The Solstice

Sometime in November of 1770, crowds took to the streets of London to gaze upwards. The sun was bright and Londoners were able to look at it directly without the use of what Benjamin Franklin called ‘smoked glasses’, for the ‘common smoke of the city’ was protection enough. What they saw was at once amazing and mysterious. Dark shadows, or clouds, or inexplicable black spots could be made out on the sun’s surface. Nobody knew for certain what they were looking at, but some had ideas.

Sunspots seen through the haze caused by wild fires in Southern California. Photo Credit: Tom Tschida.

Sunspots seen through the haze caused by wild fires in Southern California. Photo Credit: Tom Tschida.

In a letter to Humphry Marshall, cousin to the great Quaker naturalist John Bartram and a plant dealer himself, Franklin summarised the scientific debate on sun spots. ‘Some think them vast clouds of smoke and soot arising from the consuming fuel on the surface.’ These clouds reignited at their edges, at length being totally consumed. The notion of smoke combustion was intriguing to Franklin, who later designed a curious heating stove whose downward-burning flame would consume its own smoke. Other observers, continued Franklin, believed the spots to be places where the solar flame somehow ‘has been extinguished, and which by degrees are rekindled.’ The problem with this conjecture was ‘that though large spots are seen gradually to become small ones, no one has observed a small spot gradually to become a large one.’ At least, he was not aware of any such observation.

But Franklin had a new hypothesis, suggested to him by Glasgow University’s first Professor of Astronomy, Alexander Wilson. Through his telescope Wilson had noticed something remarkable about spots at the edge of the sun’s disc. Rather than issuing from or rising above the surface, the spots appeared as slight depressions, a phenomenon now known as the Wilson effect. He was sure that this meant the spots were on the surface of the sun, not clouds of smoke; he also wondered if the subsurface of the sun were not made of unkindled fuel. If this were so, Wilson had explained to Franklin, the dark shapes were probably caused by massive ruptures ‘similar to our earthqukes’, by which ‘the burning part may be blown away … leaving bare the unkindled part below, which then appears a spot.’ (Marshall did not quite agree.)

Today is the shortest day of the year. Time to celebrate: it’s more sun from here on out. (Until June, anyway.) Have a look at sunspots yourself at the image galleries on the NASA website. There are some spectacular images at the Washington Post. The Memorial Library collection is the next landing point for the universally curious. Here are some picks from the shelf:

The universe in a mirror : the saga of the Hubble Space Telescope and the visionaries who built itThe Universe in a Mirror (Princeton UP, 2008) by Robert Zimmerman.

Subtitled, The Saga of the Hubble Space Telescope and the Visionaries Who Built It, Robert Zimmerman’s book tells the big story behind many of our most beautiful images of space. The Hubble Space Telescope has transformed our understanding of the universe, revealing new information about its age and evolution, the life cycle of stars, and the existence of black holes, among other discoveries. Robert Zimmerman is an award-winning science writer and historian whose work has appeared in Natural History, the Wall Street Journal, and Astronomy, among other leading publications.

Dark Side of the MoonDark Side of the Moon: The Magnificent Madness of the American Lunar Quest (New York University Press, 2006) by Gerard J. DeGroot.

DeGroot is a Californian-born Professor of Modern History at the University of St. Andrews. In this book he takes a critical look at the American mission to the moon. Was it, in the end, really of any cultural or scientific value? Or was it simply another front of the Cold War, an expensive distraction? In an interview, DeGroot grounds his angle by paraphrasing President John F. Kennedy conversing with his NASA administrator James Webb. Said Kennedy, ‘I don’t really care about the moon. I know it’s important; I know there are people who really want to go there, but I just want to beat the Russians.’

Read this if you’re in for a bit of mythology-busting, pretention-puncturing illumination on a grand and adventurous moment in American history. By way of extract: the chapter entitled ‘Fly Me to the Moon’ is followed on by one called ‘Slaves to a Dream’.

Smithsonian Atlas of Space ExplorationSmithsonian Atlas of Space Exploration (HarperCollins, 2009) by Roger D. Launius and Andrew K. Johnston.

A beautiful book whose full-colour, glossy pages deliver gorgeous photographs and clear diagrams. The authors work at the National Air and Space Museum in the Division of Space History and the Center for Earth and Planetary Studies. It’s a bit of a textbook, which students will find helpful and easy to access and which for everyone else is enjoyable and exciting to pick through, buffet-style.

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