Expert: Courtney Seligman - 1/29/2011

Question
I have a young child that keeps asking me when time began and when it will stop.  As I'm not a religious person, I want to give her a scientific answer. So far I've told her that time probably began when the universe was formed (ie. the "Big Bang") and that some people believe it will end when the universe contracts and colapses on itself.  My answers are based on what I think I read or was taught many years ago.   I'm actually not sure there is an answer, but I thought it was worth asking someone more expert than myself.

Answer
You are correct in assuming that (according to current scientific theory) time began with the Big Bang. However, the theory that the Universe might eventually collapse on itself has been completely discredited, and we are now certain that it will expand forever. So although there was a beginning to time, it has no end.

There are theories which propose that all matter is very slightly unstable, and eventually all the atoms in the Universe will disintegrate, and cease to exist. If that were to happen there would be a sort of end to time, in that without any reference points it would be impossible to tell where you were or what time it was. However, even if such theories are correct (which is not at all certain), the gradual disintegration of matter would take place over times too vast to imagine, so for all practical purposes the future would still be infinite.