"But you would be well acquainted with the practical aspects of Earth's present energy supply, would you not?"
"Yes. That I will admit to. Is there something you want to know about it?"
"There is something that piques my curiosity, madam."
"Curiosity? In a robot?"
Daneel bowed his head. "If a robot is complex enough, he can be aware of something within himself that seeks information. This is analogous to what I have observed to be called 'curiosity' in human beings and I take the liberty of using the same word in connection with my own feelings."
"Fair enough. What are you curious about, R. Daneel? May I call you that?"
"Yes, madam. I understand that Earth's energy supply is drawn from solar power stations in geostationary orbit in Earth's equatorial plane."
"You understand correctly."
"But are these power stations the sole energy supply of this planet?"
"No. They are the primary - but not the sole - energy supply. There is considerable use of energy from Earth's internal heat, from winds, waves, tides, flowing water, and so on. We have quite a complex mix and each variety has its advantages. Solar energy is the mainstay, however."
"You make no mention of nuclear energy, madam. Are there no uses for microfusion?"
Quintana raised her eyebrows. "Is that what you're curious about, R. Daneel?"
"Yes, madam. What is the reason for the absence of nuclear power sources on Earth?"
"They are not absent, R. Daneel. On a small scale, one comes across it. Our robots - we have many in the countryside, you know - are micro fusionized. Are you, by the way?"
Daneel said, "Yes, madam."
"Then, too," she went on, "there are microfusionized machines here and there, but the total is quite trifling."
"Is it not true, Madam Quintana, that microfusion energy sources are sensitive to the action of nuclear intensifiers?"
"They certainly are. Yes, of course. The microfusion power source will blow up and I suppose that comes under the heading of being sensitive."
"Then it isn't possible for someone, using a nuclear intensifier, to seriously cripple some crucial portion of Earth's energy supply?"
Quintana laughed. "No, of course not. In the first place, I don't see anyone dragging a nuclear intensifier about from place to place. They weigh tons and I don't think they can be maneuvered through and along the streets and corridors of a City. Certainly, it would be noticed if anyone tried. And then, even if a nuclear intensifier were brought into play, all it could do would be to destroy a few robots and a few machines before the thing would be discovered and stopped. There is no chance at all - zero - of our being hurt in that way. Is that the reassurance you wanted, R. Daneel?"
It was almost a dismissal.
Daneel said, "There are just one or two small points I would like clarified, Madam Quintana. Why is there no large microfusion source on Earth? The Spacer worlds all depend on microfusion and so do all the Settler worlds. Microfusion is portable, versatile, and cheap - and doesn't require the enormous effort of maintenance, repair, and replacement that space structures do."
"And, as you said, R. Daneel, they are sensitive to nuclear intensifiers."
"And, as you said, Madam Quintana, nuclear intensifiers are too large and bulky to be of much use."
Quintana smiled broadly and nodded. "You are very intelligent, R. Daneel," she said. "It never occurred to me that I would ever sit at a table and carry on a discussion like this with a robot. Your Auroran roboticists are very clever too clever - for I fear to carry on this discussion. I'd have to worry about you taking my place in the government. You know, we do have a legend about a robot named Stephen Byerly taking a high post in the government."
"That must be merely fiction, Madam Quintana," said Daneel gravely. "There are no robots in governmental posts on any of the Spacer worlds. We are merely - robots."
"I'm relieved to hear that and will therefore go on. The matter of differences in power sources has its roots in history. At the time that hyperspatial travel was developed, we had microfusion, so that people leaving Earth took microfusion power sources with them. It was necessary on spaceships and on planets, too, in the generations during which they were being adapted for human occupation. It takes many years to build an adequate complex of solar power stations - and rather than undertake such a task, the emigrants remained with microfusion. So it was with the Spacer's in their time, and so it is now with the Settlers.
"On Earth, however, microfusion and solar power in space were developed at roughly the same time and both were used more and more. Finally, we could make our choice and use either microfusion or solar power or, of course, both. And we chose solar power."
Daneel said, "That seems strange to me, Madam Quintana. Why not both?"
"Actually, that's not a very difficult question to answer, R. Daneel. Earth, in prehyperspatial days, had had experience with a primitive form of nuclear energy, and it wasn't a happy experience. When the time came to choose between solar power and microfusion, Earthpeople saw microfusion as a form of nuclear energy and turned away from it. Other worlds, which did not have our direct experience with the primitive form of nuclear energy, had no reason to turn away from microfusion."
"May I ask what this primitive form of nuclear energy to which you refer might be, madam?"
"Uranium fission," said Quintana. "It's completely different from microfusion. Fission involves the splitting of massive nuclei, such as those of uranium. Microfusion involves the joining of light nuclei, such as those of hydrogen. They're both forms of nuclear energy, however."