scholarly journals Time Scales for Theory and Practice

1992 ◽  
Vol 9 ◽  
pp. 141-149
Author(s):  
Gernot M. R. Winkler
Keyword(s):  
Theory And Practice ◽  
The Sun ◽  
The Moon ◽  
Vernal Equinox ◽  
Perceived Needs ◽  
The Earth ◽  
Cyclical Process ◽  
The Mean ◽  
Complete Revolution ◽  
Early Human

Very early human experience has suggested a practical definition for the measurement of time: We define a unit of time by defining a standard (cyclical) process. Whenever this process completes its cycle identically, a unit of time has elapsed. This is the origin for the various measures of time in classical astronomy. Nature suggests strongly that we use as such standard processes the year (defined as a complete revolution of the earth around the Sun), the month (the completion of a revolution of the moon around the earth), and the day which again can be measured in several different ways. While the sidereal day is measured by a rotation in respect to the vernal equinox, the mean solar day is measured in respect to the mean. Sun. More recently, we have distinguished many more different ways of defining measures of time, partly in response to perceived needs of the applications, but in part also from purely aesthetic principles.

Index to Volume 277

1975 ◽  
Vol 277 (1274) ◽  
pp. 649-649
Keyword(s):  
Orbital Motion ◽  
Lunar Orbit ◽  
Artificial Satellites ◽  
Time Interval ◽  
The Sun ◽  
The Moon ◽  
Slight Effect ◽  
The Earth ◽  
Westerly Direction ◽  
Complete Revolution

Dr R. R. Newton has notified the following correction to his contribution. The paragraph at the bottom of page 16 and the top of page 17 should read: The node of the lunar orbit rotates in a westerly direction around the plane of the ecliptic, making a complete revolution in about 18.61 years. This motion, and this time interval, are important in eclipse theory, as we shall discuss in the next section. This motion results almost entirely from the perturbation of the Sun’s gravitation on the Moon’s orbital motion. The Earth’s equatorial bulge, which is almost entirely responsible for the motion of the nodes of artificial satellites near the Earth, has only a slight effect on a satellite as distant as the Moon.

scholarly journals Moon’s Planetary Perturbations

1999 ◽  
Vol 172 ◽  
pp. 413-414
Author(s):  
P. Bidart ◽  
J. Chapront
Keyword(s):  
Reference Plane ◽  
Rotating Frame ◽  
The Sun ◽  
The Moon ◽  
Keplerian Motion ◽  
The Earth ◽  
Brown's Method ◽  
Numerical Tools ◽  
The Mean ◽  
Under Construction

In ELP, the computation of planetary perturbations is about 20 years old. A better knowledge of lunar and planetary parameters, new planetary solutions under construction and progresses in numerical tools, are factors that should contribute to their improvements. The construction of planetary perturbations takes widely its inspiration from Brown’s method. In a first step, we only consider the main problem (Earth, Moon, and Sun with a Keplerian motion). The solution of the main problem is actually of a high precision and is used as a reference (Chapront-Touzé, 1980). This solution is expressed in Fourier series of the 4 Delaunay arguments, with numerical coefficients, and partials with respect to integration constants.The method based on the variation of arbitrary constants is described in (M.Chapront-Touzé, J.Chapront, 1980). Equations of Moon’s motion are written in a rotating frame where the reference plane is the mean ecliptic. In this frame, the absolutec acceleration is expressed by means of disturbing forces acting on the Moon, by the Sun, the Earth and a planet. It is the gradient of F which can be divided into several components: Fc related to the main problem, FD and FI giving rise to direct and indirect planetary perturbations.

