As an aging citizen of Scandinavian descent, I dread this time of year. Each evening the sun sets significantly earlier. Deep in the bones of us northern people is the notion that summertime is the season of life and hope while winter is, well, cold and horribly dark.
This week all of the globe enjoys roughly 12 hours of sunlight and 12 hours of night. The “reason for the season” relates to the Earth’s orbit around the sun. During summertime, our planet’s north pole points mildly toward the sun and we in the northern hemisphere get more than 12 hours of sunlight. During the winter the Earth has traveled halfway around its orbital path. At that time, the north pole is pointed away from the sun and the southern hemisphere enjoys more sunlight while we northerners shiver in the dark. Now, at the start of fall, we stand at the in-between time.
I’ve been thinking about sunlight in part because I dislike losing it so rapidly this time of year, but in part because the sun has been in the news, too. The reason our favorite star has garnered some media attention is that its poles are reversing, north to south. Here’s the scoop:
The sun has two big cycles of change. First, the number of sunspots – dark regions on the surface of the sun – wax and wane over time. That’s something you may have once learned in science class. But another cycle that’s less well known is that the magnetic poles of the sun swap places, north to south. Both of these changes occur on a cycle of about 11 years.
I recently talked about the sun to Dr. Michael Allen, a colleague of mine in the Department of Physics and Astronomy at Washington State University. Allen explained to me that the sun’s magnetic field is in the process of decaying to zero. In the coming weeks or months it will next reorganize itself with north and south poles fully reversed.