If you put a light source, lets say... a lightbulb or star, in a corner of a universe with nothing in it to block it or anything. What will happen. Will it go on forever or what and why?

Err, what do you mean?

 

As there is not an infinite amout of energy in the universe eventually the light source would run out of energy.

 

The light itself does go on forever until it is absorbed by something, but an individual photon could go on infinitely.

 

Also you can't really define a corner of the universe, but I get the idea.

I mean that a light source is put somewhere in an empty peice of space which goes on forever. Will the light produced by the source go on forever or stop somewhere in space

go on...

 

A photon travels untill it hits something, if there's nothing to hit it carries on...

but for all we know it could go round and evetually end up lighing up its own back end

 

I say for all we know, i mean for all i know - as my outlook on physics is practically made up