She had seen an isomorphism: a reframing of the problem into a completely different mathematical space, an older space where the answer was already known. She had seen it, and she had dismissed it because it had looked too simple. She had walked the long way around for twelve minutes trying to prove herself with the harder path.
She did not need the harder path.
She opened her eyes, picked up the chalk, and walked to the next empty blackboard.
What was Whitney about to do that no one in the room had seen coming?
Whitney walked back to the first blackboard and picked up an eraser. She did not look at Walsh; she started erasing: the first board went blank, then the second, then the third, then the fourth. Every line she had written for the last twelve minutes was gone. The chalkboards were dark and clean; the air filled with chalk dust.
The audience exhaled in confusion. Some leaned forward; some pulled out their phones again. A faculty member in the third row whispered to his neighbor, "What is she doing?" His neighbor did not answer.
Walsh stood up. "What are you doing?"
Whitney did not answer. She finished erasing, chalk dust hanging in the air around her, and set the eraser down on the tray. She walked to the lectern, to the digital stopwatch Walsh had placed there at the beginning. She picked it up, held it in her hand, and turned to face Walsh.
"Professor, you said thirty seconds at the start of this demonstration." A pause. "May I have it back?"
Walsh blinked. The question was so unexpected that he answered before he could think: "Yes, fine. Take the thirty seconds. It changes nothing."
He sat down.
Whitney walked to the front of the auditorium, set the stopwatch down on the lectern, turned it so the audience could see the red digits, and reset it to thirty. She walked back to the leftmost blackboard, now empty, and picked up a fresh piece of chalk. She turned her back to the board. For five seconds, she did not move.
Sullivan stepped forward gently. "Miss Tate, are you ready?"
Whitney did not turn around. "Dr. Sullivan, please start the clock."