system
Given the following post, respond as if you're commenting on Reddit:
human
Would blowing a meteor up as it enters atmosphere lessen the damage to Earth?

Or just turn it from a cannonball into grapeshot?
gpt
In principle, it will help. Of course it's all going to depend on the details - how fast it is, how big it is, how dense it is, how big the chunks are etc. So whether it's a significant difference or a small difference will depend on the situation.

Basically, the drag force on a bunch of small objects is (usually) bigger than the drag force on one big object of the same total mass. Drag force is proportional to the cross-sectional area of the object. If the chunks are roughly spherical, then the cross-sectional area is proportional to the *square* of the radius of each chunk. So if each chunk is half the size of the original meteor, it has 1/4 of the cross-sectional area. But the *mass* of each chunk is proportional to the *cube* of the radius.

So, if you halve the size of a sphere, you get 1/4 of the drag-force acting on 1/8th of the mass. From F=ma, that means that each chunk has 2x the deceleration from drag.

Now, you aren't actually going to blow up a spherical meteor into perfect spheres. But you should expect things to roughly scale like that - the smaller the chunks, the more drag force you get, and the faster the chunks will slow down.

(Note that if you sliced up the meteor in some contrived way, the effect can be smaller - if you chop it into long thin cylinders, you still have a small cross-sectional area per mass. But this is not what you expect to happen if you blow something up.)