Its science fiction, except that its true. Sooner or later a big asteroid is going to come and we have no idea what to to.
Even worse, there is no political consensus over who would pay. We have an international treaty saying "no weapons in space", so exactly how are we going to deflect or disintegrate an asteroid ?
If only there was a weapon that we could use only in space! It would have to be something that basically could never get past the earth's atmosphere, but that would pack lots of punch against an asteroid. It would have to never come back to bite us, either.
It occurred to me recently that anti-matter would be interesting. Assuming for a second that it was possible to create lots of antimatter on a moon colony or something, say anti-protons or anti-helium, we could use an accelerator to guide it into an asteroid's path. Every particle to impact the asteroid would give it a push, either backwards or sideways. A bit like using gamma rays for a cancer treatment, any misses would become dispersed in the solar system and would probably have negligible impact on anything else.
This type of antimatter stream could never be used to threaten a country. It would probably be used to draw advertisements in the sky, eventually.
Added benefit, it might be able to de-orbit space junk. It would be a great justification for a moon base, and an incredible jolt to world economy.
