The Idea of the Theory of Relativity

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

In the work under consideration the author sets himself the aim of clarifying the content of the theory of relativity and presenting it as thoroughly as possible, insofar as this can be done without making use of mathematical analysis.

Indeed, the book is written in an extremely elementary manner, with a complete absence of formulae, apart from the notes on p. 73 (the formula of the Pythagorean theorem) and p. 91 (the formula of living force).

Despite the elementary character of the exposition, the author leads the reader into the depth of the ideas of the theory of relativity. Apparently, he is an ardent supporter of the theory and not infrequently illustrates his engaging 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 deviations of atomic weights from whole numbers in connection with Prout’s hypothesis, the author remarks: “why these ratios were not obtained with sufficient exactness as whole numbers has until now been entirely 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 an 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 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, owing to which the electron’s orbit takes on such a form as though the line of apsides had a certain 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 obtained to the electron theory.

The electron theory and the theory of relativity, as in a whole series of other cases (the experiments of Michelson, Fizeau, etc.), so also 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, Professor Thirring’s book, in our opinion, deserves the most serious attention.

M. Shuleikin.