Bad Textbooks

Textbooks that contain the phony Galileo story

Careless textbook writers put things in print without checking the facts. Sometimes they copy mistakes from one another. Here are some examples of books that spread the false story about Galileo:

Sir Stewart Duke-Elder and Peter A. MacFaul
System of Ophthalmology, Vol. XIV, Part 2: Non-Mechanical Injuries
(C. V. Mosby Co., St. Louis, 1972)

On p. 888, these authors say that “Galileo, looking at the sun with his telescope, injured his eyes;” but they cite no reference for this, though their encyclopedic work contains thousands of them.

In addition, the first sentence on the next page says:

… in their study of after-images Robert Boyle, Isaac Newton and Joseph Plateau all suffered considerable inconvenience after looking fixedly at the sun.

Well, Newton and Plateau I already know about; but the reference to Boyle puzzled me. I could learn nothing about this with the standard methods; so I turned to Professor Michael Hunter, an authority on Boyle who has a fine website about him at Prof. Hunter's response was that

This sounds to me like a complete myth. It is true that Boyle had bad eyesight, but this was due to complications resulting from severe illness in the 1650s.
So it appears that Duke-Elder's book has two errors, not just one.

The English edition of this work was cited by

J. Weiter
“Phototoxic changes in the retina”, in
“Clinical Light Damage to the Eye”, edited by D. Miller
(Springer-Verlag, New York, 1987) pp. 79-125

as his authority for the Galileo myth.

Charles E. Long
Discovering the Universe
(Harper & Row, San Francisco, 1980)

On p. 103, Long says:

When Galileo decided to observe the sun, he made a dangerous mistake. He held the telescope to his eye and pointed it at the sun. The concentrated sunlight blinded his eye for a week and left permanent damage.

As is usually the case with these stories, there is no reference offered to back up this fairy tale. The amount of invented detail here is interesting.

Thanks to Fred Talbert for finding this example, and providing a photocopy.

D. Sliney and H. Wolbarsht
Safety with Lasers and Other Optical Sources
(Plenum, New York, 1980)

On p. 206, they say:

. . . a thermal mechanism … cannot be ruled out as a contributing factor (or even the major one) when the sun is viewed through magnifying optics. Galileo Galilei was the first victim of this type of retinal injury in one eye when he directly viewed the sun through his newly invented refracting telescope.

Of course, no reference is cited to support the story about Galileo, even though this well-researched volume contains hundreds of references on other subjects. And, as is well known, Galileo was not the inventor of the refracting telescope.

There is no evidence to support the assertion that he injured one eye by looking at the Sun; indeed, the existing evidence indicates that it would have been impossible to do so, and his observations of Jupiter made a year later certainly show he suffered no appreciable eye injury.

Fortunately, this book is generally more reliable than the remarks about Galileo would indicate. Unfortunately, it's still being cited as a source for the false story about Galileo (see the next item for an example).

Thanks to Martin Mainster for recommending this book.

Martin A. Mainster and Jemshed A. Khan
“Photic retinal injury&rdquo, in Retina, Second Edition; Volume 2, “Medical Retina”; edited by Andrew P. Schachat and Robert B. Murphy; Stephen J. Ryan, Editor in Chief
(Mosby, St. Louis, 1994)

A handsome encyclopedic work, in three imposing volumes on glossy paper, amounting to nearly 2500 pages. The publisher's motto is “Dedicated to Publishing Excellence” — but on p. 1768, we read:

A causal relationship between solar observation and eye damage has been suspected for millennia, and Galileo was reportedly injured by telescopic solar observation.

To support this, they cite Sliney and Wolbarsht — who give no further references. (Once these errors get into the literature, they take on a life of their own.) I would have to say that Mainster and Khan did a reasonable job here: they did cite a source for their statement; and that source is generally reliable. Their 15-page chapter has 155 references; it meets all the usual standards for scholarship. It's just that this one sentence, though literally correct — if one emphasizes the word “reportedly” — is wrong.

