Sunspots are a bit of a mystery. They appear as dark patches in the photosphere - the surface layer of the sun - that come and go. Normally the number of sunspots peaks every 11 years, coinciding with times when the sun's magnetic field is at its strongest. As the field wanes, the number of sunspots falls to a trough at which point the sun's magnetic field reverses direction and starts to regain its strength.As early as 1801 William Herschel, a British astronomer, suggested that when sunspots were plentiful the Earth would be warmer. He supported his hypothesis by reference to variations in the price of wheat published in Adam Smith's "Wealth of Nations".
As a confessed Galileo groupie, I chose to hold my personal observance of the 2009 International Year of Astronomy on this summit in the San Gabriel Mountains east of Los Angeles. All around the world, astronomy enthusiasts are collaring the uninitiated to look skyward and see the things Galileo saw, from mountains on the moon to the star lanes of the Milky Way. But here at the Mount Wilson Observatory, a few astronomers still pursue an archaic artistic activity that Galileo pioneered: They make daily drawings of sunspots.