Last year the Yankees won the World Series...
Three years ago France won the soccer World Cup. Everyone
knows that. But does anyone know who is the World Champion
next November, or who will raise the World Cup in Japan in
2002? I doubt.
Why is that? What is the difference between
past and future?
The sensation of the progression of time from a definite past
to an uncertain future is deeply rooted in us. There is a
distinct direction from past to future. Past carries the cause
and future the effect.
However, past and future can not be distinguished physically.
(Physical equations will remain the same if we replace t by
Imagine a glass of water resting on a
coffee table. If you push the glass, it will undoubtedly
break on the floor and spill the water all over the
Now suppose that you have recorded the incident on videotape
and that you run the film backward. You will see the
shattered glass pieces coming together to form the original
glass and the water jump back in the glass while the
glass finds its place back on the table.
Unbelievable! The reason these things never happen in
reality is because of what is called the Entropy
law or the second law of thermodynamics. This law states
that in an isolated physical system, the degree of disorder
(or entropy) increases with time. When the glass was
broken, its entropy increased. In order to bring it
back you need to lower its entropy and that is not possible.
That is why it is impossible for us to imagine
that the broken glass was brought back to its original state.
The second law of thermodynamics actually defines a direction
of time, and this unables us to distinguish past from future.