Q & A: The Sun, the Planets, and Gravity

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Q:

How does gravity affect the planets path around the sun?
- Herbert Ceasar, III (age 10)
Golightly Educational Center, Detroit, Michigan, USA

A:

Herbert -

Gravity is what makes the planets move around the sun. The planets are held near the sun by the sun's gravity. Without it, they would just go flying off into space. The reason that they stay in an orbit (instead of just falling into the sun) is that they move on their own in a direction that would take them further away from the sun. The sun's gravity pulls them back towards it.

Here is a picture that may make this make more sense:


(from The Physics Classroom)

In this picture, the arrow labeled 'v' is the direction that the planet would move on its own. The arrow labeled 'a' is the direction that the sun pulls on it. (The sun is not drawn but is in the middle of the circle.)

-Tamara

(published on 10/22/2007)

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