FeynmanMH42 said:If the planets are constantly orbiting the Sun won't they eventually run out of energy, succumb to the gravitational pull and fall into the Sun?
They don't seem to be doing... why not?
I'm not disputing that orbits can change under various influences. I'm disputing the form of the original question "Won't they run out of energy?".Phobos said:But wait...dust in the solar system is a kind of friction to slow down the Earth. (Granted, it's a small effect...but acting over billions of years...plus, there's the increase in mass (again, small) of the planet which affects the gravitational interaction.)
Anyway, planets' orbits can and do change due to gravitational nudges from other planets, passing stars, etc. The interaction is complex...lose some energy here...gain some there...over and over throughout its existence. The current planets in the solar system are in what turned out to be the stable/safer orbits.
Unless something wild happens (rouge interstellar body messing up our solar system in the distant future?), the net energy loss should be negligible such that the end of the Earth won't be it spiraling into the sun but rather the sun expanding out to the Earth's orbit when it becomes a red giant.
The Earth is moving under the force of gravity. An object in motion continues in a straight line, unless acted on by a force. The Earth is orbiting in an ellipse.Arian said:What is in motion will stay in motion until acted upon by an outside force.
Earth is in motion, there is no outside force.
Summary: Earth won't fall.