Dear Tom,

The sun provides almost all the heat that powers our weather, but do other stars affect our weather as well?

—John Bowermaat, Clarendon Hills

Dear John,

Other than the sun, the stars have no effect on our weather. Recent studies, however, have shown the possibility that cosmic rays bombarding the Earth aid in the formation of clouds. Increased cloudiness lowers surface temperatures. Cosmic rays knock electrons out of air molecules, producing ions that aid in the growth of cloud condensation nuclei. This results in increased cloudiness. Variations in the sun’s magnetic activity alter the amount of cosmic rays bombarding the atmosphere; more cosmic rays mean more cloudiness and a cooler climate; fewer cosmic rays, a sunnier and consequently a warmer climate.