Are There Other Universes Beyond Our Own?

[revo74]

From my understanding there is no 'proof' that there is an 'outside the Universe'. My question is, does the latest scientific data imply that there is or is not? Do we have any good reasons to believe are things outside of our Universe or not? Please elaborate.

Thanks

 

[mathman]

Brian Greene's latest book (The Hidden Reality) discusses this subject in complete detail.

 

[Chronos]

This is largely an issue of ontology and semantics. The universe is traditionally defined as all that exists. Science narrows it down to all that can be measured [observed]. In effect, anything new observed is, by definition, a part of our observable universe. For example - the big crunch [cyclical unverse]. If we detect an unambiguous imprint of a prior universe in the CMB, it will automatically be causally connected to our present universe and, hence, an extension thereof.

 

[revo74]

This is largely an issue of ontology and semantics. The universe is traditionally defined as all that exists. Science narrows it down to all that can be measured [observed]. In effect, anything new observed is, by definition, a part of our observable universe. For example - the big crunch [cyclical unverse]. If we detect an unambiguous imprint of a prior universe in the CMB, it will automatically be causally connected to our present universe and, hence, an extension thereof.

I realize the semantic problem that exists due to the definition of the Universe. Forgot that for a moment.

Is it true that the current scientific data suggests that our four dimensional space-time continuum which we occupy had a finite beginning and that it is limited in size? Wasn't there a time when our Universe didn't exist, which leads us to believe that other realms other than our own exist out there?

 

[HallsofIvy]

I realize the semantic problem that exists due to the definition of the Universe. Forgot that for a moment.

Is it true that the current scientific data suggests that our four dimensional space-time continuum which we occupy had a finite beginning and that it is limited in size? Wasn't there a time when our Universe didn't exist,

Yes, there are some farily good estimates of when the "big bang" occurred.

which leads us to believe that other realms other than our own exist out there?

? I don't see how that follows.

 

[revo74]

Yes, there are some farily good estimates of when the "big bang" occurred.

? I don't see how that follows.

If the Universe had a beginning than something must have caused it right? A quantum fluctuation, white hole, an agent(s) of some kind, etc.

It couldn't have just come about from 'absolutely' nothing.

 

[narrator]

If the Universe had a beginning than something must have caused it right? A quantum fluctuation, white hole, an agent(s) of some kind, etc.

It couldn't have just come about from 'absolutely' nothing.

As a layman, it's my understanding that in the fraction of a second when the BB first happened, the density was so great that matter did not or could not follow the rules of physics as we know them, and even realty could be an entirely different thing, which leads to several possible precursors, including coming from nothing.

 

[revo74]

As a layman, it's my understanding that in the fraction of a second when the BB first happened, the density was so great that matter did not or could not follow the rules of physics as we know them, and even realty could be an entirely different thing, which leads to several possible precursors, including coming from nothing.

When you say nothing are you referring to 'absolutely' nothing?

In my opinion it's nonsensical to think that our four dimensional space-time continuum just appeared from absolutely nothing with all of these rules and forces.

 

[narrator]

When you say nothing are you referring to 'absolutely' nothing?

In my opinion it's nonsensical to think that our four dimensional space-time continuum just appeared from absolutely nothing with all of these rules and forces.

As I say, this is what I've heard. But in that moment, when all reality is turned on its head, something from nothing isn't as big a leap. But "nothing" is only one possibility, and from what I've read, not the most popular one.

 

[Chronos]

A universe from nothing is a possibility, a bouncing [cyclical] universe is another possibility. Bounce merely evades the issue by hiding behind the skirts of eternity and demands 100% energy-momentum conversion efficiency between bounces. I do not see how that is a more satisfying answer.

 

[revo74]

A universe from nothing is a possibility, a bouncing [cyclical] universe is another possibility. Bounce merely evades the issue by hiding behind the skirts of eternity and demands 100% energy-momentum conversion efficiency between bounces. I do not see how that is a more satisfying answer.

Is there any scientific data which suggests that there 'is' or 'is likely' other Universes or dimensions or is it just speculation?

 

[Cosmo Novice]

Is there any scientific data which suggests that there 'is' or 'is likely' other Universes or dimensions or is it just speculation?

You are missing the point. Scientific data requires empirical evidence or theoretical proofs, therefore anything which can be seen/measured/quantified is (even by extension) a part of the known U.

For example if we were to detect (by some quantifiable scientific means) a higher dimension, then by extension for us to detect it must mean it has some observable property in our U, therefore must be part of our U - albeit an extended one.

 

[bcrowell]

Is it true that the current scientific data suggests that our four dimensional space-time continuum which we occupy had a finite beginning and that it is limited in size?

There is a discussion of the finite or infinite size of the universe in the sticky FAQ thread at the top of the cosmology forum.

