Blood moon (not): and the real science and history of a lunar eclipse


Well, I woke up as I often do at around 3am, so was able to look out over Ely Cathedral and see the lunar eclipse. I only had a pocket camera to hand, so the photo is pretty rubbish, and once totality approached there simply wasn’t enough light for it take an image, but it was pretty dramatic all the same. Sandy yellow here, though, rather than blood red. In fact the very phrase “Blood Moon” only dates back I believe to 2013 and book by John Hagee called “Four Blood Moons: Something is About to Change” which comes from the sort of US prophetic stable that I usually take with a pinch a salt.

I’m more interested in the real science and history.

On the science side, there is nothing unusual about a lunar eclipse, of course. There can be up to three a year, when the earth’s shadow crosses a full moon. It’s just that some of them occur when we can see them, and some don’t. Even Bede in his treatise On the Nature of Things explained it, with some interesting commentary: “Inhabitants of the East do not experience eclipses of the sun and moon in the evening, nor do those in the West experience eclipses in the morning, because of the obstruction of the earth’s sphere. For, although night and day are the same over the whole world, they do not occur at the same time over the whole world, as the contrary position of the sphere [of the heavens] brings night or its revolution brings day. For in the time of Alexander the Great the moon was eclipsed in Arabia at the second hour of the night, just as the same eclipsed moon was rising in Sicily.”

So the Anglo-Saxons didn’t think the earth was flat, and knew rather more science than you probably thought they did. They did, though, also (as was general right up to Shakespeare’s time and in fact for many now too) assume that there was some sort of linkage between earthly and heavenly events. In the Bible Joel 2: 31 looks ahead to an apocalyptic day when “The sun will be turned to darkness, and the moon to blood before the great and dreadful day of the LORD comes.” So eclipses, comets and the like, though understood and sometimes predicted, could nevertheless be seen as omens. Indeed in the Anglo-Saxon Chronicle for the year 734 a “blood moon” was taken as an omen for the death of Bede himself.

More happily, another such moon in 549 so shocked the armies of two Teutonic armies encamped against each other for battle that both ran away, fearing disaster, leaving their generals with no option but to conclude an armistice!

Second bit of science up is why the eclipsed moon remains visible and goes red(dish), rather than just disappearing into the night sky. Well, all that sunlight falling on the earth is diffracted by its atmosphere, so some of the light is bent inwards and keeps on illuminating the moon. And since the atmosphere absorbs blue light, what gets through is yellowy-orange. Seemple.

The “Super Moon” bit is also straightforward: the moon has an elliptical orbit around the earth, and when it’s closer it looks bigger. Doh!

Science and history are much more fun than dodgy prophecy, and I think it’s about time the media got over the catchy “Blood Moon” meme and helped us enjoy the real excitement too.

2 thoughts on “Blood moon (not): and the real science and history of a lunar eclipse

  1. I believe the point to be taken is the coincidence of the tetrad moons with the Jewish festivals, which as I understand it have prophetic overtones and also the Elul 29.

    If one takes this approach the last such occurrences were at particularly dramatic moments in Jewish history. Perhaps there is something in this dodgy prophetic ministry but I expect we will have to wait and see to see what, if anything.

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