“I’d describe it as a magical eeriness.” Lisa Redfern’s description to the Guardian conveys the combination of beauty and wrongness that accompanied Wednesday’s partial solar eclipse in Britain. Crowds across the country assembled as the sun’s power seemed to wane, twilight changed tone abruptly, the temperature fell and the familiar landscape took on an unnatural appearance. In a divided world, there is comfort in coming together in awe. Ms Redfern, speaking from Cornwall, was right that Britons “may not see another one. We have to make the most of these moments.” The country has to wait 55 years for another comparably deep partial eclipse.
To experience the true marvel of the eclipse, one had to be in the path of totality – which this week crossed over Greenland, Iceland and Spain. There the sun was completely obscured. Britain saw a partial version, with the moon covering part of the sun, with only a thin yellow crescent showing. Totality is another world of wonder: for a few minutes a black disc appears where the sun should be, surrounded by a fiery corona in a purplish firmament. It is 64 years before a total eclipse of the sun will be seen over Britain.
Today we understand that eclipses occur when the moon passes directly between the sun and the Earth, a rare three-way alignment known as a syzygy. The moon blocks the sun and casts a shadow across the Earth. As the moon orbits and the Earth rotates beneath it, that shadow races across our planet, tracing a thin ribbon where, for a few extraordinary minutes, day turns suddenly to darkness.
For ancient peoples without such knowledge, something appeared to be eating the sun. In China, the cosmic order appeared threatened by dragons. In India, the disruption was attributed to a demon’s disembodied head. It was a Greek philosopher, Anaxagoras, who arguably first proposed the correct theory of eclipses after experiencing one in 478BC. Astronomical knowledge became political power most memorably in 1504, when Columbus exploited his knowledge of an approaching lunar eclipse – “blood moon” – to frighten Jamaica’s Indigenous people into giving him food after they had refused.
Britain and its empire made a distinctive contribution to understanding the heavens, turning eclipse expeditions into laboratories for the emerging science of astrophysics. It was the 1868 solar eclipse over colonial India that led to the element helium being discovered jointly by the astronomers Pierre Janssen of France and Norman Lockyer of Britain. By the late 19th century, the Royal Society and the Royal Astronomical Society had a “joint permanent eclipse committee”, government funding and privileged access to the navy and colonial administrations.
The committee organised the 1919 eclipse expeditions to Príncipe island, off west Africa, and Brazil that changed science for ever. Their observations found that the sun’s gravity deflected light from distant stars, just as Einstein’s theory of general relativity had predicted four years earlier. Though the 1919 results remain debated, the irony was that British imperial scientific power ended up making a German-born physicist the most famous scientist in the world, just months after Britain and Germany had finished fighting a catastrophic war. Then science transcended divisions; today the eclipse itself does as we gather beneath it in shared amazement. It is also a reminder that some experiences still belong not to nations or individuals, but to humanity as a whole.
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