Wasn't there a time when our Universe didn't exist, which leads us to believe that other realms other than our own exist out there?

In standard cosmological models, not only is there not a time before the Big Bang, but the Big Bang itself is not a point in time. Only t>0 exists.

 

[George Jones]

Is it true that the current scientific data suggests that our four dimensional space-time continuum which we occupy had a finite beginning and that it is limited in size?

There are no data that indicate that the four-dimensional spacetime is limited in size. In fact, if it is, then time travel is possible (i.e., closed timelike curves exist). This result is independent of the cosmological model (but can't be an FRW universe, as all FRW universes are unbounded spacetimes).

There is a discussion of the finite or infinite size of the universe in the sticky FAQ thread at the top of the cosmology forum.

The sticky is not about the boundedness of four-dimensional spacetime, it is about the boundedness of three-dimensional spatial hypersurfaces (i.e., it is about the boundedness of space.) But maybe revo74 really has space in mind, not spacetime.

 

[Cosmo Novice]

There are no data that indicate that the four-dimensional spacetime is limited in size. In fact, if it is, then time travel is possible (i.e., closed timelike curves exist). This result is independent of the cosmological model (but can't be an FRW universe, as all FRW universes are unbounded spacetimes).

I don't think you can imply of definite time travel possibility given certain conditions. This is coming from a complete layman of course. If you can elaborate please that would be appreciated.

 

[George Jones]

I don't think you can imply of definite time travel possibility given certain conditions. This is coming from a complete layman of course. If you can elaborate please that would be appreciated.

Unfortunately, I find this particular result difficult to motivate at a non-technical level. Roughly, if spacetime is bounded, then time must be looped. For example, a bounded spacetime might be a 4-dimensional hypersphere (hypersurface of a 5-dimensional ball). Compare this to a 2-dimensional sphere (surface of a 3-dimensional ball, like the Earth), on which all kinds of closed loops can be formed.

The mathematical proof is a bit technical, but it is a well known result (e.g., it is in Hawking and Ellis); for a technical sketch, see

https://www.physicsforums.com/showthread.php?p=1254758#post1254758.

 

[apeiron]

If the Universe had a beginning than something must have caused it right? A quantum fluctuation, white hole, an agent(s) of some kind, etc.
It couldn't have just come about from 'absolutely' nothing.

Yes, our everyday logic would demand that there would have to be a first cause of some kind. Although more sophisticated discussions of logic allow also ideas such as final causes and vague causes which soften (but probably don't remove) the issue of initiating conditions (material causes and efficient causes).

A universe from nothing is a possibility.

What are you thinking of here? If it is a quantum fluctuation, then a fluctuation has to be a fluctuation of "something". Or are you making reference to some other particular idea?

There are no data that indicate that the four-dimensional spacetime is limited in size. In fact, if it is, then time travel is possible (i.e., closed timelike curves exist). This result is independent of the cosmological model (but can't be an FRW universe, as all FRW universes are unbounded spacetimes).

Surely the data indicates that the universe is most likely bounded and closed to the past, eternal and open to the future? Our kind of time started at the big bang. So the OP was about this beginning of "everything" apparently out of nothing. Yet because that does not seem logical, then there must be something "outside" to ground the creation of the universe.

So science has now shown that our universe has a definite beginning (ruling out that it just eternally existed).

The next question is whether that beginning had to have a beginning. Is there an "outside"? And so far, I am unaware of any good ideas about how it could come out of "absolutely nothing" - QM is not saying that.

Another get out, eternal cyclic return, is popular with some and has been worked up into a hypothesis perhaps by Loop Quantum Gravity people.

A different view is that the beginning of our universe represents a phase transition to a more ordered state. So logically, what came before was something "less" but not actually "absolutely nothing". The question then becomes how far back can we push this line of thought so that "less" becomes the "least form of existence".

As I admit, there would still be some kind of puzzle over the existence of a necessary set of initial conditions. But searching for a least state of existence is, at least, a rigorous project.

If our universe is a development of a state of potential, then what exists now will retain an imprint of what must lie "outside". A symmetry that has been broken can tell you about the symmetry that was once unbroken.

 

[Chronos]

Your objection to a 'universe from nothing' is logical. It does appear a quantum fluctuation requires 'empty space' to fluctuate within - suggesting our universe is afloat in an infinite sea of empty space, which also suggests an infinite number of other universe are also floating around in this same sea [Copernican principle thing].

 

[revo74]

We know that the Universe was once extremely small, then some 13.7 billion years ago it began to expand. Well it there had to be something, which is outside of it, that it was expanded into.

 

[revo74]

You are missing the point. Scientific data requires empirical evidence or theoretical proofs, therefore anything which can be seen/measured/quantified is (even by extension) a part of the known U.