The motion of a lunar orbiter

1966 ◽  
Vol 25 ◽  
pp. 373
Author(s):  
Y. Kozai
Keyword(s):  
Degrees Of Freedom ◽  
Dimensional Space ◽  
Artificial Satellite ◽  
Equations Of Motion ◽  
Triaxial Ellipsoid ◽  
The Moon ◽  
Secular Motion ◽  
The Earth ◽  
Close Satellite ◽  
The Mean

The motion of an artificial satellite around the Moon is much more complicated than that around the Earth, since the shape of the Moon is a triaxial ellipsoid and the effect of the Earth on the motion is very important even for a very close satellite.The differential equations of motion of the satellite are written in canonical form of three degrees of freedom with time depending Hamiltonian. By eliminating short-periodic terms depending on the mean longitude of the satellite and by assuming that the Earth is moving on the lunar equator, however, the equations are reduced to those of two degrees of freedom with an energy integral.Since the mean motion of the Earth around the Moon is more rapid than the secular motion of the argument of pericentre of the satellite by a factor of one order, the terms depending on the longitude of the Earth can be eliminated, and the degree of freedom is reduced to one.Then the motion can be discussed by drawing equi-energy curves in two-dimensional space. According to these figures satellites with high inclination have large possibilities of falling down to the lunar surface even if the initial eccentricities are very small.The principal properties of the motion are not changed even if plausible values ofJ3andJ4of the Moon are included.This paper has been published in Publ. astr. Soc.Japan15, 301, 1963.

scholarly journals The Lunar orbit paradox

2013 ◽  
Vol 40 (1) ◽  
pp. 135-146
Author(s):  
Aleksandar Tomic
Keyword(s):  
Inertial Mass ◽  
Lunar Orbit ◽  
The Sun ◽  
The Moon ◽  
The Earth ◽  
Three Body ◽  
Origin Of The Moon ◽  
Force Intensity ◽  
Critical Consideration

Newton's formula for gravity force gives greather force intensity for atraction of the Moon by the Sun than atraction by the Earth. However, central body in lunar (primary) orbit is the Earth. So appeared paradox which were ignored from competent specialist, because the most important problem, determination of lunar orbit, was inmediately solved sufficiently by mathematical ingeniosity - introducing the Sun as dominant body in the three body system by Delaunay, 1860. On this way the lunar orbit paradox were not canceled. Vujicic made a owerview of principles of mechanics in year 1998, in critical consideration. As an example for application of corrected procedure he was obtained gravity law in some different form, which gave possibility to cancel paradox of lunar orbit. The formula of Vujicic, with our small adaptation, content two type of acceleration - related to inertial mass and related to gravity mass. So appears carried information on the origin of the Moon, and paradox cancels.

scholarly journals High-resolution spectroscopy and spectropolarimetry of the total lunar eclipse January 2019

2020 ◽  
Vol 635 ◽  
pp. A156
Author(s):  
K. G. Strassmeier ◽  
I. Ilyin ◽  
E. Keles ◽  
M. Mallonn ◽  
A. Järvinen ◽  
...  
Keyword(s):  
Large Scale ◽  
Solar Spectrum ◽  
High Resolution Spectroscopy ◽  
Strong Increase ◽  
Lunar Eclipse ◽  
The Sun ◽  
The Moon ◽  
Earth’S Atmosphere ◽  
The Earth ◽  
Earth's Atmosphere

Context. Observations of the Earthshine off the Moon allow for the unique opportunity to measure the large-scale Earth atmosphere. Another opportunity is realized during a total lunar eclipse which, if seen from the Moon, is like a transit of the Earth in front of the Sun. Aims. We thus aim at transmission spectroscopy of an Earth transit by tracing the solar spectrum during the total lunar eclipse of January 21, 2019. Methods. Time series spectra of the Tycho crater were taken with the Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) at the Large Binocular Telescope in its polarimetric mode in Stokes IQUV at a spectral resolution of 130 000 (0.06 Å). In particular, the spectra cover the red parts of the optical spectrum between 7419–9067 Å. The spectrograph’s exposure meter was used to obtain a light curve of the lunar eclipse. Results. The brightness of the Moon dimmed by 10.m75 during umbral eclipse. We found both branches of the O2 A-band almost completely saturated as well as a strong increase of H2O absorption during totality. A pseudo O2 emission feature remained at a wavelength of 7618 Å, but it is actually only a residual from different P-branch and R-branch absorptions. It nevertheless traces the eclipse. The deep penumbral spectra show significant excess absorption from the Na I 5890-Å doublet, the Ca II infrared triplet around 8600 Å, and the K I line at 7699 Å in addition to several hyper-fine-structure lines of Mn I and even from Ba II. The detections of the latter two elements are likely due to an untypical solar center-to-limb effect rather than Earth’s atmosphere. The absorption in Ca II and K I remained visible throughout umbral eclipse. Our radial velocities trace a wavelength dependent Rossiter-McLaughlin effect of the Earth eclipsing the Sun as seen from the Tycho crater and thereby confirm earlier observations. A small continuum polarization of the O2 A-band of 0.12% during umbral eclipse was detected at 6.3σ. No line polarization of the O2 A-band, or any other spectral-line feature, is detected outside nor inside eclipse. It places an upper limit of ≈0.2% on the degree of line polarization during transmission through Earth’s atmosphere and magnetosphere.

