Read The Gods Themselves for Free Online Page B

What was the catch to the Electron Pump?
    Lamont knew enough of the history of para-theory to know that the matter of "a catch" had not gone unexplored. When it was first announced that the basic over-all change in the Electron Pump was the Pumping of electrons from the Universe to the para-Universe, there had not been wanting those who said immediately, "But what will happen when all the electrons have been Pumped?"
    This was easily answered. At the largest reasonable rate of Pumping, the electron supply would last for at least a trillion trillion years—and the entire Universe, together, presumably, with the para-Universe, wouldn't last a tiny fraction of that time.
    The next objection was more sophisticated. There was no possibility of Pumping all the electrons across. As the electrons were Pumped, the para-Universe would gain a net negative charge, and the Universe a net positive charge. With each year, as this difference in charge grew, it would become more difficult to Pump further electrons against the force of the opposed charge-difference. It was, of course neutral atoms that were actually Pumped but the distortion of the orbital electrons in the process created an effective charge which increased immensely with the radioactive changes that followed.
    If the charge-concentration remained at the points of Pumping, the effect on the orbit-distorted atoms being Pumped would stop the entire process almost at once, but of course, there was diffusion to take into account. The charge-concentration diffused outward over the Earth, and the effect on the Pumping process had been calculated with that in mind.
    The increased positive charge of the Earth generally forced the positively charged Solar wind to avoid the planet at a greater distance, and the magnetosphere was enlarged. Thanks to the work of McFarland (the real originator of the Great Insight according to Lament) it could be shown that a definite equilibrium point was reached as the Solar wind swept away more and more of the accumulating positive particles that were repelled from Earth's surface and driven higher into the exosphere. With each increase in Pumping intensity; with each additional Pumping Station constructed, the net positive charge on Earth increased slightly, and the magnetosphere expanded by a few miles. The change, however, was minor, and the positive charge was, in the end, swept away by the Solar wind and spread through the outer reaches of the Solar system.
    Even so—even allowing for the most rapid possible diffusion of the charge—the time would come when the local charge-difference between Universe and para-Universe at the points of Pumping would grow large enough to end the process, and that would be a small fraction of the time it would take really to use up all the electrons; roughly, a trillion-trillionth of the time.
    But that still meant that Pumping would remain possible for a trillion years. Only a single trillion years, but that was enough; it would suffice. A trillion years was far longer than man would last, or the Solar system either. And if man somehow did last that long (or some creature that was man's successor and supplanter) then no doubt something would be devised to correct the situation. A great deal could be done in a trillion years.
    Lamont had to agree to that.
    But then he thought of something else, another line of thought that he well remembered Hallam himself had dealt with in one of the articles he had written for popular consumption. With some distaste, he dug out the article. It was important to see what Hallam had said before he carried the matter further.
    The article said, in part, "Because of the ever-present gravitational force, we have come to associate the phrase 'downhill' with the kind of inevitable change we can use to produce energy of the sort we can change into useful work. It is the water running downhill that, in past centuries, turned wheels which in turn powered machinery such as pumps and