We estimate universe size by what we can detect. I think the furthest object we have detected to date is a quasar or supernova about 13.5 billion light years away.  So we ask if this is the "edge" of our universe....

Is it possible and a worthy experiment, similar to the hubble deep field, to watch a blank spot in the sky and "wait" for something to "show-up" in the field of view....indicating that the light from that object was just arriving to us from beyond the known "edge"?

Or, is the rate of expansion at that distance greater than the speed of light, therefore we will never be able to see beyond that edge?

I know that physicists have determined that there are conditions in which the universe is moving faster than c, but for practical purposes the edge of the universe is the start of the big bang, is moving away from us at the speed of light, and thus is the edge of the observable universe.





To find more stuff, we need to look at the multiverse, as described by string theory (or whatever quantum juju is the rage.)





 

what is the space outside of what we can detect called and how far does that extend?

Can there be another "universe" or many big bang events out there?

If the other than what we can see space is infinite, is it possible that big bang events are happening continuously or simultaneously many times over?

If so, could what we know to be everything, really be a equivalent to higgs boson in a much larger world?

There is no spacetime outside of the physical universe, as it is defined by existence.



One concept of infinity can be described as:  "Everything that can happen has happened, is happening now, and will continue to happen forever."



Probability, along with free will, defines the momentary point we experience in infinite possibility.



 

Can you tell me that again as one would talk to a child, or at least as you would tell it to someone who has not studied this subject mater?
How can there be nothing, anywhere, if you shined a light, there would be something, just because we can't, doesn't mean that space doesn't exist. How do you define "physical universe", what we know of or everything that could be out there?  I don't know what the definition of spacetime is.
Infinity, I can grasp that description, infinity has to allow for everything.
Probability, free will.. have only heard that in religious terms.  What's that all about.

Think of Space-time as a bubble.  Nothing exists outside that bubble, not even a vacuum of empty space as time does not exist.  But there is no barrier to cross here either, you cannot walk-across this barrier as it is not a physical barrier either.  You simply cannot approach it as it is expanding at or faster than the speed of light or our reality for that matter.

So seeing back to the moment of creation or the Big Bang is really not possible for this reason.   But as me tioned, we are seeing back pretty far.  Also keep in mind physics tend to break down at the moment around creation or near a singlularity like a black hole so "seeing" it really isn't possible.

Although not his latest work, Stephen Hawkings book, "A Breif History of Time" is excellent and a good read for us non-professors.  I read it back in high School and could grasp the concepts.  I have an Engineering Degree today and actually appreciate his written illustrations even more know as I often explain difficult concepts to my kids.

What if it turns up in part of the sky that is not empty? They scan images of the universe all the time. They use software that compares the position of the lights between one image and another to detect motion and look for novae, etc.

As the universe ages, the boundary will always move further away, but we will never see light that would take more time to reach us than has existed. You can't get there from here.

[gone]

Current belief now based on the accelerated expansion of the universe that has been observed and verified is that the current observable universe is ~93 Billion LY in diameter.  Beyond the particle horizon at that distance, there is no real consensus on how large the universe truly is as a whole.