"The light that comes from the bubble is an isotope. Like atoms of one element, photons of a single frequency also have isotopes. It's more than a matter of polarization. One of these isotopes of light tends to leak futureward through holes in space-time. Most of the light goes down the vistas visible to the other side of the audience. But one isotope is diverted through the walls of the bubble into the Time Theater. Perhaps, because of the intense darkness of the theater, you haven't realized how dimly lit the scene is. That's because we're getting only a single isotope of the original light. Incidentally, no isotopes have been discovered that leak pastward, though attempts are being made to synthesize them."
"Oh, explanations!" murmured one of the newly arrived girls. "The cubs are always angling for them. Apple-polishers!"
"I like this show," a familiar voice announced serenely. "They cut anybody yet with those choppers?"
Hal looked down beside him. "Butch! How did you manage to get in?"
"I don't see any blood. Where's the bodies?"
"But how did you get in—Butcher?"
The Butcher replied airily: "A red-headed man talked to me and said it certainly was sad for a future dictator not to be able to enjoy scenes of carnage in his youth, so I told him I'd been inside the Time Theater and just come out to get a drink of water and go to the eliminator, but then my sprained ankle had got worse—I kind of tried to get up and fell down again—so he picked me up and carried me right through the usher."
"Butcher, that wasn't honest," Hal said a little worriedly. "You tricked him into thinking you were older and his brain waves blanketed yours, going through the usher. I really have heard it's dangerous for you under-fives to be in here."
"The way those cubs beg for babying and get it!" one of the girls commented. "Talk about sex favoritism!" She and her companion withdrew to the far end of the cubicle.