Multiverse

[Thales]

What about a cyclical universe? Then there is more than one everything...

[ydoaPs]

CHEERS!!

we need some other word to describe 'universe' in physics

P.S.What language is that?

 

latin

[prokaryote]

the classic multiverse (or "many-worlds") concept, in it's scientific guise, originated from Everett's formulation of QM, where he set out to re-formulate QM without its dependence on observers' special role "collapsing" the wavefunction. iirc, in his formulation, Everett does away with the collapse of the wavefunction to a determistic eigenstate post-"measurement"; instead he considers observer as being part of the system tied to a particular eigenstate that remains a mixture even after the act of measurment. in other words, a measurement does not somehow magically "collapse" a previously probabilistic world to a deterministic one, but rather the system (with observers being part of that system) is split into two or more orthogonal "worlds". so the whole concept arose from interpretation of the formalism (result wise the two formalism, classical and Everett's, are essentially equivalent). its truth value is really matter of faith. whether the interpretation is something falsifiable, i'm not sure. at least, i'm not aware of any experimental setup to test it.

[ydoaPs]

What about a cyclical universe? Then there is more than one everything...

 

branes aren't universes. they are parts of the same one. separated by 2 dimensions.

[Sorcerer]

There is no "space" for the "universes" to coinhabit.

 

Argh reading this is driving me nuts, I can't see why you don't get it. Space is an internal feature of a universe, not an external feature.

[Sorcerer]

Distance is what separates objects.

 

IN SPACE!!!!!!!!!!!!! I think I went insane for you Jakiri.

[ydoaPs]

k, how the hell else do you separate things?

 

PS try not to post two in a row. edit if you have something else to say and no one else has posted yet.

[Sorcerer]

k' date=' how the hell else do you separate things?

 

PS try not to post two in a row. edit if you have something else to say and no one else has posted yet.[/quote']

 

They don't need to be seperate because they dont influence each other in anyway, a big fat man could be sitting on you head right now, but you don't know it, because the two universe don't exist with respect to one another.

 

SO...... they are separated by observable reality.

[BrainMan]

I posted this some time ago in another thread: http://www.geocities.com/haripaudel/Parallel_Universes.htm

 

This is a link to Max Tegmark's SA article about multiverses, where he presents his own theory about the level 4 multiverse. The ideas are perfectly testable, according to Tegmark. All the people saying that "it is unprovable" are wrong (so far as "proof" means scientific support, which is the most any scientific theory can hope for).

[Martin]

I posted this some time ago in another thread: http://www.geocities.com/haripaudel/Parallel_Universes.htm

 

This is a link to Max Tegmark's SA article about multiverses' date=' where he presents his own theory about the level 4 multiverse. The ideas are perfectly testable, according to Tegmark. All the people saying that "it is unprovable" are wrong (so far as "proof" means scientific support, which is the most any scientific theory can hope for).[/quote']

 

Hello B-man, I read Tegmark's article when it came out and could not find any reason to say multiverse version IV was testable by some definite experiment. There was no proposed experiment that one could now do----everything related to testablity was vague. There was no definite prediction of a number resulting from some measurement, which could refute the theory if it came out wrong.

 

I checked again, just now using your link, and I see where he CLAIMS his case IV is testable. But then in effect he takes the claim back and says "trust me, we are working on it":

 

---quote from Tegmark section on mulitverse scenario 4---

The Level IV multiverse hypothesis makes testable predictions. As with Level II, it involves an ensemble (in this case, the full range of mathematical structures) and selection effects. As mathematicians continue to categorize mathematical structures, they should find that the structure describing our world is the most generic one consistent with our observations. Similarly, our future observations should be the most generic ones that are consistent with our past observations, and our past observations should be the most generic ones that are consistent with our existence.

 

Quantifying what "generic" means is a severe problem, and this investigation is only now beginning. But one striking and encouraging feature of mathematical structures is that the symmetry and invariance properties that are responsible for the simplicity and orderliness of our universe tend to be generic, more the rule than the exception. Mathematical structures tend to have them by default, and complicated additional axioms must be added to make them go away.

---end quote---

 

I know of at least one multiverse theory which does make definite numerical predictions (e.g. about the maximum mass of a neutron star)

by which the theory could be refuted. But I think Tegmark's concepts missed the boat on testability.

 

to be meaningful a physical theory has to be falsifiable---it has to make a prediction about the outcome of a future experiment which, if it comes out wrong, will refute the theory.

 

If on the contrary Tegmark's scenario 4 is actually testable in an empirical quantitative way (not just using subjective notions like beautiful or symmetric or generic or "mathematically simple") then please point out to me how. I would like to know if I have overlooked anything.

[BrainMan]

No, you wouldn't find such things easily in a SA article. Here is something a bit more thorough:

 

http://arxiv.org/abs/gr-qc/9704009

 

Enjoy!

 

 

 

[Notice the full text is offered below the abstract...]

[JohnB]

If a complete tyro may make a comment?

 

Yourdads question seems to me to be similar to the one in Astronomy. "If the Universe is expanding, what is it expanding into?" The difficulty in the answer and the understanding thereof is a matter of conceptualization. It is hard to concieve of there being an "edge" to the Universe without there being something on the other side of the "edge". Likewise it is hard to concieve of two things being coexistant but separate.

 

There is also the matter of perspective.

 

If we were to consider the classical "Flatlander" in a two dimensional world. We could have an infinite number of these worlds stacked on top of each other, but, since their third dimension is zero the stack has no height. They are hence coexistant.

 

From the perspective of the inhabitants of each of these worlds, their Universe is complete and total.

 

From the perspective of a three demensional being though, all of the worlds are separate and at the same time coexistant.

 

I do realise that this is not an accurate representation of what I feebly grasp of what I've read, but thinking of it that way stops my brain dribbling out my ears.