Newton wrote his Principia - to bring the unchanging laws ruling nature
into the light of human consciousness, and to give them conceptual
expression in the language of mathematical formulae. Since, however,
science was obliged to restrict itself to what could be observed with a
single, colour-blind eye, physics has taken as its main object of
research the spatio-temporal relationships, and their changes, between
discrete, ideally conceived, point-like particles. Accordingly, the
mathematically formulable laws holding sway in nature came to mean the
laws according to which the smallest particles in the material
foundation of the world change their position with regard to each
other. A science of this kind could logically maintain that, if ever it
succeeded in defining both the position and the state of motion, in one
single moment, of the totality of particles composing the universe, it
would have discovered the law on which universal existence depends.
This necessarily rested on the presupposition that it really was the
ultimate particles of the physical world which were under observation.
In the search for these, guided chiefly by the study of electricity,
the physicists tracked down ever smaller and smaller units; and along
this path scientific research has arrived at the following peculiar
situation.

To observe any object in the sense world we need an appropriate medium
of observation. For ordinary things, light provides this. In the sense
in which light is understood to-day, this is possible because the
spatial extension of the single light impulses, their so-called
wavelength, is immeasurably smaller than the average magnitude of all
microscopically visible objects. This ensures that they can be observed
clearly by the human eye. Much smaller objects, however, will require a
correspondingly shorter wave-length in the medium of observation. Now
shorter wave-lengths than those of visible light have been found in