Decapitated Lunar Goddesses in Aztec Art, Myth, and Ritual

1997 ◽  
Vol 8 (2) ◽  
pp. 185-206 ◽  
Author(s):  
Susan Milbrath
Keyword(s):  
Solar Eclipse ◽  
Seasonal Cycle ◽  
Full Moon ◽  
The Sun ◽  
The Moon ◽  
Seasonal Transition ◽  
The Earth ◽  
New Moon ◽  
The Demonic

AbstractAztec images of decapitated goddesses link the symbolism of astronomy with politics and the seasonal cycle. Rituals reenacting decapitation may refer to lunar events in the context of a solar calendar, providing evidence of a luni-solar calendar. Decapitation imagery also involves metaphors expressing the rivalry between the cults of the sun and the moon. Huitzilopochtli's decapitation of Coyolxauhqui can be interpreted as a symbol of political conquest linked to the triumph of the sun over the moon. Analysis of Coyolxauhqui's imagery and mythology indicates that she represents the full moon eclipsed by the sun. Details of the decapitation myth indicate specific links with seasonal transition and events taking place at dawn and at midnight. Other decapitated goddesses, often referred to as earth goddesses with “lunar connections,” belong to a complex of lunar deities representing the moon within the earth (the new moon). Cihuacoatl, a goddess of the new moon, takes on threatening quality when she assumes the form of a tzitzimime attacking the sun during a solar eclipse. The demonic new moon was greatly feared, for it could cause an eternal solar eclipse bringing the Aztec world to an end.

Solar Motion and Lunar Eclipses in Philolaus’ Cosmological System

Apeiron ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Dirk L. Couprie
Keyword(s):  
The Other ◽  
The Sun ◽  
The Moon ◽  
Internal Logic ◽  
Wrong Side ◽  
The Earth ◽  
Solar Motion ◽  
Length Of The Day

Abstract In this paper, three problems that have hardly been noticed or even gone unnoticed in the available literature in the cosmology of Philolaus are addressed. They have to do with the interrelationships of the orbits of the Earth, the Sun, and the Moon around the Central Fire and all three of them constitute potentially insurmountable obstacles within the context of the Philolaic system. The first difficulty is Werner Ekschmitt’s claim that the Philolaic system cannot account for the length of the day (νυχϑήμερον). It is shown that this problem can be solved with the help of the distinction between the synodic day and the sidereal day. The other two problems discussed in this paper are concerned with two hitherto unnoticed deficiencies in the explanation of lunar eclipses in the Philolaic system. The Philolaic system cannot account for long-lasting lunar eclipses and according to the internal logic of the system, during lunar eclipses the Moon enters the shadow of the Earth from the wrong side. It is almost unbelievable that nobody, from the Pythagoreans themselves up to recent authors, has noticed these two serious deficiencies, and especially the latter, in the cosmology of Philolaus the Pythagorean.

scholarly journals Connection of large earthquakes occurring moment with the movement of the Sun and the Moon and with the Earth crust tectonic stress character

