Brian Bewley, age 12, of Princeton, Kentucky, for his question:

Why is the sun warmer in summer?

Astronomers insist that we are three million miles closer to the sun in December that we are in July. Since we get our seasonal heat from the sun, it seems logical to expect summer around Christmas time, when the sun is closest. But this is when summer moves south of the equator. The mix up is caused because the earth is round, its axis is tilted and it has an atmosphere that acts to screen out solar radiation.

In July, it is the North Pole's turn to tilt toward the sun.  In the northern hemisphere, the noon sun climbs higher in the sky and the days are longer.  Rays from directly overhead come straight down, via the shortest route through the atmosphere. They lose more radiation when the sun is lower in the sky because then they slant down longer paths through the atmosphere. So in July, even though the earth is farthest from the sun, we get more hours of daily sunshine and more heat from higher in the sky.