I recommend you go read this little article on cosmicvariance.com. It’s quite philosophical, but it deals with how time is something that goes only one way, and not the other – The Arrow of Time. The talk is based on the second law of thermodynamics, which basically says that if you have a closed system that everything will flow into an equilibrium, where the differences in energy levels are so low that no further reactions or actions is possible. To put it in other words, if you put some ice-cubes in a glass they will melt to water, but without some outside help that water will never turn into ice-cubes again. An article like that fires off my brain, give it a read and see what you think. As usual I found this one at The Bad Astronomy Blog.