َAstronomy and Physics : Why are Newton's laws laws and why is this question of importance in astrophysics ?



By R.C. Jennison

Abstract


Newton's law of gravitation has been well researched and one may now associate the cause with the geometry of space. Newton's third law is a general law not confined to inertial forces -any physically measurable force appears to require a physically measurable reaction in order that it may exist as a real observable quantity. Newton's first and second laws are in a different category for they are associated with relative motion and the physical reason for this has been an enigma since the publication of Principia Mathematica. Is the phenomenon associated with these two laws caused by the influence of the distance masses of the universe on point-like test masses, as Mach suggested but did not prove, or is it associated with a fundamental internal property of trapped energy within physically finite test masses, befitting to the principle of relativity, as has been proposed in the last decade? The resolution of this problem has profound implications for the identification of hidden matter in the Universe and for the cosmological modelling of the Universe as a whole.

SUMMARY


Newton's law of gravitation has been well researched and one may now associate the cause with the geometry of space. Newton s third law is a general law not confined to inertial forces -any physically measurable force appears to require a physically measurable reaction in order that it may exist as a real observable quantity. Newton's first and second laws are in a different category for they are associated with relative motion and the physical reason for this has been an enigma since the publication of Prlnelpla Mathematiea. Is the phenomenon associated with these two laws caused by the influence of the distance masses of the universe on point-llke test masses, as Mach suggested but did not prove, or is it associated with a fundamental internal property of trapped energy within physically finite test masses, befitting to the principle of relativity, as has been proposed in the last decade? The resolution of this problem has profound implications for the identification of hidden matter in the Universe and for the cosmological modelling of the Universe as a whole.

INTRODUCTION


Newton was impressed and intrigued by the phenomena of gravity and inertia and 300 years ago he welded them together in such a manner that he put the essential elements of mechanics and dynamics into astronomy and gave birth to the whole gamut of celestial mechanics which we are celebrating at this conference. Most of the other papers at this conference will be concerned with the progress which has been built on Newton's foundation but my contribution is somewhat different, it concerns the problem of why there should have been laws of motion for Newton to discover.

Newton beautifully stated the reluctance of a body to change its state of rest or relative motion. He recognlsed that the phenomenon was connected with the material content, or mass, of the body and he formulated his second law to fit the observed facts, but, of course he did not explain why it should be so endowed. He gave us the working formula and that alone was a magnificent achievement. His third law is somewhat different. It is not restricted to motion (which, to Newton, meant momentum) but appears to be universal. One cannot experience a static force without there being an equal and opposing counterpart, as in a roof truss or a compressed spring. No force is actually present in a so called 'field of force' unless a suitably responsive object, such as a test particle, is placed within it. The very nature and existence of a force demands a reaction.

In this paper I shall concentrate on the first two laws and examine two related phenomena: the nature of matter and the nature of inertia.

When my contemporles and I first embarked on a career in astronomy, we were taught that hydrogen made up the vast bulk of the universe and hence one assumed that the protons were the major source of mass in galaxies and the universe as a whole. Now we know from the dynamics of galaxies and clusters, and from the cherished hope that the universe may be critically closed, that there must be a preponderance of mass in a form which has so far defied direct detection and which was undreamed of in our student days. The literature now abounds with many types of exotic and even esoteric matter which have been proposed to account for the hidden, missing or dark mass that is required to satisfy the humble dynamics. Heavy neutrinos, light neutrinos, photlnos, axions, cosmic strings and superstrings are just a few of the contenders. The universe appears to be bathed in a sea of strange particles quite unlike our experience of the familiar world of our immediate surroundings on earth. Now this could well be, and a number of sophisticated experiments and a lot of effort and money are currently directed to this end, but should we not look around us a little before we leap too far?
...

Download Full Article 


Source

Post a comment

0 Comments

Ad blocker detected

Ads help us fund our site, please disable Adblocker and help us provide you with exclusive content. Thank you for your support