Monday, 2 August 2010

Siderius Nuncius

Why does Galileo's Siderius Nuncius so exaggerate the size of the crater Eratosthenes?

He's struck by it, obviously; but he places it more centrally and records it as being much larger than it actually is. It's as if he's looking for an aesthetic harmony, or balance, in what he sees. Or more fancifully: it's because he wants to give the moon a mouth. ('Ooo!' says the moon.) This is because Galileo, and his magic optic tube, and his book, is, in a manner of speaking, giving the moon a mouth ... giving it voice, that is.

1 comment:

Gareth Rees said...

I know that you're just joking here, but I was intrigued. Exactly which crater did Galileo see and exaggerate in these drawings? Whatever it is, it's surely not Eratosthenes, since that's in Mare Imbrium, which would be to the left of the terminator in these sketches.

This led me into the whole scholarly literature discussing Galileo's sketches, and in particular to E. A. Whitaker (1978), Galileo's lunar observations and the dating of the composition of Sidereus Nuncius, Journal for the History of Astronomy, Vol. 9, p.155. Whitaker identifies Galileo's crater as Albategnius, but not everyone came to this conclusion: “Righini identifies Galileo’s ‘large crater’ as the group Purbach, Regiomontanus, Wener, Blanchinus and La Caille.”

Whitaker notes, “In the original edition of [Sidereus Nuncius], these engravings present a reasonably well-executed appearance, but subsequent editions utilize woodcuts, and the quality deteriorates very rapidly to the point where they are virtually unrecognizable as Moon images. Some of the disparaging remarks made about the drawings undoubtedly stem from examinations of these cruder images.”

Also, it's Sidereus, not Siderius. The nit-pick is strong with me today.