We all talk about the big bang as this moment the Universe begins by popping into existence with simple hydrogen and some helium. Hydrogen and Helium are gases that are able to carry sound. Today, space has expanded so much that there is vacume beyond where matter clumps together to form stars/planets, which means the sound couldn’t propagate, but the early early Universe wouldn’t have clumped like today; there would have been hydrogen everywhere. This means it would have been loud everywhere.
*Edit: I know we call it the Big Bang because of the rapid expansion of spacetime, but I always just pictured the general motion of expansion as the “bang”. Never thought of how loud it would have been.
Here’s one for you. “The edge of the known universe” is that where there are no more star or galaxy formations? Or could some objects be so far away, there aren’t enough light particles left traveling those vast distances to be seen?
I wonder if: our solar system resides in a galaxy of other solar systems, then our galaxy resides with others in the universe, are there other universe clusters in another unnamed grouping we haven’t thought of yet?
I feel like we’ve often just thought of the edge of the universe as, “that’s it, that’s the end” but… is it???
The edge of the observable universe is not because of that.
It is because space expands. Therefore everything goes away from everything else. Therefore, everything goes away from us. And the more space there is between us and that other thing, the more space expands, since there is more space. Therefore, things that are farther away from us, get away from us faster than everything else. Only if it is close enough to us that gravity is strong enough would that something not move away from us.
This creates a peculiar situation. Things that are far enough away from us, actually move away from us faster than the speed of light. This means that no photon ever emitted from this far away will ever reach us.
That is the edge of the observable universe. The distance at which a photon emitted in our direction will never reach us, since for every meter the photon travels, there is at least a meter of space “created” between us. Therefore it never progresses in moving towards us, in fact, it moves away from us even though it is traveling in our direction.
It takes light a fixed amount of the to cross a fixed distance. The farther something is away the older the image you will see. In effect looking farther out is like time travel.
The edge is simply the line where not enough time has occurred for the light to reach us.
I believe that would be an area where time has some weird effects, because time is a function of space (as I understand it). There would be no space, there.
But it’s also hard to say whether such an edge even needs to exist. The universe expands everywhere all at once, not from an “edge.” It’s making more space everywhere. Like bread expanding in the oven.
That’s the “observable universe” and totally exists.