Relativity of motion: From Occam to Galileo

Early observations of the southern celestial sky were reported in many sixteenth-century books and compilations of voyages of discovery. Here we analyse these accounts in order to find out what was really seen and reported by the first navigators. Our analysis had resulted in new interpretations of the phenomena reported by Amerigo Vespucci and Andreas Corsali. Thus, a reassessment of the discovery of the Coalsack Nebula, the Magellanic Clouds, and the Southern Cross can be made. From a comparative review of the observations of the latter constellation as published between 1500 and 1600, we demonstrate that only questionable records found their way to contemporary compilations of voyages of discovery, and that as a result public knowledge about this constellation at the end of the sixteenth century was entirely unreliable. Another problem we discuss is that although the stars of the Southern Cross were the first to be discovered, and were observed again and again by many navigators, it was not until 1678 that their proper positions were found in stellar atlases and star catalogues accessible to astronomers. We explain how negligence of and subsequently confidence in Ptolemy's astronomy by, respectively, the early navigators and cartographers, were at the root of this amazingly long-lasting gap in the knowledge of the southern celestial sky.     

Le “Commentaire” d'Hipparque II. Position de 78 étoiles

Summary The following paper is the second part of a study devoted to the only preserved work of Hipparchus, his Commentary to Aratus. The first part, published in 1984, was based on the hypothesis that Hipparchus wrote his treatise with the help of a mobile sphere and led us to the determination of some features of that instrument. The coordinates of 78 stars, which are given below, have been obtained on the basis of the same hypothesis and using results already published. The stars selected are those for which the text connects numerical data to at least two events out of rising, setting or culmination. An analysis of the positions shows that the stars have been located on the sphere in an equatorial frame slightly different from the rotation axis frame. Statistical data processing shows that the stars were plotted on the sphere as circles rather than as points: the celestial coordinates of the stars are then those of the center of the disc, whose radius was determined. The position of a few stars could be evaluated thanks to the determination of an approximate value of the cubit used by Hipparchus. Lastly, the time of the observations was confirmed to be –140±25 years.The study confirms the basic hypothesis and throws light on the part played by the mobile sphere when the heavens are being described. It gives a better idea of the difficulties of constructing the instrument and of the ways of using it; a more detailed model of Hipparchus' mobile sphere will allow a more thorough investigation of all stars mentioned in the Commentary.

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Présenté par J. North     

Magnetic orientation and celestial cues in migratory orientation

Summary Young birds on their first migration possess innate information on the direction of their migration route. It is present in two forms, using celestial rotation and the geomagnetic field as references. These two systems, together with information provided by factors associated with sunset, interact in a complex way to establish the migratory direction. During ontogeny, celestial rotation appears to be dominant; during migration, however, celestial cues appear to be controlled by the magnetic field. The factors associated with sunset — the view of the setting sun, the characteristic pattern of polarized light — are important secondary cues which seem to derive their directional significance from the magnetic field. Their role appears to be more variable, with possible species-specific differences. During spring migration and later autumn migrations, flying in the migratory direction is complemented by navigational processes which enable the birds to return to a specific home site known from previous stays.     

Henry Dresser and Victorian Ornithology: Birds,Books and Business

The metaphysical commitment to the circle as the essential element in the analysis of celestial motion has long been recognized as the hallmark of classical astronomy. Part I of this paper contains a discussion of how, for Kepler, the circle also functions in geometry to select the basic polygons, in music to select the basic harmonies, and in astrology to select the basic aspects. In Part II, the discussion centres on the question of how the replacement of circular planetary orbits by elliptical orbits in the Astronomia Nova of 1609 affected Kepler's metaphysical commitment to celestial circularity that was made manifest in the derivation of planetary radii in the Mysterium Cosmographicum of 1596. The answer is found in the new and much more accurate derivation of both the planetary radii and their eccentricities in the Harmonice Mundi of 1619. It is the relationship of the diurnal movements of single planets at aphelion and perihelion to specific musical consonances that provides the first step. Then, in the second step, these ratios are ‘tempered’ so that all six planets can provide a heavenly choir. The third and final step employs the ‘mean period’, which is obtained directly from the tempered ratios given by musical theory and diurnal (not annual) motion, in the 3/2 power law to calculate the planetary radii and eccentricities with amazing accuracy. Thus the ellipse is necessary to supply the variation in angular velocities that contain the Creator's archetypal celestial circularity.     

