In his groundbreaking treatise on the comet of 1585, the German astronomer Christoph Rothmann claims that the ‘wisest men’ had already recognized, by means of astronomical observations and determination of parallax, that some comets were generated in the celestial region. Among the ‘wisest men’ Rothmann likely included the Spanish astronomer Jerónimo Muñoz (p. 71), whose Libro del Nuevo Cometa (1573), widely known in Europe thanks to Cornelius Gemma's account, interpreted the nova of 1572 as an unmoved comet in the stellar region. The two books under review here cover different aspects of this and other major developments in the history of early modern astronomy and natural philosophy.

Christoph Rothmann's Discourse on the Comet of 1585 offers the first modern edition of Rothmann's treatise, written in several phases (1585–1586, 1587, 1588–1589), but published only in 1619 after the death of its author. It includes a faithful transcription of the original Latin, with appropriate emendations whenever it proved necessary (by Granada), and an English translation (by Jardine and Mosley) with extensive annotations (by the three authors). This book also comprises a number of texts that unequivocally provide a better understanding of the origin and place of Rothmann's treatise in the context of the astronomical debate of the late sixteenth century. Three comprehensive essays reflecting the latest scholarship on the genesis, content and impact of the Rothmann treatise, on the epistemological status and strategies used by Rothmann, and on the significance of Rothmann's treatise for a new approach to the historiography of comets, written respectively by Granada, Jardine and Mosley (who in addition authored ‘A brief note on cometary parallax’), definitely make this volume a tour de force in Rothmann studies.

Disciplinas, Saberes y Prácticas consists of a collection of articles published between 1995 and 2012 by Víctor Navarro Brotóns, a leading scholar in the field of history of science in Spain and its empire in the early modern period. Despite stemming from different papers, the book is remarkably homogeneous and very well balanced in its approach to the practice of mathematical sciences and natural philosophy in the Spanish context. After discussing the sensitive problems related to the history and the historiography of science in Spain, Navarro Brotóns focuses on the institutional contexts in which the teaching of science, mathematics and natural philosophy took place during the sixteenth and early seventeenth centuries. Particular attention is given to the modifications introduced by the Counter-Reformation and its effects in late sixteenth-century Spain. The book proceeds with an insightful look into the practice of astronomy, cosmography and geography in Spain, paying special attention to the impact of the so-called ‘celestial novelties’ of 1572–1618 and the reception of the theories of Copernicus and Galileo in Spain. The second part of the book brings into focus the scientific activity of the seventeenth and the early eighteenth centuries, a great part of which deals with the role played by the Society of Jesus and the novatores, the European-inspired authors who strove to introduce in Spain the nova scientia of Newton, Galileo's disciples and, to a lesser extent, Descartes. A final chapter devoted to scientific practice in the eighteenth century (until the late 1760s) closes the volume. Throughout the book, its author takes great pains to understand Spain in its wider early modern context, which means going beyond the Iberian Peninsula and also considering Spanish America, the Philippines and European regions under Spanish Habsburg rule. In organizing the volume this way, Navarro Brotóns granted its readers an innovative, and certainly the most up-to-date, account of scientific activity in Spain and its empire during the Scientific Revolution (a concept used by Navarro Brotóns not without qualifications). This is a topic that has been usually overlooked by the historiography.

Despite being different in their scope, both books offer penetrating and novel insights into some of the major changes that characterized early modern science, and particularly astronomy and cosmology. For example, Tycho Brahe has traditionally been credited with the ‘dissolving of celestial spheres’ based upon his determination of the parallax of the comet of 1577 (or, more properly, the absence of it). In their book on Rothmann's Discourse on the Comet of 1585, Granada, Mosley and Jardine demonstrate not only that the cometary treatise by Rothmann actually comprised the first explicit denial of the existence of solid planetary spheres, but also that it played a crucial role in changing Tycho's views regarding the fluidity of the heavens. Furthermore, they argue that Rothmann came to that conclusion independently of observation of the comet. He was guided by optical considerations, and in particular by the absence of refraction (Granada, p. 38). The role of Tycho, the observation of the comet of 1577 and the role played in this process by the determination of parallax have thus to be qualified.

As Granada, Mosley and Jardine stress, Rothmann's treatise also includes clear statements that indicate Rothmann's adoption of Copernicanism. He not only interprets Copernican models as tools for making astronomical calculations, as the astronomers of the Wittenberg tradition did, but also subscribes to their cosmological implications. A different attitude was followed in Spain. Navarro Brotóns provides full evidence that the Spanish professors of astronomy and cosmographers used Copernicus's work for technical purposes. In present-day terms, Rothmann's Copernicanism is thus ‘realist’ (as Jardine acknowledges, p. 259) while the Spanish authors followed an ‘instrumentalist’ approach to Copernicus. Confessional constraints, and particularly the role of Inquisitorial prohibition, Navarro Brotóns argues (for example on p. 120), proved decisive. Yet this does not mean that, in Spain, the heliocentric theory was not widely exposed throughout the seventeenth and eighteenth centuries. It was, in fact, discussed by a plethora of Spanish astronomers, including figures such as Juan Vélez, Juan Eusebio Nieremberg, Vicente Mut, José de Zaragoza, Pedro Hurtado de Mendoza, Juan Caramuel y Lobkowitz, Carlos de Siguenza y Góngora and Gaspar Álvarez, but only insofar as it was taken as a hypothetical theory. Spain's motivation for promoting science stood above all in its vast empire. Increasingly dependent on its colonial revenues, the Spanish Crown and educational institutions boosted a tradition of practical mathematics that today is recognized to have played a pivotal role in the making of early modern science.

These books are, no doubt, two enduring pieces of scholarship that will definitely contribute to changing our perception of the emergence of modern science in Europe. They are highly recommended for historians of early modern science and all those who are interested in Renaissance and early modern astronomy, cosmology and natural philosophy.