Hinton - The Fourth Dimension.pdf

CHAPTER VII
THE EVIDENCES FOR A FOURTH DIMENSION
THE method necessarily to be employed in the search for
the evidences of a fourth dimension, consists primarily in
the formation of the conceptions of four-dimensional
shapes and motions. When we are in possession of these
it is possible to call in the aid of observation, without
them we may have been all our lives in the familiar
presence of a four-dimensional phenomenon without ever
recognising its nature.
To take one of the conceptions we have already formed,
the turning of a real thing into its mirror image would be
an occurrence which it would be hard to explain, except on
the assumption of a fourth dimension.
We know of no such turning. But there exist a multitude
of forms which show a certain relation to a plane,
a relation of symmetry, which indicates more than an accidental
juxtaposition of parts. In organic life the universal
type is of right- and left-handed symmetry, there is a plane
on each side of which the parts correspond. Now we have
seen that in four dimensions a plane takes the place of a
line in three dimensions. In our space, rotation about an
axis is the type of rotation, and the origin of bodies symmetrical
about a line as the earth is symmetrical about an
axis can easily be explained. But where there is symmetry
about a plane no simple physical motion, such as we
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