The Beinecke Rare Book & Manuscript Library is the rare book library and literary archive of the Yale University Library. Yesterday their Twitter account posted a tweet entitled Galileo: Siderius Nunc, which linked to a blog post from July 11, 2022, by Raymond Clemens, Curator, Early Books & Manuscripts.
It featured one of Galileo’s famous washes of the Moon from his Sidereus Nuncius (1610) followed by a short text.
Our mini-exhibits end with the vitrine holding several copies of Galileo’s first printed images of the moon, the first ever made with the benefit of the telescope. For the first time, most Europeans were shown the dark side of the moon. Galileo’s sketches also emphasize its barren and rocky nature—well known to us today, but something of a revelation in the sixteenth century, when most people thought of the moon as another planet, thus generating its own light. Galileo was the first person to accurately depict the moons of Jupiter (which he called “Medicean stars,” after his patron, the Florentine Medici family). A photograph at the back of the vitrine was taken in 1968, before humans landed on the moon. It shows Earth as seen from the moon—the first time we saw our own planet from another astronomical body. This rough black and white image eerily resembles Galileo’s lunar landscape.
It is a mere 152 words long, not much room for errors, one might think, but one would be wrong.
We start with the heading. The title of Galileo’s book is Sidereus Nuncius and there one really shouldn’t shorten Nuncius to Nunc, as this actually changes the meaning from message or messenger to now! Also, it is Sidereus not Siderius!
Addendum: A reader on Twitter, more observant than I, has pointed out, correctly, that 1609 and 1610 are in the seventeenth century and not the sixteenth century as stated by Clemens.
In the first line Clemens writes: Galileo’s first printed images of the moon, the first ever made with the benefit of the telescope. I shall be generous and assume that with this ambiguous phrase he means first ever printed images made with the benefit of the telescope. If, however, he meant first ever images made with the benefit of the telescope, then he would be wrong as that honour goes Thomas Harriot.
The real hammer comes in the next sentence, where he writes:
For the first time, most Europeans were shown the dark side of the moon.
The first time I read this, I did a double take, could a curator of the Beinecke really have written something that mind bogglingly stupid? By definition the dark side of the moon is the side of the moon that can never be seen from the earth. The first images of it were made, not by Galileo in 1609, after all how could he, but by the Soviet Luna 3 space probe in 1959, 350 years later.
The problems don’t end here, he writes:
Galileo’s sketches also emphasize its barren and rocky nature—well known to us today, but something of a revelation in the sixteenth century, when most people thought of the moon as another planet, thus generating its own light.
In the geocentric system the moon was indeed regarded as one of the seven planets, but in the heliocentric system, which Galileo promoted, it had become a satellite of the earth and was no longer considered a planet. There was a long and complicated discussion throughout the history of astronomy as to whether the planets generated their own light or not. However, within Western astronomy there was a fairy clear consensus that the moon reflected sunlight rather than generating its own light. A brief sketch of the history of this knowledge starts with Anaxagoras (d. 428 BCE). The great Islamic polymath Ibn al-Haytham (965–1039) clearly promoted that the moon reflected sunlight. In the century before Galileo, Leonardo (1452–1519) in his moon studies clearly stated that the moon was illuminated by reflected sunlight. However, he never published.
Maybe, Clemens is confusing this with the first recognition of the true cause of earth shine, the faint light reflected from the earth that makes the whole moon visible during the first crescent, a recognition that is often falsely attributed to Galileo. However, here the laurels go to Leonardo but who, as always, didn’t publish. The first published correct account was made by Michael Mästlin (1550–1631)
Clemens’ next statement appears to me to be simply bizarre:
Galileo was the first person to accurately depict the moons of Jupiter (which he called “Medicean stars,” after his patron, the Florentine Medici family).
Galileo was the first to discover the moons of Jupiter, just one day ahead of Simon Marius, but to state that he accurately depicted them is somewhat more than an exaggeration. For Galileo and Marius, the moons of Jupiter were small points of light in the sky, the positions of which they recorded as ink dots on a piece of paper. To call this accurate depiction is a joke.
Somehow, I expect a higher standard of public information from the Beinecke Library, one of the world’s leading rare book depositories.
