To visualize a warped space, consider a simple analogy. A man walks away from a polished globe; his image recedes into the mirror-space, shortening and thinning as it goes, and thinning (in the direction of motion) faster than it shortens. Everything around him experiences a like effect. If he tries to discover this by a footrule it automatically shortens faster as he turns it into the horizontal position, so his purpose eludes him. The mirror-space is warped in the direction of the image’s motion. So is our own. For all bodies, as evidenced by the Fitzgerald contraction, shorten in the direction of motion. And just as the image can never penetrate the mirror-space a greater distance than half its radius, so probably time-space is curved in such a way that our universe, like the surface of a sphere, is finite in extent, but unbounded.
[1] The author here comes perilously close to ascribing to this “contraction” the sort of physical reality which it does not possess. See page 96.—Editor. [↑]
XII
FORCE VS. GEOMETRY
How Einstein Has Substituted the Second for the First in Connection With the Cause of Gravitation
BY SAUL DUSHMAN
GENERAL ELECTRIC LABORATORIES SCHENECTADY, N. Y.
The theory of relativity represents a most strikingly original conception of time and space, which was suggested by Einstein in order to correlate with all our past experience certain observations made in recent years. It is therefore extremely comprehensive in its scope; it demands from us a radical revision in our notions of time and space; it throws new light on the nature of mass and energy, and finally, it furnishes a totally new conception of the old problem of gravitation.
The starting point of the theory is the familiar observation that motion is always relative: that is, to define the motion of any object we must always use some point of reference. Thus we speak of the velocity of a train as 40 miles per hour with respect to the earth’s surface, but would find it impossible to determine its absolute speed, or motion in space, since we know of no star whose position can be spoken of as absolutely fixed. These and similar considerations have led to the conclusion, pointed out by Newton and others, that it is impossible by any mechanical experiments on the earth to measure its velocity in space.