What is the edge of space?

1 Answer
Dec 15, 2015

The edge of the known universe is about 45 billion light years away.


This is a great question with no great answer. Right now astronomers have gauged the visible universe to be about 45 billion light years distant in every direction.

This question has a very complex answer though. The universe itself is about 13.7 billion years old. Logic would say that since nothing can travel faster than the speed of light, then light emitted 13.7 billion years ago for the edge of the universe would just now be arriving here. But there are two problems with that assumption.

First, in the first seconds after the big bang, literally, the universe expanded from a single point to half the size it is now. From that point on the universe continued to expand with the first stars forming between 100 and 200 million years. Those stars then formed galaxies where the existing matter clustered in hot pools of hydrogen and helium.

Over the last several decades astronomers have discovered that these galaxies are speeding away from us and that they are accelerating in speed. This explains how in a 13.7 billion year old universe the most distant visible galaxies are about 45 billion light years away. Problematic to that is the idea that galaxies might exist beyond that 45 billion light year point but our present technology does not allow us to see them.