Colliding universes destroyed?... or nothing happens?

[consciousinsane]

After listening to the infinities astronomy cast I wondered what actually happens when 2 universes collide.

here are my thoughts.....

premise 1: nothing travels faster than light
premise 2: space expands
premise 3: given great distance, light from A can never reach B
premise 4: another universe collides with this one at point A

conclusion: Point B will never know of or experience the collision at A

2ndly..... could cosmic rays and background radiation (x and gamma rays) be a beginning signature of such a collision assuming we are close enough to the collision to detect it.

i always hear that such a collision would destroy both universes or form one giant universe (or an even greater infinite one). But if nothing can go faster than light, and A & B are such a distance apart, then B will never know what happen at A. So instead of being destroyed, they will merge and B will never know it even happen... or the corner by A will be destroyed, but B will sit there safe and sound.

Thoughts??? Answers???.........

Thanks.

[Shaula]

You are making the assumption that the collision is a simple 3D impact. Premise 4 basically constrains you to this whereas if you look at something like brane cosmology the collision could be a highly complex event from a 3D perspective. Even if we ignore branes, the sort of collision you are proposing requires a finite bounded universe embedded in a larger 3D space.

We also do not know what happens when objects like this collide. Without a more fundamental theory of the way the universe works we cannot actually say what the physical laws of the other universe would be, what would actually collide and how it would affect another universe.

[antoniseb]

... I always hear that such a collision would destroy both universes or form one giant universe (or an even greater infinite one). ...

I have never heard anything authoritative on what would happen. We are very short on experimental evidence, or even a collection of observed anecdotes to try and piece a model together from. Until we know more about time, space, and the universe in general, I think we can't say. Shaula's comments are very good.

[danscope]

Just to be certain; is the op actually meaning "Galaxies colliding" ? Or ....is it concerned with a percieved
" Other" universe, of which detection is difficult or beyond our powers but for phenomena we misinterpret
or cannot percieve?

[antoniseb]

... is the op actually meaning "Galaxies colliding" ...

Good question. With the kind of questions being asked, it does seem like the OP is talking about galaxies, rather than universes, so it could be a misuse of terms.
I suggest NOT answering it as though galaxies was the real question unless the OP comes back and says it was universes, not galaxies. I'd rather not have a long thread repeating stuff already in other threads, based on a guess about a new member's intent.

[ravens_cry]

For universes to collide, wouldn't they need something to move toward each other in?

[consciousinsane]

All great replies everyone!!

I am indeed talking about Universes. NOT galaxies.

I like the idea of the 3D restraint and how higher dimensions may complicate the collision as if it wasn't complicated enough. I even spent some time thinking about how the UNIVERSES may physically collide for differing shapes [flat vs. saddle vs. torus.].
I am also going on the idea that even if the other universe has different physics, ours must remain the same. I like to believe that even though some of the constants may vary in a different universe, the basic structure of our physics wouldn't be far off. In other words, If the universe colliding with us has a stronger gravitational influence, then it still functions in the same manner, just has more of an affect.
Therefore the expansion of space and speed of light may start to be altered in our universe once the collision happens at point A, but due to the distances and time involved, the point B will still be oblivious to any collision with the other Universe.

As far as experimental data, I realize that we have no way of finding this out anytime soon. I was hoping more along the lines of what the math may tell us. Much like the math is able to suggest Brane Theory. Which brings me to what are my universes moving in?.... both are situated on a single Brane.

[WayneFrancis]

You have to understand that a if a universe has positive or negative curvature that doesn't mean it will react in a higher order dimension like you might think it would.

The maths unfortunately is very complex and even so what happens if 2 universes some how collided in some higher order space is 100% speculation. The 2 universes might be able to pass through each other completely unaffected for all we know because we have no clue to any properties of the other universe or any properties of the higher order dimension(s)

[Cougar]

After listening to the infinities astronomy cast I wondered what actually happens when 2 universes collide.

Although it has of late become rather, uh, popular to speak of universes beyond our own, I think it is premature and presumptuous to assume or expect or even to imagine that there are actually universes beyond our own, particularly when there does not appear to be any way for such a presumption to be either supported or falsified or anything in between. Yes, I've read Greene and Vilenkin and Susskind and numerous others, and Susskind in particular seems to base his multiverse proposition on little more than numerology.

[onomatomanic]

Although it has of late become rather, uh, popular to speak of universes beyond our own, I think it is premature and presumptuous to assume or expect or even to imagine that there are actually universes beyond our own, particularly when there does not appear to be any way for such a presumption to be either supported or falsified or anything in between.

Indeed. As the old saying goes, "it all depends on what your definition of 'is' is": To even frame the question of whether "other universes exist", we'd first need to come up with a conceptualization of existence which can be meaningfully extended beyond our own universe. And since our universe is all we know, and we know nothing whatsoever about that which is beyond it, that already seems like an insurmountable obstacle to me.

[Cougar]

And since our universe is all we know, and we know nothing whatsoever about that which is beyond it, that already seems like an insurmountable obstacle to me.

Yeah. Plus, we can't really look "out" into the universe very far without also looking back in time. So galaxies and clusters in our neighborhood are the most evolved, then it goes back from there the farther we look. The only distant so-called "edge" we might see is the beginning. Right now the best measurement of that is the WMAP mapping of the CMB, but that shows conditions several hundred thousand years after the beginning, and no electromagnetic signal is going to come from further back than that. If we ever figure out how to detect gravitational waves, the gravitational wave background might show something about the conditions back to near the beginning.

[danscope]

Sort of like " Much ado about nothing " .

[Gomar]

I guess the OP missed those maestro Green science shows full CGI overload. He did go into discussing universes colliding. Ifcourse, you first
have to prove multiple universes exist.
If they do, and in some exist super-intelligences far beyond ours, then they are aware of collissions. Thus, we can assume since our universe has not been destroyed or fused with by a collission with another, those aliens must've devised a way to prevent it from happening. Surely, they wouldnt want _their_ universe to be destroyed.
However, if in fact there is only 1 universe, then we have nothing to worry about... besides galactic colliisions.