Sen—The Sun has been fairly quiet of late, with just one sunspot group of any size currently crossing the visible disc, albeit crackling with X-ray bursts.
But this week astronomers in parts of the world are preparing to witness one of its greatest spectacles, a solar eclipse, on Friday, Mar. 20.
This is not due to any physical effect of the Sun’s of course, but is simply down to the geometry of celestial alignments, with the Moon passing across the face of our nearest star.
However, they are sufficiently rare from any particular place on the globe that they attract great interest. They are different from eclipses of the Moon, which are also due to alignment but which happen when our natural satellite enters the Earth’s shadow.
From a narrow track across the North Atlantic ocean, this solar eclipse will be total, meaning that the Moon will completely cover the Sun for a brief time. For this eclipse, totality can be seen from only two small areas of land, the Faroe Islands and Svalbard in the Arctic. Interestingly, the total eclipse crosses the North Pole too as it ends, which apparently is an incredibly rare event.
By an amazing coincidence, though the Moon is much smaller than the Sun, it is also about 400 times closer, and this means it looks almost exactly the same size in the sky. (In fact, it will be slightly larger, due to perigee, when the Moon is closest to the Earth, occurring just a day earlier.) So at a total eclipse, the Moon hides the Sun but allows its fiery prominences and ghostly atmospheric corona to come into view.
A number of expeditions to see the event will be made by sea, with eclipse-chasers hoping that the often stormy weather spares them so that they can catch a glimpse of the solar spectacle. (If they miss it, due to cloud, they might have to make do with the consolation prize of night-time aurorae at those northern latitudes.)
An arresting sight. A passing police officer pauses to view a partial solar eclipse over London in August 2008. Image credit: Paul Sutherland
Most people, though, will not be on the line of totality, so will have to put up with a partial eclipse where the Moon doesn’t completely obliterate the Sun. From much of Europe and Iceland, this will be a very large bite out of the solar disc. From the north of Scotland and its Western Isles, more than 95 per cent will be blotted out, and the amount is still nearly 85 per cent from London, in the south of the UK.
I describe it as a bite. In ancient times, when ordinary folk did not properly appreciate what was going on, they thought that this was really happening, with a celestial dragon devouring the source of their light and warmth.
Nowadays, most people have a better idea of what is going on and scientists are able to predict eclipses for centuries ahead, plus determine their circumstances into the distant past too. This has been useful because comparing a track of an ancient eclipse with historical records of where it was seen have helped log how the speed of the Earth's rotation has changed over time.
Yet, even without the dragons, there is still much fear and ignorance about eclipses to be overcome. Newspapers have been warning that the UK will be “plunged into darkness”—it won’t, because even a sliver of sunlight is very bright—and dire warnings given about how Europe’s power grid will cope (so how do we survive Sun-less nights?).
Eclipses are one of the natural wonders of life and something that youngsters should be encouraged to experience to help them appreciate the workings of the Universe. Yet in an over-cautious age, there have already been reports of how some UK schools plan to keep their pupils indoors to protect them from looking at the Sun. It is an attitude that Professor Brian Cox, who will present live coverage of the eclipse on BBC TV, described to me as “medieval”.
Part of the blame for this must lie with the Government’s Department of Science which appears to have failed to communicate any useful advice about a major celestial event that will begin as children are heading to school. Teachers have told me how they have had no guidance whatsoever from education authorities.
Yes, it is important that the eclipse is observed safely, and there are a number of ways to do this. It is a good opportunity to make children aware of the dangers of looking at the Sun while allowing them to share in the event. Fortunately, a number of amateur astronomers from local societies will be helping schools across the UK and, no doubt other parts of Europe.
The UK’s Society for Popular Astronomy has joined forces with the Royal Astronomical Society to produce a useful leaflet. And the SPA has a page full of tips to help members—and teachers—including a video guide presented by solar expert and Sen blogger Dr Lucie Green.
So let us keep our fingers crossed for clear skies on Friday so that sensible people, taking sensible precautions, can enjoy one of the true wonders of nature.