“Not necessarily me same thing,” muttered Denison.

“I know. That’s why I put in the ‘or.’ But it might also be that we are neither particularly stupid nor particularly backward. It might be something as simple as the fact that they offer the harder target. If the strong nuclear interaction is stronger in the para-Universe, they’d be bound to have much smaller Suns and, very likely, much smaller planets. Their individual world would be harder to locate than ours would be.

“Or then again,” she went on, “suppose it’s the electromagnetic field they detect. The electromagnetic field of a planet is much larger than the planet itself and is much easier to locate. And that would mean that while they can detect the Earth, they can’t detect the Moon, which has no electromagnetic field to speak of. That’s why, perhaps, we’ve failed to set up a Pump Station on the Moon. And, if their small planets lack a significant electromagnetic field, we can’t locate them.”

Denison said, “It’s an attractive thought.”

“Next, consider the inter-Universal exchange in properties that serves to weaken their strong nuclear interaction, cooling their Suns, while strengthening ours, heating and exploding our Suns. What might that imply? Suppose they can collect energy one-way without our help but only at ruinously low efficiencies. Under ordinary circumstances that would therefore be utterly impractical. They would need us to help direct concentrated energy in their direction by supplying tungsten-186 to them and accepting plutonium-186 in return. But suppose our Galactic arm implodes into a quasar. That would produce an energy concentration in the neighborhood of the Solar system enormously greater than now exists and one that might persist for over a million years.

“Once that quasar forms, even a ruinously low efficiency becomes sufficient. It wouldn’t matter to them, therefore, whether we are destroyed or not. In fact, we might argue that it would be safer for them if we did explode. Until we do, we might end the Pump for any of a variety of reasons and they would be helpless to start it again. After the explosion, they are home free; no one could interfere.... And that’s why people who say, ‘If the Pump is dangerous, why don’t those terribly clever para-men stop it?’ don’t know what they’re talking about.”

“Did Neville give you that argument?”

“Yes, he did.”

“But the para-Sun would keep cooling down, wouldn’t it?”

“What does that matter?” said Selene, impatiently. “With the Pump, they wouldn’t be dependent on their Sun for anything.”

Denison took a deep breath. “You can’t possibly know this, Selene, but there was a rumor on Earth that Lament received a message from the para-men to the effect that the Pump was dangerous, but that they couldn’t stop it. No one took it seriously, of course, but suppose it’s true. Suppose Lamont did receive such a message. Might it be that some of the para-men were humanitarian enough to wish not to destroy a world with cooperating intelligences upon it, and were prevented by the opposition of an oh-so-practicai majority?”

Selene nodded. “I suppose that’s possible.... All this I knew, or rather, intuited, before you came on the scene. But then you said that nothing between one and the infinite made any sense. Remember?”

“Of course.”

“All right. The differences between our Universe and the para-Universe. He so obviously in the strong nuclear interaction that so far it’s all that’s been studied. But there is more than one interaction; there are four. In addition to the strong nuclear, there is the electromagnetic, the weak nuclear, and the gravitational, with intensity ratios of 130:1:10⁻¹⁰:10⁻⁴². But if four, why not an infinite number, with all the others too weak to be detectable or to influence our Universe in any way.”

Denison said, “If an interaction is too weak to be detectable or to exert influence in any way, then by any operational definition, it doesn’t exist.”

“In this Universe,” said Selene, with a snap. “Who knows what does or does not exist in the para-Universe? With an infinite number of possible interactions, each of which can vary infinitely in intensity compared to any one of them taken as standard, the number of different possible Universes that can exist is infinite.”

“Possibly the infinity of the continuum; aleph-one, rather than aleph-null.”

Selene frowned. “What does that mean?”

“It’s not important. Go on.”

Selene said, “Instead, then, of trying to work with the one para-Universe that has impinged itself on us and which may not suit our needs at all, why don’t we instead try to work out which Universe, out of all the infinite possibilities, best suits us, and is most easily located. Let us design a Universe, for after all whatever we design must exist, and search for it.”

Denison smiled. “Selene, I’ve thought of exactly the same thing. And while there’s no law that states I can’t be completely wrong, it’s very unlikely that anyone as brilliant as myself can be completely wrong when anyone as brilliant as yourself comes to exactly the same conclusion independently.... Do you know what?”

“What?” asked Selene.

“I’m beginning to like your damned Moon food. Or getting used to it, anyway. Let’s go back home and eat, and then we can start working out our plans.... And you know what else?”

“What?”

“As long as we’ll be working together, how about one kiss—as experimentalist to intuitionist.”

Selene considered. She said, “We’ve both of us kissed and been kissed a good many times, I suppose. How about doing it as man to woman?”

“I think I can manage that. But what do I do so as not to be clumsy about it? What are the Moon-rules for kissing?”

“Follow instinct,” said Selene, casually.

Carefully, Denison placed his arms behind his back and leaned toward Selene. Then, after a while, he placed his arms behind her back.

“And then I actually kissed him back,” said Selene, thoughtfully.

“Oh, did you?” said Barren Neville, harshly. “Well, that’s valor beyond the call of duty.”

“I don’t know. It wasn’t that bad. In fact,” (and she smiled) “he was rather touching about it. He was afraid he would be clumsy and began by putting his arms behind his back so that he wouldn’t crush me, I suppose.”

“Spare me the details.”

“Why, what the hell do you care?” she fired up, suddenly. “You’re Mister Platonic, aren’t you?”

“Do you want it differently? Now?”

“You needn’t perform to order.”

“But you had better. When do you expect to give us what we need?”

“As soon as I can,” she said, tonelessly.

“Without his knowing?”

“He’s interested only in energy.”

“And in saving the world,” mocked Neville. “And in being a hero. And in showing everybody. And in kissing you.”

“He admits to all that. What do you admit to?”

“Impatience,” said Neville, angrily. “Lots of impatience.”