The universe is a strange place. It is a space-time structure, which, because of gravity, may fold back upon itself. We can only see a portion of it called the Observable Universe, which has a radius of about 47 billion miles last time I checked. And, it is universally agreed that it is much larger than that and most scientists believe that it is in fact infinite!
But…wait a minute…the latest estimates I’m aware of place it’s age at 13.7 billion years old so how could we have a visible diameter of 94 billion? As I said, a strange place. Obviously, although matter cannot accelerate past the speed of light, the universe can expand faster than the speed of light. As for how can we see objects 47 billion light years away–this is because the universe was expanding while that light was traveling toward us (I know…but that’s another post so, for now, you’ll need Google to get further explanations on this one).
A article in New discoveries indicates that the universe may not be infinite but finite. In my four-part sci-fi series, The Spiral Slayers, the ‘Slayer’s universe’ is finite. So could we ever reach the universe’s edge and, if we could, what would it look like and what would be beyond it?
Here is a very interesting documentary on this subject—it’s a bit long but really worth watching!
Both in reality (if it is finite) and in the Spiral Slayers’ universe, the answer to these questions are both ‘no’ and ‘maybe’.
The ‘no’ part of this is that space-time, as I have already pointed out, folds back upon itself because of gravity and, we are part of space-time and simply can’t remove ourselves from it. Long before we could come anywhere close to the universe’s edge, space-time would bend both our view and path away from it and we could never reach it.
The maybe part is that perhaps we are looking at the edge of the universe, at least a portion of it, every time we look at a black hole (which isn’t often, lol…one has never been observed directly).
Black Holes have 2 basic parts:
- The singularity which is a point particle with infinite density (it has no volume)
- The even horizon, the point at which not even light can escape the singularities gravity.
Most black holes are pulling in matter which spirals into it. This is called an accretion disk. In the image below this is cut off at the event horizon for clarity–in reality it extends beyond the event horizon.
This edge of the universe is probably the event horizon as nothing, not even light, can escape from it which is to say once you enter you can never return.
In reality, generally, event horizons cannot be seen. This is because the intense gravitational pull warps space-time around the event horizon (this of course includes light) hiding it! What we see is the light from behind warping around it.
If there were no accretion disk we would only see the distorted light from behind and if there were no light behind it, we wouldn’t see anything at all.
Alternately, the ‘edge of the universe’ (assuming this is correct) may be the singularity itself. I think at this point it’s really just a matter of definition. In my story, the all-knowing Spiral Slayers can return from inside the event horizon and it’s definitely the singularity that is the universe’s edge.
As for what we’d find beyond the universe, we don’t know and, in my story and probably in reality as well, anything outside the universe is, by definition, unknowable. Is the singularity all there is beyond the bounds of our universe? That is to say, is there only infinite density? In the Spiral Slayer’s universe, infinite density (the singularity of a black hole) and, an absolute vacuum (nothing, no vacuum energy, no virtual particles, nothing) are the same thing. Ergo, is there absolutely nothing beyond the bounds of our universe.
Or, is the singularity just the gatekeeper and something else…another universe or ‘the bulk’ containing other universes (the multiverse) or…?
In the next post we’ll talk about one of the more controversial elements of my story; traveling between galactic super clusters and across the Observable Universe while observing light’s speed limit.