RE: How big is the universe?
July 27, 2017 at 4:41 am
(This post was last modified: July 27, 2017 at 4:43 am by Alex K.)
(July 27, 2017 at 4:19 am)ignoramus Wrote: Alex, if we do indeed live in a many worlds or multiverse, where does the maths point to and why? IE, if we do just live in a single universe, wouldn't the maths be the same?
Also would all these other universes be nested in the same spacetime we are currently in? How do we define a "dimension" again? lol.
Those are several separate questions. The easiest way to define #of spatial dimensions is in how many orthogonal directions you can go. You can take three pencils and set them up such that they are all orthogonal to each other, but you can't do the same with four pencils.(If you can, down under is even stranger than I thought.) Parallel Universes are in most theories not thought to be literally parallel to us removed along a higher dimension of space. That theory would have to be quite complicated if the othher universe isn't to affect us very noticeably via gravity.
In Many worlds quantum mechanics, this inclusion of gravity is exactly the crux. In the simplest form without taking into account quantum gravity, many words quantum mechanics considers all the superpositions of possible events that come out of the Schrödinger equation to be equally real. In a sense, this is the simplest and most straightforward interpretation of what the Wave function and the Schrödinger equation mean. In all other interpretations you have to discuss away all the alternative superpositions. So Everett's many worlds are relatively straightforward mathematically even if hard to swallow from a philosophical perspective. Where it gets weird is once you include gravitation. If there is a quantum superposition of particle being in place A or place B, we have one universe where space gets bent in A, and one universe in which space gets bent in B. So spacetime has to exist in a quantum superposition as well, and that means all the parallel worlds in principle live in the same spacetime, but in parallel versions thereof. This gets really complicated if you go back in time to the big bang and the question is, what if some parallel universes bang later or earlier than others. What is then the status of the universe, where is the big bang actually?
The fool hath said in his heart, There is a God. They are corrupt, they have done abominable works, there is none that doeth good.
Psalm 14, KJV revised edition
