James Jeans Quotes

109 Sourced Quotes

Heisenberg finds that facts of observation lead uniquely and inevitably to the theoretical structure known as matrix mechanics. This shows that the total radiation in any region of empty space can change only by a single complete quantum at a time. Thus not only in the photo-electric phenomenon, but in all other transfers of energy through space, energy is always transferred by complete quanta; fractions of a quantum can never occur. This brings atomicity into our picture of radiation just as definitely as the discovery of the electron and its standard charge brought atomicity into our picture of matter and of electricity.

James Jeans
We saw that radiation cannot suitably be pictured as particles when it is traveling through space. There is a corresponding property for electrons; these should not be pictured as waves so long as they are traveling through empty space.

James Jeans
... when the experiment was attempted by Michelson and Morley it failed, thus showing that space and time assumed in the picture were not true to the facts of nature.... the pattern of events was the same whether the world stood at rest in the supposed ether, or had an ether wind blowing through it at a million miles an hour. It began to look as though the supposed ether was not very important in the scheme of things... and so might as well be abandoned. But if the bell-rope is to be discarded, what is to ring the bell?

James Jeans
Nature seems very conversant with the rules of pure mathematics, as our own mathematicians have formulated them in their studies, out of their own inner consciousness and without drawing to any appreciable extent on their experience of the outer world.

James Jeans
Kant, discussing the various modes of perception by which the human mind apprehends nature, concluded that it is specially prone to see nature through mathematical spectacles. Just as a man wearing blue spectacles would see only a blue world, so Kant thought that, with our mental bias, we tend to see only a mathematical world.

James Jeans
Gravitational force is simple, and a thing by itself, as also are electric and magnetic forces as long as the electric and magnetic poles stand at rest. But as soon as motion comes into the picture, the whole situation is changed. Forces of new kinds come into play, for moving electric charges exert magnetic forces in addition to the electric forces they exert when at rest, while moving magnets exert electric forces in addition to the magnetic forces they exert while at rest. When the exact laws governing these intricate laws had been discovered by a great number of experimenters, Clerk Maxwell succeeded in expressing them in a mathematical form which was both simple and elegant.

James Jeans
Any region of space-time that has no gravitating mass in its vicinity is uncurved, so that the geodesics here are straight lines, which means that particles move in straight courses at uniform speeds (Newton's first law). But the world-lines of planets, comets and terrestrial projectiles are geodesics in a region of space-time which is curved by the proximity of the sun or earth... No force of gravitation is... needed to impress curvature on world-lines; the curvature is inherent in the space...

James Jeans
The classical mechanics had envisaged the world constructed of matter and radiation, the matter consisting of atoms and the radiation of waves. Plank's theory called for an atomicity of radiation similar to that which was so well established for matter. It supposed that radiation was not discharged from matter in a steady stream like water from a hose, but rather like lead from a machine-gun; it came off in separate chunks which Plank called quanta. This... carried tremendous philosophical consequences.

James Jeans
In 1925 Heisenberg made a new attempt, on entirely novel lines, to obtain an explanation of atomic spectra. Working in collaboration with Bohr, he had come to the conclusion that the imperfections of Bohr's theory had been a consequence of assuming too simple a model for the atom. For Bohr had not only assumed that the atom consisted of particles moving through space and time, but also that the particles inside atoms were of the same kind as the electrons outside atoms.

James Jeans
If we assume that the last breath of, say, Julius Caesar has by now become thoroughly scattered through the atmosphere, then the chances are that each of us inhales one molecule of it with every breath we take.

James Jeans
A theoretical investigation which Einstein published in 1917 provides a third conspicuous landmark. It connected up he two great landmarks already mentioned by showing that the disintegration of radioactive substances is governed by the same laws as the jumps of the kangaroo electrons in the theory of Bohr. In fact radioactive atoms were now seen merely to contain a special breed of kangaroos, much more energetic and ferocious than any that had hitherto been encountered.

James Jeans
The motion of the stars over our heads is as much an illusion as that of the cows, trees and churches that flash past the windows of our train.

James Jeans
Heisenberg now approached the problem from a new philosophical angle. He discarded all models, pictures and parables, and made a clear distinction between sure knowledge we gain from observation of nature and the conjectural knowledge we introduce when we use models, pictures and parables. Sure knowledge... can only be numerical, so that Heisenberg's results were inevitably mathematical in form, and could not disclose anything about the true nature of physical properties or entities.

