Review Lecture: The dynamical properties and internal structures of the Earth, the Moon and the planets

1972 ◽  
Vol 328 (1574) ◽  
pp. 301-336 ◽  
Keyword(s):  
Internal Structure ◽  
Recent Progress ◽  
High Pressures ◽  
Artificial Satellites ◽  
The Moon ◽  
The Earth ◽  
Internal Structures ◽  
Theoretical Investigations ◽  
Dynamical Properties ◽  
Very High

The aim of this review is to bring together and relate recent progress in three subjects - the internal structure of the Earth, the behaviour of materials at very high pressures and the dynamical properties of the planets. Knowledge of the internal structure of the Earth has been advanced in recent years, particularly by observations of free oscillations of the whole Earth excited by the very largest earthquakes; as a consequence, it is clear that K. E. Bullen’s hypothesis that bulk modulus is a smooth function of pressure irrespective of composition is close to the truth for the Earth. Understanding of the behaviour of materials at very high pressure has increased as a result both of experiments on the propagation of shock waves and of theoretical investigations along a number of lines and it can now be seen that Bullen’s hypothesis is not true irrespective of chemical composition and crystal structure but that it happens to apply to the Earth because of particular circumstances. Studies of the orbits of artificial satellites and space probes have led to better knowledge of the dynamics of the Moon, Mars and Venus, and there have also been recent improvements in the traditional studies of Uranus and Neptune. Our knowledge of the dynamics of the planets is on the whole rather restricted, and Bullen’s hypothesis only applies directly to the Moon (for which the application is trivial) and possibly to Mars; the dynamical properties do none the less set fairly restrictive limits to the models that can be constructed for other planets. It would be possible for all planets to have cores of similar composition to the Earth ’s, surrounded by mantles of different sorts, silicates for the terrestrial planets and mostly hydrogen for Jupiter, Saturn, Uranus and Neptune.

Automated Determination of the Position of Ships by Satellites

1967 ◽  
Vol 20 (03) ◽  
pp. 281-285
Author(s):  
H. C. Freiesleben
Keyword(s):  
Celestial Body ◽  
World Wide ◽  
Artificial Satellites ◽  
Radio Waves ◽  
The Moon ◽  
Position Determination ◽  
The Earth ◽  
Navigational Aids ◽  
Automated Determination

It has recently been suggested that 24-hour satellites might be used as navigational aids. To what category of position determination aids should these be assigned ? Is a satellite of this kind as it were a landmark, because, at least in theory, it remains fixed over the same point on the Earth's surface, in which case it should be classified under land-based navigation aids ? Is it a celestial body, although only one tenth as far from the Earth as the Moon ? If so, it is an astronomical navigation aid. Or is it a radio aid ? After all, its use for position determination depends on radio waves. In this paper I shall favour this last view. For automation is most feasible when an object of observation can be manipulated. This is easiest with radio aids, but it is, of course, impossible with natural stars.At present artificial satellites have the advantage over all other radio aids of world-wide coverage.

scholarly journals Είμαστε μόνοι στο συμπάν; Οι μετεωρίτες δίνουν απαντήσεις;

2016 ◽  
Vol 47 (1) ◽  
pp. 32
Author(s):  
Ι. Μπαζιώτης ◽  
L. A. Taylor
Keyword(s):  
High Pressures ◽  
Geochemical Data ◽  
The Moon ◽  
Martian Surface ◽  
The Earth ◽  
Past Life ◽  
Celestial Bodies ◽  
Meteorite Fall ◽  
Event Based ◽  
Moon Landing

The humankind, despite the recent technological achievements, does not yet have the ability to carry out routine trips to nearby celestial bodies. However, space science is a reality. The “Apollo” missions, that took place during the period 1969-1972, included the moon landing, the walk of astronauts and collection of valuable samples. Since then, no similar space journey has been carried out. The possibility for future missions such as the return to the Moon or Mars, or to an asteroid (e.g., Vesta), seems small enough to be implemented in the next decades. Nevertheless, nature has the mechanism and procedures to resolve this problem by sending extra-terrestrial rocks in earth in the form of meteorites. Meteorite fall on Earth is a major event, as it reveals important information about the primordial stages of formation of our solar system, or the creation processes of other planets. However, the big question still remains; whether these rocks host or have traces of past life in turn employs researchers in the last twenty years. McKay et al. (1996) studied the meteorite ALH 84001 originating from Mars, claimed for important discoveries such as structures corresponding to nanobacteria. In the current paper, we focus on the origin of Martian meteorites, presenting their complete geological history; from the genesis of their protoliths till their falling to the earth. We attempt to shade light in the understanding of meteorite formation using mineralogical-petrological-geochemical data, and the assignment of timing for each event based upon contemporary geochronological data. Recently, studies of the Martian meteorite Tissint, allegedly discovered structures rich in carbon and oxygen. Furthermore, recent field observations from Curiosity rover, indicates the existence of surface water that flowed once in the past at the Martian surface. We conclude that the planet Mars might not be a "dead" planet. But it turns out that many of the meteorites that reach the Earth, have undergone a complex history which is associated with the development of very high pressures and temperatures on the surface of the planet (e.g., Mars) from which they originate, able to destroy any trace of life before them. After all, we should be very sceptic and evaluate all the possibilities before the acceptance for the existence of life out there. 