2010 ◽  
Vol 10 (7) ◽  
pp. 1629-1633 ◽  
Author(s):  
M. K. Kachakhidze ◽  
R. Kiladze ◽  
N. Kachakhidze ◽  
V. Kukhianidze ◽  
G. Ramishvili
Keyword(s):  
Tectonic Stress ◽  
Point Of View ◽  
The Sun ◽  
Compression Stress ◽  
The Moon ◽  
Caucasus Region ◽  
The Earth ◽  
Triggering Factor ◽  
Exogenous Factors ◽  
Large Earthquakes

Abstract. It is acceptable that earthquakes certain exogenous (cosmic) triggering factors may exist in every seismoactive (s/a) region and in Caucasus among them. They have to correct earthquake occurring moment or play the triggering role in case when the region is at the limit of the critical value of the geological medium of course. Our aim is to reveal some exogenous factors possible to initiate earthquakes, on example of Caucasus s/a region, taking into account that the region is very complex by the point of view of the tectonic stress distribution. The compression stress directed from North to South (and vice versa) and the spread stress directed from East to West (and vice versa) are the main stresses acted in Caucasus region. No doubt that action of the smallest external stress may "work" as earthquakes triggering factor. In the presented work the Moon and the Sun perturbations are revealed as initiative agents of earthquakes when the directions of corresponding exogenous forces coincide with the directions of the compression stress or the spreading tectonic stress in the region.

Flights of Imagination: Avicenna’s Phoenix (ʿAnqā) and Bedil’s Figuration for the Lyric Self

2020 ◽  
Vol 2 (1) ◽  
pp. 28-72
Author(s):  
Jane Mikkelson
Keyword(s):  
First Person ◽  
The Sun ◽  
The Moon ◽  
The Earth ◽  
Philosophical System ◽  
Personal Experiences ◽  
The World ◽  
The Phoenix

Abstract The phoenix (ʿanqā) appears in the philosophy of Avicenna (d.1037) as his example of a “vain intelligible,” a fictional being that exists in the soul, but not in the world. This remarkable bird is notable (along with the Earth, the moon, the sun, and God) for being a species of one. In this essay, I read the poetry Bedil of Delhi (d.1720) in conversation with the philosophical system of Avicenna, arguing that the phoenix in Bedil’s own philosophical system functions as a key figuration that allows him simultaneously to articulate rigorous impersonal systematic ideas and to document his individual first-personal experiences of those ideas. The phoenix also plays a metaliterary role, allowing Bedil to reflect on this way of doing philosophy in the first person—a method founded on the lyric enrichment of Avicennan rationalism. Paying attention to the adjacencies between poetry and philosophy in Bedil, this essay traces the phoenix’s transformations from a famous philosophical example into one of Bedil’s most striking figurations in his arguments about imagination, mind, and self.

scholarly journals Precise Reduction to the Apparent Places of Stars

1974 ◽  
Vol 61 ◽  
pp. 319-319
Author(s):  
S. Yumi ◽  
K. Hurukawa ◽  
Th. Hirayama
Keyword(s):  
The Sun ◽  
Maximum Difference ◽  
The Moon ◽  
Uniform System ◽  
Outer Planets ◽  
The Mean ◽  
Astronomical Constants

For a precise reduction to the apparent places of the stars in a uniform system during the 19th and 20th centuries, the ‘Solar Coordinates 1800–2000’ by Herget (Astron. Papers14, 1953) may conveniently be used, because no coordinates of the Sun, referred to the mean equinox of 1950.0, are given in the Astronomical Ephemeris before 1930.A maximum difference of 0″.0003 was found between the aberrations calculated from both the Astronomical Ephemeris and Herget's Tables for the period 1960–1969, taking into consideration the effect of the outer planets, which amounted to 0″.0109.The effect of the inner planets on the aberration is estimated to be of the order of 0″.0001 at the most and the correction for the lunar term due to the change in astronomical constants is 0″.00002. It is recommended that the solar coordinates be calculated directly from Newcomb's formulae taking the effects of all the planets into consideration, but the effect concerned with the Moon can be neglected.

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