Celestial Measurement in Babylonian Astronomy

Late Babylonian astronomical texts contain frequent measurements of the positions of the Moon and planets. These measurements include distances of the Moon or a planet from a reference star and measurements of the position of celestial bodies within a sign of the zodiac. In this paper, I investigate the relationship between these two measurement systems and propose a new understanding of the concepts of celestial longitude and latitude in Babylonian astronomy. I argue that the Babylonians did not define latitude using the ecliptic but instead considered the Moon and each planet to move up or down within its own band as it travelled around the zodiac.     

A Study of Babylonian Observations of Planets Near Normal Stars

The present paper is an attempt to describe the observational practices behind a large and homogeneous body of Babylonian observation reports involving planets and certain bright stars near the ecliptic (Normal Stars). The reports in question are the only precise positional observations of planets in the Babylonian texts, and while we do not know their original purpose, they may have had a part in the development of predictive models for planetary phenomena in the second half of the first millennium B.C. The paper is organized according to the following topics: (I) Sections 1–3 review the format of the observations and the texts in which they are found; (II) Sections 4–6 discuss the composition of the Normal Star list; (III) Sections 7–8 concern the orientation of the reported celestial directions from star to planet; (IV) Sect. 9 concerns the relationship between the reported distances and the actual angular distances between planet and star; and (V) Sect. 10 discusses the reports of planetary stations, which are the most common reports giving precise locations of planets when they are not near their closest approach to stars, and draws some brief general conclusions about the utility of the Babylonian observations for estimating planetary longitudes and calibrating models in antiquity.I wish to thank Lis Brack-Bernsen, John Britton, Peter Huber, Hermann Hunger, Teije de Jong, Norbert Roughton, John Steele, and Noel Swerdlow for comments on drafts of the paper, for access to work before publication, and for help in various forms.     

Visual spatial memory in desert ants,Cataglyphis bicolor (Hymenoptera: Formicidae)

Summary For navigation, desert ants apply piloting and dead-reckoning strategies based on terrestrial and celestial visual cues, respectively. Visual spatial memories, rather than general concepts derived from landmark constellations, are most probably used to define points on earth by nearby landmarks. The visual field of a specialized dorsal part of the ant's retina is mapped on to the celestial sphere to consider the possibility that similar mechanisms are used to define directions on earth by exploiting skylight patterns present at infinity.Supported by the Hescheler Foundation (Zurich) and the Swiss National Science Foundation grants Nos 3.529-0.75 and 3.313-0.78.     

Solving the Giant Stars Problem: Theories of Stellar Evolution from The 1930s to The 1950s

Historiography has pointed out that the time between the mid 1910s and the early 1930s can be considered a pivotal period in the history of stellar astrophysics. In those years, scholars like Saha and Eddington first applied atomic physics to astrophysics. Theoretical astrophysics was born. This led to the development of the first physically sound models for stellar interiors and atmospheres. These landmark achievements spurred scholars to elaborate theories for stellar evolutions, and in the following decades several astrophysicists focused on this problem. The evolutionary role of red giants turned out to be the main issue. Those stars were initially assumed to be young ones going through the formation stage, but astrophysicists gradually realized that they were rather to be considered old, evolved stars. The solution of the giant stars issue required a couple of decades: it was not until the mid 1950s that a satisfactory explanation was obtained. This provides a detailed picture of the theories of stellar evolution from the 1930s to the 1950s and of the solution to the red giants problem, with special emphasis on how such a solution was made possible by a series of subsequent steps: the identification of changing chemical composition as a main evolutionary feature of a star, the inclusion of nuclear physics within the theoretical framework of stellar astrophysics, the recognition of the importance of inhomogeneities that settle within stars as nuclear processes go on.     