Addendum 18:30 CEST: The post on the Beinecke blog that this post refers to has now been heavily edited. Everything I criticised has been either removed or corrected but without acknowledgement anywhere!
Renaissance Mathematicus 1 Beinecke Library 0!
The Renaissance Mathematicus 
It’s also worth mentioning that the large crater in the lower half of the drawing doesn’t exist and even if it did, the shading of it is in the wrong place. Galileo wasn’t a very good draftsman.
Galileo was actually a first class draftsman, a fact that makes his Luna fantasy pictures all the more strange
Maybe the problem is that the disk Galileo drew isn’t the face of the Moon, it’s the image in his telescope. Round lens = round image. So this could be a part of the Moon — maybe Clavius.
It’s actually a well established fact that Galileo’s washes should be regarded as impression rather than accurate pictures of the Moon
Careful that 0!=1 😉
The edits to the Beinecke blog post have actually made things WORSE. I just looked at it and the current version contains the statement: “He shows the shadow the earth casts on the moon and the moon’s rocky surface.”
WHAT??? Galileo did not, as far as I know, every draw sketches of a lunar eclipse. Certainly, the sketch shown is NOT of a lunar eclipse but rather of a moon in first quarter phase (which could not possibly be eclipses, since lunar eclipses take place only at full moon). So what are they talking about with this “shadow of Earth” nonsense???? Do they not know how lunar phases work? The Earth’s shadow has absolutely ZERO to do with the appearance of the moon in Galileo’s sketch. They have gone from bad history to absolutely wretched astronomy!
It’s third quarter, not first quarter. And if you want to see what it really looks like: https://www.rawpixel.com/search/third%20quarter%20moon?page=1&sort=curated&topic_group=_topics
The two images are slightly different because of libration, but close inspection allows you to see the shadows in the craters which Galileo falsely represented. You can also see that he grossly exaggerated deviations in the terminator, caused by lunar mountains and craters. If you compare them with Thomas Harriot’s drawings (e.g. from the Museo Galileo web site https://brunelleschi.imss.fi.it/galileopalazzostrozzi/object/ThomasHarriotThreeDrawingsOfTheMoonZoom.html ), Harriot’s are much closer to reality. I think that it tells us that Harriot was much more committed to rendering what he saw, while Galileo thought that anything that looked vaguely right would do for his punters who would never do any serious observation even if they owned one of his telescopes.
You are of course right about it being third quarter. I wrote first quarter without going back to look at the image first, and what I remembered was the reverse of the actual image. Oops. Thanks for the correction.
I agree with your assessment of Galileo to some extent, but I don’t know if it was a lack of respect for his audience or a desire to emphasize (and exaggerate) certain features that led to his plus-sized craters, wildly winding terminator, etc. His drawings show qualitative features that are real, but there is no denying that they are not strictly accurate but are instead exaggerated.
But I’m still chapped that the edits to the blog post imply that lunar phases are due to the shadow of the Earth on the moon. I understand that the poster may not have specialized knowledge of astronomy, but that’s grade school stuff. As misleading as the original historical claims were, that astronomical gaffe is much worse in my opinion.
Todd, I absolutely agree with you about the scientific illiteracy shown in the edits to the Beinecke blog post. Sadly it happens only too often and even British broadsheet newspapers are offenders in this regard. Generally, I recommend articles in “The Conversation” https://theconversation.com/uk (there are a dozen different country-based editions producing articles written by academics) and “Quanta magazine” https://www.quantamagazine.org/ as sources that are fairly free of obvious errors.
I find the ‘without acknowledgement anywhere’ most worrying.
A curator can’t be an expert in every subject of every manuscript in is/her care, and must rely on others often, and sometimes on acquisition and catalogue notes written as much as a century ago. I work in a cross-disciplinary field myself and can’t criticise others for not being polymaths.
So I find a curator’s errors may be understandable, if regrettable.
But not thanking a fellow scholar for correcting one’s error – that’s a whole different matter – a genuine problem.
The problem is when people publish about a field they obviously only know from hearsay. They do not recognise that what they think is a minor difference makes a total nonsense.
Walter- you are no doubt right. But there was a time we knew only a little of whatever subject has since become our speciality. But ethics is something else – because any scholar in any field should have learned that from the beginning.