Edward Duren, age 11, of Winston‑Salem, N.C., for his question:

 Do the other planets have four seasons?

First let's make sure what causes the seasons on earth. Are we nearer the blazing sun in summer? Not at all. On January 1st we are 3,000,000 miles closer to the sun than on July 1st. What's more, the southern hemisphere has its summer while we have our winter. The changing seasons happen because the earths equator is inclined to its orbit.

The orbit, of course, is its almost circular path around the sun. The equator is the waist of the world, just half way between the two poles. The two poles are the ends of the earth's axis. The axis is the line through the middle around which it spins, The earth spins or rotates once each day and night as it goes around its orbit

The axis, however, does not stand at right angles to the orbit. The earth does not go around the sun standing straight up. It leans or inclines to its orbit at an angle of 23.5 degrees. In July the North Pole points towards the sun. The northern hemisphere gets more direct sunlight and more hours of daylight. In January the South Pole points towards the sun. The northern hemisphere gets slanting sunlight and fewer hours of daylight.

Whether a planet has seasons, then, depends upon whether its equator inclines to its orbit. Little Mercury, nearest the scorching suns is almost at right angles to its orbit. It has no changing seasons. What's more, one side of the little planet always faces the sun in blazing daylight. The other side knows only colds dark night.

The face of Venus has never been seen from the earth. It is veiled in clouds too dense for the telescope to pierce. We do not know whether our golden neighbor is inclined to its orbit so we do not know whether it has seasons.

Mars, the Red Planet, has changing seasons as we do. It is inclined, like the earth, about 23.5 degrees to its orbit. However, it is further from the sun and takes longer to go around its orbit. The Martian year is equal to 687 earth days ‑ almost two years. Telescope pictures show that white polar caps build up and fade with the changing seasons. The Martian summer lasts almost an earth year, alternating in each hemispheres

Beyond Mars come the four big planets, Jupiter, Saturn, Uranus and Neptune. These giant planets are so far from the sun that summer and winter make little difference. Each has below zero temperatures the year round. Nevertheless, the equator of each big planet is inclined to its orbit. These giants, then, do have changing seasons.

Jupiter is inclined three degrees. Its year lasts 12 earth years. So the Jupiter spring, summer, autumn and winter each last three earth years. Saturn, inclined 26.8 degrees, has a year equal to 29 earth years. Imagine a winter over seven years long. Uranus is inclined 82 degrees and has a year lasting 84 earth years. Neptune is inclined 35 degrees and has a year lasting 165 earth years.

We do not know whether little Pluto's equator is inclined or not. It is too far away to be figured. The little fellow is also too far from the sun to notice any difference at all between its frozen summer and its frozen winter.