Lunar eclipses and the 'Dark Ages'

Did anyone else watch the lovely lunar eclipse last night? I gather it was visible across a lot of the world, including all of Europe and eastern parts of the Americas. The BBC has a handsome picture gallery here if you missed it.

Eclipses are strange and eerie phenomena, even with a rational explanation for their cause. It’s tempting to assume that past ages regarded eclipses with superstitious awe, explaining them as magic, or monsters eating the sun, or something similar. Particularly in post-Roman Europe, whose popular sobriquet “The Dark Ages” implies an image of savages huddled in mud huts burning cakes and waiting for some external agency – William the Conqueror, or the Renaissance, or whatever – to come along and turn the lights back on. As ever, the reality is more complicated and more interesting.

Bede, scholar and monk at the monastery at modern Jarrow in Northumbria, wrote a treatise in about 725 AD called On the Reckoning of Time. His main purpose was to set out, probably for the instruction of students, the correct methods of measuring time and constructing a Christian calendar. This was far from an academic exercise, as disputes over the dating of Easter provoked endless arguments in the early Christian church, on a few occasions leading to (or perhaps being used as an excuse for) outright schism. Bede’s book is most commonly cited now as the source for the names of the early English months and the consequent sidelight these throw on English paganism, but his treatise displays detailed and accurate knowledge of the motion of the sun and moon, the shape of the earth and the pattern of the tides, derived from other books and from his own observations. For example, Bede knew that the earth was spherical

It is not merely circular like a shield or spread out like a wheel, but resembles more a ball, being equally round in all directions
--Ch. 32

and explains that this spherical shape governed the difference in day length between summer and winter in the northern hemisphere. Bede’s source for this was Pliny’s Natural History, with a comment that it can be verified by observing the heavens from a village close to a large mountain. Just as the mountain will get in the way of seeing the sun and stars from the village, so, on a larger scale, the spherical shape of the earth gets in the way of seeing the sun from high latitudes in winter. Interestingly, this indicates that Bede, despite being a devout orthodox Christian, was happy to use learning from non-Christian sources (he comments elsewhere in the book that Pliny was a pagan), and that he considered empirical observation to be useful in testing statements found in books.

Bede also explained the tides as the waters of the ocean following the motion of the moon. Earlier sources thought that the high tide was caused by additional water pouring into the ocean and thus that the high tide occurred at the same time in all places. Bede, however, had information that the tide along the coasts of Britain rises in some places at the same time as it falls at others, and thus he argued that the idea of extra water pouring into the oceans was wrong. He did not know how the waters of the oceans could follow the moon around (there was a while to wait before gravity was discovered), but he could observe that they did and that this observation could be used to test a theory and prove it wrong (Ch. 29).

Bede knew that solar eclipses occurred when the moon came between the sun and the earth, and lunar eclipses when the moon passed through the earth’s shadow, and that as a result solar eclipses can only happen when the moon is new and lunar eclipses can only happen when the moon is full. He quotes Pliny’s Natural History as the source, with a rather rueful comment that Pliny was a pagan, and then backs it up with a Christian commentary from St Jerome arguing that the daytime darkness recorded in the Gospels at the time of the crucifixion could not have been a solar eclipse because the crucifixion occurred at Passover, held at full moon, and solar eclipses can only happen at new moon (Ch. 27).

So it’s fair to say that Bede would have understood last night’s eclipse as a natural phenomenon. It’s also fair to say that Bede was at the intellectual apex of his society – probably his nearest modern equivalent would be an Oxbridge professor or maybe a top-flight consultant – and his ideas may not have extended very far into the rest of society. Quite possibly much of the population did see eclipses as terrifying supernatural portents. But it's not justified to assume that everybody did.

Bede: The Reckoning of Time. Translated by Faith Wallis. Liverpool University Press, 1999, ISBN 0-85323-693-3