Albert Einstein was undoubtedly one of the great geniuses of our time. Between his twenty-first and thirty-eighth birthdays he completed a revolution in science, with profound repercussions at many levels. The two great breakthroughs were the Special Theory of Relativity (1905) and the General Theory of Relativity (1915). Special relativity deals with high speeds, general relativity with gravity.

Despite their extremely abstract character, Einstein’s theories were ultimately derived from experiments, and were successfully given practical applications, which confirmed their correctness time and again. Einstein set out from the famous Michelson-Morley experiment, “the greatest negative experiment of the history of science” (Bernal), which exposed an inner contradiction in 19th century physics. This experiment attempted to generalise the electromagnetic theory of light by demonstrating that the apparent velocity of light was dependent upon the rate at which the observer travelled through the supposedly fixed “ether”. In the end, no difference was found in the velocity of light, in whatever direction the observer was travelling.

JJ Thomson later showed that the velocity of electrons in high electrical fields was slower than predicted by the classical Newtonian physics. These contradictions in 19th century physics were resolved by the special theory of relativity. The old physics was unable to explain the phenomenon of radioactivity. Einstein explained this as the release of a tiny part of the enormous amount of energy trapped in “inert” matter.

In 1905, Einstein developed his special theory of relativity in his spare time, while working as a clerk in a Swiss patent office. Setting out from the discoveries of the new quantum mechanics, he showed that light travels through space in a quantum form (as bundles of energy). This was clearly in contradiction to the previously accepted theory of light as a wave. In effect, Einstein revived the old corpuscular theory of light, but in an entirely different way. Here light was shown as a new kind of particle, with a contradictory character, simultaneously displaying the properties of a particle and a wave. This startling theory made possible the retention of all the great discoveries of 19th century optics, including spectroscopes, as well as Maxwell’s equation. But it killed stone dead the old idea that light requires a special vehicle, the “ether”, to travel through space.

Special relativity starts from the assumption that the speed of light in a vacuum will always be measured at the same constant value, irrespective of the speed of the light source relative to the observer. From this it is deduced that the speed of light represents the limiting speed for anything in the universe. In addition, special relativity states that energy and mass are in reality equivalents. This is a striking confirmation of the fundamental philosophical postulate of dialectical materialism – the inseparable character of matter and energy the idea that motion (“energy”) is the mode of existence of matter.

Einstein’s discovery of the law of equivalence of mass and energy is expressed in his famous equation E = mc2, which expresses the colossal energies locked up in the atom. This is the source of all the concentrated energy in the universe. The symbol e represents energy (in ergs), m stands for mass (in grams) and c is the speed of light (in centimetres per second). The actual value of c2 is 900 billion billion. That is to say, the conversion of one gram of energy locked up in matter will produce a staggering 900 billion billion ergs. To give a concrete example of what this means, the energy contained in a single gram of matter is equivalent to the energy produced by burning 2,000 tons of petrol.

Mass and energy are not just “interchangeable”, as dollars are interchangeable with euros; they are one and the same substance, which Einstein characterised as “mass-energy”. This idea goes far deeper and is more precise than the old mechanical concept whereby, for example, friction is transformed into heat. Here, matter is just a particular form of “frozen” energy, while every other form of energy (including light), has mass associated with it. For this reason, it is quite wrong to say that matter “disappears” when it is changed into energy.

Einstein’s law displaced the old law of the conservation of mass, worked out by Lavoisier, which says that matter, understood as mass, can neither be created nor destroyed. In fact, every chemical reaction that releases energy converts a small amount of mass into energy. This could not be measured in the kind of chemical reaction known to the 19th century, such as the burning of coal. But nuclear reaction releases sufficient energy to reveal a measurable loss of mass. All matter, even when at “rest”, contains staggering amounts of energy. However, as this cannot be observed, it was not understood until Einstein explained it.

