Incoming wall of text...
The Korolev wrote...
Alternate realities and different dimensions are the same in that they are a part of the greater multiverse. They both describe and explain the same thing, just with different names. The multiverse could also include alternate universes and parallel worlds.
The multiverse has several different theories and hypothesi describing it, and there are different ways of viewing it. Although the two different view point you described could be seen as different takes, I see the second with the same explanation as the first.
The reason I see them both the same is because the second take (altered environment) if you traced it back far enough, could have just been a branch of the first. Even if it was way back at the Big Bang, the entire universe could be altered, but I would still consider it an alternate reality of the first stated example.
Actually that isn't entirely true. You cant say that two things are the same thing because they are part of the same thing. My hard drive in my computer is not the same as my processor just because they are both part of my computer. Alternate realities are part of the different dimensions, and the different dimensions are part of the multiverse you describe - although if you believe string theory there is no 'multiverse' because its all contained in the 10th dimension. If there was a 5th dimension, it would be made up of all the possible 4th dimensional realities. Just like the 4th dimension is made up of all the possible 3 dimensional realities - this is what we perceive as life (although I should note that view is controversial).
I haven't really studied the whole subject but I know a bit about it in general. There are scientific grounds to support the existence of alternate realities and higher dimensions. You see, gravity - as a force - is actually quite weak compared to the other three fundamental forces. Although we can accurately model gravity, something is still missing from the equation. If however you consider the possibility of a 5th dimension, and that gravity acts across all of the alternate realities that compose the 5th dimension, then gravity suddenly fits in with all the rest of the forces. So while we don't have any concrete evidence, I would say that there is a strong possibility of at least one higher dimension.
You are right about the two examples tsuyoshiro gave being the same thing though.
tsuyoshiro wrote...
So in all there are two general takes on the possibility of alternate realities. One where your daily decisions are fractured into several paths that branch off into possible alternate realities, each one possibly very close to your current reality...and one where there is a fundamental change to the environment that impacts everyone in some manner. Like a world without shrimp...or one with just shrimp. Or does that count as a different dimension rather than an alternate reality....
It gets a bit confusing.
The reason why you are perceiving these two 'possibilities' as different from each other, is because you are trying to view the world in terms of human and non-human. Humans aren't special. We aren't some sort of special matter in the universe that everything else revolves around. We are comprised of the same basic building blocks as everything else, and the particles that make up a person obey the same laws that everything else does. At this point if we were discussing philosophy we would run into the mind-body problem, which is essentially the conflict of free will and determinism. The following theory I'm about to outline fits more with free will, I'll get back to determinism in a moment.
The set of possible alternate realities is infinite. At each moment an infinite number of new realities are created branching off from our own and at the next moment after that each one of those infinite different realities will create a new set of realities. You have to consider the possible directions of movement of every particle in our universe. If you believe in this approach, then there exists every possible reality you could imagine, and several that you cannot. There is a reality where none of us exist, and countless realities branching from it where we also do not exist. There is a reality identical to our own save for one electron with a different spin. There is a reality identical to our own save for two electrons with different spins. You get the ideal. Infinite.
After that, in some variations of string theory, there is a 6th dimension. Where the 5th dimension holds all the possible realities branching off from one starting point, the 6th dimension holds all of the possible 5th dimensional realities. Although I wouldn't really know, it is thought that all of the 4th dimensional realities that make up a 5th dimensional reality will share certain properties - like gravity, and basic laws of physics. 5th dimensional realities would be different however, in that each one would have a different set of laws governing their 4th dimensional realities. There would be an infinite set of different laws and starting conditions for these realities, and all of those different possibilities, along with all the possibilities that could branch from all of those infinite different laws and starting conditions would make up the 6th dimension.
Confused yet?
Of course, I don't personally like the idea of the 5th dimension as I explained it up there. I'm one of those rare people you would call a hard determinist - I believe everything is predictable. Or in other words I believe in fate. If you look at it from that perspective then there is only one possibility for the next moment from now, so there can be no alternative universes branching off from our own. If you take this stance you are forced to eliminate the 5th dimension I explained above. Instead the 6th dimension becomes that 5th dimension. There is still an infinite number of alternate realities, but they don't branch from our own. Rather they simply start from different laws and starting conditions. That being said, even in this view there will still be every possible reality you could imagine - they just are less interactive with each other. This was the view Einstein was most fond of I believe - he was fairly famous for the saying "god does not throw dice".
744268 wrote...
Well, say alternate realities are real and what if in one reality humanity evolved much earlier than we did in this reality (let's say 1 million years earlier). What are the chances that this race of highly advanced humans discovered a way to cross realities and is out there enslaving weaker human races, say in a Hitler kinda way. And what are the chances that another group of highly advanced civilization is waging war against them in this inter-reality plane? I'm just thinking outloud here
While hypothetically gravity does cross the different realities, I think it is fairly safe to say that it is an exception. You see, if we assume that there are an infinite number of possible realities, and that it is possible to travel from one reality to another, then we can be fairly certain that there would be a reality somewhere (remember there is an infinite number of them) where a civilization had acquired that technology. Of all of these infinite possibilities, there would be at least one where that civilization had already interfered with ours. There would be no way we wouldn't know about it. Basically though, what you suggest would create a paradox if true.