This practically exhausts the list of accepted and accredited
indications of hyper-dimensionality in our physical environment. But
if the collective human consciousness is moving into the fourth
dimension, such indications are bound to multiply out of all measure.
It should be remembered that in Franklin's day electricity was
manifest only in the friction of surfaces and in the thunderbolt.
To-day all physical phenomena, in their last analysis, are considered
to be electrical. The world is not different, but perception has
evolved, and is evolving.
There is another field, in which some of our ablest minds are
searching for evidences of the curvature of space, the field of
astronomy and astro-physics. But into this the layman hesitates to
enter because the experts themselves have found no common ground of
understanding. The ether of space is a battlefield strewn with dead
and dying hypotheses; gravitation, like multiplication, is vexation;
the very nature of time, form and movement is under vivid discussion,
in connection with what is known as the Theory of Relativity.
Notwithstanding these counter-currents of speculation, which should
make the wise man speak smilingly of his wisdom, this summary
remains incomplete without a reference to the pressure of higher
space upon those adventurous minds that essay to deal with the
profound problems of the greater universe, and a statement of the
reasons for their feeling this pressure. These reasons are well
suggested by Professor B.G. Harrison, in his _Popular Astronomy_. He
says: "With the idea of a universe of finite dimensions there is the
obvious difficulty of the beyond. The truth is that a universe of
finite proportions is equally difficult to realize as one of
infinite extent. Perhaps the nearest analogy to infinity that we can
understand lies in our conception of a closed curve. It seems easier
to imagine the endless movement of a sphere in a circular path than
the case of one travelling in a straight line. Possibly this analogy
may apply in some way to fourth-dimensional space, but the manner of
its application is certainly not easy to understand. If we would
imagine that all co-ordinates of time and space were curved, and
eventually return to the same point, it might bring the ultimate
comprehension one degree nearer."