space-field. Remember, mass is a measure of energy. Two centuries
ago a scientist of our world proposed the idea that energy could be
measured by mass, and proceeded to prove that the relationship was the
now firmly intrenched formula E=Mc^{2}.

"The sun is giving off energy. It is giving off mass, then, in the form
of light photons. The field of the sun's gravity must be constantly
decreasing as its mass decreases. It is a collapsing field. It is true,
the sun's gravitational field does decrease, by a minute amount, despite
the fact that our sun loses a thousand million tons of matter every four
minutes. The percentage change is minute, but the energy released
is--immeasurable.

"But, I am going to invent a new power unit, Afthen. I will call it the
'sol,' the power of a sun. One sol is the rating of our sun. And I will
measure the energy I use in terms of sun-powers, not horsepower. That
may tell you of its magnitude!"

"But," Zezdon Afthen asked, "while you men of Earth work on this
problem, what is there for us? We have no problems, save the problem of
the fate of our world, still fifty thousand years of your time in the
future. It is terrible to wait, wait, wait and think of what may be
happening in that other time. Is there nothing we can do to help? I know
our hopeless ignorance of your science. Stel Felso Theu can scarcely
understand the thoughts you use, and I can scarcely understand his
explanations! I cannot help you there, with your calculations, but is
there nothing I can do?"

"There is, Ortolian, decidedly. We badly need your help, and as Stel
Felso Theu cannot aid us here as much as he can by working with you, I
will ask him to do so. I want your knowledge of psycho-mechanical
devices to help us. Will you make a machine controlled by mental
impulses? I want to see such a system and know how it is done that I may
control machines by such a system."

"Gladly. It will take time, for I am not the expert worker that you are,
and I must make many pieces of apparatus, but I will do what I can,"
exclaimed Zezdon Afthen eagerly.

So, while Arcot and his group continued their work of determining the
constants of the space-energy field, the others were working on the
mental control apparatus.

Chapter XV

ALL-POWERFUL GODS

Again there was a period of intense labor, while the ship drifted
through time, following Earth in its mad careening about the sun, and
the sun as it rushed headlong through