arXiv subjects
Publications and source records attributed to J. Dunning-Davies.
This article has been withdrawn by arXiv administrators due to excessive unattributed and verbatim text overlap with the pre-existing Wikipedia article on redshift
In 1983, Thornhill showed that Planck's energy distribution for a black-body radiation field could be derived for a gas-like aether with Maxwellian statistics. Further, it was shown that the frequency of electromagnetic waves correlates with the energy per unit mass of the particles, not with their energy, thus differing from Planck's quantum hypothesis. He pointed out that de Broglie, in a paper of 1922, was on the way to achieving this result but did not pursue the matter to its logical conclusion. Here a translation of de Broglie's paper is presented to draw attention to this point. Some brief additional comments are included also.
Climate change is an important current issue and there is much debate about the causes and effects. This article examines the changes in our climate, comparing the recent changes with those in the past. There have been changes in temperature, resulting in an average global rise over the last 300 years, as well as widespread melting of snow and ice, and rising global average sea level. There are many theories for the causes of the recent change in the climate, including some natural and some human influenced. The most widely believed cause of the climate change is increasing levels of Greenhouse gases in the atmosphere and as the atmosphere plays an important role in making our planet inhabitable, it is important to understand it in order to protect it. However, there are other theories for the cause of climate change, the Sun and cosmic rays, for example, are felt by some to have a significant role to play. There is also well-established evidence that the three Milankovitch cycles change the amount and alter the distribution of sunlight over the Earth, heating and cooling it. There are many influences on our planet and they all have differing levels of impact. The purpose of this article is to review the present overall position and urge open, reasoned discussion of the problem.
The modern notion of a black hole singularity is considered with reference to the Schwarzschild solution to Einstein's field equations of general relativity. A brief derivation of both the original and the modern line elements is given. The argument is put forward that the singularity occurring within the Schwarzschild line element that has been associated with the radius of the black hole event horizon is, in fact, merely a mathematical occurrence and does not exist physically. The real aim here, however, is to attempt to open up the whole problem, draw some conclusions, but finally to urge everyone to consider the points raised with no preconceived opinions and then come to their own final conclusion.
A brief outline of the history of the discrepancies within Newtonian mechanics at the end of the nineteenth century is given. The framework of general relativity is described briefly and the famous 'tests' of general relativity are considered and alternative solutions discussed, with particular attention concentrating on the advance of the perihelion of the planet Mercury. The implications for the claims of relativity are discussed, all with reference to both pre and post 1915 publications.
Courses in mathematical methods for physics students are not known for including too much in the way of mathematical rigour and, in some ways, understandably so. However, the conditions under which some quite commonly used mathematical expressions are valid can be of great importance in some physical circumstances. Here one such expression, which figures frequently in the manipulations leading to the isothermal compressibility appearing in formulae, is examined as an illustrative example.
Discussion of the constancy, or otherwise, of the various so-called universal constants which abound in physics has continued for many years. However, relatively recent observations, which appear to indicate a variation in the value of the fine structure constant, have reignited the subject. These observations relate to quasars and that in itself raises questions. Also, since many of the arguments utilise the Bekenstein-Hawking expression for the entropy of a black hole, further controversy is introduced into the discussion immediately. In what follows these two points will be examined and some less well-known theoretical considerations introduced which, hopefully, will instigate wider examination of this topic.
The position of the various tired light theories is reviewed briefly and it is noted that one of the biggest objections to them concerns the mechanism by which light might lose energy as it travels through space. Here some new work relating to the constancy of the speed of light is highlighted as providing a possible solution to this conundrum, thus making more feasible explanation of phenomena via theories involving the notion of tired light.
The mathematical properties associated with the widely accepted concept of the extensivity of many of the common thermodynamic variables are examined and some of their consequences considered. The possible conflict between some of these and currently accepted results of special relativistic thermodynamics is highlighted. Although several questions are raised, answers are not advanced as this seems an area demanding calm, widespread reflection which could conceivably lead to radical revision of part, or parts, of theoretical physics.
Some of the more powerful results of mathematical statistics are becoming of increasing importance in statistical mechanics. Here the use of the central limit theorem in conjunction with the canonical ensemble is shown to lead to an interesting and important new insight into results associated with the canonical ensemble. This theoretical work is illustrated numerically and it is shown how this numerical work can form the basis of an undergraduate laboratory experiment which should help to implant ideas of statistical mechanics in students' minds.
The question of whether extreme value statistics should be introduced into courses for physics students has been broached recently. Here it is argued that the topic should be taught but the many and varied physical applications should be stressed; emphasis should not be confined purely to abstract theory.
Now that an English translation of Schwarzschild's original work exists, that work has become accessible to more people. Here his original solution to the Einstein field equations is examined and it is noted that it does not contain the mathematical singularity normally associated with the existence of a black hole. Einstein's own views on this subject are considered also and it is seen that, at the very least, grave questions exist over the possible existence of these somewhat esoteric stellar objects.
Attention is drawn to problems associated with superstatistics, including the apparent lack of knowledge of previous work in statistical physics displayed by workers in this supposedly new field.
Recent references to the commonly accepted expression for the entropy of a black hole to questions concerning the constancy of some of the so-called 'universal constants of nature' are questioned, as is the validity of the said entropy expression.
Once again the possibility of the existence of particle statistics intermediate between those of Fermi-Dirac and Bose-Einstein surfaces. Here attention is drawn to the fact that some fifteen years ago it was shown that such so-called 'intermediate' statistics correspond to no physical process and the stationary probability distributions of intermediate statistics are not compatible with any mechanism which allows a variation between Fermi-Dirac and Bose-Einstein statistics.
New varying speed of light (VSL) theories as alternatives to the inflationary model of the universe are discussed and evidence for a varying speed of light reviewed. Work linked with VSL but primarily concerned with deriving Planck's black body energy distribution for a gas-like aether using Maxwell statistics is considered also. Doubly Special Relativity, a modification of special relativity to account for observer dependent quantum effects at the Planck scale, is introduced and it is found that a varying speed of light above a threshold frequency is a necessity for this theory.
It is pointed out that the usual derivation of the well-known Maxwell electromagnetic equations holds only for a medium at rest. A way in which the equations may be modified for the case when the mean flow of the medium is steady and uniform is proposed. The implication of this for the problem of the origin of planetary magnetic fields is discussed.
The global requirements for energy are increasing rapidly as the global population increases and the under-developed nations become more advanced. The traditional fuels used in their traditional ways will become increasingly unable to meet the demand. The need for a review of the energy sources available is paramount, although the subsequent need to develop a realistic strategy to deal with all local and global energy requirements is almost as important. Here attention will be restricted to examining some of the claims and problems of using nuclear power to attempt to solve this major question.