With all of the info we have available, scientists believe the universe is about 15 billion years old. The universe seems to be ever expanding, with objects accellerating (not just speeding away but actually going faster and faster) away from one another. Can we actually see to the edge?Let’s speculate that at the moment of the Big Bang, we sped off in one direction and another galaxy sped off in exactly the opposite direction. If we are both travelling away from each other at a relative speed of just slightly more than the speed of light (accelleration at [(c/2)+1] on both sides) then light from one source would never be able to reach the other. This means we would be absolutely unaware of the existence of this other galaxy. That’s assuming a 180 degree perfect “bee-line” away from each other. Over billions of years of constant relative accelleration I have to believe that there is a lot of mass that has crossed this visibility threshold relative to us.
In English, that could mean there is a lot more mass out there that we can’t see anymore than what we actually can see. Science estimates the mass of the universe based on what we can see. Where the numbers don’t quite match they try to find mass in black holes, dark matter, and alternate universes (a multiverse). It seems perfectly reasonable to me that we just don’t have the data we need to figure out how old the universe is, or where the edge of the universe is – we’re somewhere “in the middle” and we just have no idea how far ahead others have been racing ahead of us.