For example if we were to detect (by some quantifiable scientific means) a higher dimension, then by extension for us to detect it must mean it has some observable property in our U, therefore must be part of our U - albeit an extended one.

The scientific data tells us that the Universe was a singularity at one time, which then expanded 13.7 billion years ago. What it expanded into IS outside of the Universe, right? So doesn't the scientific data suggest there must be an outside of the Universe? Perhaps indirectly, but none-the-less.

 

[Ryan_m_b]

The scientific data tells us that the Universe was a singularity at one time, which then expanded 13.7 billion years ago. What it expanded into IS outside of the Universe, right? So doesn't the scientific data suggest there must be an outside of the Universe? Perhaps indirectly, but none-the-less.

Again, I think you are missing the point. It didn't expand into anything because the expansion was the expansion of space itself.

"Outside" is a relative measure within space, you can no more be outside of space than you can be before time.

 

[Cosmo Novice]

The scientific data tells us that the Universe was a singularity at one time, which then expanded 13.7 billion years ago. What it expanded into IS outside of the Universe, right? So doesn't the scientific data suggest there must be an outside of the Universe? Perhaps indirectly, but none-the-less.

The data does not tell us that U was a singularity, only t>0 actually exists and in reality only t>plancke time can be discussed scientifically. There is no outside, at least not one that can ever be quantifiably proven, for their to be an outside would require an edge to the universe. The Universe (in both open and closed models) does not have an edge - barring the exception of a temporal edge.

The U did not expand into anything - expansion is space/time expansion not space expanding into a pre-existing space.

I think the problem you have is you are thinking of U as analogous to a 3d expanding sphere (maybe when you are thinking of n-spheres) and not taking into account that conceptually and mathematically it is very difficult to visualise U in any topology.

I am in no way trying to discourage you though :O) It is very hard to comprehend.

 

[DavidMcC]

From my understanding there is no 'proof' that there is an 'outside the Universe'. My question is, does the latest scientific data imply that there is or is not? Do we have any good reasons to believe are things outside of our Universe or not? Please elaborate.

Thanks

IMO, an "outside the universe" is implied to the extent that only loop quantum cosmology makes sense of all the observations without arbitrary add-ons like inflation and slight parity violation in particle physics, etc. The "outside" is not of course, a location that can be reached, as it is not "space" in the usual sense of the word, which is something we cannot leave, because a particle is an excitation of a loop of space, and is therefore fundamentally bound to that space, even though it can move from loop to loop without energy input (Newton's first law and the non-appearance of an aether).

 

[Lost in Space]

If the Big Bang resulted from a singularity changing state (exploding?), could every other singularity in the present universe similarly do the same? If singularities are 'outside' our universe and there are supposed to be singularities at the core of every galaxy, could they be be interpreted as 'seed' universes? I find it hard to conceive of a Big Bang occurring without a prior temporal dimension to occur in. If a quantum fluctuation causes a phase change in a black hole, it seems to me it would require this in order to happen. There is no time inside a singularity but if it has an event horizon maybe this could be where the temporal dimension resides?

 

[Imax]

From my understanding there is no 'proof' that there is an 'outside the Universe'. My question is, does the latest scientific data imply that there is or is not? Do we have any good reasons to believe are things outside of our Universe or not?

It depends on whether we live in a closed or open Universe. In a closed Universe, it doesn’t matter in which direction you travel in 3D space (i.e. x, y, or z) or how long you travel in time. You will eventually come back to the point where you started from, your origin. In an open Universe, you can choose a direction in 4D space-time and you will never come back to your origin, where you started from, many years ago.

 

[Shenstar]

I'm finding a lot of confusion in this thread.

Firstly I thought "nothing" meant an infinite density zero mass zero volume, nil time

Secondly the quantum fluctuations I thought occurred in empty space, nothing, but then zero mass is something? Also another thought is shouldn't the quantum fluctuations only exist and appear from a universe with something, when there is nothing then can these fluctuations be caused?

Thirdly, if there is something I.e. A singularity then the only way to differentiate that singularity from what is not a singularity and what the singularity expanded to become means there was the other thing (call it empty space) where the expansion was not. What I'm trying to say by very definition of a singularity does it not necessitate other than it. And therefore an outside of a universe? If the singularity gave birth to everything we know i.e. The entire universe, then there must be a border to distinguish between the singularity and outside of it. Regardless of the shape of the universe, open, closed, finite or infinitely expanding - there must be a realm outside of it, free from the universe as we know it, without space-time, all we can know it is notvour universe?

 

[DavidMcC]

If singularities are 'outside' our universe and there are supposed to be singularities at the core of every galaxy, could they be be interpreted as 'seed' universes?

Provided that the "singularity" isn't a Godel-style, classical one, then yes, IMO, based on Smolin's loop quantum gravity, with loops that only link within that universe/space/vacuum/"big bang". It would be rather a small one, though.