Quantum theory says that energy comes in tiny, indivisible chunks, called quanta. There is also a "quantum of time", the smallest measurement of time with any meaning, equal to a second divided by a huge number - one followed by 43 zeroes (this represents the length of time a photon moving at light speed takes to travel the smallest meaningful distance).Well other ideas include "Time will come to an end", "There is more than one kind of time," and "Time does not exist."

This could be the smallest unit of time possible, and thus of that blend of space and time, spacetime. By this reasoning there is no continuous flow of time, but rather spacetime moments running like grains of sand through an hourglass.

Not all are convinced, however.

"Some theorists think that there are 'atoms of spacetime' but I strongly think this is wrong," says Dr Nima Arkani-Hamed of the Institute for Advanced Study in Princeton. "I think everyone would agree that spacetime itself is on the chopping block, but it will be replaced in my view by something infinitely more interesting than 'atoms of spacetime'."

Well, we all know that psychologically there is more than one kind of time - waiting in line and watching a good film are two completely different experiences as far as time is concerned.

Anyway, no matter what the theory, when it's time to move on, ... we move on.

See also:

"Hints of a time before the big bang? Or of reaching for a story?"

"Does time's one-way street prove that other universes exist?