Dennis Ray Frazier, aged 11, of Galena; Kansas, for his question:

Why is it coldest when the earth is nearest the sun?

The earth goes round the sun in a. slightly oval shaped orbit. Throughout the year its average distance is about 93,005,000 miles. At times it is closer to the sun than at others. Strange to say, we are some three million miles closer to the sun in the dead of winter than we are in high summer. Since the earth is heated by the sun, this does not seem very reasonable. Our hottest days, you would think, should be in January when we are closest to the fiery furnace.

This might be true if the earth's axis were at right angles t o its orbit. Day by day it spins around its axis, an imaginary line through the middle from dole to pole. And this axis leans towards the orbit at an angle of twenty three and one half degrees. This makes a great deal of difference as to how the sums rays fall upon the earth's two hemispheres.

In summer, the northern hemisphere is tipped to receive the lion's share of sunshine. In winter, the southern hemisphere gets its quota of longer days. As it travels its yearly orbit, the earth seems to nod to the sun with its north pole in the summer and its south pole in the winter. Twice a year, between midsummer and midwinter, the sun shines equally on the two hemispheres.

Since the earth is a round ball, the sunlight must fall upon sloping sides. Rays fall straight down only upon the bulge that is tipped towards the sun. At these times the sun seems to us to be almost directly overhead.

The sun s rays are hottest when they fall straight down upon the earth For one thing, the sloping rays must cut through a thicker layer of atmosphere. But more important, a sloping beam must cover a larger area than one from straight overhead. In fanning out, it has less heat to give to each square inch of the ground.

All these things combine to cancel out the three million miles of difference in our distance from the sun. Our summer days are longer.  The earth gets more heat during the days than it can lose during the short nights. It is able to store up some if this heat from day to day. The summer gets hotter as it goes along. The rays fall straight down upon the northern hemisphere during the summer. They can concentrate their heat into the smallest possible area.