At one place, Einstein himself observes: "With the discovery of the theory of relativity of simultaneity, space and time were merged in a single continuum in the same way as the three dimensions of space had been before. Physical space was thus increased to a four-dimensional space which also included the dimension of time. The four-dimensional space of the special theory of the relativity is just as rigid and absolute as Newton's space."[1] Thus, according to Dr. Einstein, "Space and time are forms of intuition, which can no more be divorced from consciousness than can our concepts of colour, shape, or size. Space has no objective reality except as an order or arrangement of the objects we perceive in it, and time has no independent existence apart from the order of events by which we measure it."[2]
The philosophical implication of the theory of relativity in Einstein's view is: It must not be thought, however, that the spacetime continuum is simply a mathematical construction. The world is a space-time continuum; all reality exists both in space and in time, and the two are indivisible. All measurements of time are really measurements in space, and conversely measurements in space depend on measurements of time."[3] Einstein has considered the space-time continuum to represent the objective reality. His view is: "But except on the reels of one's own consciousness, the universe, the objective world of reality, does not happen - it simply exists. It can be encompassed in its entire majesty only by a cosmic intellect. But it can also be represented symbolically, by a mathematician, as a four-dimensional space time continuum."[4]
We find that some scientists such as Sir James Jeans, Eddington, Weyl, Mach and Minkowski have made identical interpretations. All of them regard that when we divide the continuum into three dimensions of space and one of time, space and time separately become subjective realities but that when space and time are welded together to form a four dimensional continuum, through it we can get the knowledge of the objective universe. Sir James Jeans expresses this fact thus: "Yet, just because we can exhibit all nature within this framework (i.e. the four-dimensional continuum), it must correspond to some sort of an objective reality. But its division into space and time is not objective; it is merely subjective."[5] He further asserts that the main substance of the theory of relativity is that nature knows nothing about the division of continuum into space and time.[6]
As we have already quoted, Minkowski considers separate space and time as mere shadows and the continuum as the objective reality. Hermann Weyl puts the thought in following words: "In the realm of physics, it is perhaps only the theory of relativity which has made it quite clear that the two essences, space and time, entering into our intuition have no place in the world constructed by mathematical physics."[7]
He further writes, "The great advance in our knowledge described in this chapter consists in recognising that the scene of action of reality is not a three-dimensional Euclidean space but rather a four-dimensional world, in which space and time are linked together indissolubly. However deep the chasm may be that separates the intuitive nature of space from that of time in our experience, nothing of this qualitative difference enters into the objective world which physics endeavours to crystallise out of direct experience. It is a four-dimensional continuum, which is neither "time" nor "space."[8] Thus, these scientists conceive space as a mere frame of reference, whose existence is just as real and just as unreal, as that of the equator, or the north pole, or the meridian of Greenwich.