Gravitation universe

Helium is the second most abundant element in the universe (76% H, 23% He) as a result of its synthesis from hydrogen (p. 9) but, being too light to be retained by the earth s gravitational field, all primordial helium has been lost and terrestrial helium, like argon, is the result of radioactive decay ( He from a-decay of heavier elements, " °Ar from electron capture by... 

In addition to ordinai y matter, scientists have evidence for the existence in the universe of dark matter. Some of the dark matter is ordinai y matter, such as dust in outer space and planets going around other stars. Astronomers cannot see ordinai y dark matter because any light coming from such matter is too faint to be observed in telescopes. However, most of the dark matter in the universe is believed not to be ordinary matter. At the present time it is not known what this mysterious dark matter is, or what it is made of. Scientists know that this dark matter exists because it exerts a gravitational force on stars (which are made of ordinary matter), causing the stars to move faster than they otherwise would. According to present estimates, there is perhaps five times as much dark matter in the universe as ordinary matter. 

Will, C.M., 1993, Theory and experiment in gravitational physics, (Cambridge University Press, Cambridge), contains descriptions of the various experiments in the field of gravitation. Requires some background in general relativity (for example, path one of the MTW or the book by Weinberg). 

The phenomenon of attraction of masses is one of the most amazing features of nature, and it plays a fundamental role in the gravitational method. Everything that we are going to derive is based on the fact that each body attracts other. Clearly this indicates that a body generates a force, and this attraction is observed for extremely small particles, as well as very large ones, like planets. It is a universal phenomenon. At the same time, the Newtonian theory of attraction does not attempt to explain the mechanism of transmission of a force from one body to another. In the 17th century Newton discovered this phenomenon, and, moreover, he was able to describe the role of masses and distance between them that allows us to calculate the force of interaction of two particles. To formulate this law of attraction we suppose that particles occupy elementary volumes AF( ) and AF(p), and their position is characterized by points q and p, respectively, see Fig. 1.1a. It is important to emphasize that dimensions of these volumes are much smaller than the distance Lgp between points q and p. This is the most essential feature of elementary volumes or particles, and it explains why the points q and p can be chosen anywhere inside these bodies. Then, in accordance with Newton s law of attraction the particle around point q acts on the particle around point p with the force d ip) equal to... 

Electrons with the same spin behave as if there is a repulsive force acting between them. This apparent force is sometimes called the Pauli force. However, it is preferable not to speak of Pauli forces, since they are only apparent forces, not real forces like electromagnetic or gravitational forces. In fact, the Pauli principle implies that there is an intimate interconnection between the constituent parts of matter in the universe. Strictly speaking, no part can be isolated from the rest, except in an idealized way. The Pauli force acts at any time and over huge distances, much larger than atomic dimensions, but its effect becomes dramatic only when electrons of the same spin happen to be close to each other. 

D.G. Blair The Detection of Gravitational Waves, Cambridge University Press, Cambridge (1991)... 

A. de Waard MiniGRAIL The First Spherical Gravitational Wave Antenna Ph.D. Thesis Leiden University, The Netherlands (2003)... 

S. Weinberg, Gravitation and Cosmology, Wiley 1972, in E. W. Kolb and M. S. Turner, The Early Universe, Addison-Wesley Press 1990, and in the comprehensive introduction to modern cosmology... 

In 1687, Newton summarized his discoveries in terrestrial and celestial mechanics in his Philosophiae naturalis principia mathematica (Mathematical Principles of Natural Philosophy), one of the greatest milestones in the history of science. In this work he showed how his (45) principle of universal gravitation provided an explanation both of falling bodies on the earth and of the motions of planets, comets, and other bodies in the heavens. The first part of the Principia, devoted to dynamics, includes Newton s three laws of motion the second part to fluid motion and other topics and the third part to the system of the (50) world, in which, among other things, he provides an explanation of Kepler s laws of planetary motion. 

Harrison, B. K., Thome, K. S., Wakano, M., Wheeler,J.A. (1965). Gravitational Theory and Gravitational Collapse Chicago, University of Chicago Press. 

As just described, the most precise measurements of masses come from double neutron star systems. There are currently five such systems known, three of which will coalesce due to gravitational radiation in less than the age of the universe, 1010 yr (Taylor 1994). These three systems in particular allow very precise measurements of the masses of the components, which are between 1.33 M and 1.45 M0 (Thorsett Chakrabarty 1999). The other two double neutron star systems also have component masses consistent with a canonical 1.4 M . It has been suggested that the tight grouping of masses implies that the maximum mass of a neutron star is 1.5 M0 (Bethe Brown 1995). However, it is important to remember that double neutron star systems all have the same evolutionary pathway and thus the similar masses may simply be the result of a narrow selection of systems. 

B.K. Harrison, K.S. Thorne, M. Wakano, and J.A. Wheeler. Gravitation theory and gravitational collapse , University of Chicago Press, 1965. 

We have thought of affinity or chemical force as an attractive force, like a form of universal gravitational... 

Calling hydrogen the "comet" of the chemical universe 13 was laden with levels of meaning for a new mechanistic chemistry. The metaphor expressed a hypothesis that hydrogen is a finite particle, that it is in continuous and repetitive motion within a dynamic molecule, and that the gravitational analogy for chemical affinity is an apt one. 

---