The size of the entire universe is currently unknown, but there doesn't have to be a relationship with the size of the visible universe which is just a result of age+expansion it could be infinite for all we know. Or at least orders of magnitude larger than what we see.

(July 26, 2017 at 11:36 pm)Alex K Wrote: The size of the entire universe is currently unknown, but there doesn't have to be a relationship with the size of the visible universe which is just a result of age+expansion  it could be infinite for all we know. Or at least orders of magnitude larger than what we see.

Yea but you still have theories of parallel and bubble "multiverse".

But just with the one we know, there is a strong indication that the one we are in will run out of energy. If I am not correct. Also known as "heat death".

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.

(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?

It's at least big enough to contain my ego

I guess that means it's very, very vast to say The least.

Also, OP, 23 bilion across would be fine with 14 bilion years, no? The universe probably didn't expand in just one direction, right? Or am I misreading?

(July 27, 2017 at 4:43 am)Mr.Obvious Wrote: It's at least big enough to contain my ego

I guess that means it's very, very vast to say The least.

Maybe your ego is rolled up in some higher dimensions to save space...

Was the main reason for the inspiration of the many worlds hypo to try to logically explain the double slit/spooky distance?
Or was the idea justified to solve other dilemmas?

Do strings do anything to help our understanding of the double slit?

I enjoy this video made by two brothers 'The Scale of the Universe":

https://www.youtube.com/watch?v=uaGEjrADGPA

If me and my brothers made this video it would say "Your Momma's Butt" at 3:00.

(July 27, 2017 at 5:43 am)ignoramus Wrote: Was the main reason for the inspiration of the many worlds hypo to try to logically explain the double slit/spooky distance?
Or was the idea justified to solve other dilemmas?

Yes, the double slit and all the related superposition experiments. But I don't tire to point out that theoretically, quantum superposition is directly tied to Schrödinger's wave equation and the wave function. Once you accept that Schrödinger's equation describes the world, you are automatically confronted with the question: what if I include not only that tiny atom over there, but also myself as the observer into the system which is described by Schrödinger's equation, what does it mean if I myself am in a superposition (which I will automatically be according the Schrödinger's equation if I observe an atom which is in a superposition).

If at this point you simply say: I accept that the wave function corresponds to something which really exists in nature, you automatically get Many Worlds, because all those superpositions of different possibilities are there in the wave function always, including you yourself being in one. It's only if you want to reject Many Worlds that you have to make the additional intellectual effort to explain why the wave function describes reality, but only very certain parts of it correspond to something that actually exists, or throw out any attempts to even say what superposition means and which things really exist (the pragmatic but philosophically unsatisfactory Copenhagen interpretation).

Quote:Do strings do anything to help our understanding of the double slit?

Not that I am aware. Quantum theory is kind of put on top of Superstring Theory (or vice versa depending on your perspective), but I am not aware that String Theory helps address the weirdness of Quantum Theory in any significant way.

OK.

#theist hat on (because I'm bored)

So we know that nature "seems" to defy logic and reason and "seems" to act in a spooky "supernatural" way. IE: double slit.
Are we as science "indoctrinated" people completely oblivious to other preposterous explanations such as godly intervention?

It sounds wrong, but we are also the first to state we don't know most things. Why are respectable science people comfortable entertaining hypotheses of an equally absurd explanation?
Sure, I think all woo is bs, but logically and only because it can't be proven to be true, no matter how absurd. No different to the double slit spooky stuff.
Scientists are more than happy to come up with their own woo and basically call it a proper hypothesis and is taken seriously?
Why can't something like a god (not as described by the babble of course) be a missing factor to be entertained?
We know first hand weird spooky shit happens! Why can't god be one of those "real" spooky things?