I think (you read it here first) that the first step towards actual planetary defense will be the moon. That is: humanity's first, actual, somewhat working syst

I think (you read it here first) that the first step towards actual planetary defense will be the moon. That is: humanity's first, actual, somewhat working system realistically able to defeat an incoming asteroid will consist of moving the moon. Not that that is easy - absolutely not. But it is genuinely something that we can prepare for. We can start building an infrastructure on the moon for vaporising moon rocks, providing thrust. Energy can come from sunlight. You could well argue that moving the moon is nigh impossible. It probably is. But it is (1) feasible and (2) an engineering challenge. The most daunting one ever faced by humanity, but the pay off is equally great: we get to save the planet. The key point is that the moon can easily stop incoming asteroids. It reduces the entire problem to "simply" moving the moon. Which is something I think is achievable with roughly today's tech.