Can We Go "Outside the Universe"?

[narrator]

Sorry if my question seems naive, but is it theoretically possible to be somewhere outside the universe? (Ignoring our own limitations in getting there...)

I'm pretty sure the answer is no, but I'd rather learn than assume.

 

[Cosmo Novice]

Hello Narrator,

I don't think it would - by definition U=the totality of everything. If you can "go" somewhere physically then it has to exist within U. Our limitations currently are that we cannot travel beyond time/space.

While there are arguments that postulate the existence of a multiverse or brains that exist outside our U, these are conjecture as far as I am aware without any empirical evidence (of course due to their very nature)

One possible idea would be that traveling into a BH may take you somewhere external to U - although you would be stretched/incinerated before entering the singularity and again this is just speculation and fringe theory.

All very interesting though!

 

[JaredJames]

One possible idea would be that traveling into a BH may take you somewhere external to U

Do any scientists still believe that? Or has there been anything put out there in published form on the matter?

 

[Cosmo Novice]

Do any scientists still believe that? Or has there been anything put out there in published form on the matter?

I am not sure if there is any evidence or theories on this - let alone whether there are any papers, just throwing out the idea for more knowledgeable folk to comment on. :)

I think I have read some ideas comparing the U to a BH, in particular the overall topology of U being a closed manifold similar to a BH - again I have no real scientific knowledge so this is more food for though and ideas for those who understand to expand on.

 

[phinds]

while as stated above there are hypotheses about "outside the U" these are purely theological, not religious but not falsifiable and therefore not science.

 

[mdmaaz]

That's an interesting question. I believe that we can leave our universe. But if we leave our universe, we will just end up in a different universe. Theoretically, we will have to be in one universe or the other. For example, I want to leave my universe, so I will do just that (I'm not sure how I'll do that... but let's just assume I leave my current universe.) I will enter a different universe. Thus I succeeded in leaving the universe, but I'm still in another universe.

 

[Khashishi]

It's more of a matter of definition than of actual physics. If you can leave the universe and enter another one, then, you'd better have a really good reason for calling it another universe and not just part of our universe. Like, radically different laws of physics.

 

[DavidMcC]

Narrator, AFAIK, no cosmology allows for anyone to actually go to another universe. However, some cosmologies allow for the existence of other universes. Eg, Smolin's old "fecund universes" cosmology. (This was sadly rejected because of a prediction that failed, but was anyhow based on a dubious additional postulate of biological-style "natural selection" of BHs.)
Anyhow, the big snag is that, if you are foolish enough to try going to another universe through a BH, you will end up as just a minute quantity of dark energy in that other universe. So, you could say you can get there, but perhaps not in the form you would like!

 

[George Jones]

One possible idea would be that traveling into a BH may take you somewhere external to U - although you would be stretched/incinerated before entering the singularity and again this is just speculation and fringe theory.

Do any scientists still believe that? Or has there been anything put out there in published form on the matter?

There is another universe in the extended Schwarzschild solution for a spherical, uncharged black hole, but:

1) most of extended Schwarzschild spacetime is not thought to be physical;

2) even for ideal extended Schwarzschild, the other universe is not accessible by travel, even though it is viewable.

Most physical black holes are thought to be rotating, and the spacetime of an ideal rotating black hole, does allow worldlines that miss the (ring) singularity. and that arrive at other universes. A rotating black hole has two horizons, and a rotating black hole into which stuff falls likely has a singularity (that isn't present for an ideal rotating black hole) at the inner horizon. This singularity at the inner horizon might be weak enough to travel through, but a theory of quantum gravity is probably needed to figure out what is on the other side of the inner horizon.

See the figure between pages 14 and 15 from the link below.

There is a weak curvature singularity at the inner (Cauchy) horizon of a rotating black hole. Seminal work on this was done by Poisson and Israel, and this work was continued by Ori. See

http://physics.technion.ac.il/~school/Amos_Ori.pdf ,

particularly pages 15, starting at "Consequence to the curvature singularity at the IH: (IH = Inner Horizon), 16, and 24. On page 24, Ori says that classical general relativity cannot predict what happens inside the inner horizon,

For Novikov's take on this, see

http://arxiv.org/abs/gr-qc/0304052.

Roughly, if components of g (the metric) are continuous but "pointy" (like the absolute value function), then first derivatives of g have step diiscontinuities (like the Heaviside step function), and second derivatives of g (used in the curvature tensor) are like Dirac delta functions. If a curvature singularity blows up like a Dirac delta function, then integration produces only a finite contribution to the tidal deformation of an object, which, if the object is robust enough, it can withstand.

