Astronomical Theory Research Articles

Cosmological sources of critical cosmopolitanism

AbstractCritical cosmopolitan orientation has usually been embedded in a non-geocentric physical (NGP) cosmology that locates the human drama on the surface of planet Earth within wide scales of time and space. Although neither a necessary nor a sufficient condition for critical cosmopolitanism, NGP cosmology provides a contrast to the underpinnings of centric cosmologies, such as those of Aristotle, which see the world as revolving around a particular observer, theorist and/or communal identity. NGP cosmology makes it plausible to envisage all humans as part of the same species. The connection works also through homology and analogy. An astronomic theory can be isomorphic with an ethico-political theory, that is, a structure-preserving mapping from one to the other is possible. Key cosmopolitan theorists have situated morality within a cosmic framework. However, the ethico-political implications of the NGP cosmology are ambiguous. Nietzsche was among the first to articulate its sceptical and nihilist implications. Various reactions have encouraged territorial nationalism and geopolitics. I suggest that critical cosmopolitical orientation should now be grounded on the notion of cosmic evolution, which is not only contextual, historical, pluralist and open-ended but also suggests that humanity is not a mere accident of the cosmos.

Milutin Milanković and the astronomical theory of climate changes

changes in the geological past has become widely accepted only in the first half of the 19th century, due to the work of Playfair, Schimper, Venetz, Charpantier and many others, and somewhat later in particular of L. Agassiz [1]. ey claimed that the moraines present in many alpine valleys, or the erratic granite blocks standing on the geologically unfitting bedrock are due to the fact that “the big ice-sheets like those seen at present-day Greenland once covered all the territories where such stones have been found”. At the same time the expression “Die Eiszeit” was introduced in an ode written by K. Schimper. Even the famous German poet Johann Wolfgang von Goethe back in 1829 states: “to have a lot of ice a cold weather is needed, thus I presume that an epoch of great cold at least over Europe passed”. Still, there were many who opposed the idea of the Ice Ages, and the debate lasted for the entire century. At the very beginning of the 20th century A. Penck and E. Bruckner [4] proposed that the glaciations took place four times in the Quaternary geological period, with three interglacial intervals of unequal duration in between. Although we now know that the climate changes were much more complex than this simple scheme predicts, the fact that the Ice Ages did take place in the past has been firmly established and not seriously disputed aerwards. Different mechanisms have been considered to explain the changes of Earth’s climate, including also astronomical ones. Soon aer the publication of Agassiz’ work, J. Adhemar [2] proposed that the precession of the Earth’s axis of rotation is responsible for the Ice Ages. Although the simple mechanism he considered was soon rejected, Adhemar actually showed that the astronomical and geological phenomena can be related, and that the long term variations of the Earth’s motion can possibly lead to climate changes. e most remarkable early theory of the Ice Ages, which consistently combined the achievements of different sciences, was undoubtedly the theory by J. Croll [3]. Croll correctly interpreted the influence of the eccentricity of Earth’s orbit upon the duration of the seasons and its coupling with the precession of the rotation axis. He was the first to consider the changing obliquity of the rotation axis, thus completing the list of relevant astronomical mechanisms causing climate changes. He also pioneered the idea of the feedback effect due to the reflectance of the incoming radiation from the surface covered by ice, and proposed that the eccentricity-driven amplification of the ocean currents augments the heat exchange between equatorial and polar regions. Croll’s theory at first attracted geologists, but it has soon been found that its results do not match the observations. As later explained by Milankovic, the failure of Croll’s theory is due mostly to the fact that the influence

Climate and the orbital parameters of the Earth

The discovery of glacial ages in the 19th century triggered the first scientific questions on the evolution of climate through time, and thus corresponds to the dawn of palaeoclimatology. Since then, scientists have attempted to reconstruct past climatic changes and to understand their physical basis. Two competing theories have been suggested to explain the sequence of glacial–interglacial epochs: either the variations of the Earth orbital elements, or the atmospheric composition in carbon dioxide. If the astronomical theory has been largely confirmed since the last 30 years, a physical modeling of the climatic processes at work is still in its infancy. Besides, the most recent results of palaeoclimatology are clearly demonstrating that, more than never, a synthesis of these two old hypotheses is needed.

