If there’s one thing you can count on in this world–or out of it–it’s the sun, right? Always there, always shining behind the clouds, perfect, never-changing.
It was a cherished belief of people for many centuries that the sun was perfect and constant. But then along came the telescope. Galileo naturally turned his on the sun as he did on everything else in the heavens, taking furtive glimpses through it and risking blindness until he hit upon the idea of focusing the telescope on a white card. What he saw was as surprising as the moons of Jupiter–he saw spots, dark blotches that meandered and changed from week to week. Each had a dark centre, which he called the umbra, or shadow, and a lighter rim, the penumbra, or partial shadow. The sun was not constant.
Galileo didn’t publish his discovery for a long time, probably because he’d already been stung once by public (or at least papal) opinion; following up his claim that the Earth moved around the sun instead of vice versa with the notion that the sun wasn’t perfect would not have been a good career move. As a result, the first person to publish findings concerning sunspots was the German scientist Johannes Fabricius, in 1611.
Sunspots continued to be favorite targets of astronomers for centuries (a Jesuit monk named Christopher Scheiner even wrote a book about them in 1630; 784 pages long and written entirely in Latin, it was not a best-seller and no mini-series is planned), but nobody had the faintest idea what they were, because nobody knew exactly what the sun was.
Theories ranged from dark clouds over a bright surface to dark holes in bright clouds. (Sir William Herschel, the discover of Uranus, figured the Sun was inhabited beneath its bright exterior.)
Today, we’re a little better off. We have a much better grasp of how the sun works and we have better instruments with which to observe it. We know that sunspots aren’t really black, they just look that way because they’re 2,000 degrees cooler than the normal surface of the sun. (Of course, that still makes them a toasty 4,000 degrees Celsius.) We know sunspots have magnetic fields about 10,000 times stronger than Earth’s.
We don’t know how they’re formed. One theory is that because different parts of the sun rotate at different speeds, the lines of force in its magnetic field get twisted together and develop kinks that erupt through the surface as sunspots.
There is a regular pattern to sunspot activity of approximately 11 years. At the peak of the cycle, not only are there lots of sunspots, there are also violent solar flares–explosive expulsions of matter from the surface of the sun–and an increase in the solar wind, the bits of solar material that stream throughout the solar system all the time.
The cycle peaked about a year ago, at one of the highest levels since Galileo & Co. started watching the sun all those centuries ago, and even before it peaked caused havoc here on Earth. An intense series of solar flares in March of 1989, heralded by the appearance of huge group of sunspots, interfered with satellites, messed up geomagnetic surveys and caused a power blackout over the entire province of Quebec. As well, auroras danced in the sky as far south as the Caribbean.
These kind of effects are well-known and well-documented. The solar flares bombard the Earth with all kinds of electromagnetic radiation from gamma rays to radio waves; it would be surprising if this didn’t effect our own planet’s electromagnetic equilibrium.
However, for decades people have been trying to link the sunspot cycle to other cyclical phenomena on Earth: everything from the length of women’s skirts to the number of Republicans in the U.S. Senate. As far back as Herschel, people have suggested a connection between financial markets and sunspots, and the waters in Africa’s Lake Victoria definitely rose and fall in perfect synchronization with sunspot counts between 1900 and 1923. (Unfortunately, after 1923 the connection vanished and has never reappeared.)
Recently, a new correlation has been proposed between sunspots and climate.
Statistically, there’s a definite correlation between the level of sunspot activity and the severity of winters in North America–dependent also on which way a particular stratospheric wind called the “quasi-biennial oscillation” is blowing. When it’s from the west, the polar temperature rises and falls with solar activity. When it’s from the east, the correlation is reversed. When the quasi-biennial oscillation is blowing from the west, and the sun is at the peak of a cycle, we tend to get high wintertime air pressures here, while the southeastern United States has colder-than-normal temperatures.
Unfortunately, this is all based on only 35 years of records, so don’t make any plans based on these predictions just yet. Remember Lake Victoria. When you’re dealing with an 11-year cycle, it takes a long time to acquire accurate data.
One prediction you can make, though, is that a lot of astronomers, amateur and professional, will keep watching the sun and its spots. As the ultimate source of energy for all life on Earth, and by far the most eye-catching object in the sky, it’s not surprising the sun commands a lot of attention–even if it’s not perfect.
The sun may be a star, but unlike the ones in Hollywood, it doesn’t have to worry about its complexion.