The Clock in the Sun

by Pierre Sokolsky

Columbia University Press, 2024

"You cannot see My face; for no one shall see Me and live." Pierre Sokolsky quotes from Exodus in the introduction of his book, drawing the extended analogy of Sun as god. Indeed, for most cultures in history the Sun was an actual god, and the Medusan idea expressed in this verse from Exodus probably struck us originally embedded in its blinding rays. And yet humanity has not only looked at the face of the Sun but has even made a study of its blemishes. These dark areas, called sunspots, appearing and disappearing with regularity on our star's surface, have turned out to be manifestations of phenomena with biblical potential. The Clock in the Sun tells the fascinating history of solar physics and how we came to understand these mysterious spots.

The title refers to an inherent periodicity in solar phenomena, which results from the Sun's rotation and structure. Sokolsky, a retired particle physicist and seasoned teacher, explains the physics of our star masterfully if without flair. But what mostly concerns his discussion is how this solar cycle is felt by humans. That is mainly through the Sun's magnetic field, which is so strong that it extends all the way to the Earth and beyond. Disturbances in this magnetic field are known as solar storms (one of the disappointingly few alliterative terms in physics).

Sokolsky writes what he calls a "historico-scientific exposition", from antiquity to the current day. To begin with, he performs a skilled survey of the well trod ground that is ancient astronomy: Astronomical cultures observed sunspots as far back as the Shang dynasty in the 11th century BCE. Later, the observational and numerical astronomy of the Mesopotamians stands in contrast with the abstract astronomy of the Greeks. After the fall of the Western Roman Empire, astronomy becomes the thriving domain of the Arabs. With the Arabic conquest of Spain their science seeps into Europe. More importantly for Sokolsky's narrative, they bring to the Christians the works of Aristotle, whose pronouncements about the heavens were adopted by the Church. Sokolsky manages to present the ensuing heliocentrism affair through a not too stale view. He is concerned not only with history and science, but with the relevant philosophy as well, without ever crossing into the academic mundane. His gripping chapter on Galileo opens like this:

What do sunspots have to do with the centuries-long debate about Aristotle’s, Ptolemy’s, and Copernicus’s models of the solar system? That disagreement could seem to be about Earth’s position: is it the center of the universe or just another planet orbiting the Sun? But an equally and perhaps more important debate is about the geometrical perfection of the celestial sphere.

The portion about the dispute between Galileo and Christoph Scheiner on sunspots is a highlight, with Sokolsky employing extensive quotations in thrilling succession. In fact the whole work is filled with quotations, as the author lets his historical subjects speak for themselves, making the book a polyphonic testament of solar science through the centuries. Sokolsky's own voice is unobtrusive and his register subdued even at its most excited:

The direct solar influence on magnetic storms and auroras became particularly dramatic on September 1, 1859. On that day, Richard Carrington [...] was examining a particularly large sunspot group when he suddenly saw two very bright white beads of light along its edges. Though they appeared like tiny new moons, he estimated that they were spaced 12,000 miles apart and were 8,000 miles long and 2,000 miles wide. He noted that the flare lasted for five minutes and then faded completely.[...] Eighteen hours later, there was a truly memorable auroral display over large parts of the world.[...] At its peak, the aurora was so bright that newspapers could be read by its glow. [...] Carrington traveled to the Kew Observatory, which had instruments that monitored Earth’s magnetic field, and asked to see the records of the magnetic measurements. In fact, a short-lasting magnetic disturbance had been recorded.

Sokolsky's book succeeds because of his insistence on particulars. He never shies away from the scientific detail, with one of the thirteen chapters being entirely devoted to spectroscopy, the science that taught us the composition and structure of the Sun by discerning the hues in its rays. Everything is related clearly from the bottom up, without making the reader feel like they're being led by the hand. Maybe less particulars were needed in the two chapters about failed sunspot-based economic theories, which are distractions in this otherwise focused work. All in all, The Clock in the Sun catches the pulse of our favorite star as well as that of our intellectual history with it. Interested readers of all levels will have something to learn and enjoy.

Nikolas Mavreas is a reader living in Athens, Greece.