It was all over the news earlier in the week. Even though I was nowhere near the path of totality, I was very aware that a total eclipse of the sun was due on Monday. Many people that I know were excited. Some taking the day off and/or traveling to an optimum viewing location. I had no good excuse to be in the US, so I was not amongst them.
This got me thinking about eclipses and their significance …
There has only been a single total eclipse, visible from my vicinity, in my lifetime. That was in 1999 and it was only visible from parts of Cornwall in the far south west. We – my late wife, myself and my two young daughters – decided to have a short break in Munich, Germany, where visibility was due to be good. We figured that, if the weather was unfavorable, at least we would have been somewhere interesting for our mini-vacation. As it turned out, the weather was not great anywhere for viewing in Western Europe. As I recall, there was a slight break on the clouds, so we can say that we saw it.
I have found the coverage of the eclipse in the media quite interesting. Some folks have just focused on the aesthetics – isn’t it beautiful? That is fine, as nobody could deny that it is a most spectacular event. Others have talked about the mystical and religious angle. I will not comment on that. The scientific discussion is, I think, the most interesting. Much discussion was about the predictable nature of eclipses. This is unsurprising, as it seems obvious that if a body [like the Earth] orbits a star [like the Sun] and is itself orbited by by a satellite [the Moon], the satellite will apparently pass in front of the star from time to time. It is only a question of geometry to make the calculations that lead to predictions. As the late, lamented Patrick Moore described it: it is the clockwork of the Solar System.
However, one aspect of eclipses is really surprising. Our Moon is quite large, compared with the relative size of other planets’ satellites. It orbits at just such a distance that its apparent size in the sky is almost exactly the same as the Sun. If it were bigger or smaller or closer or farther away, the effect would be very different. It has not always been that way. The Moon’s orbital distance has changed over time, as has the actual size of the Sun. They will change again, but I think that is unlikely for some millennia. So, both the beauty and the scientific usefulness of a total eclipse are both caused by an amazing coincidence.
So, when will be my next chance to see a total eclipse? If I do not wish to travel far, the answer is 2090! In the unlikely event of my being alive then, I will be 133, so I expect I may have other priorities. If I do not mind traveling a bit, the next opportunity is in 9 years time – 2026. I will need to go to Iceland or Spain. Maybe I need to book some travel now …