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BOOK REVIEW

Sunspotting

Alex Soojung-Kim Pang

The Sun Kings: The Unexpected Tragedy of Richard Carrington and the Tale of How Modern Astronomy Began. Stuart Clark. xii + 211 pp. Princeton University Press, 2007. $24.95.

 

Sketch%20of%20solar%20flaresClick to Enlarge ImageOn September 1, 1859, English amateur astronomer Richard Carrington, who had been studying the face of the Sun for six years, observed a vast sunspot complex. Startling in scale, it stretched nearly a 10th of the way across the disk, which meant it was almost 10 times the diameter of the Earth. Carrington sketched the spots, and then as noon approached, he saw something he thought to be unprecedented: Two beads of white light (solar flares) appeared over the group of sunspots, intensified for a few minutes, then faded and vanished. [His drawing of what he saw is reproduced here.] As far as he knew, no one had ever described such a phenomenon before.

Within a few days, Carrington began to learn of other remarkable events. At the observatory at Kew, recordings made on photographic paper by a ray of light bounced off a compass needle showed that the Earth's magnetic field had been disturbed at the exact same time that Carrington had seen the solar flares. Other strange things happened about 18 hours after the solar flares: Telegraph operators in Europe and the Americas had to struggle to keep their lines open and functioning. Around the globe, sailors and others saw remarkable auroras. And scientists measuring the Earth's magnetic field saw their instruments fluctuate wildly.

Were the sunspots and flares related to, or perhaps even the cause of, these events? Had the Sun released a vast burst of energy that later reached the Earth and was powerful enough to disrupt global communications and light up the night sky? The idea seemed farfetched. The Sun was normally steady and predictable in its provision of light and heat. Carrington thought the possibility that the sunspots and auroras were linked should be considered; if the Sun were capable of huge swings in its behavior and unseen solar energy could somehow reach and affect the Earth, that would be important to know.

Such arguments were not entirely new, but they were hard to accept. And Carrington's own work did not prove definitively that the phenomena were connected. Nevertheless, science journalist Stuart Clark, in his new book The Sun Kings, places Carrington at the fulcrum of a century-long debate over the effects of sunspots, because he drew on two very different sorts of scientific observations—studies of sunspots and of the Earth's magnetic field—that together would eventually allow astronomers to see the relation between solar and terrestrial activity.

In England, the first notable speculations about the influence of the Sun on the Earth's magnetic field and climate had been made more than half a century earlier by William Herschel, best known as the discoverer of the planet Uranus. In the decades between Herschel and Carrington, a number of scientists developed new tools to study the Sun or oversaw careful, decades-long studies of solar behavior. Herschel's son, John, was a pioneer in solar photography, which helped automate the work of sunspot observation. Astronomers and geologists established magnetic stations, and from 1802 to 1839, what Clark refers to as "the magnetic crusade" (Alexander von Humboldt was a leading participant) focused on mapping and detecting changes in Earth's magnetic field, a task made more urgent by the dramatic growth in world trade and the expansion of European navies. Physicists determined that chemical elements, when burned, emit light at particular wavelengths; chemists' success mapping spectral lines raised the tantalizing possibility that the Sun's chemical composition could be deduced from its light. In 1850, Humboldt, in one of the volumes of his massive masterwork, Kosmos, published a chart based on observations made over a 42-year period by German pharmacist Heinrich Schwabe, who found that sunspots followed a roughly 11-year-long cycle, having been very numerous in 1828, 1837 and 1849.

Richard Carrington is almost unknown today; even most historians of Victorian astronomy probably have no more than a passing familiarity with the name. But it would have come as little surprise to his contemporaries that Carrington had the good fortune to observe his remarkable sunspot or that he speculated that it was connected to the unusual auroras. He was part of a generation of Victorian amateurs who, supported by industrial wealth (his father was a brewer), were pushing back the frontiers of knowledge. Educated at Trinity College, Cambridge, Carrington built his own state-of-the-art observatory in 1852 and proceeded to refine Schwabe's theory. In 1857, he published a notable star catalog. The following year he was forced to take over the family business after the death of his father. In 1859, he won the Royal Astronomical Society's Gold Medal for the catalog, and after seeing the September sunspots and solar flares, he was elected to the Fellowship of the Royal Society.