The earth's mantle

1965 ◽  
Vol 55 (3) ◽  
pp. 619-625
Author(s):  
L. Don Leet ◽  
Florence J. Leet
Keyword(s):  
Plastic Deformation ◽  
Superheated Steam ◽  
High Pressures ◽  
Water Molecules ◽  
Earth’S Mantle ◽  
Primary Mechanism ◽  
The Earth ◽  
State Of Matter ◽  
Solid Liquid ◽  
Very High

Abstract It has been generally accepted for some time that the earth's mantle is “solid” (crystalline). But increasing complications arise as attempts are made to rationalize that state of matter with the growing list of properties of the mantle. We suggest that materials of the earth's mantle are in a fourth state of matter, which we propose calling soliqueous—a combination of solid, liquid, and gaseous. It includes elements for forming water molecules and allows expanding superheated steam to supply the principal force for elevating and distorting land masses. Bridgman's experiments on plastic deformation of materials at very high pressures revealed that spasmodic jerky yielding is characteristic. We propose plastic rupture in shear as the primary mechanism by which energy in the earth is converted to the vibrations of earthquakes.

scholarly journals Rotation of the Solar System Bodies

1992 ◽  
Vol 9 ◽  
pp. 508-536
Author(s):  
B. Kolaczek
Keyword(s):  
Solar System ◽  
Solid Body ◽  
Artificial Satellites ◽  
The Moon ◽  
The Earth ◽  
Photometric Observations ◽  
Solar System Bodies ◽  
Rotation Of The Earth ◽  
Better Than

Solar System bodies are different. They have different sizes, from large planets to small asteroids, and shapes. They have different structure, from solid body to solid body with fluid atmosphere or core, to gaseous bodies, but all of them rotate. The Solar System is a big laboratory for studying rotation of solid and fluid bodies.Different observational methods are applied to determine the rotation of the Solar system bodies. They depend on the position of the observer and on the structure of the bodies. The most accurate methods, laser ranging to the Moon and artificial satellites and Very Long Base radio Interferometry have been applied to the determination of the rotation of the Earth and the Moon. Their accuracy is better than 0.001”, which on the surface of the Earth corresponds to about 3 cm. Radiotracking of artifical satellites have been used for Earth, Moon, Venus, Mars. In the case of Jupiter, Saturn, Uranus, Neptune and Pluto-Charon magnetic and photometric observations have been used respectively. Their accuracy is of the order of one tenth of a degree.

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 Some Differences Between Geometrical and Dynamical Figures of the Moon

1972 ◽  
Vol 47 ◽  
pp. 32-34 ◽  
Author(s):  
I. V. Gavrilov
Keyword(s):  
Gravity Field ◽  
Lunar Surface ◽  
Homogeneous Model ◽  
Artificial Satellites ◽  
Geometrical Shape ◽  
The Moon ◽  
Geometrical Figure ◽  
Centre Of Gravity ◽  
The North ◽  
The Earth

The geometrical shape of the Moon is determined from measurements of absolute heights of the lunar surface, while its dynamical shape is described by means of the Moon's gravity field parameters. All these data are derived from observations of the lunar artificial satellites (‘Luna-10’, ‘Orbiters 1-4’) and astronomical measurements.In the paper differences of the lunar geometrical and dynamical figures are analysed. It is shown, that the homogeneous model of the Moon is not capable of explaining these differences. It is found, that the lunar centre of gravity situated about 0.9 km to the north, and 1.1 km nearer to the Earth, than the centre of its geometrical figure.

scholarly journals DECOHERENCE AND GRAVITATIONAL BACKGROUDS

2002 ◽  
Vol 17 (06n07) ◽  
pp. 1003-1012 ◽  
Author(s):  
SERGE REYNAUD ◽  
BRAHIM LAMINE ◽  
ASTRID LAMBRECHT ◽  
PAUOLO MAIA NETO ◽  
MARC-THIERRY JAEKEL
Keyword(s):  
Gravitational Waves ◽  
Effective Temperature ◽  
Planetary Motion ◽  
The Moon ◽  
The Earth ◽  
Gravitational Scattering ◽  
Decoherence Process ◽  
Very High ◽  
Negligible Influence

We study the decoherence process associated with the scattering of stochastic gravitational waves. We discuss the case of macroscopic systems, such as the planetary motion of the Moon around the Earth, for which gravitational scattering is found to dominate decoherence though it has a negligible influence on damping. This contrast is due to the very high effective temperature of the background of gravitational waves in our galactic environment.

CELESTIAL OPTICAL INTERFEROMETRY: A NEW TOOL FOR ULTRAHIGH PRECISION STUDIES IN GRAVITY

2008 ◽  
Vol 17 (03n04) ◽  
pp. 617-626 ◽  
Author(s):  
C. S. UNNIKRISHNAN ◽  
G. T. GILLIES
Keyword(s):  
Gravitational Waves ◽  
Equivalence Principle ◽  
Gravitational Constant ◽  
Low Frequency ◽  
Artificial Satellites ◽  
Length Scale ◽  
The Moon ◽  
The Earth ◽  
Tremendous Progress ◽  
Laser Sources

The tremendous progress in the science and technology of timing devices and laser sources has reached a stage where their stability and coherence are sufficient for implementing unbalanced interferometers over a length scale exceeding the Earth–Moon distance. This opens up the possibility of optical homodyne interferometry over such distances, either to the Moon or to artificial satellites that are at large distances from the Earth. The precision of the measurement of changes in the orbital distance would increase by a factor of 104 or more, enabling new ultrahigh precision tests of the equivalence principle, study of gravitomagnetism, and of subtle gravitational phenomena, including the constancy of the gravitational constant and possible gravitational expansion of space. It would enable geodesy and tide studies with unprecedented precision. Such interferometers would also be useful for the detection and study of low frequency gravitational waves.

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.

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