9781422283721

The Earth and eight other planets form the main part of the Solar System, the family of bodies that travels through space around the Sun. The planets are spread out over distances so great that they are almost impossible to imagine. Even Venus, the planet that comes closest to the Earth, never comes nearer than about 26 million miles (42 million km). Yet we can consider it a neighbor among the planets. ∆ Earth and its three neighbors lie much closer together than the other planets. But all the planets travel around the Sun in the same direction.   Earth and its planetary   neighbors lie near the   Solar System's center. Neighbors

Mars and Mercury are further away than Venus. But they are both close enough to be called neighbors when we see how far away the other planets are. The other planets lie hundreds of millions and even thousands of millions of miles away. If we set off in the space shuttle to visit Venus, it would take us only about two months. But it would take us 25 years to reach Pluto, now a dwarf planet.

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