scholarly journals Analysis of the Secular Variations of Longitudes of the Sun, Mercury and Venus from Optical Observations

2002 ◽  
Vol 12 ◽  
pp. 330-333
Author(s):  
Y.B. Kolesnik
Keyword(s):  
Secular Variation ◽  
Optical Observations ◽  
Lunar Theory ◽  
The Sun ◽  
The Moon ◽  
Significant Discrepancy ◽  
Secular Variations ◽  
Tidal Acceleration

AbstractAbout 240 000 optical observations of the Sun, Mercury and Venus, accumulated during the era of classical astrometry from Bradley up to our days, are incorporated to analyse the secular variation of the longitudes of innermost planets. A significant discrepancy between modern ephemerides and optical observations is discovered. The possible sources of discrepancy are discussed. The tidal acceleration of the Moon has been revised to conform the lunar theory with the ephemerides of the planets. The offset and residual rotation of Hipparcos-based system with respect to the dynamical equinox is determined. Interpretation of this rotation is given.

scholarly journals Encounter in the Keplerian Field: Analytical Treatment

1993 ◽  
Vol 132 ◽  
pp. 289-289
Author(s):  
V.A. Brumberg ◽  
T.V. Ivanova
Keyword(s):  
Point Of View ◽  
Lunar Theory ◽  
Theoretical Point ◽  
The Sun ◽  
The Moon ◽  
Type Solution ◽  
Analytical Treatment ◽  
Hill’S Problem ◽  
Hill's Problem ◽  
Resonance Character

AbstractIn extending the results of Henon and Petit (Celes.Mech., 38,67, 1986) an algorithm is suggested to construct the series representing the general encounter-type solution of the spatial eccentric Hill’s problem. The series are arranged in powers of the eccentricity E of Hill’s problem and two integration constants e and k characterizing eccentricity and inclination of the relative motion. A particular non-periodic solution of Henon and Petit corresponding to E = e = k = 0 is taken as an intermediary. The perturbations to this solution are constructed similar to the Lunar theory of Hill and Brown with; the Universal Poissonian Processor. From theoretical point of view Hill’s problem for the encounter case is of particular interest. In distinction from the Lunar problem we do not have here angular arguments with different frequencies. Moreover, the perturbations related with the external eccentricity E (analogous to the perturbations in the motion of the motion of the Moon caused by the eccentricity of the orbit of the Sun) are of resonance character.

scholarly journals Linking the Dynamical Reference frame to the ICRF

1998 ◽  
Vol 11 (1) ◽  
pp. 310-312
Author(s):  
E.M. Standish
Keyword(s):  
Reference Frame ◽  
Optical Observations ◽  
The Sun ◽  
The Moon ◽  
Vlbi Observations ◽  
Celestial Reference Frame

Abstract The latest JPL planetary and lunar ephemerides, DE405, are referenced to the International Celestial Reference Frame (ICRF) with an accuracy that approaches 1 mas for the four innermost planets, the sun, and the moon. This has been accomplished mainly by 18 VLBI observations of the Magellan Spacecraft in orbit around Venus. The ephemeris of Jupiter, however, is not well-determined since the various observations are not consistent within each other. The outer four planets continue to rely almost entirely upon optical observations; their ephemeris uncertainties lie in the 100-200 mas range.

scholarly journals Theory of the Libration of the Moon

1983 ◽  
Vol 74 ◽  
pp. 37-37
Author(s):  
M. Dubois-Moons
Keyword(s):  
Gravity Field ◽  
Orbital Motion ◽  
Lunar Theory ◽  
The Sun ◽  
Lunar Gravity ◽  
The Moon ◽  
Fourth Degree ◽  
Lunar Gravity Field ◽  
The Earth ◽  
Second Degree

AbstractThe paper presents a new theory of the libration of the Moon, completely analytical with respect to the harmonic coefficients of the lunar gravity field. This field is represented through its fourth degree harmonics for the torque due to the Earth (the second degree for the torque due to the Sun). The Moon is assumed to be rigid and its orbital motion is described by the ELP 2000 solution (Chapront and Chapront-Touzé 1981) for the main problem of lunar theory with planetary perturbations and influence of the non-sphericity of the Earth. Comparisons with other theories (Migus 1980 and Eckhardt 1981) are also presented.

scholarly journals Figures and Mirrors in Demetrios Triklinios's 'Selenography'

