Today, August 21, marks the day of the so-called Great American Eclipse, predicted decades in advance, and with the Earth crossing the shadow of the Moon, creating a total solar eclipse.
Yes, eclipses do happen about every half year, but this one is quite special, as it would be the first time in about a century that the path of the Moon’s shadow passes through the entire contiguous United States (the previous total solar eclipse was visible on June 8, 1918 and crossed the United States from Washington State to Florida).
The swath of the shadow will touch the United States for only about an hour and a half, and if you miss it, you will have to wait for another 7 years, travel along its way over the Atlantic to Africa, or to Northwestern Europe, where you could sight a partial eclipse near sunset. Alternatively, there is the Total Eclipse of the Sun Forever stamp, issued a month ago by the United States Postal Service to commemorate the event. The stamp uses thermochromic ink, activated by heat, and when pressed with a finger, the black image of a solar eclipse in the centre turns into an image of the Full Moon.
When it comes to the very term solar eclipse – the adjective solar derives from the Latin solaris ‘of the sun,’ from sol ‘sun’, and the noun eclipse entered English from Old French eclipse, via Latin eclīpsis, stemming from the Greek ekleipsis, literally ‘fail to appear’
There is historical data for the observation of the sun failing to appear dating back some 4000 years, yet the first telescopic observation of a total solar eclipse was made in France in 1706, and the first British record to explain the spectacular sight comes from 1602, from The Theoriques of the Seven Planets where the English mathematician and astronomer Thomas Blundeville not only offers an explanation but also illustrates with an image how an eclipse affects different parts of the Earth.
It was the London total solar eclipse from 1715, the first the town had seen for 500 years, to light up a fair share of interest amongst scientists. And while some interpreted the event as a bad omen, and at a reasonable ground, as a connection between eclipses and omen had been drawn in recent events – like the execution of Charles I (1649), the Great Plague (1665-66) and the Great Fire of London (1666), others approached it from its pure scientific side, like The Black Day or a Prospect of Doomsday, for example: “An Eclipse of the Sun…proceeds only from natural Causes; and is nothing else but the direct Interposition of the Body of the Moon between our Sight and the Sun.”
The Royal Astronomer, Edmond Halley (best known for computing the orbit of the Halley’s Comet) and William Whiston (a leading figure in the popularisation of the ideas of Isaac Newton) had produced calculations on the Great Eclipse, describing the eclipse’s construction and predicting its path and timing, to extend their observations thanks to the three more major eclipses in Britain during the first half of the eighteenth century: in 1724, 1737 and 1748. With the last one, finding spectators prepared, as the London Magazine (in an article so popular it had to be repeated) advised readers to make a pin-hole projector or hold a piece of glass over a candle until it was entirely blackened: “and then the eclipse may be viewed through it, either with the naked eye, or through a telescope.”
Today, we have powerful telescopes and eclipse glasses made of black polymer which could filter up to 100% of harmful ultra-violet and infrared light, yet the modern society has other problems with solar eclipses, as the reduction in solar radiation affect the output of our photovoltaics capacities, hence renewable energy production.
With all said, a total solar eclipse is one of the most spectacular sights in nature, when the Moon – obviously smaller than the Sun, yet thanks to been closer to the Earth and to a fortunate coincidence – covers the entire disk of the Sun and its shimmering corona and reddish plasma reveal for only a several minutes to create a memory for a lifetime.