Department of Energy Argonne National Laboratory Office of Science NEWTON's Homepage NEWTON's Homepage
NEWTON, Ask A Scientist!
NEWTON Home Page NEWTON Teachers Visit Our Archives Ask A Question How To Ask A Question Question of the Week Our Expert Scientists Volunteer at NEWTON! Frequently Asked Questions Referencing NEWTON About NEWTON About Ask A Scientist Education At Argonne Planets distances from each other
Name: N/A
Status: N/A
Age: N/A
Location: N/A
Country: N/A
Date: N/A


Question:
Why are planets so far from each other?



Replies:
Well, the planets are pretty far apart compared to their sizes - the size of a planet is generally a few thousand miles (maybe 10s of thousands for the big ones) while the distances between them are tens or hundreds of millions of miles. Why that huge factor of a thousand or so? It probably has a lot to do with the average density of matter in the original dust-cloud that (we think) formed the solar system and the sun itself. There really is not much matter out there in space (it is "empty"!) and even the big nebulas astronomers like to photograph are still very much less dense than the planets. If there are nebulas that are much denser than the one our solar system started, they might have planets closer together... On the other hand, there could be something else going on. The gravitational interactions between the planets even as far apart as they are still pretty complex, and the solar system is really not all that stable - maybe if we had extra planets closer together long ago, they would have been ejected from the solar system by now.

Arthur Smith



Click here to return to the Physics Archives

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (help@newton.dep.anl.gov), or at Argonne's Educational Programs

NEWTON AND ASK A SCIENTIST
Educational Programs
Building 360
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: June 2012
Weclome To Newton

Argonne National Laboratory