10. Why are there inner and outer planets? (A K2S Question)

From The Space Library

There are nine planets orbiting the Sun at various distances. It just so happens that the four smaller planets—Mercury, Venus, Earth, and Mars—are far different and much closer than the remaining planets which are relatively much farther away from the Sun. Thus, it is convenient to refer to the two groups of planets as the "inner" planets and the "outer" planets.

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Answer provided by Ed Frederick, Ph.D.

Question and Answer extracted from the book Kids to Space - by Lonnie Schorer

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