Pearce took a final puff of his cigarette crushed it out in the grass, and continued. "Nela explained how it was possible to travel in time, but in the sort of terms a kid would understand. Even what I've figured out up to now isn't specific enough to be worth detailing, except to say that what we consider space and time are merely illusions of sense perception. They are really one stationary system or complex--stationary, yet dynamic and changing within itself--and under certain conditions one can travel through this system, from future to past, or the other way around, like through a museum--the biggest museum that can possibly be imagined. "Nela's machine operated on energy principles that won't be known for a great many years yet, and it will be even longer before those principles are put into application. She was, in effect, making a round-trip from one part of the museum to another--a trip that took her across two thousand years of what we call time, or across a couple of hundred light years of what we call space. It's one and the same thing. Actually, she was following a sort of huge orbit, and was, so to speak, stopping off along the route. A trip between one point and another can be made only once, because even that one trip brings changes which affect the whole system, or complex. One point, it seems, is always shifted so that it lies outside of any orbit which can be plotted from the other. "Nela told me about the kind of world she came from, too, and it sounded--and still sounds--like a perfect place. There was, so she said, practically no government, practically no laws, restrictions, or penalties. In two thousand years enough had been learned about the mind to make these unnecessary. Men at last were truly equal. There was no longer any need to work for a living. Machines of all sorts attended to every task and human requirement. Earth was one huge garden--and there was plenty of room for everyone. Men had reached the stars and had found new homes almost beyond number. "An ideal picture--but there was a catch to it. The machines on which Nela's people depended were breaking down, and it seemed nobody knew even how to begin repairing them. The men of her time could take suns apart and put them back together again, but the machines baffled them in much the same way that our atomic scientists would be baffled when it came to repairing a suit of Medieval armor. The answer to the problem was to obtain the help of persons who understood the construction and operation of the machines at least as well as Medieval armorers understood their steel suits. And that answer--in both cases--lay back in time." * * * * *