The Time Traveller (that is what I will call him) was explaining a difficult idea to us. His grey eyes were shining, and his usually pale face was red with excitement. The fire was burning brightly. We sat in his comfortable chairs after dinner and listened lazily. We thought it was just another of his clever games with ideas.
“Follow me carefully,” he said. “You know that a cube has length, width and height. But can a cube really exist if it lasts for no time at all? Not even for a second?”
“I don’t follow you,” said Filby, a red-haired man who loved to argue.
“Every real thing has four dimensions,” the Time Traveller went on. “Length, width, height, and time. Time is the fourth dimension. There is no difference between time and the other three, except one: our minds move along it, from the beginning of our lives to the end.”
“That,” said a very young man, who was trying to light his cigar over the lamp, “that is very clear.”
“But if time is just another dimension,” said the Medical Man, “why can’t we move about in time, as we move about in space?”
The Time Traveller smiled. “Are you sure that we move freely in space? We can go left and right, forwards and backwards. But up and down is harder. Before balloons, people could only jump a little.”
“But you cannot move in time at all,” said the Psychologist. “You cannot leave the present moment.”
“My dear sir, that is just where you are wrong. When I remember something very clearly, I go back to that moment for a second. Of course, we cannot stay there. But a man can rise against gravity in a balloon. So why should he not hope that one day he can stop his journey through time, or make it faster, or even turn round and travel the other way?”
“It’s against reason,” said Filby.
“What reason?” said the Time Traveller.
“You can prove that black is white by argument,” said Filby, “but you will never convince me.”
“Perhaps not,” said the Time Traveller. “But long ago I had an idea for a machine—”
“To travel through time!” cried the very young man.
“—that can travel in any direction through space and time, as the driver wishes.”
Filby just laughed.
“But I have tested it,” said the Time Traveller.
“Think of the future!” said the very young man. “You could put all your money in the bank, let it grow, and hurry on ahead!”
“Let’s see your experiment,” said the Psychologist, “though it’s all nonsense, you know.”
The Time Traveller smiled at us all. Then, with his hands deep in his pockets, he walked slowly out of the room, and we heard his slippers going down the long corridor to his laboratory.
“I wonder what he’s got,” said the Psychologist.
“Some trick or other,” said the Medical Man. Filby began to tell us about a magician he had once seen, but before he could finish, the Time Traveller came back.