Gravity is a force that pulls objects together. On Earth, gravity keeps people’s feet on the ground. In space, gravity makes the planets move around the sun. Bigger objects have stronger gravity. The sun is much bigger than the planets. The sun’s strong gravity pulls the planets toward it.
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Compared to Earth, Mercury has long days. If you could spend your time doing anything for a whole day on Mercury, what would you do?
Have you read other books about planets? How are those planets similar to or different from Mercury?
People cannot survive on Mercury. What do people need to be able to live on a planet?
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