David Johnson, age 13, of Louisville, Ky., for his question:

IS THE NORTH POLE COLDER THAN THE SOUTH POLE?

A month or so ago, we heard that ships serving the Alaskan oil field were ice‑bound in the Arctic Sea. Life up there must be pretty grim during the long polar winter, when the sun doesn't rise for weeks at a time. However, things are much worse in the South Polar region. Even the summers are too cold to melt the frozen snow.

There are reasons why the South Pole gets much colder than the North Pole. It so happens that the South Pole is on land, near the middle of the vast continent of Antarctica. The North Pole is in the Arctic Ocean, under a mile or so of salty sea water. Land and sea areas react very differently to the warm radiation that pours from the sun.

Both land and sea areas absorb warmth from the sun, but the land absorbs it more quickly. It heats up faster than the oceans. But the oceans hold on to their stored solar heat longer. After sunset and during the cooler winter months, the land is in a hurry to lose much of its heat. But the seas retain much of their heat during the night and during the winter.

During the winter, the seas tend to be warmer than the land. But since they heat up more slowly, in summer they tend to be cooler than the land. In winter the Arctic Ocean is cold enough to freeze, and the region is covered with ice. But the temperature rarely if ever drops below minus 60 degrees.

When spring melts the Arctic ice, the surface of the sea absorbs from 60% to more than 90$ of the solar radiation it gets. Things soon become comfortably warm and stay that way through the summer months, while the sun stays above the horizon. Meantime currents from warmer oceans stream in and mingle with the North Polar sea water.

At the opposite end of the world, the continent ofAntarctica is under an enormous glacier of frozen snows. In summer its surface absorbs no more than 25$ of the solar radiation it gets. The rest is reflected back into space.

Unlike the Arctic, the Antarctic never gets a chance to build up any reserve of heat. The ice never thaws, and the midsummer temperatures rarely rise above freezing.

The coldest temperatures on earth definitely occur in the South Polar region. The coldest on record was minus 126.9 degrees. The place was not far from the South Pole, and this bitterest of cold days was Aug. 24, 1960. An average winter day at the North Pole is perhaps 40 degrees warmer than an average winter day at the South Pole.