2021 ◽  
pp. 54-73
Author(s):  
Divna Manolova
Keyword(s):  
Fourteenth Century ◽  
Visual Cognition ◽  
The Other ◽  
Lunar Theory ◽  
The Sun ◽  
The Moon ◽  
The Earth ◽  
Mediterranean World ◽  
The One

This article is about the interplay between diagrammatic representation, the mediation of mirrors, and visual cognition. It centres on Demetrios Triklinios (fl. ca. 1308–25/30) and his treatise on lunar theory. The latter includes, first, a discussion of the lunar phases and of the Moon's position in relation to the Sun, and second, a narrative and a pictorial description of the lunar surface. Demetrios Triklinios's Selenography is little-known (though edited in 1967 by Wasserstein) and not available in translation into a modern scholarly language. Therefore, one of the main goals of the present article is to introduce its context and contents and to lay down the foundations for their detailed study at a later stage. When discussing the Selenography, I refer to a bricolage consisting of the two earliest versions of the work preserved in Bayerische Staatsbibliothek, graecus 482, ff. 92r–95v (third quarter of the fourteenth century) and Paris, Bibliothèque nationale de France, graecus 2381, ff. 78r–79v (last quarter of the fourteenth century). I survey the available evidence concerning the role of Demetrios Triklinios (the author), John Astrapas (?) (the grapheus or scribe-painter), and Neophytos Prodromenos and Anonymus (the scribes-editors) in the production of the two manuscript copies. Next, I discuss the diagrams included in the Selenography and their functioning in relation to Triklinios's theory concerning the Moon as a mirror reflecting the geography of the Earth, on the one hand, and to the mirror experiment described by Triklinios, on the other. Finally, I demonstrate how, even though the Selenography is a work on lunar astronomy, it can also be read as a discussion focusing on the Mediterranean world and aiming at elevating its centrality and importance on a cosmic scale.

Methodological Issues concerning the Astronomy of Qumran

2015 ◽  
Vol 22 (2) ◽  
pp. 202-209 ◽  
Author(s):  
Eshbal Ratzon
Keyword(s):  
Dead Sea Scrolls ◽  
Dead Sea ◽  
Angular Distance ◽  
Lunar Theory ◽  
The Sun ◽  
The Moon ◽  
Methodological Issues ◽  
Astronomical Data ◽  
The Times

In the 21st issue of Dead Sea Discoveries, Dennis Duke and Matthew Goff offered their collaboration as physicist and Dead Sea Scrolls scholar in order to study the lunar theory of the Aramaic Astronomical Book (aab). They use the astronomical model of lunar elongation—the angular distance between the moon and the sun on the observed heavenly sphere—to compute the times of the moon’s visibility and invisibility. They conclude that the times written on the Aramaic fragments are closer to reality than the times written in the Babylonian sources of the aab. This paper concludes that lunar elongation is not the best explanation of the astronomical data of the aab, and Duke and Goff’s computations should be refined according to some astronomical, cosmological, textual, and historical considerations.

Modelling Lunar Extremes

2018 ◽  
Vol 3 (2) ◽  
pp. 207-216 ◽  
Author(s):  
David Fisher ◽  
Lionel Sims
Keyword(s):  
High Precision ◽  
Celestial Mechanics ◽  
Computer Modelling ◽  
Landscape Context ◽  
The Sun ◽  
The Moon

Claims first made over half a century ago that certain prehistoric monuments utilised high-precision alignments on the horizon risings and settings of the Sun and the Moon have recently resurfaced. While archaeoastronomy early on retreated from these claims, as a way to preserve the discipline in an academic boundary dispute, it did so without a rigorous examination of Thom’s concept of a “lunar standstill”. Gough’s uncritical resurrection of Thom’s usage of the term provides a long-overdue opportunity for the discipline to correct this slippage. Gough (2013), in keeping with Thom (1971), claims that certain standing stones and short stone rows point to distant horizon features which allow high-precision alignments on the risings and settings of the Sun and the Moon dating from about 1700 BC. To assist archaeoastronomy in breaking out of its interpretive rut and from “going round in circles” (Ruggles 2011), this paper evaluates the validity of this claim. Through computer modelling, the celestial mechanics of horizon alignments are here explored in their landscape context with a view to testing the very possibility of high-precision alignments to the lunar extremes. It is found that, due to the motion of the Moon on the horizon, only low-precision alignments are feasible, which would seem to indicate that the properties of lunar standstills could not have included high-precision markers for prehistoric megalith builders.

