Let me say some things both as a physicist and an Elements player:
1) Arun is NOT trolling at all. The existence of time has troubled a lot of philosophers or scientists and it still troubles them even today.
2) Arun's opinion that something must has an opposite in order to exists is against our common sense, but it is a respected opinion in scientific social circles. Most theoretical scientists believe in dark-matter and dark-energy, which are somewhat the opposites of normal matter and energy (note:
dark-matter shouldn't be confused with
anti-matter, though anti-matter is also somewhat the opposite of normal matter). The number "zero" (0) has no opposite (it is neither positive or negative number) and that's a reason it describes the "lack of existence" of a value. Zero kilogrammes is nothing, zero miles is nothing, zero acceleration is nothing etc. Other theories go as far as to support the existence of a universe parallel to ours, which is either exactly the same or exactly the opposite,.
3) The problem with time is that it is considered a dimension (like width, length and height) and, as a dimension, must has two directions (like width alone has two directions, like length alone has two directions, like height alone has two directions).
Alone here means without combining it with another dimension, because the directions would be infinite then (e.g. width and length together have two-dimensional infinite directions, width and length and height together have three-dimensinal infinite directions etc.). So, if time goes forward and it is indeed the fourth dimension, that means it can go backwards too. However, let aside time-traveling science-fiction, the scientific community hasn't detected any signs of time flowing backwards, so it is either a special 4th dimension which doesn't follow all the rules the rest of the dimensions follow or time is not a dimension at all.
4) Many scientists and philosophers believe that time is just an "illusion". That means it doesn't literally exists, but it is used to describe the action/re-action of the objects in the universe, which would be totally chaotic otherwise. Like mathematics and numbers, time is a human foundation in order to be able to count things with greater accurasy and ease.
5) However, we all know that
has an opposite;
! And if anyone defies its existence shall be devoured by Scarab swarms!!
A few useful links:
http://en.wikipedia.org/wiki/Multiversehttp://en.wikipedia.org/wiki/Dark_matterhttp://en.wikipedia.org/wiki/Antimatterhttp://en.wikipedia.org/wiki/Dimensionhttp://en.wikipedia.org/wiki/Time