"Science progressed on _well-established lines in the nineteenth century, but the twentieth will have to record the shattering of a large part of that foundation." This was the anticipation of Dr. J. H. Jeans in expounding the theory of relativity, at the Royal Institution, London.
He said that though many philosophic inquirers must have been prepared to recognize the subjective character of time and space, Einstein's revolutionary theory had to a great extent taken the world of science by surprise, and had gained the more adherents through confirmation obtained from experiment and fulfilled astronomical prediction. Time and space were postulated as indivisible components: of one continuum, and of changing relativity according to the angle of "'world-lines" of observation. This had a direct bearing on questions of velocity in space. It was estimated, the lecturer said, that Nova Persei was so far away that light from its blazing outburst must have. taken 350 years to reach the earth; but an observer on the star would calculate that the event was coincident with the battle of Waterloo, and other distance measurements based on the old ideas of time, dynamics, and gravitation would give similarly discordant results. 'They assumed that light travelled in a straight' line, but a straight line was not always the shortest distance be. tween two points. For instance, owing to the curvature of the earth, the shortest route from Madras to Panama was shown to be not a straight line on the map, but a curve. An ingenious demonstration of the shifting conditions of relativity in combined time and space helped the audience to understand that light, as the lecturer said, could not be timed as a police. man timed a motor-car with a stop watch.
Tseory or Revativiry.
Neither physics nor gravitation could establish a distinction between time and. space, but there was no justification for saying that they' were indistinguishable. Space and time, according to the theory of relativity, were subjective con ceptions; the product of the two was the reality. But in the final simplification of the theory time and space were both eliminated, no ether was needed to give a framework for the measurement of distance, and there remained only a system of "world-lines." The lecturer offered no definition of this term, which is rather elusive, but may be understood to stand for a psychological conception of the connexion between particles, observers, and events. These lines, Dr. Jeans said, intersected at certain points, and it was on those points that the events of!
Text read from the printed page and cleaned; old type leaves the occasional error.