The Sun Kings

A large solar storm can cause quite a lot of trouble on Earth in the form of power cuts, communication failures and the like. The link between solar activity and happenings on Earth isn't obvious though. This book tells the story of how this link came to be recognised.

William Herschel was a keen observer of the sun. His observations led him to discover infrared radiation, and he was also concerned with the effects of variation of the solar output on the Earth’s climate. He found correlation between large numbers of sunspots and high wheat prices, suggesting that there was such an influence, but this link was too far fetched for the scientists of the day and just resulted in ridicule.

At the start of the 19^th Century it was realised that the magnetic poles weren’t fixed. To the maritime nations the reliability of the magnetic compass was vital to their prosperity, so considerable resources were devoted to measuring the Earth’s magnetic field, and in particular Britain set up stations throughout its empire. One of the people involved in this was William Herschel’s son John. It soon became clear to him that there was indeed a link between sunspots and the Earth's magnetic field, but others weren't willing to accept such a mysterious influence.

As the title suggests, much of the book looks at the work of Richard Carrington, who did regular solar observation, and in September 1859 saw a large solar flare coming from within a sunspot. This coincided with a huge magnetic storm - there were widespread aurorae, and the telegraphic system was disrupted. Indeed telegraph operators found it best to disconnect the batteries and work using the energy from the magnetic storm. This wasn't enough to convince the doubters though. Despite his valuable results Carrington was unable to get the academic position he sought. His family owned a brewery, so, like many scientists of the day he was able to fund his work himself, but a university post would have enabled him to spend more time on astronomy and less on managing the business.

Clark tells how one evening Carrington experienced 'love at first sight'. He proposal of marriage to Rosa Rodway was initially rejected, but eventually she accepted - one imagines the fact that Carrington was considerably more wealthy than she was used to must have influenced her decision. But all was not as it seemed. William Rodway, who she claimed was her brother, was in fact her lover. It seems he profited from the arrangement, but his jealousy resulted in the tragedy alluded to in the title of the book

When Carrington died the consensus was that the link between sunspots and magnetic storms was pure speculation. Indeed in 1892 Lord Kelvin's calculations seemed to show that there was no way that the sun could have such a magnetic effect on the Earth. The sceptics influence was gradually being worn down though. Clark tells of the work of George Ellery Hale, who invented the spectrohelioscope. Hale continued the tradition of the self financed amateur, building his own observatory. This wasn't because he couldn't get an academic post, rather he was waiting until he could negotiate such a position on his own terms. The book looks in particular at the work of Edward Walter Maunder who, with his wife Annie, made regular solar observations. They also went to observe solar ecilpses in 1898 and 1902, when Annie took some spectacular photographs. Eventually Maunder's correlation of magnetic variation with solar variation persuaded the majority of the scientific community of the link.

Just as at the start of the 19^th century it was necessary to monitor the state of the Earth's magnetic field , so today the importance of radio transmissions and satellite communications, not to mention the health of astronauts, means that it is vital to keep an eye on the state of the sun. The book describes some of the current research into solar activity, telling how the SOHO satellite has detected several large solar storms, in particular one around Halloween 2003.(I'd note here that the first results of the STEREO mission would have been available before the book was finished but don't get a mention) None of these storms were as large as the one Carrington saw in 1859, but the next solar maximum starting after 2010 might just produce such a flare. Clark also discusses ideas of how sunspots may influence climate (via a roundabout route involving cosmic rays), indicating that Herschel's 'grand absurdity' may eventually be confirmed after all. The book ends with a description of a magnetar eruption in December 2004, suggesting that the sun isn't the only astronomical object we need to keep an eye on.

The book describes quite a bit of the politics behind the astronomy of the 19th century, discussing who did and who didn't get the jobs which were available. It thus illustrates the transition from the grand amateur to the professional astronomer as well as showing the gradual acceptance that plotting positions on the sky wasn't all there was to astronomy. On that basis it may well be useful to those wishing to understand a similar transition a century later, when astronomy moved from being purely visual to include radio waves, X-rays and other wavelengths. It's a well written book and doesn't require any previous knowledge of the subject and, most important of all I found it to be a highly enjoyable read. I'd suggest it as a possible winner of the 2008 Royal Society Science Book Prize