I think I have read some ideas comparing the U to a BH, in particular the overall topology of U being a closed manifold similar to a BH - again I have no real scientific knowledge so this is more food for though and ideas for those who understand to expand on.

As topological spaces, a Schwarzschild black hole and a closed universe are somewhat similar (but not identical).

 

[Cosmo Novice]

Most physical black holes are thought to be rotating, and the spacetime of an ideal rotating black hole, does allow worldlines that miss the (ring) singularity. and that arrive at other universes. A rotating black hole has two horizons, and a rotating black hole into which stuff falls likely has a singularity (that isn't present for an ideal rotating black hole) at the inner horizon. This singularity at the inner horizon might be weak enough to travel through, but a theory of quantum gravity is probably needed to figure out what is on the other side of the inner horizon.

Ok I just have a few questions.

Once you cross the EH you are destined for the singularity - I thought this was always the case?

Can singularities be weak and strong? I thought by definition they were the point at which all known science effectively breaks down?

Can you expand on this in general a little more please?

 

[George Jones]

Once you cross the EH you are destined for the singularity - I thought this was always the case?

All observers that enter a spherical, uncharged black hole hit the singularity, but observers that fall into a rotating and/or charged black hole can choose to miss the singularity. This is true for ideal, eternal black holes. This situation is more complex for astrophysical black holes that form from collapsing matter, and into which stuff falls.

Can singularities be weak and strong? I thought by definition they were the point at which all known science effectively breaks down?

I am not sure that there is a completely accepted technical definition of "singularity".

Roughly, a spacetime is singular if there is a timelike curve having bounded acceleration that ends after a finite amount of proper time. Singular spacetimes have "edges".

What does this mean? "timelike curve" means a path that a person (say, Alice) or particle could traverse in a rocket. "bounded acceleration" means that the rocket always has zero or finite acceleration. "ends after a finite amount of proper time" means that after a finite of time elapses on Alice's watch, Alice falls "off of spacetime" and "into the singularity."

At a singularity, science breaks down. Things can disappear "over the edge" of a future singularity, and science can't predict what, if anything, will appear from over edge of a past singularity. 100 gold bars? 100 clones of Charlie Sheen?

A singularity is strong if along at least some paths that lead to the singularity, things get crushed to zero volume. If there is no path for which this occurs, then the singularity is weak.

 

[Cosmo Novice]

At a singularity, science breaks down. Things can disappear "over the edge" of a future singularity, and science can't predict what, if anything, will appear from over edge of a past singularity. 100 gold bars? 100 clones of Charlie Sheen?

Charlie Sheen the original probably came from a BH!

 

[phinds]

100 clones of Charlie Sheen?

Now you're getting scary !

 

[DavidMcC]

George Jones: "At a singularity, science breaks down. Things can disappear "over the edge" of a future singularity, and science can't predict what, if anything, will appear from over edge of a past singularity. 100 gold bars? 100 clones of Charlie Sheen?"
IMO, George, this idea that "physics breaks down" is one of the worst half-truths in science history. The point is to find a physics that doesn't break down. For example, regarding the mass of a black hole, its gravitational binding energy becomes extremely high, and without a great deal of internal energy conversion, would result in an extremely negative mass, which obviously isn't the case with real BHs. A reasonable hypothesis is that the gravitational energy has been converted into new space (but space whose quantum loops do not intersect with those of the old space, and therefore do not allow light or any other particle, as an excitation of those loops to pass between the two).

 

[phinds]

George Jones: "At a singularity, science breaks down. Things can disappear "over the edge" of a future singularity, and science can't predict what, if anything, will appear from over edge of a past singularity. 100 gold bars? 100 clones of Charlie Sheen?"
IMO, George, this idea that "physics breaks down" is one of the worst half-truths in science history. The point is to find a physics that doesn't break down. For example, regarding the mass of a black hole, its gravitational binding energy becomes extremely high, and without a great deal of internal energy conversion, would result in an extremely negative mass, which obviously isn't the case with real BHs. A reasonable hypothesis is that the gravitational energy has been converted into new space (but space whose quantum loops do not intersect with those of the old space, and therefore do not allow light or any other particle, as an excitation of those loops to pass between the two).

I think in this context the phrase "physics breaks down" is just the commonly used shorthand for "the currently understood and accepted physical model breaks down", not any implication that there is no possibility of some day figuring out a model that does NOT break down and in that sense it is not in any way a "half-truth" but a completely accurate statement.

