Expert: Steve Nelson - 2/18/2009

Question
Hi Steve.
I've just read the question asked about the Big bang and it being the same in all directions. Following on from this, is it actually the same in ALL directions? Its just i would understand that to mean that the earth was at the centre of the Big bang and as such sits at the centre of this big sphere of space-time?
I do have one more question, i was thinking about space-time and was wondering, regarding Einsteins general relativity, are we supposed to think of time as kind of matter, like the flawed 'ether' or is it just something thats hypothetical and just used as a tool? If we are supposed to think of time as a kind of matter then is it true to say that all time exists in the present and we move through time that is already there?
Thank you and sorry for all the questions!
Simon

Answer
No, the Earth is not the center of the universe.  Since the Big Bang defines all of space, it will still expand the same in all directions, there is no center.  That's like asking where's the center axis of a perfectly symmetric and non-rotating sphere, you could pick any number of them.  If you were to inflate that sphere, anywhere you sat on it you would look out and see points on the sphere getting further away from you at a uniform rate.

Time is not a kind of matter, it's a dimension.  We are moving through that dimension in the forward direction, if you want to think of it that way.  Objects in spacetime exist along what are known as world-lines, they have one space location at any one point in time but are travelling forward in time, thus forming a line through 4-dimensional spacetime.