I. Introduction
The Time Traveller (it will be convenient to call him that) was explaining a deep and difficult subject to us. His grey eyes shone and twinkled. His face, which was usually pale, was red and lively. The fire burnt brightly. The electric lamps sat in silver holders shaped like lilies. Their soft light caught the bubbles that flashed and disappeared in our glasses. Our chairs were his own patent design. They seemed to hug us and stroke us, instead of just letting us sit on them. There was that luxurious feeling after dinner, when thoughts run freely and do not need to be exact. He explained it to us in this way, and he marked each point with his thin forefinger. We sat lazily and admired his seriousness about this new paradox (as we thought it). We also admired his endless flow of ideas.
“You must follow me carefully. I shall have to argue against one or two ideas that almost everyone accepts. For example, the geometry that they taught you at school is based on a mistake.”
“Isn’t that rather a big thing to expect us to begin with?” said Filby. He was a man with red hair who loved to argue.
“I do not mean to ask you to accept anything without good reason. You will soon agree to as much as I need from you. Of course you know that a mathematical line, a line with a thickness of nil, has no real existence. They taught you that? A mathematical plane does not really exist either. These things exist only as ideas in the mind.”
“That is all right,” said the Psychologist.
“A cube has only length, breadth and thickness. So a cube cannot have a real existence either.”
“There I object,” said Filby. “Of course a solid body can exist. All real things—”
“So most people think. But wait a moment. Can an instantaneous cube exist?”
“Don’t follow you,” said Filby.
“Can a cube really exist if it does not last for any time at all?”
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Filby became thoughtful. “Clearly,” the Time Traveller went on, “any real body must stretch in four directions. It must have Length, Breadth, Thickness, and—Duration. But we tend to forget this fact, because of a natural weakness of the flesh. I will explain that to you in a moment. There are really four dimensions. Three of them we call the three planes of Space, and the fourth is Time. However, we tend to make an unreal difference between the first three dimensions and the last one. This is because our consciousness moves along Time in one direction, stopping and starting. It moves from the beginning to the end of our lives.”
“That,” said a very young man, who was trying hard to relight his cigar over the lamp, “that . . . very clear indeed.”
“Now, it is very strange that so many people overlook this,” the Time Traveller continued, a little more cheerfully. “Really, this is what the Fourth Dimension means. But some people who talk about the Fourth Dimension do not know that they mean it. It is only another way of looking at Time. Time is no different from the three dimensions of Space, except that our consciousness moves along it. But some foolish people have got hold of the wrong side of that idea. You have all heard what they say about this Fourth Dimension?”
“I have not,” said the Provincial Mayor.
“It is simply this. Our mathematicians say that Space has three dimensions. We can call them Length, Breadth and Thickness. Space can always be described by three planes, and each plane is at right angles to the others. But some philosophical people have been asking why there are three dimensions in particular. Why not another direction, at right angles to the other three? They have even tried to build a Four-Dimensional geometry. Professor Simon Newcomb was explaining this to the New York Mathematical Society only a month or so ago. You know how we can draw a three-dimensional solid on a flat surface. And a flat surface has only two dimensions. In the same way, they think that models of three dimensions could show a thing of four. They would only need to master the perspective of it. See?”
“I think so,” said the Provincial Mayor quietly. He frowned and seemed to go deep into his own thoughts. His lips moved like the lips of someone who repeats magic words. “Yes, I think I see it now,” he said after some time. His face brightened, but only for a moment.
“Well, I do not mind telling you that I have been working on this geometry of Four Dimensions for some time. Some of my results are curious. For example, here is a picture of a man at eight years old. Here is another at fifteen, another at seventeen, another at twenty-three, and so on. All these are clearly sections, as it were, of his Four-Dimensioned being. They are Three-Dimensional pictures of it. And his Four-Dimensioned being is a fixed thing that can never change.”
The Time Traveller paused, so that we could take this in. “Scientific people,” he went on, “know very well that Time is only a kind of Space. Here is a popular scientific diagram, a weather record. This line that I follow with my finger shows the movement of the barometer. Yesterday it was this high. Last night it fell. Then this morning it rose again, and went gently upward to here. Surely the mercury did not trace this line in any of the usual dimensions of Space? But it certainly traced a line. So we must decide that the line was along the Time-Dimension.”
The Medical Man was staring hard at a coal in the fire. “But if Time is only a fourth dimension of Space,” he said, “why is it seen as something different? And why has it always been seen that way? And why can’t we move about in Time, as we move about in the other dimensions of Space?”