Musings on the Transit of Venus

The transit of Venus yesterday has me thinking about rare celestial phenomena and their meanings. It was incredibly cool to read about people viewing the transit and also to watch the NASA live webcam. I watched the transit from my sitting room in London, as the 100% cloud cover made it impossible to see. (The first transit to be recorded was by an Englishman, Jeremiah Horrocks, who saw it while he was actually in England. Talk about a lucky break, given the weather here.) That was my last chance, unless I live to see 2117 (doubtful). 

All of the news coverage I saw referred to the importance of this predictable astronomical event in terms of helping astronomers ascertain more precise information about the Sun. One of the astronomers on the NASA feed talked about how the transit could end up causing disturbances in Earth's electromagnetic field, perhaps leading to patchy cell phone coverage (AT&T, you finally have a legit excuse!). 

Medieval astronomers and scholars thought that celestial bodies emitted cosmic rays absorbed by Earth. These rays had measurable effects on earthly bodies, especially plants and minerals. Certain plants harvested while certain planets or stars were ascendant would have particular potency. Minerals, especially gemstones, would be imbued with particular powers by cosmic rays. William of Auvergne, a scholastic philosopher of the early thirteenth century explained the link between gemstones and celestial bodies:
…they [planets] might be collections of lights in parts of heaven itself, just as it appears among us in certain gems. For in fact I recollect when I saw an emerald, which in brilliance it appeared three shining stars. And this is true of the stone that is called heliotrope, because it is itself a green stone, growing brilliant red by means of a star… (De universo, 1.1.42).

And rare celestial phenomena were believed to portend important events on earth. Halley's Comet appeared over England in 1066, portending Harold's defeat at the hands of William the Bastard. Though now that I've experienced how difficult it is to see any celestial bodies over England, given the cloud cover, I'm beginning to wonder if the whole thing hasn't been completely made up.

Halley's Comet, in the Bayeux Tapestry.

 

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