ps, in a dim, primitive
fashion, he showed the way, but I--_I_, van Manderpootz--am the first to
seize time, drag it into my laboratory, and perform an experiment on
it."

"Indeed? And what sort of experiment?"

"What experiment, other than simple measurement, is it possible to
perform?" he snapped.

"Why--I don't know. To travel in it?"

"Exactly."

"Like these time-machines that are so popular in the current magazines?
To go into the future or the past?"

"Bah! Many bahs! The future or the past--pfui! It needs no van
Manderpootz to see the fallacy in that. Einstein showed us that much."

"How? It's conceivable, isn't it?"

"Conceivable? And you, Dixon Wells, studied under van Manderpootz!" He
grew red with emotion, then grimly calm. "Listen to me. You know how
time varies with the speed of a system--Einstein's relativity."

"Yes."

"Very well. Now suppose then that the great engineer Dixon Wells invents
a machine capable of traveling very fast, enormously fast, nine-tenths
as fast as light. Do you follow? Good. You then fuel this miracle ship
for a little jaunt of a half million miles, which, since mass (and with
it inertia) increases according to the Einstein formula with increasing
speed, takes all the fuel in the world. But you solve that. You use
atomic energy. Then, since at nine-tenths light-speed, your ship weighs
about as much as the sun, you disintegrate North America to give you
sufficient motive power. You start off at that speed, a hundred and
sixty-eight thousand miles per second, and you travel for two hundred
and four thousand miles. The acceleration has now crushed you to death,
but you have penetrated the future." He paused, grinning sardonically.
"Haven't you?"

"Yes."

"And how far?"

I hesitated.

"Use your Einstein formula!" he screeched. "How far? I'll tell you. _One
second!_" He grinned triumphantly. "That's how possible it is to travel
into the future. And as for the past--in the first place, you'd have to
exceed light-speed, which immediately entails the use of more than an
infinite number of horsepowers. We'll assume that the great engineer
Dixon Wells solves that little problem too, even though the energy
out-put of the whole universe is not an infinite number of horsepowers.
Then he applies this more than infinite power to travel at two hundred
and four thousand miles per second for _ten_ seconds. He has then
penetrated the past. How far?"

Again I hesitated.

"I'll