Far from overthrowing materialism, Einstein’s theory establishes it on a firmer basis. In place of the old mechanical law of the “conservation of mass”, we have the far more scientific and more general laws of the conservation of mass-energy, which expresses the first law of thermodynamics in a universal and unassailable form. The mass does not “disappear” at all, but is converted into energy. The total amount of mass-energy remains the same. Not a single particle of matter can be created or destroyed. The second idea is the special limiting character of the speed of light: the assertion that no particle can travel faster than the speed of light, since as it approaches this critical velocity, its mass approaches infinity, so that it becomes harder and harder to go faster. These ideas seem abstract and difficult to grasp. They challenge the assumptions of “sound common sense”. The relationship between “common sense” and science was summed up by the Soviet scientist Professor Lev D. Landau in the following lines:

“So-called common sense represents nothing but a simple generalisation of the notions and habits that have grown up in our daily life. It is a definite level of understanding reflecting a particular level of experiment.” And he adds: “Science is not afraid of clashes with so-called common sense. It is only afraid of disagreement between existing ideas and new experimental facts and if such disagreement occurs science relentlessly smashes the ideas it has previously built up and raises our knowledge to a higher level.”[35]

How can a moving object increase its mass? Such a notion contradicts our everyday experience. A spinning top does not visibly gain in mass while revolving. In point of fact, it does, but the increase is so infinitesimal that it may be discounted for all practical purposes. The effects of special relativity cannot be observed on the level of everyday phenomena. However, under extreme conditions, for example, at very high speeds approaching the speed of light, relativistic effects begin to come into play.

Einstein predicted that the mass of a moving object would increase at very high speeds. This law can be ignored when dealing with normal speeds. Nevertheless, subatomic particles move at speeds of nearly 10,000 miles per second or more, and at such speeds as these relativistic effects appear. The discoveries of quantum mechanics demonstrated the correctness of the special theory of relativity, not only qualitatively, but quantitatively. An electron gains in mass as it moves at 9/10th the speed of light; moreover, the gain in mass is 3 1/6th times, precisely as Einstein’s theory predicted. Since then, special relativity has been tested many times, and so far it has always given correct results. Electrons emerge from a powerful particle accelerator about 40,000 times heavier than when they started, the extra mass representing energy of motion.

At far higher velocities the increase in mass becomes noticeable. And modern physics deals precisely with extremely high velocities, such as the speed of subatomic particles, which approach the speed of light. Here the classical laws of mechanics, which adequately describe everyday phenomena, cannot be applied. To common sense the mass of an object never changes. Therefore a spinning-top has the same weight as a still one. In this way a law was invented which states that mass is constant irrespective of speed.

Later, this law was shown to be incorrect. It was found that mass increases with velocity. Yet, since the increase only becomes appreciable near the speed of light, we take it as constant. The correct law would be: “If an object moves with a speed of less than 100 miles per second, the mass is consistent to within one part in a million.” For everyday purposes, we can assume that mass is constant irrespective of speed. But for high speeds, this is false, and the higher the speed, the falser is the assertion. Like thinking based on formal logic, it is accepted as valid for practical purposes. Feynman points out:

… Philosophically, we are completely wrong with the approximate law. Our entire picture of the world has to be altered even though the mass changes only by a little bit. This is a very peculiar thing about the philosophy, or the ideas, behind the laws. Even a very small effect sometimes requires profound changes in our ideas.[36]

The predictions of special relativity have been shown to correspond to the observed facts. Scientists discovered by experiment that gamma rays could produce atomic particles, transforming the energy of light into matter. They also found that the minimum energy required to create a particle depended on its rest energy, as predicted by Einstein. In point of fact not one, but two particles were produced: a particle and its opposite, the “anti-particle”. In the gamma-ray experiment, we get an electron and an anti-electron (positron). The reverse process also takes place: when a positron meets an electron, they annihilate each other, producing gamma rays. Thus, energy is transformed into matter, and matter into energy. Einstein’s discovery provided the basis for a far more profound understanding of the workings of the universe. It provided an explanation of the source of the sun’s energy, which had been a mystery throughout the ages. The immense storehouse of energy turned out to be – matter itself. The awesome power of the energy locked up in matter was revealed to the world in August 1945 at Hiroshima and Nagasaki. All this is contained in the deceptively simple formula E = mc2.

  1. Landau, L. and Rumer, G. What is Relativity? pp. 36 and 37.

  2. Feynman, R. op. cit., Vol. 1, 1-2.