What Do Dog Fleas and Sunspots Have in Common?

To a flea, within his scale of experience, his dog is his world. To a traditional human his village is his world. To modern humans our polluted blue planet is our world. The differences between a flea's world and our modern world are mostly scale and perspective.

Just as the cartoon doomsday prophet on the street carries a sign saying, "The end of the world is coming!" ­ why not imagine a cartoon flea on its cartoon dog carrying a sign saying, "The end of the dog is coming!"

Every flea also has bacteria and viruses on its body. We could imagine another cartoon where a bacterium is carrying a sign among its fellow bacteria saying, "The end of the flea is coming!" And a smaller virus on the bacterium is carrying a sign saying, "The end of the bacterium is coming!"

What does this bizarre narrative have to do with our Sun's solar cycles? Nothing and everything.

We are now in Solar Cycle 24, ready soon for Solar Cycle 25. Each cycle is about 11 years. Very tidy. However, the Sun is some five billion years old, and it should be around for another five billion years, long after Andromeda and the Milky Way merge. What will future solar cycles look like; and how long did they typically last millions of years ago? Twenty-four modern solar cycles is 264 years. Even 264 million years is only about five percent of the Sun's age so far.

We don't consider the Sun to be alive, but it does have an atomic "life" cycle. Different types of stars come and go at different paces. Some blue giants last ten million years ­ whereas red dwarfs can last for hundreds of billions of years. Our Sun (spectral class G2) is a main sequence yellow dwarf; and stars of this type have "lives" of about ten billion years.

In Earth's biosphere we naturally obsess over what the Sun is doing. Sun spots are the easiest way to measure surface mini-cycles within a full life cycle of the Sun. But what do variable spot cycles really mean?

Recently, several types of measurements strongly indicate that the Sun is ready to skip one or more sun-spot cycles. This aberration from the observed normal pattern seems to be a very irregular and disturbing event. Does a quiet Sun foretell the Second Coming, or the end of the Mayan calendar, or maybe a real sci-fi story? Can't say, because it's all too sketchy ­ hardly a random sample of five billion years. The best model we have for the relationship between the Sun's surface spots and life on Earth is the Maunder Minimum, the period roughly spanning 1645 to 1715 when sunspots became exceedingly rare, as noted by solar observers of the time. (Edward Maunder was a noted solar astronomer publishing in the 1890s.) During one 30-year period within the Maunder Minimum, astronomers observed only about 50 sunspots, as opposed to a more typical 40,000-50,000 spots in modern times. Interestingly, this period coincided with the coldest, middle period of the Little Ice Age in Europe, which lasted from the 12th century until about 1850.

So, have we actually established that the Sun caused the Little Ice Age, and that a second Maunder Minimum could offset global warming? Hardly. For one, during most of the so-called Little Ice Age the Sun behaved "normally." For another, the effects of humans on the currently accelerating global warming are much greater than the cooling effects of any extended solar minimum.

From an astronomer's perspective this sunspot puzzle is just another reason for stepping back from hasty conclusions based upon short-term data, however precise and mathematically correlated.

Here are some links for additional data: