Expert: Courtney Seligman - 6/9/2009

Question
hypothetical question what if the only galaxy created from the big bang was our own, would life exist as we know it,would it be possible, are we presently,historically reliant on the vast size of the universe and what went before,or would we be cosy in our own milky way,if the rest of the universe disapeared

Answer
There are theories which propose that 'local' conditions can be affected by the nature of the Universe as a whole, but the laws of physics as we currently know them don't rely on such concepts. So although it's conceivable that if ours were the only galaxy things would be different than they are, the odds are that everything would go on pretty much the same.

In fact, the rest of our Galaxy could also disappear without significantly affecting things in our Solar System. The only certain difference that would make is that as present comets die, they would not be replaced by other comets, and within a couple of hundred million years, comets would be a thing of the past.

(Note added afterward: The statement that the rest of our Galaxy could disappear without much effect on us only applies to the future of our Solar System. If not for the prior existence of our Galaxy, the Solar System couldn't have formed. In a similar way, it's not likely that reasonable theories of the origin of the Universe would allow the creation of only enough matter for one galaxy. It's probably 'all' or 'nothing', so to speak. But if you COULD create just our galaxy, or just our Solar System, starting with their current state, then things would stay more like they are than not.)