James Jeans
When two hypotheses are possible, we provisionally choose that which our minds adjudge to be simpler, on the supposition that this is the more likely to lead in the direction of truth. It includes as a special case the principle of Occam's razor-entia non multiplicana praeter necessitatem.

James Jeans
Physics tries to discover the pattern of events which controls the phenomena we observe. But we can never know what this pattern means or how it originates; and even if some superior intelligence were to tell us, we should find the explanation unintelligible.

James Jeans
Precisely similar ideas are applicable to the molecules that form the air in a room.... The classical mechanics now predicts that the whole energy of motion will be changed into radiation [heat], so that the molecules will shortly be found lying at rest on the floor... In actual fact they continue to move with undiminished energy, forming a perpetual-motion machine in defiance of classical mechanics.... We have passed from one to another of three worlds... from the man-sized world to the world of the electron.

James Jeans
A second conspicuous landmark... is the enunciation of the fundamental law of radioactive disintegration by Rutherford and Soddy in 1903. This law was in no sense a consequence or development of Plank's theories; indeed fourteen years were to elapse before any connection was noticed between the two. The new law asserted that the atoms of radioactive substances broke up spontaneously, and not because of any particular conditions or special happenings. This seemed to involve an even more startling break with classical theory than the new laws of Plank; radioactive break-up appeared to be an effect without a cause, and suggested that the ultimate laws of nature were not even causal.

James Jeans
This fallacious result is not... a peculiarity of classical mechanics; it is given also by a very wide class of possible systems of mechanics. This being so, no minor modification of the classical mechanics can possibly put things right. Something far more drastic is needed; we are called upon to surrender either the continuity or the causality of classical mechanics, or else the possibility of representing changes by motions in time and space.

James Jeans
Bohr had... discovered that the frequencies corresponding to very large integers could be calculated accurately from the classical mechanics; they were simply the number of times that an ordinary electron would complete the circuit of its orbit in one second when it was at a very great distance from the nucleus of the atom to which it belonged. This could only mean that when an electron receded to a great distance from the nucleus of its atom, it not only assumed the properties of an ordinary electron, but also behaved as directed by the classical mechanics. Yet the classical mechanics failed completely for the calculation of frequencies corresponding to small orbits.

James Jeans
An extension of Plank's ideas, due to Prof. Niels Bohr of Copenhagen, went on to suggest that... the ultimate particles of matter would be seen to move not like railway trains running smoothly on tracks, but like kangaroos hopping about in a field.

James Jeans
Nebulae are the birthplaces of the stars, so that each nebula consists of stars born and stars not yet born.

James Jeans
The physical universe never has any choice — it must inevitably move along a single road to a predestined end. Contributions to a British Association Discussion on the Evolution of the Universe

James Jeans
The plain fact is that there are no conclusions. If we must state a conclusion, it would be that many of the former conclusions of the nineteenth-century science on philosophical questions are once again in the melting-pot.

James Jeans
Choose a point in space at random and the odds against it being occupied by a star are enormous.

James Jeans
Nature seems very conversant with the rules of pure mathematics, as our mathematicians have formulated them in their studies, out of their own inner consciousness and without drawing to any appreciable extent on their experience of the outer world.

James Jeans
Most sciences progress by pursuing nature into the realms of infinitely small, but for astronomy and cosmogony progress lies in the direction of the infinitely great, or, to be more exact, of the unthinkably great.

James Jeans
Physics tries to discover the pattern of events which controls the phenomena we observe. But we can never know what this pattern means or how it originates; and even if some superior intelligence were to tell us, we should find the explanation unintelligible.

James Jeans
Because we are human beings and not mere animals, we try to discover as much as we can about the world in which our lives are cast. We have seen that there is only one method of gaining such knowledge - the method of science, which consists in a direct questioning of nature by observation and experiment.

James Jeans
The physicist who can discard his human spectacles, and can see clearly in the strange new light which then assails his eyes, finds himself living in an unfamiliar world, which even his immediate predecessors would probably fail to recognize.

James Jeans
The motion of the stars over our heads is as much an illusion as that of the cows, trees and churches that flash past the windows of our train.

James Jeans