Does the Moon travel round the Sun slower than the Earth?

"Is the speed at which the moon travels around the sun much slower than that of the Earth?" - Question posed by Meadow
The Sun/Earth/Moon system: Yellow = Sun; Grey = Earth; Black = Moon

Imagine* a friend of yours is standing in the middle of a circular field with a big sign pointing at him or her saying "The Sun". Now imagine that you're running around the outside of the field, and you're wearing a T-shirt that says "Earth" on it. Next, imagine that you have a tennis ball attached to the end of a piece of string, and you're swinging it around your head as you run. The ball is playing the part of the Moon.

The tennis ball circles your head as you run around your friend. Similarly, the Moon orbits the Earth as it orbits the Sun. If you run around the field once, which completes the lap first: you, or the tennis ball? The answer, of course, is that you both finish at the same time because the ball is travelling along with you. The same is true for the Earth and the Moon: they orbit the Sun together, so one doesn't really travel faster than the other.

The quick answer:
No! The Earth and Moon travel around the Sun at the same speed.



* You could actually do this, I suppose.

Comments

  1. I got a question: Would humans really explode if they accidentally wound up in outer space without a space suit?

    ReplyDelete
  2. Good question! Have just answered it here: http://blogstronomy.blogspot.com/2010/12/would-human-explode-in-space-without.html

    ReplyDelete

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