"Call them ghosts, the word is as good as any other." His voice grew calmer; he went on earnestly, "I want you to understand me—it's necessary—and yet I must not be too technical with you. Let me ask you this—you'll see in a moment that none of this is irrelevant. How many dimensions has a point?"
At my puzzled look he smiled. "I'd better not question you, Rob, but you won't find me hard to understand. A point—an infinitesimal point in space—has no dimension. It has only location. That's clear, isn't it? A line has one dimension—length. A plane surface has length and breadth; a cube, length, breadth and thickness. The world of the cube, Rob, is the world we think we live in—the world of three dimensions. You've heard of that intangible something they call the fourth dimension? We think it does not concern us—but it does. We ourselves have four dimensions. We are the world of the fourth dimension. But the fourth is not so readily understood as the other three."
He paused for an instant, then added, "The fourth dimension is time, Rob. Not a new conception to scientists—think a moment—how would you define time?"
"Time," I said, "Well, I read somewhere that time is what keeps everything from happening at once."
He did not smile. "Quite so. It is something in the universe of our consciousness along which we progress in measured rate from birth to death—from the beginning to the end.
"We are living in a four-dimensional world—a world of length, breadth, thickness and time. The first three, to our human perception, have always been linked together. Time—I do not know why—seems to our minds something essentially different. Yet it is not. Our universe is a blending of all four.
"Let me give you an example. That book there on the table—it exists because it has length, breadth and thickness. But Rob, it also has duration. It is matter, persisting both in space and in time. You see how the element time is involved? I'll go further. We know that two material bodies cannot occupy the same space at the same time. With three of the dimensions only—that is, if theoretically we remove the identical time-factor—they do not conflict. You're confused, Rob?"
"I'm not quite sure what you're aiming at," I said.
"You'll understand in a moment. Matter, as we know it, is merely a question of vibration. It is, isn't it?"