If life imitated art, or at least followed its narrative conventions, Carrington would have produced a triumphant demonstration of the link between solar and terrestrial atmospheres, and The Sun Kings would have ended as hagiography. But life followed other rules. Within two years, Carrington's time as a leading astronomer was over. He hated the brewery and had exhausted himself trying to juggle two careers. Failed efforts to secure a professorship at Oxford and then one at Cambridge left him depressed. In 1861 he sold off his astronomy equipment, and with the publication of a sunspot catalog in 1863, he brought his involvement in solar astronomy to an end.

A few years later, he finally sold the brewery and attempted to move back into astronomy, but accomplished little. His marriage in 1869 proved difficult and distracting. In 1871, a scandal arose when his wife was stabbed by her lover, a man she had passed off to Carrington as her brother. Carrington died in 1875, a few weeks after his wife was found dead of a drug overdose; rumor had it that he had murdered her and perhaps killed himself.

It would take almost another three decades for the link between sunspots and terrestrial magnetism to be definitively established, by Edward Maunder, an astronomer at the Royal Observatory at Greenwich. By that time, scientists with the Indian Meteorological Service were speculating that the severity of monsoons and droughts was affected by sunspot activity, and the discovery of x-rays and advances in electromagnetic theory had made it easier to accept the idea that solar events could have terrestrial consequences. Maunder first refined Schwabe's and Carrington's studies of sunspot periodicity, showing that sunspots tended to cluster in certain solar latitudes. But it was Maunder's success correlating the appearance of specific sunspots with particular magnetic storms—both following the Sun's 27-day rotation—that clinched the argument.

The Sun Kings is breezily written, but hardly light-headed. Without dumbing the story down, Clark spends great effort making it as entertaining as a decades-long scientific mystery can be. Although the title places Richard Carrington at the center of the story, the book is really a tale of a community of scientists, some toiling to build up catalogs of observations, others squabbling over how best to move solar astronomy forward. Given that sunspots wax and wane following an 11-year cycle and that magnetic surveys required the coordinated effort of governments and scientists around the world, it's understandable that progress took decades. In its unpretentious way, The Sun Kings demonstrates one of the central claims of the social construction of science: that for all the popular attention to great minds and breakthroughs, most science is a cumulative, community activity. It takes a village to raise a theory.

Actually, it can take a global village. One of the remarkable features of Victorian astronomy was how far-flung it was. In that era, astronomers could jump-start their careers by spending a few years abroad—John Herschel spent several years in South Africa, and Carrington briefly considered emigrating. But also, the global communications, transportation and political networks that provided an infrastructure for global trade and European imperialism were priceless resources for Victorian astronomers. Although accounts of magnificent auroras were certainly dramatic, some of the most compelling information about magnetic storms came from telegraph operators. Because their work required them to have technical facility and to be attentive to detail and conscious of the clock, the timing and strength of magnetic storms could be fairly precisely figured from operators' accounts of system-wide disturbances and failures. Indeed, telegraph systems were essentially gigantic astronomical anomaly detectors: When all the lines stretching across Europe or North America suddenly failed, it was a certainty that the cause was extraterrestrial.

Modern scientists should take note. We tend to think of our era as one that's uniquely global and information-rich, but the Victorians dealt with the same kinds of exciting opportunities and with similar challenges. New technologies were opening amazing frontiers in science, but as Carrington's life tragically shows, it was much harder to make a life in science than to do good science. Victorian scientists fretted over what kinds of contributions amateurs could make to an increasingly specialized, arcane field.

We can still learn a great deal about ourselves, and about how to do good science, by studying the Victorians. Stuart Clark deserves praise for making the period so accessible.


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