Halley’s Comet and the Generations! May 12, 2013Posted by Beachcombing in : Ancient, Medieval , trackback
***Dedicated to Larry who got me interested in this and provided, through his emails and forwards, much of the information***
It recently struck Beach that Halley’s comet would be a perfect measure of the continuity of knowledge in ancient and medieval civilizations. After all, here is a comet that returns every 75 (and a bit) years and that is typically visible across much of the globe. What are the odds that some of our ancestors worked out that this was the same repeating comet, using records and archives (rather than calculations as Halley did)?
First, let’s get an obvious point out of the way. Ancient and medieval records are packed full of sightings of what we call Halley’s comet. But it is one thing to see ‘a hairy star’ and worry about what it will do to the kingdom. It is quite another to say: ‘that is the same comet my Dad told me about’ and another things still to say ‘that is the seventy five year repeater comet’. When Beach began thinking about this he assumed that it would be necessary to see Halley’s comet twice to have a chance of understanding that it was the same comet. But, of course, twice is not enough. Sure there is a fiery star in the sky and there is another fiery star in the sky seventy odd years later. But just think how many other fiery stars (or unusual phenomenon) there will be in the heavens in that time. Even if a twelve-year-old has a vivid memory of seeing the comet and, then, sees the comet again in his or her late eighties there is no reason that he or she should assume that this is the same thing: particularly given the variability of how things in the sky are seen and given too the fallibility of memory.Then, even if they did make the connection (see below for a possible example), there would need to be a third occurrence to show the pattern and a fourth occurence to confirm it. This means an attentive dynasty of astronomers (China? Babylon?) taking careful records over at least, three centuries and a smart record keeper with curiosity: one person is not enough.
Then, of course, this attentive dynasty would need visible passes. If even one pass is undramatic the whole count has to begin again and here we are not talking about the frustrated shopkeeper who loses the tally of coppers in his hand… This failure to notice Halley’s Comet may have been an important problem in antiquity, upending any ‘smart record keeper’. For example, Chinese observers saw ‘a broom star’ in 240 BC (the earliest note of HC on record). But subsequently failed to note the comet in 164 BC and were vague in 87 BC: Halley’s was presumably not that dramatic on those occasions. Next, even if we assume that there were ten consecutive dramatic passes and a sprinkling of ‘smart record keepers’ how many civilizations could guarantee continuity of records over two to four centuries? A random example. We know now that early medieval Irish monks paid special attention to the heavens (perhaps particularly in the seventh and eighth centuries) and that they recorded unusual phenomenon. But their records, that come down to us in the Irish annalistic tradition, do not invite comparison. And any monk who had a theory about a returning comet would have to wade through records of murrains and battles to pick out Halley’s references, even if the comet had been visible in the northern hemisphere consistently over three or four centuries. (It wasn’t.)
So taking the totality of records did any ‘smart record keeper’ work out what was happening prior to Halley? There has been some muttering about cuniform tablets and records of Halley’s comet: but this is the elementary point that we began this post with – seeing the comet not recognizing that it was the same, let alone understanding its periodicity. More interesting is a comment in the Talmud that describes a star that returns every seventy years and which confuses navigators. It seems unlikely, though, that the Talmudic writers would have called a comet a star without qualification: other ancient sources tend to talk of hairy stars, broom stars etc. In other terms, comets and stars are clearly different even for a one time, random observer. Then would sailors really have been confused by a comet in the sky? It is surely more likely that the star in question was a star (perhaps a brightening one) that threw off observers looking at a suddenly distorted constellation? (A Hebrew-studies colleague at the university here notes that ‘seventy years is probably formulaic.’)
For Beach at least the most interesting pre-Halley record comes from late Anglo-Saxon England (see image above). Towards the end of his life the monk Eilmer (seen previously in this place trying and failing to fly) observed the comet and became painfully lyrical. The Latin is lovely and Eilmer had a point as we are in 1066 with the Normans (damn their pointy hats) knocking at the door:
Venisti… venist, multis matribus lugende; dudum est quod te vidi, sed nunc multo terribiliorem te intueor patriae huius excidium vibrantem. [William of Malmesbury]
You’ve come, have you? You’ve come, you source of tears to many mothers. It is long since I saw you; but as I see you now you are much more terrible, for I see you brandishing the downfall of my country.
Eilmer seems to be saying here that he has already seen the comet. (Was the 991 comet brighter? Absence of records suggest not). Eilmer died an old man – not something to take for granted in any century prior to the twentieth – so this is plausible in terms of years. Of course, he could have confused Halley’s Comet with another. And, yes, even if he did recognize, somehow, that it was the same comet, that is a very different matter from understanding how long each pass took. Any other early candidates ready to out-Halley Halley? drbeachcombing AT yahoo DOT com
Beach can’t quite do this justice (give him a month) but Halley’s comet was perhaps sent by our cosmic betters as a reminder of the fragility of the accumulation of knowledge. Beach suspects that a fifty year or a sixy year repeater would have been marked down in ancient times pdq. Seventy five is just pushing the limits of living memory a little too far out… Forget 42, perhaps 75 (and a bit) is the answer to life, the universe and everything.
15 May 2013: Zenobia writes in with this gem of a post on the Magi and Christmas. Thanks Zenobia!