# Constant acceleration of gravity

1. Apr 5, 2015

### quincy harman

It's a combination of centrifugal force and gravity that allows constant acceleration of a rotating object? also is it just coincidence that the most dense objects are near the sun?

2. Apr 6, 2015

### davenn

no its not, as the sun formed and started shining and the solar wind started radiating out from the sun, it blew much of the lighter
material further out into the outer reaches of the of the early solar system

Note how the outer planets are gas giants Jupiter, Saturn, Uranus and Neptune

Dave

3. Apr 6, 2015

### |Glitch|

I am not sure what your asking in your first question. An object that is rotating will continue to rotate unless acted upon by an external force (Newton's first law of motion). In order to obtain "constant acceleration" you have to apply constant thrust. Also, enough centrifugal force can nullify the effects of gravity. For example, if Earth had a rotation of only 2 hours, 15 minutes per day (~18,000 mph), the centrifugal force would overcome Earth's gravity and break the planet apart.

As to your second question, the prevailing theory is that as the solar nebula collapses it gradually begins to rotate and the heavier elements in the nebula are drawn closer to the center of this rotating mass by gravity. Therefore, the planets with the highest density should be closest to their parent star. Particularly, those planets that are closer to their star than the star's snow line (a.k.a. frost line). Once the protostar reaches an internal core temperature of ~15 million degrees Kelvin, hydrogen fusion begins and it becomes a star. When that happens, solar winds are created that clear out the majority of the remaining gas in the solar system.

It should be noted that we have found solar systems that fly in the face of prevailing theory. Such as a 10 Jupiter mass exo-planet orbiting only 1 AU from its parent Type F5 star. And other solar systems where "hot" gas giants are much closer to their parent star where it should be impossible for them to form. The only explanation is that they formed beyond the snow line of the star and somehow migrated into a much closer orbit.