He goes on to make another application of this principle, which is suggestive, though perhaps not intended to be treated too solemnly. The curvature of the universe, if it exists, is only in space, not in time. This leads him to say:[14] “By consideration of extension in time-like directions we obtain a confirmation of these views which is, I think, not entirely fantastic. We have said that an electron would not know how large it ought to be unless there existed independent lengths in space for it to measure itself against. Similarly it would not know how long it ought to exist unless there existed a length in time for it to measure itself against. But there is not radius of curvature in a time-like direction; so the electron does not know how long it ought to exist. Therefore it just goes on existing indefinitely.” But even if the size of an electron should ultimately prove, in this way, to be related to the size of the universe, that would leave a number of unexplained brute facts, notably the quantum itself, which has so far defied all attempts to make it seem anything but accidental. It is possible that the desire for rational explanation may be carried too far. This is suggested by some remarks, also by Eddington, [Pg 158] in his book, Space, Time and Gravitation (p. 200). The theory of relativity has shown that most of traditional dynamics, which was supposed to contain scientific laws, really consisted of conventions as to measurement, and was strictly analogous to the “great law” that there are always three feet to a yard. In particular, this applies to the conservation of energy. This makes it plausible to suppose that every apparent law of nature which strikes us as reasonable is not really a law of nature, but a concealed convention, plastered on to nature by our love of what we, in our arrogance, choose to consider rational. Eddington hints that a real law of nature is likely to stand out by the fact that it appears to us irrational, since in that case it is less likely that we have invented it to satisfy our intellectual taste. And from this point of view he inclines to the belief that the quantum-principle is the first real law of nature that has been discovered in physics. This raises a somewhat important question: Is the world “rational,” i.e., such as to conform to our intellectual habits? Or is it “irrational,” i.e., not such as we should have made it if we had been in the position of the Creator? I do not propose to suggest an answer to this question. [12] Eddington, op. cit., pp. 30-32. [13] Space, Time and Gravitation, p. 147. [14] The Mathematical Theory of Relativity, p. 155. [Pg 159] APPENDIX BOHR’S THEORY OF THE HYDROGEN SPECTRUM THE mathematics involved in this theory is so simple that only a very slight acquaintance with elementary dynamics is required in order to understand it.