Puzzle

Due to 'popular' demand, here is a test for your noggins!

You have a metre long stick, and some miniscule myrmecophobic ants from your local children's playgroup's ant farm (note: such activity is not condoned in any way!). These little ants can (and do) scurry along the stick at a constant speed of a metre per minute. They can only move in two directions, that is, towards either end of the stick. If their tiny heads bump into each other, they both quickly jump around in fear and then scurry off in the other direction. They are so frightened, in fact, that if they reach the end of the stick they will happily jump off, noticing that there appears to be a welcoming safety net prepared for them, with a rather friendly looking eight-legged creature sitting by it.

Now for the tricky bit, what is the shortest time you must wait until you are SURE that all ants have jumped off the stick, if you started off with 60 ants (randomly placed, facing a random direction) on the stick? What if you started with 120 ants?

Whisper answers with a short reason on this person's profile! One answer only each please, and correct answerers will be announced at some point. Guess more than once and you will be ignored, so don't do it ;)

Hint: 'miniscule', and 'quickly' mean negligible.