To understand a total solar eclipse requires no special knowledge beyond the simple fact that the phenomenon is caused by the Moon blocking the Sun from view (ie, the Earth, a new Moon and the Sun in syzygy). Celestial mechanics operate in such a way that from Earth, the Sun and Moon appear to be the same size as they make their stately transit across the firmament. That’s because while the Sun’s diameter is 400 times that of the Moon, it is also almost exactly 400 times further away. As the Moon orbits the Earth and the Earth orbits the Sun, every now and then they line up in such a way that the Earth is plunged into localised temporary darkness. That’s a solar eclipse in a nutshell, and by the time you reach page nine of Mark Littmann and Fred Espenak’s superb ‘Totality: The Great American Eclipses of 2017 and 2024’ (Oxford University Press, £25, ISBN 9780198795698), by their own admission you know everything there is to know.
The next brace of key facts is that total eclipses don’t happen very often and they don’t happen everywhere. The next one, which occurs on 21 August 2017, can only be properly seen from the mainland of the United States, and the one after that – on 8 April 2024 – with be in North America too. Littmann and Espenak’s enthusiasm for the alignment of our Moon and closest star appears to have no limits, and while there will be stick-in-the-muds who will talk about confirmation bias – essentially the idea that we don’t notice when eclipses don’t happen – there is something about their sense of wonder at these events that is quite contagious. With almost child-like glee they urge the reader to skip the technical bits at the beginning about oblong orbits, tilts, danger zones and angular size. But as their thesis develops, it becomes clear that these are the building blocks of understanding what they call “the heavenly rhythm”.
‘Totality’ races along, drawing in historical and cultural perspectives that go way beyond the academic maths and physics. There is even a useful chapter on how to photograph eclipses, whether you choose to do so with the latest digital equipment or a time-honoured pinhole camera obscura. There are plenty of warnings about eye-safety too, with humorous examples of misleading safety information disseminated over the years. These include an exhortation from an Australian broadcaster that the only safe way to watch the eclipse is on television, while keeping your children indoors. During the 11 August 1999 total eclipse in Europe there were even signs on motorways advising motorists to reduce their speed to 70km/h during totality. In essence, this book is as good a primer for the forthcoming eclipse events as you could wish for.
Different in approach, ‘Eclipse: Journeys to the Dark Side of the Moon’ by Frank Close (Oxford University Press, £12.99, ISBN 9780198795490), is less of an event-specific reference work and more of a technically informed memoir of solar eclipses. With a more informal tone – Close’s epigraph is a quotation from Pink Floyd’s 1973 record-breaking album ‘The Dark Side of the Moon’ – we are taken back to the author’s childhood when, at the age of eight, witnessing a partial eclipse at his school in Peterborough provided him with the inspiration to dedicate his life to science, and to make a date with destiny, when he promised that he would see the next British total eclipse – more than 40 years into the future – for himself.
Today, a leading research theoretical physicist in nuclear and particle physicist, the Oxford professor (who also has under his belt the Royal Society’s Michael Faraday Prize for communicating science), spends his free time planning expeditions around the globe to experience total eclipses first hand. One of the main attractions for Close is the comparative rarity of good sightings. In straight forward numbers, when a total eclipse happens only 0.5 per cent of the Earth’s surface will experience totality, and then only for a few minutes. But there’s more to it than that. He freely admits early on in his brilliant book that “anyone who hasn’t experienced totality might struggle to understand why people are prepared to adventure to the far side of the Earth, by plane, ship, even the hump of a camel, to be there”. As you might expect from a man of science, his explanation is remarkable for both its clarity of thought and unambiguous exposition: “Stay at home and you will miss it.”
It’s hard not to feel sorry for the author whose eclipse-viewing trip to Cornwall for the 11 August 1999 event was a washout. Dawn broke to pouring rain, and even though the rain lifted, the impenetrable dark clouds refused to clear. Despite the fact that the exact time of the conjunction had been known for decades, he ruefully explains how the British weather cannot be predicted with such confidence. Cut to the 2006 total eclipse in Libya and Close is understandably nervous about it being obscured by dust-devils and sand-fog in the 100°F swelter of the Sahara. Luck prevailed and the eclipse was crowned by a unique experience in the author’s viewing career. As totality reigned he could clearly see the Moon’s surface illuminated by light reflecting back of our planet and onto the lunar surface: so-called ‘earthshine’.
Two different books united by one passion. While the American authors serve up a dense and yet somehow highly readable torrent of good-natured data, it’s left to an Oxford scientist to express the magic of total eclipses in an entertaining memoir that will stick in the mind long after the next eclipse has been and gone.