In The Spinning Magnet, science journalist Alanna Mitchell crafts a comprehensive history charting the discovery of Earth's electromagnetic field. The planet is a giant magnet spinning in space with two poles: north and south. Between them, "stretchy magnetic field lines" extend beyond the planet "where they interact with the magnetic fields of the sun and the galaxy" before reentering the Earth at the opposite pole in "unending, erratic loops." This force field protects Earth from harmful solar radiation and has mystified humans since ancient Greece. Even now, scientists worry about what will happen when--not if!--the poles reverse direction, as they have done hundreds of times over the centuries.
Mitchell's accounting of the studies of the earth and its forces is densely packed with historical data, like walking a timeline through a museum devoted to magnetism, electricity, geology and solar radiation. It is a slow read, yet one that leaves readers tingling with anticipation and a bit of anxiety as they learn the electromagnetic field is diminishing and has even started to reverse, in what is called the South Atlantic Anomaly. The last big reversal happened more than 700,000 years ago, so we are due for a change at any time, but will the modern world, with much of its infrastructure hooked to a global electric and technological grid, survive? Mitchell's excellent research provides the background to potential answers, but the future remains unwritten. --Lee E. Cart, freelance writer and book reviewer