If you have an hour to spare, I suggest watching this talk by astrophysicist David Dearborn entitled "The Use Of Nuclear Explosives To Disrupt or Divert Asteroids". It starts with a general introduction to the problem of NEOs (Near Earth Objects) and how, as the efficiency of our observation methods increased, we've come to realize that the inner solar system is literally packed with them — and that among them, quite a few large ones are bound to cross Earth's orbit in the near or distant future.
It then goes on to explain that even if you can detect an asteroid early, and observe it for a sufficient period of time (say 10 years) to calculate its orbit, you may not actually have any assurance that the object won't be a threat, because of non-gravitational forces:
- light bouncing off an object in space changes its trajectory, because photons carry momentum and exert a non-negligible force (an effect known as solar radiation pressure)
- more importantly, since the object also radiates heat, the emission of thermal photons modifies the object's orbit in non-predictable ways depending on its shape and composition (the Yarkovsky effect)
The meat of the talk is a presentation of two computer simulations: one where a nuclear device is used to heat an asteroid enough to change its trajectory and prevent a collision ("nudging"), and a second scenario where a nuclear explosive is used to blow the object into smaller chunks which can then simply burn in the atmosphere, or in the worst case cause less damage than a single collision (if they remain on a collision trajectory at all).
Overall, it makes a good case in favor of nuclear explosives as tools and nuclear technology as the most efficient method of transporting energy, beyond the other uses (military or civil) we already have for it. I find this very interesting.
Oh, and if you're not into astrophysics you might be interested in this talk by Mike Pinkerton on open-source and the early days of Mozilla instead; it's very good too.
