This is is hurtling towards the earth. All seems lost, but then Bruce Willis sacrifices his own life to detonate

a thermonuclear bomb on the asteroid. And then you hear this from Mission Control.

The two halves are going to miss us by 400 miles,

and most of the small particles have been vaporized.

Breaking a rock that big into two halves that somehow miraculously dodged the earth, it's a bit of

Hollywood magic. But scientists are studying what would really happen in such a scenario.

A big part of what we do is basically looking at how things break,

smashing things together, and what happens after that.

Charles Almeer is a mechanical engineer who studies planetary science at Johns Hopkins

University.

He and his colleagues modeled what might happen if you smashed up a 15 mile wide asteroid made

a basalt.

They started by assuming the asteroid has some tiny cracks already running through it, based on studies of real rock.

And then they struck the hypothetical space rock with another smaller rock,

just a mile wide, screaming towards the asteroid at more than 11,000 miles per hour.

When it hit, they tracked how stress waves propagated through the asteroid

and expanded the network of cracks. Previous impact models predicted that an impact like that would completely pulverize the asteroid,

basically turning it into sand.

But not this new model.

When what we're seeing after the impact,

you have this big chunk of rock that was still held together that was still not completely broken down and this piece of rock creates its own gravitational field which attracts the particles that were ejected from it and they

start reaccumulating over it.

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