Kepler's Optical Part of Astronomy (1604): Introducing the Ecliptic Instrument

The year 2009 marks the 400th anniversary of the publication of one of the most revolutionary scientific texts ever written. In this book, appropriately entitled, Astronomia nova , Johannes Kepler (1571–1630) developed an astronomical theory which departs fundamentally from the systems of Ptolemy and Copernicus. One of the great innovations of this theory is its dependence on the science of optics. The declared goal of Kepler in his earlier publication, Paralipomena to Witelo whereby The Optical Part of Astronomy is Treated (Ad Vitellionem Paralipomena, quibus astronomiae pars optica traditvr , 1604), was to solve difficulties and expose illusions astronomers face when conducting astronomical observations with optical instruments. To avoid observational errors that had plagued the antiquated measuring techniques for calculating the apparent diameter and angular position of the luminaries, Kepler designed a novel device: the ecliptic instrument. In this paper we seek to shed light on the role optical instruments play in Kepler's scheme: they impose constraints on theory, but at the same time render astronomical knowledge secure. To get a comprehensive grasp of Kepler's astonishing achievements it is required to widen the approach to his writings and study Kepler not only as a mathematico-physical astronomer, but also as a designer of instruments and a practicing observer.

Cyrano de Bergerac y el relato de viajes

This article presents Cyrano de Bergerac’s Voyage dans la lune as one of the most important planetary utopias in the modern age. First, the text handles the construction of Cyrano de Bergerac himself as a literary myth; afterwards it discusses Bergerac’s utopia and how it has been transformed and mutilated throughout the history of its publication. Cyrano’s tale is an excuse to question the astronomical theory of Ptolemy, in favor of thesis such as Copernicus’s, Galileo’s or Kepler’s. Throughout Voyage dans la lune several biblical stories are criticized and caricaturized, and so are the Christian moral, the belief in miracles belief, the notion of immortality and the existence of God.

The U-series dating of (biogenic) carbonates

U- and Th-series offer a large array of isotopes that constitute magnifying "lenses" into recent temporal dimensions of Earth System processes. Whereas mass spectrometry (MS) measurements of 238U-234U-230Th and 235U-231Pa disequilibria give access to time ranges varying between about a million of years to hundreds of thousand years, MS or counting methods of shorter-lived daughter isotopes (e.g., 226Ra, 210 Pb, 234 Th, 228 Th, 228 Ra) inform on time scales varying from 50 ka (226Ra- 230Th "pseudo-concordias"), 10 ka (226Ra-excess method), 100 a (210Pb-226Ra "pseudo-Concordia" or 210Pb-excess method), 30 a (228Ra-excess), 10 a (228Th-228Ra-232Th disequilibria) and up to 3 months (234Th-excess). U-series isotopes, and especially the sequence 238U-234U-230Th revealed essential in validating the astronomical theory of climate through the dating of high interglacial sea levels and provided the means to calibrate the radiocarbon time scale into "calendar years". Shorter-lived natural isotopes of these series (e.g., 210Pb, 226Ra) also revealed essential for the documenting of more recent processes. Here, we examine U-series systematics in biogenic minerals with special attention to biogenic carbonates. We also discuss the impact of diagenetic conditions on dating applications.

High-resolution climate stratigraphy across the Matuyama–Brunhes transition from palynological data of Osaka Bay sediments in southwestern Japan

This study presents a high-resolution palynological analysis of a sedimentary core from Osaka Bay (Japan) straddling Marine Oxygen Isotope Stage (MIS) 19, i.e. across the Matuyama–Brunhes magnetic polarity Boundary (MBB). Comparison with the standard marine oxygen isotope curve ([Bassinot, F.C., Labeyrie, L.D., Vincent, E., Quidelleur, X., Shackleton, N.J., Lancelot, Y., 1994. The astronomical theory of climate and the age of the Brunhes–Matuyama magnetic reversal. Earth and Planetary Science Letters 126, 91–108.]) demonstrates that variations in vegetation and the basinal environment coincided with global ice volume changes. The late MIS 20 is characterized by boreal climate with coniferous forest. In MIS 19, the forest was generally dominated by Fagus and Quercus ( Lepidobalanus), suggesting onset of humid climatic conditions slightly cooler than the present. Excluding coastal vegetation components, climate during MIS 19 can be subdivided into three stages. The early stage, including substage 19.3, is characterized by high seasonality in precipitation. This contrasts with the very abundant, year-round precipitation that is inferred for the late stage, from substage 19.2 to substage 19.0, which is characterized by cool-temperate coniferous taxa including Cryptomeria. The very high precipitation rates of the latter persisted at least up to substage 18.4. There was no apparent vegetational response to the sea level highstand of 19.3. In contrast, a short-lived thermal maximum event took place ca. 6–7 kyr later, i.e. in middle MIS 19. This event is characterized by increases in the warm-temperate element Quercus ( Cyclobalanopsis). The MBB, the recommended criterion for defining the Lower–Middle Pleistocene boundary, took place in middle MIS 19. These lines of evidence indicate that the occurrence of the MBB corresponded with a shift towards warmer and wetter climatic conditions. Similar warming and wetting events across the MBB are also observed in pollen records from southern Italy and central Japan. This possibly provides long-distance correlation, and may suggest a connection between the Earth's magnetic field and climate.

