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Barb guppy., age 13, of Peterborough.. Ont., Canada., for her question: do.

All of the planets rotate from west to east?

It seems a simple matter to decide whether a planet rotates from the west toward the east. But remember, in order to know which is east and west., you must first decide which directions are north and south. On one of the planets, we could argue about the north and south poles. And if we take one side of the argument, then we must decide that this planet rotates in a westerly direction.'

The sun rotates from west to east on its axis, and all the planets revolve around the sun in the same direction. The earth rotates 3n an easterly direction, and the moon also orbits the earth from west to east. In fact, the general swing of the entire solar system seems to be in the same easterly direction.

We call this path the direct  motion of the heavenly bodies, when an object travels in the opposite direction, we say that its motion is retrograde. The planets sometimes make a retrograde loop against the background of fixed stars. And one of the planets may be said to rotate in a retrograde direction which is to say that it spins around its axis from east to west.

All the other planets that can be observed rotate from west to east. But when we cannot tell which are the north and south poles of a planet, we cannot be sure whether they rotate toward the east or toward the west. We cannot observe the poles of Venus or Pluto. And the north and south poles of the planet Uranus are open to question.

The earth and other planets revolve around the sun on fairly flat planes. The axis of the earth is tilted 23.5 degrees toward the plane of its orbit. It leans as it travels around the sun, but its north pole still _ points in the northerly direction of the solar system. With this basic direction in mind, the earth rotates toward the east.

The axis of Uranus is tilted so far that this planet orbits the sun lying on its side. We can say that the angle is 98 degrees or turn the picture around and say that the angle is 82 degrees. If we say that the angle is 98 degrees, which is more than a right angle, then Uranus rotates in a direct or easterly direction. If we say that the angle is 82 degrees, then we must exchange the planets north and south poles  and Uranus would rotate in a retrograde motion from the east toward the west.

Uranus is out beyond Saturn, too dim to be spotted except by an expert who knows just where to look. It is big enough to swallow our world 60 times, but is only 1.7 times as heavy as an equal amount of water. It rotates in 10 hours 41 minutes, which is very fast. But Uranus takes 84 earth years to crawl once around its huge orbit.


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