Matt Clark, age 10, of Irvine, California, for his question:

Are we going to have another ice age?

Some scientists suspect that the next ice are is just about ready to begin. In about 10,000 years, its thick glaciers may cover many parts of North America. This, of course, would give the people plenty of time to move farther south to warmer climates nearer the Equator. But it may not be necessary. Nobody is certain that this ice age really is on the way.

The Earth has suffered through many cruel ice ages in the past, and most scientists expect there will be more in the future. Naturally they would like to be able to predict the next one's arrival. But there is a very good reason why they cannot do this. Scientists are very careful people, especially when it comes to proving the facts. They never predict what will happen unless they are sure what made it, happen dozens of other times.

And at present, nobody knows for sure what caused the ice ages of the past. Some suspect it may have been a lot of extra dust and debris in the Earth's atmosphere. This could shut out some of the Sun's radiation and cool off the world wide climate. After all, several past ice ages arrived when the Earth was busy building our mightiest mountain ranges    while fiery volcanos erupted countless tons of dust and fumes into the atmosphere.

However, this is just a theory, an educated guess that cannot prove what causes an ice age. At present, furnaces and factories and cars are pouring pollution into the air and our high flying jets are adding, more to the upper atmosphere. Scientists are checking to learn whether this is changing the global climate. Some of the tests suggest that pollution may be making the world warmer. Others hint that it may make things a lot cooler, perhaps cool enough to bring on another ice age. But nobody knows enough to be certain.

Changes in the oceans or the Antarctic ice cap might make the world climate warmer or cooler. Changes in the Sun might shed more or less warm radiation on the Earth. Nobody is sure how many different events could chill the global climate and bring on the next ice age. But most scientists feel sure that one will come sooner or later. After all, we have had four ice ages in the last million years, with nice long warm spells between them. Right now, we seem to be enjoying one of those long warm spells, but nobody knows how long it will last.

Perhaps next week or next year, scientists may prove what causes an ice age and gather enough evidence to predict when the next one will arrive. All it needs is a slight drop in the temperature of the weather. This would bring lots of extra winter snows. The summers would be too cool and too short to melt them. Year by year, the frozen snows would grow thicker and build up great glaciers. This has happened so many times in the past that most likely it will happen again. But at present, nobody knows when to expect it.