Summary of parallel session B1: relativistic astrophysics

The B1 parallel session on relativistic astrophysics at GR-18 contained an impressive variety of papers on key astronomical topics. Many of the papers involved sophisticated applications of general relativity and mathematical physics to areas of current interest in astronomy. The development of a number of the results and ideas presented at GR-18 will have an important bearing on future astronomical theories and observation.

The Contribution of the Jews of Spain to the Transmission of Science in the Middle Ages

The Jews of Spain in the Middle Ages played an important role in the transmission of Graeco-Arabic learning by translating, or participating in translations, of scientific texts. They also composed original works on mathematics, astronomy, astrology and medicine in which they adapted the theories of the ancients for their own time. Science was used by the ruling powers as an element of prestige, and by the Jewish scientists as a way to obtain a high social status. The policy of cultural sponsorship of Muslim caliphs, as well as of Christian kings, was fundamental in the process of transmission of the Greek sciences to the Western world. The School of Translators of Toledo is an example of this process. The astronomical theories developed by Jewish scientists at the end of the 15th century played an important role in the Spanish and Portuguese discoveries of the 16th century. Their knowledge of astronomy, astrology, mathematics, and medicine was also used by the Jewish intellectuals to provide a rational and scientific support for the Jewish religion and tradition, as is reflected in the interpretations of the Bible by medieval Spanish Jewish authors.

Kepler’s theory of the soul: a study on epistemology

Kepler is mainly known among historians of science for his astronomical theories and his approaches to problems having to do with philosophy of science and ontology. This paper attempts to contribute to Kepler studies by providing a discussion of a topic not frequently considered, namely Kepler’s theory of the soul, a general theory of knowledge whose central problem is what makes knowledge possible, rather than what makes knowledge true, as happens in the case of Descartes’s and Bacon’s epistemologies. Kepler’s theory consists of four issues: the theory of the different sorts of soul—that is, the human soul, the animal soul, the vegetable soul, and the Earth soul—concerning their faculties, the differences and the resemblances emerging among them, the relation they maintain with their own bodies and the world, and the distinction soul–world. The paper discusses these issues from a historical perspective, that is, it reconstructs the way they appear in three periods of Kepler’s career: the period prior to the publication of the Mysterium cosmographicum, the period from 1596 to 1611, and the period of the Harmonices mundi libri V. Finally, Kepler’s epistemology is briefly contrasted with Descartes’s and Bacon’s in order to suggest that Kepler’s could be seen as a third way to understand the philosophical origins of Modernity.

The Climate Response to the Astronomical Forcing

Links between climate and Earth's orbit have been proposed for about 160 years. Two decisive advances towards an astronomical theory of palaeoclimates were Milankovitch's theory of insolation (1941) and independent findings, in 1976, of a double precession frequency peak in marine sediment data and from celestial mechanics calculations. The present chapter reviews three essential elements of any astronomical theory of climate: (1) to calculate the orbital elements, (2) to infer insolation changes from climatic precession, obliquity and eccentricity, and (3) to estimate the impact of these variations on climate. The Louvain-la-Neuve climate-ice sheet model has been an important instrument for confirming the relevance of Milankovitch's theory, but it also evidences the critical role played by greenhouse gases during periods of low eccentricity. It is recognised today that climatic interactions at the global scale were involved in the processes of glacial inception and deglaciation. Three examples are given, related to the responses of the carbon cycle, hydrological cycle, and the terrestrial biosphere, respectively. The chapter concludes on an outlook on future research directions on this topic.

