Our observable universe is a 93 billion light-year wide imaginary spherical shell around us.
This is the distance we can see things. Light within this sphere, may have been around long enough emitting light, for the light to reach us.
Anything outside of this sphere can't be seen, even if it started shining when the Universe began, some 15 billion years ago, Even with the strongest theoretical telescopes, we cannot see that far, because the light from there, just isn’t here yet.
An analogy is being on a boat far enough away from land that all you see is ocean to the horizon in every direction:
From your point of view on the boat, everything you can see is within the portion of the ‘observable ocean’. Outside of that, is just more ocean.
What’s outside of the observable universe, is, just more universe. That does raise the question of how big is the entire universe, outside the ‘walls’ of our observable universe shell?
Well, we don’t know.
But, we have estimates or, rather, the maths. Some of our current cosmological theories suggest competing answers to this question, although we do not have enough information to come to any certainties yet.
For all we know it could be infinite, but some research has indicated that our “full universe” is at least 250 times larger than our observable Universe. There are estimates of our Universe being 10^10^10^122 times larger than the observable universe.
And the estimate of 10 to the 10th to the 10th to the 122th power, is just ridiculously large.
- If you wrote down a “1”,
- Then turned every atom in the observable Universe into a “0” (that’s about 10^80 zeroes)
- Placed them in a line after the 1.
- The number you wrote down there, would not be 1% of 1% of 1% of 1% of the number of “0”’s you would have to write after a “1”, to indicate how many times large the complete universe is, to the 93 billion light-year wide observable universe.