I just finished re-reading Carl Sagan&#x27;s Pale Blue Dot, in which he devotes a chapter to this subject. His conclusion is that, at our current level of civilizational maturity, we&#x27;re better off crossing our fingers rather than learning how to redirect asteroids, since the technology required to save the planet from a massive impact is <i>exactly</i> the same as that used to conduct asteroid bombardment.