Question: How do you believe the asteroid belt was created?

Alan Fitzsimmons answered on 10 Mar 2014:

Astronomers believe the asteroid belt was created the same time as the planets, 4.5 billion years ago. Small bits of rock stuck together and grew into asteroids and planets over a period of about 10 million years.

(We know the age because when bits of asteroid fall to the ground as meteorites , we can measure how old they are using radioactivity.)

The asteroids didn’t come together to make a planet, because the giant planet Jupiter formed first. It’s gravitational force is so big, it stirs up the nearby asteroid belt, stopping the asteroids coming together.

One thing we still don’t understand is why the planet Jupiter formed first. But some astronomers are working on it!