Observational Accuracy of Sunrise and Sunset Times in the Sixth Century China

The Daye Calendar was compiled in AD 597 in the Sui Dynasty. We investigate the records of sunrise and sunset times on the 24 solar-term days in the calendar. By converting the ancient Chinese time units, Chen, Ke and Fen to hour, minute and second, and carrying out a comparison between the ancient records and values computed with modern astronomical theory, we find that the accuracy of solar measurements in the Sui period is remarkably high: for sunrise times, the average absolute deviation is 3.63 min (this value can be further reduced to 3.03 min when erroneous data are excluded), and for sunset times it is 3.48 min. We also find that the observed sunrise and sunset times are strictly symmetrically distributed with respect to both the Winter Solstice and the Summer Solstice, with their deviations showing a similar symmetrical distribution as well. We give a discussion on the date of observation, the feature of the data, and possible reasons of the deviation.

The astronomic theory of climatic changes of Milutin Milankovich

The astronomic theory of climatic changes of Milutin Milankovich

Vegetation dynamics amplifies precessional forcing

The astronomical theory of climate variations predicts that the climatic precession which changes the seasonal distance between Earth and Sun does not affect the annual mean irradiation at any given latitude. However, previous modeling studies suggest that during interglacials, the interaction between atmosphere, vegetation and ocean can transform the seasonal forcing by precession into an annual mean global signal. Here, we show that this result can be generalized. A distinct precessional signal emerges in a climate system model over many precessional cycles. While neither the atmosphere‐ocean nor the atmosphere‐vegetation model are able to produce a large amplitude of global temperature in the precessional band, only the mutual amplification of biogeophysical feedback and sea ice‐ albedo feedback allows a strong amplification of the precessional signal.

A radiometric calibration of the SPECMAP timescale

The astronomical theory of climate change asserts that Earth's climate is affected by changes in its orbit, which vary the seasonal and latitudinal distribution of solar radiation. This theory is the basis of the orbitally tuned SPECMAP timescale. A key constraint for this important chronology was the mid-point of the Penultimate Deglaciation, initially dated to 127,000 years ago. Recent work suggests this event may be considerably older, casting doubt on the astronomical theory, the SPECMAP timescale, and the accuracy of orbitally tuned chronologies. Difficulties with U/Th coral dating of sea-level events have impeded progress on this problem, because most corals are not closed systems. Here, we use a new approach to U/Th dating that corrects for open-system behavior and produces a sea-level curve of sufficient resolution to confidently correlate with SPECMAP over the last 240,000 years, permitting a reassessment of both this critical chronology and a central tenet of climate change theory. High-precision ages for 24 oxygen isotope events provide a 240,000-year chronology for marine δ 18O records that is independent of orbital tuning assumptions. Although there appear to be significant differences between the radiometric and orbitally tuned timescales near the lastglacial maximum and at the Marine Isotope Stage 7/6 boundary, a comparison of radiometric and SPECMAP ages for identical isotope events suggest that the SPECMAP timescale is quite accurate and that its errors were, in general, overestimated. Despite suborbital complexity, orbital cyclicity is clearly evident in our record. High-amplitude sea-level oscillations at periods greater than ∼20,000 years are very close in phase to summer insolation in the Northern Hemisphere. Although sea-level changes cannot be uniquely tied to a specific season or latitude of insolation forcing, the simplest explanation is that long-period, high-amplitude sea-level change is linked to Northern Hemisphere insolation forcing. These results validate the principles of orbital tuning and suggest such timescales are generally robust.

남병철의 혼천의 연구 II 『의기집설』에 나오는 <혼천의용법>의 역해설

<TEX>$\ulcorner$</TEX>의기집설<TEX>$\lrcorner$</TEX>의 <혼천의설(渾天儀說)>, <혼천의제법(渾天儀製法)>에 이어서 이 논문에서는 <혼천의용법(渾天儀用法)>을 연구하였다. <혼천의용법(渾天儀用法)>의 원문을 해석하여 혼천의 의 설치, 관측 및 사용법, 천문이론과 계산방법 등을 15개 항목으로 정리하였다. 그리고 원문에서 제시하고 있는 그림을 이해하기 쉽도록 표현하였고 풀이과정을 상세히 기술하였다. 혼천의 사용법에서 소개하고 있는 천문학적 계산방법은 주로 구면 삼각법과 비례법을 이용하고 있으며, 천문학적 이론이나 계산과정을 체계적으로 자세히 다루고 있어 당시의 천문과학 수준을 알아 볼 수 있었다. This study is about <Honcheonui-yongbeop(Instructions for Use of an armillary sphere)>, which constitutes Honcheonui(an armillary sphere) put of <TEX>$\ulcorner$</TEX>Uigijipseol<TEX>$\lrcorner$</TEX> (Volume I) together with <Honcheonui-seol> and <Honchoenui-jebeop>-dealt with earlier than this subject. The study's construction on the text of <Honcheonui-yongbeop> is organized into 15 categories, including installation, observations, instructions for use, astronomical theories and formulas, etc. This study provides easy-to-understand illustrations of the figures shown in the original and contains detailed descriptions of the related calculation procedures. In the 'Instructions for Use of Honcheonui' discussed here, the readers are introduced to astronomical computation systems, mainly based on spherical trigonometry and proportional methods. The section also provides systematic and detailed reviews of astronomical theories and calculation procedures, allowing you to assess the level of astronomy knowledge at that time.

