She knocked loud.
Mr. Pryor opened the door in shirtsleeves and an apron, with safety glasses pushed up on his forehead, and if he was surprised to see her he hid it beautifully. "Mrs. Carter," he said. "Come in. Find a stool. Don't touch anything that's humming."
In the far corner, beside a tall frame of PVC pipe with a measuring tape running up one side, stood Emmett and a small, fierce-looking girl with a long braid and safety goggles. The girl was holding a basketball over her head at the top of the frame. Emmett was crouched at the bottom with a tablet propped on a stack of textbooks, pointing its camera at the floor.
"Three, two, one," Emmett said.
The girl dropped the ball. It hit the floor with a flat, unhappy *thwack* and came back up not very far.
"Fifty-one," Emmett said, reading the screen. "Fifty-one centimeters. That's the one that was in the freezer."
"*That's* the dead one," the girl said with satisfaction.
Then Emmett looked up and saw his mother on a stool by the door.
His face did not do anything dramatic. It closed a little, the way a hand closes, and then, after a second, it opened a little, less than it had closed. "Hi," he said.
"Hi," said Yolanda. "Don't stop. Please. I'm just going to sit."
He stared at her for a moment more. Then he turned back to the frame. "Priya," he said, "do the room-temperature one."
So she sat. She sat for an hour and forty minutes on a stool with a wobbly leg, with her purse on her knees and her phone in the purse, and she watched her son work.
She learned that the project had begun, not in December, but in January a year ago, at a Saturday game when the heat had been turned down in the Fulton Heights gym to save money on a weekend, and Dante had missed nine shots in a row and come home and thrown his bag on the floor and said, "The ball's dead. The ball was dead the whole game. I'm telling you." And everyone had laughed at him, Yolanda included, she remembered laughing, and Emmett had gone into the garage that night and found the bin of Dante's old basketballs, eleven of them, going back to the little rubber one from first grade, and had started wondering if it was true.
It was true. That was the shape of it. Emmett and Priya had dropped those eleven balls from a fixed height at different temperatures and different pressures, hundreds of times, in Mama Ruth's chilly basement and Priya's warm kitchen and a borrowed walk-in cooler at the restaurant where Priya's uncle worked. They had measured the bounce. They had measured how long it took a ball to recover its bounce after being carried from a cold car into a warm gym. They had graphed it. They had found the temperature at which a regulation ball lost enough rebound that a shooter would feel it in his wrist, even if he couldn't name it, and then Emmett had gone to the school's maintenance office and politely asked for the gym thermostat logs for the past two winters, and the maintenance man, astonished, had printed them out.
"On cold Saturdays it's fifty-eight degrees on the floor at tip-off," Emmett said, not to her, to Priya, who already knew, but Yolanda understood he was saying it to the room. "It takes the ball about forty minutes to get back to normal. The first half of every cold Saturday game, the ball is basically a different ball."
"So Dante was right," Yolanda said.