[jman05 (OP)]

From what I understand space time are only in the universe.  SO what is outside the universe and at the point it ends what is the end like.  Is it sudden or gradual.  And what happens if u somehow make it outside of the universe or space time.  I mean theroticaly  if u could what woud it be like.  Would u just not age or what.  Im having trouble grasping the concept of what "nothing" is outside the universe.

[Solvay_1927]

How can you be outside of spacetime?

Isn't the universe, by definition, everything that exists / everything that we could ever know?

So if ever something were to move outside of the universe, then its location would immediately become part of the universe - because something that exists is at that location.

No?

[DoctorBeaver]

The concept of nothingness is very hard to grasp. There is nothing outside of the universe because there is no outside (possibly). It's not like inflating a balloon where it expands into the air surrounding it. The universe is not expanding into anything, it is creating space as it expands. There may be other universes apart from ours, but they are totally disconnected and ours is not expanding into any of them, nor they into ours.
Stephen Hawking said that a baby universe could be expanding in your pocket right now & you'd know nothing about it because its space time would be totally separate from our own.
As for time... if, as most theories seem to state, space & time began with the big bang, then the time that exists in this universe cannot exist outside of it. Whether there is such a thing as multiversal time as opposed to universal time is a question we will probably never know the answer to.

[another_someone]

Actually, I think someone pointed out in one of the threads, there is no way for us to be able to discriminate between our universe expanding, and we ourselves shrinking within a fixed size universe.  If there is no external reference of space/time, then it is not just that we inside the universe cannot tell the difference, there is no point of reference where any distinction between the two could be made.

Is it not contradictory to say that one universe shares no space/time with another universe, and then suggest that it could be inside your pocket?  If your pocket, which is within our universe, is in a separate space/time from the other universe, how can one be inside the other?

[DoctorBeaver]

quote:Is it not contradictory to say that one universe shares no space/time with another universe, and then suggest that it could be inside your pocket? If your pocket, which is within our universe, is in a separate space/time from the other universe, how can one be inside the other?

No, it isn't contradictory. What Hawking was suggesting is that the quantum fluctuation could occur in your pocket but the resulting universe would form its own spacetime separate from our own

[DocN]

I like the description Einstein may have given, if one heads out into spacetime you would eventually return to where you were in the beginning or if you had a infinitely powerful telescope you could see the back of your head.
Doc

[ukmicky]

quote:i think someone pointed out in one of the threads, there is no way for us to be able to discriminate between our universe expanding, and we ourselves shrinking within a fixed size universe.

Hold on, how do we know the universe is expanding if the light from the galaxies and supernova's thats redshifted has taken billions of years to reach us

Michael                 HAPPY NEW YEAR                    

[DoctorBeaver]

I think all we can say is that the universe was expanding at the time the light left those distant galaxies. The nearer to our own galaxy you get, the more recently in time we can say it was expanding as the light has taken less time to reach us. Except, of course, in the case of the Andromeda galaxy and the Megellanic clouds, they are moving towards us.

[ukmicky]

So in theory the universe could be getting smaller but we just haven't been around long enough to see it yet.
which could also mean there no such thing as  dark matter

Michael                 HAPPY NEW YEAR                    

[DoctorBeaver]

Dark matter is probably not responsible for expansion. It is theorised that it's dark matter that holds galaxies together. Therefore it must have gravity and so could not drive an expansion.

[ukmicky]

ok dark energy[]

Michael                 HAPPY NEW YEAR                    

[Solvay_1927]

dark energy - is that a euphemism for guinness?

(I really love that animation in your signature, Michael)

[ukmicky]

GO ON PAUL I'LL LET YOU BORROW IT

Michael                 HAPPY NEW YEAR                    

[Soul Surfer]

There are some linguistic problems buried in this question and we have to be careful when we use the word "universe".  

The problem is, does the word "universe" refer to what we can observe and find out about or absolutely everything.  If it means absolutely everything without exception the the question is pointless because there cannot be anything outside of absolutely everything.  

I do not prefer that definition and would rather use the term multiverse to mean absolutely everytning.

Our universe is bounded by what we can observe and experiment with and what we know about what is outside of our universe depends on the cosmological model that you adopt.

For example if we accept an inflationary cosmology in which the extreme smoothness of the microwave bacground radiation was caused bt an ingredible fast stretcing of a turbulant big bang.  we can say that what is outside of our obsevable universe is very similar to what we have inside it until we get a very long way outside our universe when things could be very different.

On the other hand if the big bang originated in material that had adopted (or been forced to adopt) a very smooth thermal equilibrium.  Say for example associated with the formation of a hawking radiation and time dominated pseudo singularity in the core of a black hole  (see statements I have made elsewhere on these pages)  Our universe could be quite small and we may even be able to see all of it.  In that case our knowledge of what is outside our universe is limited to our knowledge of the material that is inside it and using that as a model for alternative initial conditions.

One final thought.  What is the possibility that things outside our universe could affect us.  Well, if our universe was one of the things that can happen inside a black hole it would in theory possible for material to drop into it from outside but detecting this would be very difficult unless it represented a large amouint of energy.  on the other hand our black hole could be evaporating and we might after a long time vanish into nothing but one thing that does not appear to be possible is that there is someone out there (GOD?) twiddling the knobs to affect the way things work in detail around here.

Learn, create, test and tell
evolution rules in all things
God says so!

[DocN]

Maybe God is the "knobs" and everything else.
There is a new viewpoint been taken in the understanding of basic cosmic activities--turning the microscopic study to a more macro-direction.  Would that mean we have been looking for answers at the wrong end(quantum particles)?  Could large scale cosmic  constructs provide a better source?
Doc