Because it’s too dangerous to look at the sun, we don’t notice that it sometimes has a spotty face. Cooler regions of the sun, called sunspots, are depressions that appear as dark patches on the surface of the sun. Sunspots have a typical life span of a few days. They follow a twenty two year cycle, involving two distinct periods of eleven years.
The first eleven year period begins with a few sunspots clustered high above the sun’s equator. They gradually multiply and float towards the equator, until they reach a maximum. At this point the sun’s atmosphere, called a corona, arcs wildly from its surface in huge plumes of gas called solar flares or prominences. These flares may last for several days. Occasionally, they spew large amounts of material into space. When particles from a solar flare reach earth, they can disrupt radio communication for days.
The second period begins when the magnetic field of the sun reverses itself. Curiously, the more sunspots there are, the brighter the sun is, because they’re accompanied by patches so bright that they more than compensate for the darkness of the sunspots.
People have linked sunspot cycles to everything from the price of wheat to the Dow Jones average, but there’s no scientific evidence that they really affect human activity.
So next time you wonder what influences cycles like flu epidemics, or hem lines, don’t blame the appearance of sunspots!