Patricia West, age 12, of Charleston, WestVirginia, for her question:

What is the earth's magnetic field?

In some mysterious way, the core of our planet acts like an enormous magnet, tilted so that its opposite ends are near the North and South Poles. As do all magnets, it surrounds itself with an invisible force field. Its lines of magnetic force are loops that extend high above the equator and dip down toward the surface at the opposite magnetic poles. This magnetic field is the earth's magnetosphere.

Magnetism is related to electricity and the realms spanned by the magnetosphere are strewn with an assortment of charged particles. Some are streams of protons and electrons from the sun, others are cosmic ray particles from outer space. All this radiation would be dangerous to life on earth. But vast numbers of the charged particles are captured by the magnetosphere. Some are deflected toward the magnetic poles. Others are swirled in spirals and trapped in the enormous Van Allen radiation belt. The earth's magnetic field acts as a sort of umbrella to shield us from the rain of charged particles out there in space.