Theory and practice in the latest science are still allied, otherwise neither of them would prosper as it does; but each has taken a leap in its own direction.  The distance between them has become greater than the naked eye can measure, and each of them in itself has become unintelligible.  We roll and fly at dizzy speeds, and hear at incredible distances; at the same time we imagine and calculate to incredible depths.  The technique of science, like that of industry, has become a thing in itself; the one veils its object, which is nature, as the other defeats its purpose, which is happiness.  Science often seems to be less the study of things than the study of science.  It is now more scholastic than philosophy ever was.  We are invited to conceive organisms within organisms, so minute, so free, and so dynamic, that the heart of matter seems to explode into an endless discharge of fireworks, or a mathematical nightmare realised in a thousand places at once, and become the substance of the world.  What is even more remarkable—­for the notion of infinite organisation has been familiar to the learned at least since the time of Leibniz—­the theatre of science is transformed no less than the actors and the play.  The upright walls of space, the steady tread of time, begin to fail us; they bend now so obligingly to our perspectives that we no longer seem to travel through them, but to carry them with us, shooting them out or weaving them about us according to some native fatality, which is left unexplained.  We seem to have reverted in some sense from Copernicus to Ptolemy:  except that the centre is now occupied, not by the solid earth, but by any geometrical point chosen for the origin of calculation.  Time, too, is not measured by the sun or stars, but by any “clock”—­that is, by any recurrent rhythm taken as a standard of comparison.  It would seem that the existence and energy of each chosen centre, as well as its career and encounters, hang on the collateral existence of other centres of force, among which it must wend its way:  yet the only witness to their presence, and the only known property of their substance, is their “radio-activity”, or the physical light which they shed.  Light, in its physical being, is accordingly the measure of all things in this new philosophy:  and if we ask ourselves why this element should have been preferred, the answer is not far to seek.  Light is the only medium through which very remote or very minute particles of matter can be revealed to science.  Whatever the nature of things may be intrinsically, science must accordingly express the universe in terms of light.