SPECIAL
The Sun’s 11-year cycle and its upcoming peak have been making headlines recently. Here’s how it could affect us on Earth
Wlight, and luckily for us, it produces both of these at a virtually constant rate, day after day, year after year. The small fluctuations in the Sun’s brightness, for as long as people have been measuring them, have never been more than one part in a thousand. In less obvious ways, however, the Sun’s behaviour is anything but constant, swinging between two extremes on a roughly 11-year cycle. For the most part this variability can only be observed with telescopes and other scientific instruments, but occasionally it can have more dramatic consequences. It was one such consequence that tabloid newspapers were referring to when they blazed headlines about a potential ‘internet apocalypse’ in June 2023.
The first hint that there might be more to the Sun than a constant source of heat and light came with the discovery of sunspots – black spots on the surface of the Sun. No one knows for sure who first observed these, but their existence seems to have been known long before the invention of the telescope. Sunspots can’t have been easy to observe in those days, due both to a lack of magnification and the fact that it’s extremely dangerous to look directly at the Sun. It’s likely that ancient astronomers only did this when the Sun was very low on the horizon, or covered by haze. But even under these conditions, don’t try it yourself, as it’s not worth the risk to your eyes. A small telescope will give a much clearer view of our star, as long as it’s used with a proper solar filter or by projecting the Sun’s image onto a white card to protect your eyes.
The advent of telescopes early in the 17th century gave astronomers their first chance to study sunspots in detail, and it soon became clear that some years see far more of them than others. The basic 11-year cycle was fully established by the middle of the 19th century. Around the same time, as people learned more about the physics of the Sun, they began to realise that sunspots were simply the most visible consequence of the solar cycle, and that a lot more was going on beneath the surface. The situation was clarified further still after the true nature of sunspots was worked out by American astronomer George Ellery Hale in the early years of the 20th century.