Thanks to Jim Mosher for finding this example.

Jim notes that this statement finally disappeared in the 4th Edition of this work, which appeared in 2006. So, eventually, the errors do get corrected!

Eric Chaisson and Steve McMillan
Astronomy Today
(Prentice Hall, Englewood Cliffs, 1993)

On p. 44, these authors say

Looking at the Sun — something that should not be done directly and which eventually blinded Galileo …

I have had some correspondence with Eric Chaisson about this; the last I heard from him, he was still insisting his claim was correct.

Thanks to Richard Rand for discovering this example, and to Fred Talbert for providing a photocopy.

Perhaps one has lower standards for popularizations than for textbooks. Here's a popularization with an egregious treatment of the false story about Galileo:

Stephen P. Maran
Astronomy for Dummies
(IDG Books, Foster City, CA, 1999)

On p. 146, in a chapter entitled “Don't make Galileo's Blinding Mistake: Protect Your Sight from the Sun,” Steve says of Galileo:

He also made a terrible mistake. He looked at the Sun through his telescope. This error caused him severe eye damage.

Well, it wasn't Galileo who made the “terrible mistake” here. I wrote to Steve Maran, and he says he will try to correct this in a later edition.

Thanks to Tom Koonce for finding this example.

To his credit, Steve Maran pointed out that the same story probably had appeared earlier in his textbook co-authored by Jack Brandt. Sure enough,

J. C. Brandt and S. P. Maran
New Horizons in Astronomy
(W. H. Freeman and Co., San Francisco, 1972)

says on p. 90:

Galileo … later became blind, perhaps because of eye damage suffered previously when he first viewed the sun through a telescope.

Thanks to Steve Maran himself for suggesting this example, and to Fred Talbert for finding the book locally and providing a photocopy.

Speaking of popularizations, how about Alexander von Humboldt's Kosmos? P. 383, Vol. 3 of this great work,

Alexander von Humboldt
Kosmos. Entwurf einer physischen Weltbeschreibung.
(J. G. Cotta'scher Verlag, Stuttgart und Tübingen, 1850)

refers to

… blauen und grünen Blendgläser, deren Nichtgebrauch viel zu Galilei's Erblindung beigetragen hat.

— or, as the 1871 English translation (available at Google Books) by Otte and Paul has it,

… blue and green stained glasses … . The neglect of this precaution contributed much to Galileo's blindness.

(I would have used the more standard term shade glasses; and said “non-use” in place of “neglect”; but the intent is clear, either way.) Evidently the error was well established by 1850, when Humboldt published his book. As usual, no citation is offered to support the incorrect remark about Galileo.

Thanks to Jim Mosher for finding this example.

Cmdr. Bruce A. Bauer, USN (ret)
The Sextant Handbook: Adjustment, Repair, Use and History (Second Edition)
International Marine; Camden, Maine 04843 (1992)

This isn't exactly a textbook, nor is it a popularization. It's more of an instruction manual for mariners; maybe that makes it a popular textbook. In any case, on p. 110, we read:

The probable cause of the blindness of Galileo, maker of telescopes and champion of heliocentricity, was too much gazing at the sun without sufficient protection. The sun is the single most important navigational body. There is little danger of damage to the eyes for two reasons: low powered telescopes and efficient shades. Galileo made and used magnifiers of up to 30 power while the highest power sextant scope currently in use is eight.

Let's hope Cmdr. Bauer is better at “Adjustment, Repair, and Use” than he is at History.

It turns out that International Marine is “an imprint of McGraw-Hill, Inc.”. We don't have this, but our Inter-Library Loan people got me a copy of the first paperback printing (1995).

Thanks to Jim Mosher, again, for finding this example.

Copyright © 2000, 2003, 2005, 2006, 2012 Andrew T. Young

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