this of the ether to the winds. In that case we would at least have a
real material cause for the phenomena with which we deal. While the
current theory of the ether has so many inconsistencies, and attempts to
bridge over so many real chasms in our thinking that it seems truly
astonishing to see it taught so long. By the theory of the ether the
problems are not solved, they are merely postponed or evaded; for while
solving one difficulty it creates a multitude of its own. How then are
we better off than before without any such theory?

Being at liberty to invent any sort of qualities for their ether,
scientists have tried to imagine such a substance as they think they
need. The ether must be a kind of matter; but unlike any matter that we
know of it cannot have weight, or else it would gravitate together here
and there, thus becoming more abundant in some places than in others;
whereas the _need_ is for a material absolutely uniform throughout
space, even throughout the interiors of solid bodies, such as the earth
and the bodies upon the earth.

Another reason for supposing the ether to be a _plenum_, filling
absolutely all space, is that it must be perfectly frictionless; and for
this reason it cannot be composed of particles with spaces between them.
It must be frictionless, for otherwise the planets would be retarded in
their motions through space. The earth, for instance, is moving along
its orbit at the rate of eighteen miles a second; and yet the ether does
not pile up in front of it, nor is it made rarer in the wake of the
earth. Moreover, during the thousands of years during which astronomers
have been making observations absolutely no retardation has been
detected in the motions of the earth or of any of the heavenly bodies,
even to the smallest fraction of a second.