The Copernican Revolution 101

This is a review of a book that is intended to deliver what the post title implies, Todd Timberlake and Paul Wallace, Finding Our Place in the Solar System: The Scientific Story of the Copernican Revolution (CUP, 2019).


The book was developed as a textbook for a course–Astronomy 120: The Copernican Revolution–which Todd Timberlake teaches as a science requirement for students majoring in non-scientific fields at Berry College in Georgia (USA). The course was originally taught by Paul Wallace and when he left Berry College, Todd Timberlake, an astronomer and physicist, took over the course using Wallace’s teaching material, hence the double authorship. It will come as no surprise that I very much support the idea of introducing students to science through its history, as is done here. Timberlake is an astronomer and not a historian so the emphasis is very much on the scientific content and less on the context in which it developed but he includes potted biographies of the main figures involved.

After a brief introduction on the nature of science and the evolution of scientific knowledge, which is well done, Timberlake moves on in the next three sections of the book to explaining how the ancient picture of the cosmos developed introducing all of the astronomical terminology as he progresses. This is excellently done but I do have one minor objection. In basic astronomy there is a lot of terminology that is not part of everyday language, to start with there are three different coordinate systems for locating objects in the heavens. I have read numerous accounts of all this over the years and I still sometimes get confused and I find a glossary of the technical terms very useful for a quick check, this book doesn’t have one.

What the book does have is at the end of each section a short chapter titled Reflections on science, a sort of philosophy of science light. Having actually studied philosophy of science with some first class teachers I was prepared to be highly sceptical of these but they are actually very well done and add, in my opinion, a lot to the value of the book as a teaching text.

The next sections of the book, each of which consists of five or six short chapters, deal successively with Copernicus, Tycho Brahe, Kepler, Galileo and Newton. Mainlining the mainstream figures, which despite my own love of the minor and oft unheralded contributors, is OK for what is intended as an introductory text. I was particularly impressed with his sensitive and sympathetic treatment of Kepler’s, quite frankly, totally bizarre cosmological heuristic. The tenth and final section of the book is titled, Confirming Copernicus: evidence for Earth’s motion, which takes the reader in quick short steps down to the nineteenth century. The book closes with twenty short appendices that present to mathematics of the various historical developments, which had been largely left out of the main texts.

The book has extensive endnotes that are mostly references to the equally extensive and comprehensive bibliography. There is also a detailed and extensive index.

Timberlake writes well and lucidly. His text is easy to read and his explanations are clear and straightforward. He covers the material well and I on the whole would thoroughly endorse his book as an excellent textbook and introduction to the history of European astronomy.

There are several minor historical errors in the potted biographies that I shall leave without comment, as to do so would make this review appear more negative than it should. However there is one major historical falsehood that I simply cannot and will not ignore. Having delivered a good account of ancient Geek astronomy Timberlake has a section titled, Astronomy and cosmology after Ptolemy. The third sentence of this section reads as follows:

The rise of Christianity in Europe led to the neglect of mathematical astronomy, and of the “pagan” knowledge of the ancient Greeks and Romans generally. At the same time astronomy flourished in the Arabic world. Many Greek astronomical and philosophical works, including the Almagest and Planetary Hypotheses, were translated into Arabic. (p. 96)

This is of course the classic ‘Christianity killed ancient science’ myth, which in the year 2019 should not be part of a college level historical textbook. Let us examine the facts one more time. Classical Greek learning began to decline in the ancient world from the middle of the second century CE due to a general socio-political and cultural decline, which had absolutely nothing to do with the rise of Christianity. It had basically disappeared in the Western Empire (Europe) by the end of the fifth century CE. The only places, within the Western Empire where it survived, was within the Christian monasteries, which preserved a modicum of the classical learning. The late encyclopaedists such as Boethius and Isidore, who rescued what could still be rescued, were Christians. The Islamic Empire did not begin to appropriate Greek knowledge until the eighth century CE. Their first sources of Greek scientific and philosophical works were those that had been translated into Syriac by Nestorian Christians, within the Persian Empire. Their second, and major, source was Byzantium, the Eastern Empire, which was Christian. By the eighth century there began the first low level returns of Greek astronomical knowledge into Europe during the Carolingian Renaissance in the form of calendrical and computus studies. Christianity didn’t neglect Greek astronomy it played a leading role in conserving and transmitting it during a period of general cultural collapse[1].

A second historical howler, that I can’t ignore, is not as important as his propagation of the classic Christianity killed ancient science myth and in fact I’m not sure whether it should make me laugh or cry. He points out correctly that the heliocentric system establishes a relative measure of the planetary orbits based on the average distance between the Earth and the Sun, the Astronomical Unit of AU. (p.126) To this he adds the following footnote:

Copernicus did not in fact, use the Astronomical Unit in this way, but modern astronomers do. Copernicus typically assigned some large number (say 10,000) of undefined units to the Earth-Sun distance and then found the radii of the planetary orbits in terms of these units. He used a large number in order to avoid having to deal with fractions –or decimals, which did not come into common use until after the French Revolution. [my emphasis]

Decimals were known and used both in Chinese and Arabic mathematics before they entered Europe. The first European author to introduce decimals was Simon Stevin in his De Thiende published in Dutch in 1585 and translated into French as Disme and English as Decimal Arithmetic. Stevin’s system of decimals did not use the decimal point, which was introduced by Christoph Clavius or by Bartholomaeus Piticus in his trigonometrical tables. Decimals were in common use throughout the seventeenth century particularly in both trigonometrical and logarithmic tables. I can only surmise that Timberlake is confusing decimals with the metric system.

