mathematician and physicist could read without too great an expenditure of time and energy, and with few exceptions, only those which could be found in a rather meager scientific library.
In spite of the fact that the relativity theory rests on a firm basis of experiment, and upon logical deductions from such experiments, and notwithstanding also that this theory is remarkably self-consistent, and is in fact the only theory which at present seems to agree with all the facts, nevertheless it perhaps goes without saying that it has not been universally accepted. Some objections to the theory have been advanced by men of good standing in the world of physics, and a fair and impartial presentation of the subject would of necessity include a brief statement of these objections. I shall not attempt to answer these objections. Those who have adopted the relativity theory seem in no wise concerned with the arguments put forward against it. In fact, if there is one thing which impresses the reader of the articles on relativity, it is the calm assurance of the advocates of this theory that they are right. Naturally the theory and its consequences have been criticized by a host of persons of small scientific training, but it will not be necessary to mention these arguments. They are the sort of objections which no doubt Galileo had to meet and answer in his famous controversy with the Inquisition. Fortunately for the cause of science, however, the authority back of these arguments is not what it was in Galileo's time, for it is not at all certain just how many of those who have enthusiastically embraced relativity would go to prison in defence of the dogma that one man's now is another man's past, or would allow themselves to be led to the stake rather than deny the doctrine that the length of a yardstick depends upon whether one happens to be measuring north and south with it, or east and west.
In general it may be said that the chief objection to the relativity theory is that it is too artificial. The end and aim of the science of physics is to describe the phenomena which occur in nature, in the simplest manner which is consistent with completeness, and the objectors to the relativity theory urge that this theory and especially its consequences, are not simple and intelligible to the average intellect. Consider, for example, the theory which explains the behavior of a gas by means of solid elastic spheres. This theory may be clumsy, but it is readily understood, rests upon an analogy with things which can be seen and felt, in other words is built up of elements essentially simple. But the objectors to the relativity theory say that it is based on ideas of time and space which are not now and which never can be intelligible to the human mind. They claim that the universe has a real existence quite apart from what any one thinks about it, and that this real universe, through the human senses, impresses upon the normal mind certain simple notions which can not be changed at will. Minkowski's
