One fundamental question is whether or not the universe is infinite. Is there an edge, or does space and time just keep on going forever? We may never know, as we can only observe as far as the cosmic horizon. That is the point at which we can no longer see anything because there has not been enough time (in the 13.7 billion years of existence) for light to travel to, and be seen by earth. So it’s a bit like trying to determine the shape of the earth without being able to get out of your chair.
Read more here Deskarati – Universe