Do planets linearly accelerate?

Question

I know it sounds crazy....but in elliptical orbits, in order for the angular momentum to be conserved...at different points of the ellipse...when 'r'(distance from sun) increases, the linear velocity decreases....and we all know that a change in linear velocity is a linear acceleration!
so....where am i wrong?????

Answer 1

I am going to send you on a hunt, sorry about that, but the question leads to some complicated math that is hard to type in this editor. Remember, the earth only *apparently* orbits the sun, when in fact they *both* orbit their barycenter (the term you should google). So, the conservation of angular momentum you are after is the conservation within the two-body problem, and not the earth in isolation. The earth's motion around the sun-earth barycenter is not quite circular because of the influence of the moon on the earth and the other planets (especially Jupiter) on the sun.

You question quite naturally leads to the many-body problem, which has no exact solution.

In a word, there is a path through the sun planet system which conserves momentum for everybody involved...it just happens to be a very complicated path!

HTH

Charles

Answer 2

You're right. The planets do accelerate as they fall inwards towards the sun. Then they whip around the sun and hurtle back outwards, decelerating as they climb back up into the outer reaches of the solar system. Of course it is a small effect, because the orbits are nearly circular, but it is there.

The Earth is closest to the sun in January, and going fastest, so summers in the southern hemisphere are hotter and shorter than summers in the northern hemishphere, when the earth is moveing slowest and is at its furthest from the sun.

Answer 3

Yes, there is no such thing as a straight line.

Answer 4

I get what your saying, but i dont know either.