As already stated above, Timberlake’s book is an excellent entry level introduction to the history of European mathematical astronomy as well as serving as an introduction to the process of science for non scientists and anybody looking to teach themselves or looking for a textbook for an advanced school class or a college level course should definitely consider using this volume and at an official retail price of just £29.99 for an excellent produced hardback it should be well within the buying power of the average student.


[1]For details read Stephen C. McCluskey, Astronomies and Culture in Early Medieval Europe, CUP, ppb. 2000 and Dimitri Gutas, Greek Thought, Arabic Culture: The Graeco-Arabic Translation Movement in Baghdad and Early ‘Abbāsid Society (2nd–4th/8th–10thcenturies), Routledge, ppb. 1998.


Filed under Book Reviews, History of Astronomy, Renaissance Science

6 responses to “The Copernican Revolution 101

  1. James Evans The History and Practice of Ancient Astronomy is another very good book that takes this approach. Quite a bit pricier, though.

    • Oh, and as the titles indicate, Evans places more emphasis on the pre-Copernican stuff. Though not exclusively.

    • Also somewhat more demanding of its readers than Timberlake. However, the book that Timberlake quotes most often is Evans.

    • Michael Weiss comments often here; I have sometimes confused him with Michael White (“weiss” or “weiß” is German for “white”), a writer of, among other things, some stuff having to do with history of science (mainly biographies). He was also in an early incarnation of the Thompson Twins. Anyway, wanting to make sure that it was Michael White and not Michael Weiss, I noticed that the latter had died recently, quite young.

  2. Tony Angel

    A good review. I hope that Timberlake and Wallace appreciate it. 🙂

  3. Thony, I want to thank you for this review. I am glad that much of the book met with your approval. I am particularly happy to hear that you found my Reflections on Science sections useful. I make no claim to be a philosopher of science, but I have read extensively on the philosophy of science and it is a subject of great interest to me. I feel that it is my duty when teaching science courses of this type to ask students to reflect on the practices of science and to “complicate” their notion of how science works. Some of my college students have never moved beyond the six step “scientific method” they learned in grade school and I want to challenge the notion that science is simple or straightforward (or infallible!).

    Let me take a brief moment to address my “howlers.” First of all, I do appreciate you pointing out these errors. In a work of this scope mistakes are inevitable (at least, they are for me), so I am not surprised that there are a few embarrassing bits. It certainly wasn’t my intent to blame Christianity for the downfall of classical science, but that statement does come across that way. It was just sloppy writing – I was trying to make a quick transition to Arabic astronomy and I didn’t do it well. I am aware that Hellenistic science declined BEFORE Christianity rose to prominence. I also know that, even in those early days, Christianity was a complex and multi-faceted thing. Although there were some early Church Fathers who argued against pagan knowledge, I do know that others defended such knowledge (Augustine’s defense of the spherical heaven in his De Genesi comes to mind). I did not know that Nestorian Christians were primarly responsible for translations of Greek works into Syriac (thanks for educating me!), although I was aware that Byzantium was the source from which Arabic astronomers received original Greek manuscripts. I was also aware of the work of the medieval encyclopedists. So, well, I apologize for a hasty misrepresentation of that part of history. My bad.

    As for decimals, I have read in a few places that decimal notation came into common use in Europe after the French Revolution. I recall seeing it in several places, but I should have cited a source. Here’s one I just found: in “Notes on the Origin and Use of Decimals” by Dora Forno (Mathematics News Letter, vol. 3, no. 8, pp 5-8) I find near the top of page 7 “It was not until the eighteenth century that decimal fractions found much footing and not until the nineteenth century that their use became general.” I wasn’t confusing decimals with the metric system, but I do believe there is a connection. It is only with the metric system that decimals become useful for common measurements and currencies (as opposed to specialized use in astronomy, etc). I would argue that my statement is not as much of a howler as you claim – but it hinges on the phrase “common use.” Admittedly, I was talking about Copernicus, who was a mathematician not a tradesman, so in that context maybe discussing when decimals came into “common use” was not appropriate. So I agree that I could have done better, but what I wrote was not as ridiculous as you make it sound, I think. My main point – that decimal notation would haven been unfamiliar to Copernicus (who died five years before Stevin was born) – was valid.

    Again, I thank you for your careful and thoughtful review of the book. If I ever get a chance to do a revised edition I will be sure to correct the errors you point out. Actually, I would love to hear about the other criticisms for which you did not provide details in your review (either here or by personal message). Although my course is meant to be an historical science course, not a history course, I do take my responsibility toward history very seriously. I have done my best to educate myself on the relevant history, even though it is impossible for me to provide a fully nuanced account of what I have learned in the context of my course or this book. I am also aware that there are significant gaps in my knowledge of both the history and the science (I still haven’t fully wrapped my mind around the Mercury theories of Ptolemy or Copernicus, for example). The book is now published, but I hope to keep learning more about the history of planetary astronomy and I welcome any further contributions you can make to my education!

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