Concurrent Astronomical Observations for Studying Continental Drift, Polar Motion, and the Rotation of the Earth

Author(s):  
Wm. Markowitz
1968 ◽  
Vol 32 ◽  
pp. 25-32 ◽  
Author(s):  
Wm. Markowitz

The analysis of 66 years of concurrent latitude observations of the ILS shows that the mean pole has a secular motion which consists of a progressive component of about 0′′.0035/yr (10 cm/yr) along the meridian 65°W and a librational component (oscillation) of 24-year period along the meridian 122°W (or 58°E). Crustal displacements in latitude are not found within the errors of observation, about 1 cm/yr.Comparable, concurrent observations for time (longitude) have not been made but programs are being organized. From 30 to 50 years will be needed for detection of continental drift with PZT's and astrolabes if relative drifts in longitude of 3 cm/yr are occurring.


1974 ◽  
Vol 3 ◽  
pp. 221-222
Author(s):  
R. O. Vicente

It is well known that the knowledge of precession and nutation is essential for the computation of astronomical coordinates and the comparison of values obtained at different dates. It is therefore important to compute the nutations from the best available observations.Unfortunately, there are not many long series of reliable observations that can be used for the calculation of the several nutations. Nowadays, we need more accurate values and, therefore, it is fundamental to have observations reduced in an homogeneous way. For this purpose, Commission 19 (Rotation of the Earth) set up a ‘Working Group on Pole Coordinates’, during the last IAU meeting in 1970 (Vicente, 1972), with the objective of reducing the 70 years of variation of latitude observations done by the International Latitude Service (called the International Polar Motion Service at the present time) that constitute a remarkable set of astronomical data. It is expected to obtain more reliable values for the coordinates of the pole and be able to calculate the nutations.The Working Group on Pole Coordinates is transferring to punched cards all the observations registered in the original observation books and that involves nearly 2 million cards. This work has been hampered by financial difficulties, but it should be supported by the international astronomical community in order to obtain the best results from so many years of observations, done by international cooperation.The theoretical researches done in the last decades have shown that the values of the nutations depend on the structure of the Earth (Jeffreys and Vicente, 1957). Lately, the researches done in seismology have resulted in a better knowledge about the structure of the Earth, leading to the setting up of many Earth models due to the availability of computers. This fact has led to the situation where one cannot propose better theoretical values for the nutations because they depend on the model adopted for the structure of the Earth.


2019 ◽  
Vol 50 (2) ◽  
pp. 192-220
Author(s):  
María José Martínez Usó ◽  
Francisco J. Marco Castillo

Existing research dealing with astronomical observations from medieval Europe have extensively covered topics such as solar and lunar eclipses and sightings of comets and meteors, but no compilation of occultations of planets by the Moon has been carried out and, till now, the data have remained scattered in different publications. The main reasons for this are the small number of observations that has reached us, their limited use for calculation of parameters associated with the rotation of the Earth, and the fact that between the fifth and fifteenth centuries, the period that we consider, almost none of these observations were made scientifically, since they usually appear in narrative texts, be they chronicles or annals. Our purpose is to make a compilation of these phenomena, trying to shed light on some of the most controversial observations after examining them in their historical context. We will examine European sources, but, occasionally, we will also consider reports from other parts of the world to make comparisons, when necessary.


1997 ◽  
Vol 165 ◽  
pp. 307-312
Author(s):  
R. Molina ◽  
A. Vigueras

AbstractIn this paper, we consider the problem of the rotation of the Earth, using a stationary triaxial gyrostat as a model. The problem is formulated by means of dimensionless canonical variables of Serret-Andoyer, referred to the mean ecliptic of date, in a similar way to Kinoshita (1977). We choose the constant components of the gyrostatic momentum in such a way that the period of the polar motion corresponds to Chandler’s period. Finally, the problem is integrated by means of Deprit’s perturbation method.


1975 ◽  
Vol 26 ◽  
pp. 63-77
Author(s):  
E. P. Fedotov

AbstractThe axes of coordinate systems used in geodynamics are believed to be attached to a number of physical points on the surface of the Earth. This is true when measurements of the distances (ranging) are dealt with. On the other hand, the axes of reference systems used by the BIH and IFMS are attached not to the points themselves but to a pencil of plumb lines at these points. For the case of observations with radio interferometers being used for the study of Earth’s rotation, the rotating frame of reference could be attached in some prescribed way toihebaselines of the interferometers.But in no case is rigid attachment possible, because both the above points and lines move relative to each other. We should search for another way to define the reference systems for geodynamics. With that end in view, a knowledge of magnitudes of pertinent dynamical phenomena becomes vital.This paper considers the effects of some dynamical phenomena upon the distances between the points on. the Earth’s surface and upon the angles between plumb lines and, possibly, also between baselines of radio interferometers. In particular, this paper discusses body tides, continental drift, internal motion within crustal blocks, redistribution of mass which can affect the directions of plumb lines, etc. Polar motion and variations in the rate of Earth’s rotation will be also touched upon as far as these phenomena contribute to deformation of the Earth and its gravitation field.The results are summarised in diagrams showing how the variations of the above distances and angles depend upon both time and positions on the Earth. In other words, the power spectrum of the variation will be presented as a function of time and distance expressed either in kilometers or in degrees of arc on the Earth’s surface.


1972 ◽  
Vol 48 ◽  
pp. 49-55
Author(s):  
Toyozo Okuda

Guinot and Feissel (1968), Okazaki and Nasaka (1970) reported the marked discrepancy between annual terms of the polar motion obtained by time and latitude observations. The disturbing effects of local non-polar terms in latitude variation on pole coordinates are discussed in the first half of this paper.From an analogy between time and latitude observations, we can conclude that Δx and Δy in the pole coordinates obtained from time observations are proportional to a part of the common fictitious term ΔT in the rotation of the Earth. Using ΔT obtained from Okazaki's data for the same interval as Guinot's and Feissel's data, a test example is given as follows: If we apply the above corrections to the pole coordinates obtained from time observations, we can derive the coordinates x and y which are comparable to those of the ILS. Δαα, ΔS and local non-polar terms (z5 – z4) in the ILS latitude determination may be considered as the sources of ΔT.


1980 ◽  
Vol 78 ◽  
pp. 235-237
Author(s):  
G. P. Pilnik

It is possible, in principle, to derive from astronomical observations both the tidal and nutational variations in the rotation of the Earth. However, in practice there are a number of difficulties. To detect the waves with periods of 18.6, 1.0 and 0.5 year one could use UT1-TAI. Unfortunately, this is impossible because of the lack of sufficiently long series of observations and because of significant non-periodic irregularities in the rate of the Earth's rotation. In addition, the annual wave consists of several harmonics of different natures which cannot be separated from one another. Investigation of short-period nutations is more promising, but it is also connected with specific difficulties.


1968 ◽  
Vol 32 ◽  
pp. 80-85
Author(s):  
S. K. Runcorn

The relations between paleomagnetic observations, polar wandering curves, and changes in the speed of rotation of the Earth are discussed.


1980 ◽  
Vol 78 ◽  
pp. 59-66 ◽  
Author(s):  
Ya. S. Yatskiv

The first attempts to take into account the dynamic effect of a liquid core on the rotation of the Earth were made as far back as the end of the 19th century.


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