?What force makes the planets turn on themselves
!A force... which is not one: inertia
While the planets are moved only by the gravitational attraction of their neighbors and their star, which encloses them in an elliptical trajectory around the Sun, their rotation on themselves is not maintained by any force: it is the remainder of the movement that animated them... in the first hours of the solar system! To understand this phenomenon, astrophysicists take us back 4.5 billion years. At the time, the planets in formation orbit with billions of pebbles which do not stop hitting them.
It is the era of spring cleaning: the very young planets, Mars, Earth, Venus... are growing by taking in their gravitational nets all the bodies that cross their orbit. The laws that govern the solar system are then the same as those used to describe the behavior of balls on a billiard table: with each collision with an asteroid, the trajectory of future planets changes; as soon as the impact is not exactly centered, they begin to swirl on themselves...until their rotation stabilizes.
The planets in a game of space billiards
This stabilization is due to the fact that, in a solar system, the more the bodies gravitate far from the center, the faster they go. From shock to shock, the Earth is therefore further pushed from the outside and begins to turn on itself. This game of space billiards animates all the bodies of the solar system with the same movement, until the last pebbles have been absorbed or disintegrated.
Finally, seen from their North Pole, all the planets rotate counter-clockwise… except Venus. The heat and pull of the nearby Sun disrupted its path so much that it reversed its rotation. Apart from this exception, all the planets have remained, by inertia, on their momentum and have been dancing at the same rhythm for 4.5 billion years!
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