How has the average distance between asteroids in the asteroid belt changed over time? Just about every webpage related to asteroids states that, on average, asteroids are about 600,000 miles apart from one another.  Have planetary scientists hazarded a guess at how close they might have been 4 billion years ago?  2 billion years ago?  200 million years?  I'm not looking for a particular age range, just an understanding of the trend over time.  Unfortunately, I'm having trouble looking up an answer to this question on my own because the keywords I've thought of keep grabbing other unrelated things
Thank you!
The asteroids formed roughly where they are now, from matter in the sun's protoplanetary disc that didn't form into a larger body (at least partly under the influence of Jupiter's gravity)
Since early in the solar system's story, the asteroids have been stable. Most asteroids haven't changed significantly in 4.5 billion years.  And 4.5 billion years ago the separation between asteroids was comparable to how it is now.