“I dare say it will, more or less, but we have other things in mind. You might as well know now. Energy is not the only conserved phenomenon that becomes limitless once universes are crossed.”
Denison interrupted. “There are a number of conservation laws. We realize that.”
“I’m glad you do,” said Neville, turning a hostile glare in his direction. “They include those of linear momentum and angular momentum. As long as any object responds to the gravitational field in which it is immersed, and to that only, it is in free fall and can retain its mass. In order to move in any other way than free fall, it must accelerate in a non-gravitational way and for that to happen, part of itself must undergo an opposite change.”
“As in a rocketship,” said Denison, “which must eject mass in one direction in order that the rest might accelerate in the opposite direction.”
“I’m sure you understand, Dr. Denison,” said Neville, “but I explain for the Commissioner’s sake. The loss of mass can be minimized if its velocity is increased enormously, since momentum is equal to mass multiplied by velocity. Nevertheless, however great the velocity, some mass must be thrown away. If the mass which must be accelerated is enormous in the first place, then the mass which must be discarded is also enormous. If the Moon, for instance—”
“The Moon!” said Gottstein, explosively.
“Yes, the Moon,” said Neville, calmly. “If the Moon were to be driven out of its orbit and sent out of the Solar system, the conservation of momentum would make it a colossal undertaking, and probably a thoroughly impractical one. If, however, momentum could be transferred to the cosmeg in another Universe, the Moon could accelerate at any convenient rate without loss of mass at all. It would be like poling a barge upstream, to give you a picture I obtained from some Earth-book I once read.”
“But why? I mean why should you want to move the Moon?”
“I should think that would be obvious. Why do we need the suffocating presence of the Earth? We have the energy we need; we have a comfortable world through which we have room to expand for the next few centuries, at least. Why not go our own way? In any case, we will. I have come to tell you that you cannot stop us and to urge you to make no attempt to interfere. We shall transfer momentum and we shall pull out. We of the Moon know precisely how to go about building cosmeg pump stations. We will use what energy we need for ourselves and produce excess in order to neutralize the changes your own power stations are producing.”
Denison said, sardonically, “It sounds kind of you to produce excess for our sake, but it isn’t for our sake, of course. If our Electron Pumps explode the Sun, that will happen long before you can move out of even the inner Solar system and you will vaporize wherever you are.”
“Perhaps,” said Neville, “but in any case we will produce an excess, so that won’t happen.”
“But you can’t do that,” said Gottstein, excitedly. “You can’t move out. If you get out too far, the cosmeg pump will no longer neutralize the Electron Pump, eh, Denison?”
Denison shrugged. “Once they are as far off as Saturn, more or less, there may be trouble, if I may trust a mental calculation I have just made. It will, however, be many years before they recede to such a distance and by that time, we will surely have constructed space stations in what was once the orbit of the Moon and place cosmeg pumps on them. Actually, we don’t need the Moon. It can leave—except that it won’t.”
Neville smiled briefly. “What makes you think we won’t? We can’t be stopped. There is no way Earthmen can impose their will on us.”
“You won’t leave, because there’s no sense to doing so. Why drag the entire Moon away? To build up respectable accelerations will take years where the Moon-mass is concerned. You’ll creep. Build starships instead; miles-long ships that are cosmeg-powered and have independent ecologies. With a cosmeg momentum-drive, you can then do wonders. If it takes twenty years to build the ships, they will nevertheless accelerate at a rate that will enable them to overtake the Moon’s place within a year even if the Moon starts accelerating today. The ships will be able to change course in a tiny fraction of the time the