Tidal dissipation in the oceans: astronomical, geophysical and oceanographic consequences

1977 ◽  
Vol 287 (1347) ◽  
pp. 545-594 ◽  
Keyword(s):  
Energy Dissipation ◽  
Solid Earth ◽  
Global Ocean ◽  
Ocean Tide ◽  
The Moon ◽  
Tidal Dissipation ◽  
Tidal Forces ◽  
Degree Harmonic ◽  
Tidal Acceleration ◽  
Second Degree

The most precise way of estimating the dissipation of tidal energy in the oceans is by evaluating the rate at which work is done by the tidal forces and this quantity is completely described by the fundamental harmonic in the ocean tide expansion that has the same degree and order as the forcing function. The contribution of all other harmonics to the work integral must vanish. These harmonics have been estimated for the principal M 2 tide using several available numerical models and despite the often significant difference in the detail of the models, in the treatment of the boundary conditions and in the way dissipating forces are introduced, the results for the rate at which energy is dissipated are in good agreement. Equivalent phase lags, representing the global ocean-solid Earth response to the tidal forces and the rates of energy dissipation have been computed for other tidal frequencies, including the atmospheric tide, by using available tide models, age of tide observations and equilibrium theory. Orbits of close Earth satellites are periodically perturbed by the combined solid Earth and ocean tide and the delay of these perturbations compared with the tide potential defines the same terms as enter into the tidal dissipation problem. They provide, therefore, an independent estimate of dissipation. The results agree with the tide calculations and with the astronomical estimates. The satellite results are independent of dissipation in the Moon and a comparison of astronomical, satellite and tidal estimates of dissipation permits a separation of energy sinks in the solid Earth, the Moon and in the oceans. A precise separation is not yet possible since dissipation in the oceans dominates the other two sinks: dissipation occurs almost exclusively in the oceans and neither the solid Earth nor the Moon are important energy sinks. Lower limits to the Q of the solid Earth can be estimated by comparing the satellite results with the ocean calculations and by comparing the astronomical results with the latter. They result in Q > 120. The lunar acceleration n , the Earth’s tidal acceleration O T and the total rate of energy dissipation E estimated by the three methods give astronomical based estimate —1.36 —28±3 —7.2 ± 0.7 4.1±0.4 satellite based estimate —1.03 —24 ±5 — 6.4 ± 1.5 3.6±0.8 numerical tide model — 1.49 —30 ±3 —7.5± 0.8 4.5±0.5 The mean value for O T corresponds to an increase in the length of day of 2.7 ms cy -1 . The non-tidal acceleration of the Earth is (1.8 ± 1.0) 10 -22 s ~2 , resulting in a decrease in the length of day of 0.7 ± 0.4 ms cy -1 and is barely significant. This quantity remains the most unsatisfactory of the accelerations. The nature of the dissipating mechanism remains unclear but whatever it is it must also control the phase of the second degree harmonic in the ocean expansion. It is this harmonic that permits the transfer of angular momentum from the Earth to the Moon but the energy dissipation occurs at frequencies at the other end of the tide’s spatial spectrum. The efficacity of the break-up of the second degree term into the higher modes governs the amount of energy that is eventually dissipated. It appears that the break-up is controlled by global ocean characteristics such as the ocean­-continent geometry and sea floor topography. Friction in a few shallow seas does not appear to be as important as previously thought: New estimates for dissipation in the Bering Sea being almost an order of magnitude smaller than earlier estimates. If bottom friction is important then it must be more uniformly distributed over the world's continental shelves. Likewise, if turbulence provides an important dissipation mechanism it must be fairly uniformly distributed along, for example, coastlines or along continental margins. Such a global distribution of the dissipation makes it improbable that there has been a change in the rate of dissipation during the last few millennium as there is no evidence of changes in ocean volume, or ocean geometry or sea level beyond a few metres. It also suggests that the time scale problem can be resolved if past ocean-continent geometries led to a less efficient breakdown of the second degree harmonic into higher degree harmonics.

Sweat of the Sun and Tears of the Moon. Gold and Silver in Pre-Columbian Art

1967 ◽  
Vol 71 (2) ◽  
pp. 215
Author(s):  
Earle R. Caley ◽  
Andre Emmerich
Keyword(s):  
The Sun ◽  
The Moon
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