Home > Work > The Mysterious Universe
1 " The universe looks more and more like a great thought rather than a great machine. "
― James Hopwood Jeans , The Mysterious Universe
2 " The Universe begins to look more like a great thought than like a great machine. Mind no longer appears to be an accidental intruder into the realm of matter... we ought rather hail it as the creator and governor of the realm of matter. "
3 " concrete example will explain this more clearly. It is known that the atoms of radium, and of other radio-active substances, disintegrate into atoms of lead and helium with the mere passage of time, so that a mass of radium continually diminishes in amount, being replaced by lead and helium. The law which governs the rate of diminution is very remarkable. The amount of radium decreases in precisely the same way as a population would if there were no births, and a uniform death-rate which was the same for every individual, regardless of his age. Or again, it decreases in the same way as the numbers of a battalion of soldiers who are exposed to absolutely random undirected fire. In brief, old age appears to mean nothing to the individual radium atom; it does not die because it has lived its life, but rather because in some way fate knocks at the door. "
4 " While philosophers were still debating whether a machine could be constructed to reproduce the thoughts of Newton, the emotions of Bach or the inspiration of Michelangelo, the average man of science was rapidly becoming convinced that no machine could be constructed to reproduce the light of a candle or the fall of an apple. "
5 " We now know that a large part of this radiation, generally described as “cosmic radiation,” has its origin in outer space. It falls on the earth in large quantities, and its powers of destruction are immense. Every second it breaks up about twenty atoms in every cubic inch of our atmosphere, and millions of atoms in each of our bodies. It has been suggested that this radiation, falling on germplasm, may produce the spasmodic biological variations which the modern theory of evolution demands; it may have been cosmic radiation that turned monkeys into men. "
6 " Since every body is a collection of electrically charged particles, the theoretical investigation already mentioned shews that the mass of every moving body must vary with its speed of motion. The mass of a moving body may be regarded as made up of two parts—a fixed part which the body retains even when at rest, known as its “rest-mass,” and a variable part which depends on the speed of its motion. Both observation and theory have shewn that this second part is exactly proportional to the energy of motion of the body; the masses of two electrons, or any two other bodies similar to one another, differ to just the extent to which their energies differ. "
7 " The possible abolition of determinism and the law of causation from physics are, however, comparatively recent developments in the history of the quantum theory. The primary object of the theory was to explain certain phenomena of radiation, and to understand the question at issue we must retrace our steps as far back as Newton and the seventeenth century. The most obvious fact about a ray of light, at any rate to superficial observation, is its tendency to travel in a straight line; everyone is familiar with the straight edges of a sunbeam in a dusty room. As a rapidly moving particle of matter also tends to travel in a straight line, the early scientists, rather naturally, thought of light as a stream of particles thrown out from a luminous source, like shot from a gun. Newton adopted this view, and added precision to it in his “corpuscular theory of light.” Yet it is a matter of common observation that a ray of light does not always travel in a straight line. It can be abruptly turned by reflection, such as occurs when it falls on the surface of a mirror. Or its path may be bent by refraction, such as occurs when it enters water or any liquid medium; it is refraction that makes our oar look broken at the point where it enters the water, and makes the river look shallower than it proves to be when we step into it. "
8 " The “quantum theory” came into being as an effort to cure the wave theory of light of these defects. It has been completely successful. It has shewn that Newton was not wholly wrong in regarding light as corpuscular, for it has proved that a beam of light may be regarded as broken up into discrete units, called “light-quanta” or “photons,” with almost the definiteness with which a shower of rain may be broken up into drops of water, a shower of bullets into separate pieces of lead, or a gas into separate molecules. At the same time, the light does not lose its undulatory character. Each little parcel of light has a definite quantity, of the nature of a length, associated with it. We call this its “wave-length,” because when the light in question is passed through a prism, it behaves exactly as waves of this particular length of wave would do. Light of long wavelength is made up of small parcels, and vice-versa, the amount of energy in each parcel being inversely proportional to this wave-length, so that we can always calculate the energy of a photon from its wave-length, and vice-versa. "
9 " In this way it appears that the seventeenth century, which regarded light as mere particles, and the nineteenth century, which regarded it as mere waves, were both wrong—or, if we prefer, both right. Light, and indeed radiation of all kinds, is both particles and waves at the same time. In Professor Compton’s experiments, X-radiation falls on single electrons and behaves like a shower of discrete particles; in the experiments of Laue, Bragg and others, exactly similar radiation falls on a solid crystal and behaves in all respects like a succession of waves. And it is the same throughout nature; the same radiation can simulate both particles and waves at the same time. Now it behaves like particles, now like waves; no general principle yet known can tell us what behaviour it will choose in any particular instance. Clearly we can only preserve our belief in the uniformity of nature by making the supposition that particles and waves are in essence the same thing. And this brings us to the second, and far more exciting, half of our story. The first half, which has just been told, is that radiation can appear now as waves and now as particles; the second is that electrons and protons, the fundamental units of which all matter is composed (p. 62), can also appear now as particles, and now as waves. A duality has recently been discovered in the nature of electrons and protons similar to that already known to exist in the nature of radiation; these also appear to be particles and waves at the same time. "
10 " وبذلك لا يكون أهم ما نريد أن نقرره هو ان لدى علم اليوم أحكامًا يصدرها، بل يجب أن يكون ما نقرره أن من واجب العلم أن يمتنع عن إصدار الأحكام _ذلك أن نهر المعرفة كثيرًا ما التوي على نفسه "
