The point isn&#x27;t the vaporize them, it&#x27;s to nudge them ever so slightly.<p>Consider a comet- you fire one or more lasers to a specific spot on the comet, causing heat. The heat causes the water to expand, and shoot off from the comet. Does this destroy the comet? Certainly not much of it. But as that water vapor shoots away from it, Newtons Third Law comes into play and the comet, ever so slightly, is pushed in the opposite direction.<p>You may rightfully say that this would be a very minuscule push, so what good will it do? Well, if you play Kerbal Space Program you&#x27;ll quickly learn that tiny nudges can have huge effects in the long-run, especially on big orbits. Add a few mm&#x2F;s to the velocity of a comet two years ahead of time, and it can make the difference between that comet hitting a planet, or not. It can mean the comet is ever so slightly closer to Jupiter, causing it to be pulled by its gravity just a bit more.