James Jeans

"The complete closed world consists of three parts-substratum, phenomenal world, and observer. By our experiments we drag up activities from the substratum into the phenomenal world of space and time, but there is no clear line of demarcation between subject and object, and by performing observations on the world, we alter it, much as a fisherman dragging up fish from the depths of the seas disturbs the waters and also damages the fish."

"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."

"Physics and philosophy are at most a few thousand years old, but probably have lives of thousands of millions of years stretching away in front of them. They are only just beginning to get under way..."

"It can hardly be a matter for surprise that our race has not succeeded in solving any large part of its most difficult problems in the first millionth part of its existence. Perhaps life would be a duller affair if it had. For to many it is not knowledge but the quest for knowledge that gives the greater interest to thought - to travel hopefully is better than to arrive."

"Minkowski... supposed that this fourth dimension of time was not detached from and independent of the three dimensions of space. He introduced a new four-dimensional space to which ordinary space contributed three dimensions, and time one; we may call it 'space-time'. ...The succession of positions which a particle occupied in ordinary space at a succession of instants of time would be represented by a line in space-time; this he called the 'world-line' of the particle. ...Newton's absolute space and absolute time fell out of science, and they carried much with them in their fall. First to go was the concept of simultaneity. ...It now became necessary to find a way of treating gravitation which should not involve simultaneity. Einstein found through the medium of his 'Principle of Equivalence'."

"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..."

"To be historically accurate, Hubble failed to acknowledge two of his pivotal sources for those ideas which now bear his name: Reynolds and Jeans. As agreed by Allan Sandage, the graphical representation of the Hubble tuning fork [style diagram of the Hubble sequence] must be attributed to Sir James Jeans - a scientist who adored music, and who wrote the famous book Science and Music on that theme. In the Lowell Observatory archives, Hubble revealed to Slipher that he had "been trying to construct a classification of non-galactic nebulae analogous to Jeans' evolution sequence, but from purely observational material.""

"What philosophical conclusions should we draw from the abstract style of the superstring theory? We might conclude, as Sir James Jeans concluded long ago, that the Great Architect of the Universe now begins to appear as a Pure Mathematician, and that if we work hard enough at mathematics we shall be able to read his mind. Or we might conclude that our pursuit of abstractions is leading us far away from those parts of the creation which are most interesting from a human point of view. It is too early yet to come to conclusions."

"He pointed out that amongst the hindrances to a joint discussion by philosophers and physicists are differences of idiom, if not language. He stated that, whether one understands the meaning of a sentence in Newton or not, one knows at least the meaning of the words, whereas philosophy has no agreed terminology. He was right in pointing out that various old problems in philosophy owed their existence to imperfections of language... he argued that the philosopher thinks and speaks in the subjective, the scientist in objective, terms."

"He then embarked on a criticism of causality, as expressed by Kant or Bertrand Russel. He says that there is no scientific justification for supposing that the happenings of the world can be divided into detached events, and 'strung in pairs, like a row of dominoes, each being the cause of the event which follows and at the same time the effect of that which precedes.' He warned... at the same time against the other extreme... it was not necessary for all previous events in the history of the world to be considered as separate causes. For one thing, the effects of the earlier of them were already taken into account in the later..."

"Two particular cross-sections, he claimed, were of special interest: first, a cross-section near the beginning of time (the creation of the world); secondly, a cross-section only slightly differing from the present. In the latter case, all those parts of the universe not in our immediate vicinity could be disregarded..."

"Jeans was not a man of many friends, partly because of his temperamental shyness and reticence and partly because of his intolerance of what he deemed to be second-rate. With his own quick perception he lacked the patience which would have enabled him to understand and appreciate a slower-moving mind and consequently he missed those intimacies which he fundamentally desired."

"Therefore the observer may well look to Jeans' theory for the thread of physical significance that shall vitalize a system of classification of non-galactic nebulae. In the scheme presently to be proposed, a conscious attempt was made to ignore the theory and to arrange the data purely from an observational point of view. The analogy however was so suggestive that at several points... there was no hesitation in accepting the one favored by Jeans' theory of spirals."