James Jeans

The stability of a spherical Nebula

It is usual to take as the theoretical basis of the nebular hypothesis the established fact that the equilibrium of a rotating mass of liquid becomes unstable as soon as the rotation exceeds a certain critical value. The present paper attempts to examine whether it is justifiable to argue by analogy from the case of a liquid to that of a gaseous nebula, and it is found that, on the whole, this question must be answered in the negative. The paper is written with especial reference to a paper by Professor G. H. Darwin, in which it is shown that a swarm of meteorites may, with certain limitations, be treated as a mass of gas. The result obtained for a gaseous nebula can accordingly be at once transferred to the case of a meteoric swarm.

Problems of cosmogony and stellar dynamics

1. Introductory chapter 2. General dynamical principles 3. Ellipsoidal configurations of equilibrium 4. The gravitational potential of a distorted ellipsoid 5. Pear-shaped configurations of equilibrium 6. Motion when there are no stable configurations of equilibrium 7. The motion of compressible and non-homogeneous masses 8. The evolution of gaseous masses 9. The evolution of rotating nebulae 10. The evolution of star-clusters 11. The evolution of binary and multiple stars 12. The origin and evolution of the solar system.

The Physics of the Universe 1

THE ancients were for the most part content to regard the universe as a theatre which had been specially constructed for the drama of human life. Men, and even the gods that man had created in his own image, came, lived, and disappeared after strutting their tiny hour upon a stage to which the eternal hills and the unchanging heavens formed a permanent background. While some thought was given to the birth of the universe, and its creation or emergence from chaos, very few thought of it as living its life and passing from birth to death in the same way as a man or a tree passes from birth to death.

Contributions to a British Association Discussion on the Evolution of the Universe

WE are, of course, discussing only the physical universe. Here strict determinism reigns, because even if there is no determinism in the behaviour of individual atoms, there are so many atoms in even the tiniest bit of matter that we may take an average. The laws of probability provide something which is, for our present purpose, equivalent to a strict causal determinism.

EVOLUTION IN ASTRONOMY

ONE of the most important, and also one of the most fascinating, of the problems of astronomy as the tracing out of the steps by which the universe has evolved from primitive beginnings to its present complex form. But until recently it was like trying to piece together a jig-saw puzzle from which some of the more important pieces were missing. Happily the situation has changed rapidly of late ; more pieces of the puzzle have come to light, and one in particular—a better knowledge of the possible sources of stellar energy—is found to fit very convincingly into a big vacant gap, with the result that the whole picture begins to assume a logical and satisfying shape.

The Physical Condition of the Planets

AS the power of telescopes increases the astronomical horizon for ever recedes, drawing many astronomical workers with it, but leaving a few to continue their labours in the older fields. I propose here to discuss some recent work in the oldest field of all—the planets.

The Structure of the Universe

IN the last quarter of a century, our picture of the astronomical universe has changed almost beyond recognition, and yet we seem to be standing only on the seashore of the great ocean of knowledge.

The Mysterious Universe

“The Mysterious Universe” was the subject of the Rede Lecture delivered by Sir James Jeans at Cambridge on Nov. 5, 1930. The lecturer began with a characteristic figure to express the littleness of our world in space. A few stars were known, he said, which were hardly bigger than the earth, but the majority were so large that hundreds of thousands of earths could be packed inside each and leave room to spare; here and there we came upon a giant star large enough to contain millions of millions of earths. And the total number of stars in the universe was probably something like the total number of grains of sand on all the seashores of the world.

Beyond the Milky Way

OUR earth is one of a system of nine planets which, with millions of smaller bodies—asteroids, comets, and meteors circle round the sun; our sun is one of a system of millions of stars which circle about one another; this star-system is one of millions of star-systems—and here, so far as we know, the sequence ends abruptly. These star-systems are the biggest objects known to science; there is nothing beyond them except the great universe itself. They form the largest subdivision of the universe, and it is from this circumstance that they derive their special importance to science.

The Origin of the Solar System

The astronomer of to-day has at his disposal telescopes which range in aperture from his naked eye, of aperture about one-fifth of an inch, up to the giant Mount Wilson telescope of more than 100 inches. If we lived in the midst of a uniform infinite field of stars, or in a field which was uniform as far as our telescopes could reach, the numbers of stars visible in different telescopes would be proportional to the cubes of their apertures.