Hans Thirring. Die Idee der Relativitätstheorie. pp. II + 170. Verlag von J. Springer. Berlin. 1921.

In the work under review the author sets himself the aim of clarifying the content of the theory of relativity and presenting it as thoroughly as possible without making any use of mathematical analysis.

Indeed, the book is written in an extremely elementary manner, with a complete absence of formulas, apart from the notes on p. 73 (the formula for the law of Pythagoras) and p. 91 (the formula of vis viva).

Despite the elementary character of the exposition, the author leads the reader into the depths of the ideas of the theory of relativity. Apparently he is an ardent supporter of the theory and not infrequently illustrates his captivating exposition with the views of critics, immediately answering them.

However, one cannot agree with all the author’s conclusions, which he adduces as confirmation of the theory. Thus, for example, on p. 93, speaking of the deviation of atomic weights from whole numbers in connection with Prout’s hypothesis, the author remarks: “why these ratios have not hitherto been obtained with sufficient accuracy as whole numbers was completely incomprehensible,” and further supposes that the indicated deviations can be explained on the basis of the equivalence of mass and energy. We

We think that the answer to the author’s perplexities can also be found in Aston’s works.

On p. 83 the author says that in recent years the theory of relativity has achieved a striking triumph, when the German physicist Sommerfeld in Munich succeeded in interpreting and explaining the so-called fine structure of the spectral lines of hydrogen and helium. Sommerfeld interpreted and explained the fine structure of the H and He lines by taking into account the dependence of the electron’s mass on velocity, whereby the electron’s orbit takes on the form it would have if the line of apsides had a definite angular velocity. It is true that Sommerfeld himself, in his book, says that he proceeds from the theory of relativity; nevertheless, Lorentz’s theory gives exactly the same result. Starting from it, one can write the same equations with the same variable mass of the electron and, with equal success, attribute the triumph thus obtained to the electron theory.

The electron theory and the theory of relativity, both in a whole series of other cases (the experiments of Michelson, Fizeau, etc.) and in the present one, give an identical result, which with equal success may serve as confirmation of both the one and the other.

Among books popularizing the ideas of the theory of relativity, Prof. Turing’s book, in our opinion, deserves the most careful attention.

M. Shuleikin.