 

[DavidMcC]

That's the point I was trying to make, phinds. When people make statements like you might get "100 gold bars", it looks as if they are taking it too literally, and anything really can happen.

 

[narrator]

That's the point I was trying to make, phinds. When people make statements like you might get "100 gold bars", it looks as if they are taking it too literally, and anything really can happen.

David, perhaps you're being too pragmatic. Maybe George could have been less flippant, but unless the reader is more into fantasy I think people would get the "who knows" point. A sense of humor is important in any vocation. And the phrase that "science breaks down" isn't so inaccurate - current science does fail to explain what happens in these circumstances, which is not a criticism, just as it's not a criticism to point out my lack of understanding or that of any novice.

What I would be interested to know is where science is headed on that subject. I guess it's all up to theory and the only "experiments" that can be done are some sort of modeling, by computer or good old fashioned blackboard (whiteboard?). But it would be interesting to know.

 

[marcus]

I'm not sure that George Jones meant to say that at a singularity Science as a whole breaks down. We should probably let him clarify if he wants. I think what is usually meant is that at a singularity some particular scientific theory or model breaks down.

Science is a process of testing and improving theories/models. There is an identifiable self-selecting community with customs, traditions etc. It hasn't broken down in the past when there were singularities in theories.

(Like the socalled "ultraviolet catastrophe" and the singularity plaguing classical atomic models of 100 or so years ago.)

Science as a traditional community-based activity keeps chugging right along---at least that has been the experience so far---and eventually singularities get fixed.
I don't know of any case where that has not happened. Perhaps someone else does. It is what people tend to expect to happen.

I think most cosmologists would probably be quite surprised if the familiar pattern should turn out not to happen in this case---if it should turn out that the cosmo singularity was actually real and there had actually been infinite density and curvature in Nature, with a temporal terminus. This is just my two cents---I'm repeating something the Albert Einstein Institute public outreach website said, which I thought was pretty sensible.

 

[DavidMcC]

Marcus: "I think most cosmologists would probably be quite surprised if the familiar pattern should turn out not to happen in this case---if it should turn out that the cosmo singularity was actually real and there had actually been infinite density and curvature in Nature, with a temporal terminus."
My point is that not even a black hole as such (in this universe, or any other) is really a singularity. GR is a continuum-based approximation which breaks down at the Planck scale.

 

[DavidMcC]

Narrator, I was only trying to point out that expressions like "physics breaks down" seem absolute, as if the situation is fundamentally unfixable, which it isn't.

 

[DavidMcC]

Another point that George raised concerns the rotation of black holes as a reason wy they aren't like a universe. Clearly, any collapsing lobject does, indeed, spin up. However, the so-called Kerr ring "singularity" thus formed (in the case of a black hole) is thought to radiate its spin energy away as gravitational waves before collapsing completely. (I put the word "singularity" in quote marks, because I'm pretty sure it doesn't get to be a mathematical singularity.)

 

[DavidMcC]

...even though he was obviously being flippant about it!

 

[Lost in Space]

Isn't 'hyperspace' an example of 'outside' our universe?

 

[phinds]

Isn't 'hyperspace' an example of 'outside' our universe?

And what exactly is hyperspace (in the real world, not in Star Trek) ?

 

[Lost in Space]

And what exactly is hyperspace (in the real world, not in Star Trek) ?

Well, from what I understand, hyperspace is the initial state boundary of the Big Bang. As far as I know even Star Trek hasn't been there!

 

[narrator]

Well, from what I understand, hyperspace is the initial state boundary of the Big Bang. As far as I know even Star Trek hasn't been there!

Is this a reference to Minkowski space?

 

[Lost in Space]

Minkowski space could be said to be hyperspatial going by its description, but M-Theory predicts that there are eleven hyperspatial dimensions so I guess that hyperspace is pretty much what you interpret it to be. My own thoughts are that whatever it is, it's beyond the confines and boundaries of our universe but that's just my humble opinion!

 

[DavidMcC]

IMO, the problem with Minkowski spaces (and Calabi-Yau spaces for that matter) is that they are purely continuum spaces. The only kind of hyperspace that can predict all the peculiarities of particle physics and astronomical phenomena involves a hyperspace continuum, supporting quantized spaces that in turn support particles (as excitations of the quantum loops - a bit likes strings with something to actually tie the strings to!).

 

[Lost in Space]

So I suppose the next question is, can hyperspatial continnuum spaces exist outside our universe?

 

[ZapperZ]

Closed, pending moderation.

Zz.