in two places, and we measure it in one of the places, the part of the wave function that is in the other place immediately gets information that the particle isn't there, and is updated accordingly. So if we make a measurement there, we know we won't detect the particle. The problem with this approach is that, as I mentioned before, for a different observer the measurements can take place in the opposite order, so the flow of information happens in the opposite direction. This is what Einstein called "spooky action at a distance", and it makes quantum mechanics in this interpretation non-local (btw this can't be used to transfer any actual information between the two places, but that's a different story).

So let me tell you what I think about all this. As I wrote in this blog before, when it comes to fundamental laws of physics, both directions of time should work the same way. Which means that the wave function should propagate in both directions - not only forward in time from the place where the particle was emitted, but also backward in time from the place where it (or lack of it) was measured. This way it contains only the information that is consistent with all events that happened in the past and will happen in the future. There's no need to collapse the wave function, and we avoid the "spooky action" and non-locality. What we get in return is retrocausality, which means that events happening now can be caused not only by things that happened in the past, but also by things that will happen in the future. In the above example, there is a connection between both measurements and the event where the particle is emitted that goes locally along all possible paths of the particle, and all 3 events are determined in a way that makes them consistent with each other. Note that with this approach the wave function can still be a superposition of different histories of the particle, if all of them are consistent with all the events happening before and after, which, for example, explains the interference pattern in the double slit experiment.

So, if I'm right, what does it tell us about the universe as a whole? Well, the way I see it it's a complex four (or more) dimensional object that consists of a huge number of events, interconnected in a consistent way. And time is not a fundamental property of it. It's an emergent property that is important only in large scales (larger than single particles), and originates from the boundary conditions that (for whatever reason) are imposed on the universe, by making one "end" of it have high density and low entropy (aka the Big Bang). This creates a "trend" that goes through the entire universe and makes it expand and the entropy grow. Why are the boundary conditions like this? I have no idea. The only thing that comes to my mind is the anthropic principle, which doesn't really explain it, it simply states that it must be like this because otherwise we wouldn't exist.