embarrassment: "Don't do that, Joggy. It's just the electronic interpreter. It senses our development and hears our questions and then it automats background and answers. But it's no more alive than an adolescer or a kinderobot. Got a billion microtapes, though."

The interpreter continued: "The skin-clad men we are viewing in Time in the Round seem to be a group of warriors of the sort who lived by pillage and rapine. The hooded figure is a most unusual find. We believe it to be that of a sorcerer who pretended to control the forces of nature and see into the future."

Joggy whispered: "How is it that we can't see the audience through the other side of the bubble? We can see through this side, all right."

"The bubble only shines light out," Hal told him hurriedly, to show he knew some things as well as the interpreter. "Nothing, not even light, can get into the bubble from outside. The audience on the other side of the bubble sees into it just as we do, only they're seeing the other way—for instance, they can't see the fire because the tree is in the way. And instead of seeing us beyond, they see more trees and sky."

Joggy nodded. "You mean that whatever way you look at the bubble, it's a kind of hole through time?"

"That's right." Hal cleared his throat and recited: "The bubble is the locus of an infinite number of one-way holes, all centering around two points in space-time, one now and one then. The bubble looks completely open, but if you tried to step inside, you'd be stopped—and so would an atom beam. It takes more energy than an atom beam just to maintain the bubble, let alone maneuver it."

"I see, I guess," Joggy whispered. "But if the hole works for light, why can't the people inside the bubble step out of it into our world?"

"Why—er—you see, Joggy—"

The interpreter took over. "The holes are one-way for light, but no-way for matter. If one of the individuals inside the bubble walked toward you, he would cross-section and disappear. But to the audience on the opposite side of the bubble, it would be obvious that he had walked away along the vista down which they are peering."

As if to provide an example, a figure suddenly materialized on their side of the bubble. The wolflike dogs bared their fangs. For an instant, there was only an eerie, distorted, rapidly growing silhouette, changing from blood-red to black as the 

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