Where is the end boundary of our universe.?
The cosmic radiation background, 45 billion light years distant.
But that is just a theory. Some say the universe is shaped a lot like a soccer ball while others say it is flat. These seeming contradictory theories can each be explained by the "red shift." The red shift is the bending of light as it passes near certain gravitational fields.
The problem is extremely enigmatic because, by definition, regardless of where you are looking in the universe you are looking backwards in time. The closest we come to seeing things where they really are is within the quadrant of our galaxy where we reside.
The Andromeda Galaxy, for example, is 2.5 million light years away. That simply means were are looking at it as it existed 2.5 million years ago.
Now, we know our galaxy is expanding and that expansion is happening at an ever accelerating rate. In turn, everything in the universe is in motion. This means that not only are we looking at things as there were millions and billions of years ago, we are looking at them where the used to be and not where they are now.