‘Let the stars shine in peace!’ Niels Bohr and stellar energy, 1929–1934

Faced with various anomalies related to nuclear physics in particular, in 1929 Niels Bohr suggested that energy might not be conserved in the atomic nucleus and the processes involving it. By this radical proposal he hoped not only to get rid of the anomalies but also saw a possibility to explain a puzzle in astrophysics, namely the energy generated by stars. Bohr repeated his suggestion of stellar energy arising ex nihilo on several occasions but without ever going into detail. In fact, it is not very clear what he meant or how seriously he took the stellar energy hypothesis. This paper relates Bohr's comments to the period's attempts to find a mechanism for stellar energy and also to the role played by astrophysics at the Copenhagen institute. Moreover, it looks at how Bohr's hypothesis was received not only by physicists but also by astronomers. In this regard the disciplinary status of astrophysics and its contemporary relation to the new quantum mechanics is of relevance. It turns out that, with very few exceptions, the hypothesis was met with silence by astronomers and astrophysicists concerned with the problem of stellar energy production. And yet, for a brief period of time it did have an impact on how physicists thought about the interior of the stars.     

Measuring the probability of a business cycle turning point by using a multivariate qualitative hidden Markov model

A two‐step procedure to produce a statistical measure of the probability of being in an accelerating or decelerating phase of economic activity is proposed. It consists of, first, an extraction of the individual linear innovations of a set of relevant macroeconomic variables whose signs are accumulated into a qualitative vector process and, second, of a factor analysis applied to this vector. The factor process is a two‐state Markov process of order one whose states are described as favourable and unfavourable. Estimated on French business surveys, this measure appears to be a competitive coincident indicator. Copyright © 2000 John Wiley & Sons, Ltd.     

The coming-to-be of Hansen’s method

This article by Curtis Wilson is an account of the origin of Hansen’s powerful systematic method for finding contributions of higher order perturbations in celestial mechanics. Hansen’s method was developed in the course of improving on Laplace’s treatment of the mutual perturbations of Jupiter and Saturn. This method, an entirely new way of doing celestial mechanics when it first appeared, later made possible the successful treatment of the complicated motions of our moon (see Wilson 2010). In this paper Wilson gives a brief historical introduction followed by an account of relevant technical details of the Laplacian background, an account illustrating technical details in Hansen’s initial development in his Disquisitions of 1829, and a treatment illustrating details contributing to the achievement of Hansen’s more refined development in his Untersuchung of 1831. These details include conditional equations Hansen provides for checking the accuracy of calculations. Wilson also includes a detailed assessment showing the extraordinary improvement in empirical accuracy of Hansen’s treatment over the best earlier treatment of the Jupiter-Saturn  interactions.     

An unusual silver celestial planisphere in the Whipple Museum

An unusual silver celestial planisphere is held in the collection of the Whipple Museum of the History of Science (Wh.1762); little information about this object is recorded in the museum’s documentation. A comparison of this silver example with celestial planispheres printed on paper, coupled with the consideration of other aspects of the lives and work of the cartographers and instrument-makers involved in producing such objects, suggests some possibilities regarding its production. Through this individual case study, I aim to demonstrate that the careful examination of an individual instrument, coupled with an understanding of the class of instruments to which it belongs and the milieu in which it was produced, can result in a deeper understanding of any given artefact, its circumstances of design and manufacture, and its intended use and users.     

