make matter clearer. "They still have a great deal of empty space, but not as much as we do. Particles need a certain amount of empty space and if all they have is that much, then other particles can't squeeze in. If particles are forced in, there is pain. That's why the Hard Ones don't like to be touched 1?y us. We Soft Ones have more space between the particles than are actually needed, so other particles can fit in."
Dua didn't look at all certain about that. Odeen hastened onward. "In the other Universe, the rules are different. The nuclear-force isn't as strong as in ours. That means the particles need more room."
"Why?"
Odeen shook his head, "Because - because - the particles spread out their wave-forms more. I can't explain better than that. With a weaker nuclear-force, the particles need more room and two pieces of matter can't melt together as easily as they can in our Universe."
"Can we see the other Universe?"
"Oh, no. That isn't possible. We can deduce its nature from its basic laws. The Hard Ones can do a great many things, though. We can send material across, and get material from them. We can study their material, you see. And we can set up the Positron Pump. You know about that, don't you?"
"Well, you've told me we get energy out of it. I didn't know there was a different Universe involved . . . What is' the other Universe like? Do they have stars and worlds the way we do?"
"That's an excellent question, Dua." Odeen was enjoying his role as teacher more intensely than usual now that he had official encouragement to speak. (Earlier he always had the feeling that there was a kind of sneaking perversion in trying to explain things to an Emotional.)
He said, "We can't see the other Universe, but we can calculate what it must be like from its laws. You see, what makes the stars, shine is the gradual combination of simple particle-combinations into more complicated ones. We call it nuclear fusion."
"Do they have that in the other Universe?"
"Yes, but because the nuclear-force is weaker, fusion is much slower. This means that the stars must be much, much bigger in the other Universe otherwise not enough fusion would take place to make them shine. Stars of the other Universe that were no bigger than our Sun would be cold and dead. On the other hand, if stars in our Universe were bigger than they are, the amount of fusion would be so great it would blow them up. That means that in our Universe there must be thousands of times as many small stars as there are larger stars in theirs - "
"We only have seven - " began Dua. Then she said, "I forgot."
Odeen smiled indulgently. It was so easy to forget the uncounted stars that could not be seen except by special instruments. "That's all right. You don't mind my boring you with all this."
"You're not boring me," said Dua. "I love it. It even makes food taste so good." And she wavered between the electrodes with a kind of luxurious tremor.
Odeen, who had never before heard Dua say anything complimentary about food, was greatly heartened. He said, "Of course, our Universe doesn't last as long as theirs. Fusion goes so fast that all the particles are combined after a million lifetimes."
"But there are so many other stars."
"Ah, but you see they're all going at once. The whole Universe is dying down. In the other Universe, with so many fewer and larger stars, the fusion goes so slowly that the stars last thousands and millions of times as long as ours. It's hard to compare because it may be that time goes at different rates in the two Universes." He added, with some reluctance, "I don't understand that part myself. That's part of the Estwald Theory and I haven't got to that very much so far."
"Did Estwald work out all of this?"
"A great deal of it."
Dua said, "It's wonderful that we're getting the food from the other Universe then. I mean, it doesn't matter if our Sun dies out, then. We can get all the food we want from the other Universe."
"That's right."
"But does nothing bad happen? I have the - the feeling that something bad happens."
"Well," said Odeen. "We transfer matter back and forth to make the Positron Pump and that means the Universes mix together a little. Our nuclear-force gets a tiny bit weaker, so fusion in