“Is it going to hit us?” was their only question.

“No.”

“Bye …”

But if we were to discover an asteroid with a non-zero probability of impacting Earth, and if it were of a size to be dealt with using nuclear weapons, then two things would be true:

1. The sooner we blast it, the more spread out its fragments will be if it does hit us.

2. The longer we wait before we blast it, the more precisely we’ll know whether or not it will hit us.

So it becomes a difficult balancing act. When do we blast it? When we’re 10% sure of impact? 50% sure? 100% sure? If we blast it too soon, we may end up sending deadly fragments our way that otherwise would have missed us if we hadn’t done anything. If we blast it too late, the blast’s effectiveness is diminished.

So your idea has merit, but actually making it work is a lot more complicated than it sounds. Depending on the circumstances, it could make things far worse without much potential to make things better.

Of course, this applies only to potential impactors discovered shortly before their potential impact, since their orbits are not well known. Paths of currently known objects with well-known orbits can be calculated to a very precise degree decades in advance. If such an object is calculated to impact us in, say, 40 years, then instead of blasting it, we may be able to deal with it simply by splattering it with white paint so that photonic pressure from the sun pushes it into a different orbit over the next 40 years.

I’d contribute a gallon to that effort! Titanium oxide, to the rescue!

They might… but when that happens their kinetic energy doesn’t just vanish. All those little fragments hit the atmosphere, compress the gas in front of them to heat it up, and then ablate to vapour…

So the kinetic energy of this huge object has been converted into a zillion little chunks of kinetic energy, which is delivered to the atmosphere and pretty effectively converted to heat. That heat doesn’t magically go away.

It doesn’t seem like much because you might get a few hundred sand-sized grains per hour making a light show during a meteor shower. This would be like dumping billions of tons of sand all at the same time.

It would be bad.

Like I said, I’m not an astronomer, but I’m sort of thinking about it like this. Take rain on soft soil. Rain comes down, it makes some craters from where it hit, some puddles, etc. Take that same rain, somehow compress it, and drop it instantly in one spot. Rather than having a sprinkling all day of rain, you have a high volume splash of water thats going to do some serious (scale) damage.

What I really want to know is…

… how many people have rubbed something glass or plastic on their cat in the last few days just out of curiosity about why I’d pick cats to rub on asteroids.