What do the scientists do if they establish, with a high degree of probablity, for example, that a large asteroid will strike the earth?
Do we just hang around waiting for the inevitable.
Blowing it up may not be practical and might be more dangerous, I suspect. If we calculate, for example, that a large asteroid will hit earth on a future pass, can we take advantage of earlier 'close' passes to maybe bombard it with some kind of chemical combo to dissolve it (maybe over years) into something much less destructive?
That was always my idea how to avert the disaster, but I am not a scientist - in fact, I'm widely regarded as an idiot. :-)
Or is all this skywatching so that we will have some notice of a catastrophe, so at the very least we can get it catered and arrange for a good band.
If the lead time is long enough, you could induce a lateral delta-V (VASIMR, NERVA, ion engine etc.) to alter the orbit of the asteroid.