Newton's Contribution to the Science of Heat

The contents of Scala Graduum Caloris are described, supplemented by unpublished material. Both temperature measurements by his linseed oil thermometer and those based upon his law of cooling are shown to be reasonably accurate to 300°C, but above that value they are much too low. The apparent agreement and the deviation are explained by the differences between the assumptions that Newton made in deriving his law of cooling and the conditions in which he used it. Newton's attempts to link terrestrial and celestial science in applications in the Principia are shown to fail from his confounding the concepts of temperature, heat and radiant intensity and his ignorance of most factors affecting the temperature rise of irradiated materials. Other comments on varied aspects of heat, mainly published in the Queries, are set out and analysed. His originality is assessed.     

The Accuracy and Use of Sextants and Watches in Rupert's Land in the 1790s

The purpose of this paper is to draw attention to the sextants and watches employed at the end of the eighteenth century in surveying Rupert's Land, the vast territory of the Hudson's Bay Company (HBC), and to discuss their usage and accuracy. The results provide information on the standards of manufacture at the time, on the reliability of the contemporary latitude and longitude of various fur-trading posts, and on the careers of the surveyors themselves. The sextant readings are shown to have a standard deviation of about 20 arcseconds when used in a vertical position to find altitudes of the Sun and stars, and about 40 arcseconds otherwise, for finding lunar distances. Because of the use of artificial horizons, these conclusions imply that, at a 95% (2σ) confidence level, a single determination of latitude is reliable to ±20 arcseconds (600 m on the Earth's surface), of longitude ±20 arcminutes (approximately 60 km in Rupert's Land), and a single determination of local apparent time is reliable to ±3 s. The watches, it appears, could run at a steady rate with errors of less than a minute for a period of a week or two.     

Failure of ontological excess baggage as a criterion of the ontic approaches to quantum theory

This article presents a discussion of the notion of quantum ontological excess baggage, first proposed by Hardy. It is argued here that this idea does not have the significance suggested in his paper. It is shown that if this concept is properly analyzed, it fails to pose any threat to the ontic approach to quantum theory in general.     

可用于被动式交通调查的GPS接收仪器评估

交通出行调查是交通规划和模拟不可或缺的数据收集手段，GPS能提高交通信息获取的效率和精度，因此利用GPS交通调查技术辅助或替代传统交通调查成为发展和应用的重要趋势。本文评述了这种趋势的必要性，总结了国外GPS技术在交通调查中运用的经验和局限，结合对国内商业化GPS仪器以及国外交通调查专用GPS仪器的调研和评比，为如何选择GPS仪器进行交通调查提出一些评估指标和建议。     

Le problème des étoiles doubles

Summary A review is given of what we know of binary stars. Leaving out the historical development, the difficulties are shown, which astronomers encountered in their studies of visual as well as spectroscopic or photometric binaries. Thus the reader gets an idea of the methods used both for observing and for explaining the existence of these double stars.The importance of this problem for modern cosmology and for theoretical physics is pointed out.     

Zur Stereochemie der enzymatischen Dehydrierung von Butyryl-CoA

Summary The stereochemistry of the formation of crotonyl CoA from butyryl CoA catalyzed by the appropriate pig liver enzyme was investigated using samples of butyric acid specifically labelled with tritium in the two methylene groups. It is shown that oxidation involves specific removal of the pro-R hydrogen atoms from positions 2 and 3 of the substrate.     

Google's MIDAS Touch: Predicting UK Unemployment with Internet Search Data

Internet search data could be a useful source of information for policymakers when formulating decisions based on their understanding of the current economic environment. This paper builds on earlier literature via a structured value assessment of the data provided by Google Trends. This is done through two empirical exercises related to the forecasting of changes in UK unemployment. Firstly, economic intuition provides the basis for search term selection, with a resulting Google indicator tested alongside survey‐based variables in a traditional forecasting environment. Secondly, this environment is expanded into a pseudo‐time nowcasting framework which provides the backdrop for assessing the timing advantage that Google data have over surveys. The framework is underpinned by a MIDAS regression which allows, for the first time, the easy incorporation of Internet search data at its true sampling rate into a nowcast model for predicting unemployment. Copyright © 2016 John Wiley & Sons, Ltd.