In recent decades it's been common to blame increasing cancer rates on human pollution of our planet. While this may be one factor, some scientists now believe a major culprit could be a decrease in the strength of our magnetic field, a situation outside our influence or control.

Like a force-field around the fictional starship, Enterprise, earth's magnetic field acts as a vast shield protecting us not from Klingon photon torpedoes but from a solar wind, billions of tons a day of electrically charged particles pouring out from the sun.

The magnetic field also helps protect us from a variety of powerful cosmic rays. As more of them reach the earth's surface and smash through our bodies, cancer risks increase. While the field wanes toward zero, it is anticipated that overall cancer rates will double, though the effect may be even more concentrated in some areas.

Although Mars once had a magnetic field and later lost it, leading, many think, to its gradually also losing its atmosphere and most of its surface moisture from erosion by the solar wind, the forecast for earth is not so dire.

A periodic reversal of our magnetic field is normal and has been occurring for billions of years. Statistically, we are overdue for such a shift now. Once it has occurred, people may no longer speak of locations relative to magnetic north, but to magnetic south instead.

© Jan Curtis - Images of the Aurora

Shortly before such a flipping of the field there is a time of decreasing intensity in the shield, when it is less effective against both the cosmic ray and solar wind assaults. We appear to be in that stage of the cycle now.

The good news is that almost certainly, after the magnetic field has been greatly reduced, it will return, though reversed, just as it has done scores of times down through the geological ages.

How long will all this take? On average, the magnetic field reversals have occurred about every 200,000 years. The field decline that precedes one can take thousands of years, but it's rate increases greatly shortly before a reversal occurs. In fact, the recent rate of decline has become much more rapid than just three hundred years ago. Within several score more years the field could all but disappear. In the lifetimes of today's children's grandchildren this might finally occur, with the next magnetic field reversal following relatively soon thereafter.

Besides the increasing penetration of cosmic radiation to our planet's surface, with its quite negative effects on both plant and animal life, the rapid waning of our magnetic field will result in more frequent and dramatic aurora borealis phenomena, and they'll be visible much farther south.

There may be a reasonably adequate time to prepare for the changes that a loss of magnetic field may portend. Along the way toward that goal, our current generation's descendants can celebrate the looming reversal with festive nights and lavish parties beneath a sky of shimmering curtains, perhaps the most spectacular northern lights humans have ever witnessed.

Source: PBS' NOVA, "Magnetic Storm," 11/18/03