Re: Water from comets or asteroids?
@Big John - that all assumes the sun started to shine long before the earth was formed (along with its water). The maths is easier if we assume the accretion disc was a uniform disc but given its quite possible that it was not a uniform disk or gravitational collapse was locally accelerated due to shock waves from a nearby supernova it's all a bit 'best guess' and not, IMHO, best science.
The 'most popular theory' is a good solution to the problem - but there are many more.
Biting the hand that feeds IT
