Earth's Motion: Beginning and End

According to Newtons law's of motion, a body stays in its state of rest or motion. From where did Earth get the initial momentum to start rotation and revolution around the sun? And will this notion ever stop due to loss of energy? Is earth in the danger of stopping for ever?
- Arjun V Pillai (age 17)
Tiruvalla, Pathanamthitta, Kerala

We've discussed the solar system's beginning some before: http://van.physics.illinois.edu/qa/listing.php?id=28836. The key idea is that there's no special state of rest. So just by accident different nearby things were in motion with respect to each other. There's very little energy loss from the orbit. A tiny bit is lost to gravitational radiation. like the waves recently found by LIGO but much weaker. I guess there's also a bit of friction with particles in space. The end of the Earth will not come from just losing orbital motion, however. Someday the Sun will follow the behavior of similar stars and greatly expand into something like a red giant. Not much will be left of the Earth after that.

Mike W.

(published on 03/01/2016)