The connection between geomagnetic secular variation and long-range development of climate changes for the last 13,000 years: the data from NNE Europe

One of the possible mechanisms of the connection between long-term climate changes and geomagnetic field variations is discussed. Climate fluctuations with periods of n×(10 4–10 5) years can be explained by Milankovitch's astronomic theory. The fluctuations with periods of n×(10 2–10 3) years are discussed in the framework of a hypothesis on the connection with secular variations of the geomagnetic field. On the basis of palaeomagnetic data from N–W Russian lake sediments (basically from Karelia and the Kola Peninsula) for the time interval 13,000–5000 years ago, the drift of virtual geomagnetic poles is calculated. Analysis of this data with regard to palaeotemperature and palaeoclimate phases in N–NE Europe is carried out. The alternation of stadial (cold) and interstadial (warm) stages as a function of approaching (receding from) the virtual geomagnetic pole to N Europe is established. For the last 5 kyr the correlation is confirmed for archaeomagnetic data from the Ukraine.

La regeneración de la astronomía y la meteorología españolas: Augusto Arcimís (1844-1910) y el institucionismo

The article is about the attempts for regenerating Spanish astronomy and meteorology in the last quarter of the twentieth century through the human and scientific trajectory of Augusto Arcimís (1844-1910), amateur astronomer and the first Spanish professional meteorologist. The role of personalities linked to the Institución Libre de Enseñanza in the creation of the Instituto Central Meteorológico in 1887 and the spread of modern astronomical theories is analyzed.

Les causes astronomiques des grandes variations du climat au Quaternaire

Astronomical origin of the large climatic variations during the Quaternary. The astronomical theory of palaeoclimates aims at explaining the recurrence of glacial–interglacial cycles during the Quaternary. It is based upon the long-term variations of the latitudinal and seasonal distributions of the energy that the Earth receives from the Sun. The response of the climate system to this forcing has been simulated by means of the Louvain-la-Neuve (Belgium) model of intermediate complexity. This model reproduces the main climatic features of the last 3 Myr: the entrance into glaciation 2.75 Myr ago; the obliquity cycles from Late Pliocene to Early Pleistocene; the emergence of the 100-kyr cycle 900 kyr ago, the glacial–interglacial cycles of the last 600 kyr, and the climatic variations of the last 200 kyr. In addition to the role played by insolation and greenhouse gases, the model stresses the importance of the feedbacks related to the water vapour, the planetary albedo, the vegetation, the inlandsis and the isostatic rise. Moreover, the analysis of the Quaternary climate has shown that Marine Isotopic Stage 11, 400 000 years ago, was the best analogue of our Holocene. Simulations and sensitivity analyses show that our interglacial will last much longer than most of the others, even without taking into account the impact of human activities on the climate. To cite this article: A. Berger, C. R. Palevol 5 (2006) .

Reconstructing the variability of the climate system: Facts and theories

Abstract On the 10 2 - to 10 3 -year timescale, internal reorganizations of the climate system result in abrupt climatic changes of great magnitude. Although a large body of data has been obtained, the physical mechanisms responsible for these changes are still poorly understood. Instrumental data are too short to fully record the variability of the climate system. Palaeoclimatic records provide estimates of the past atmospheric composition, temperature, precipitation, vegetation, extension of glaciers, and past ocean circulation. On the 10 4 - to 10 6 -year timescale, the astronomical theory of palaeoclimates accounts for most of the reconstructed variations. To cite this article: J.-C. Duplessy et al., C. R. Geoscience 337 (2005).