Vanya shook his sister awake. She’d barely eaten. Barely spoken since they’d lost Sasha. He didn’t know what to do, only that she wasn’t well. He held her, when she let him, ignoring his own pain, whispering the old stories he used to tell when they were children after their parents died. But she only cried.
He walked with her up and down the train’s corridor, trying to keep both of their strengths up. Erik had been replaced by a simple conductor, and that man kept the door to their berth unlocked and ignored them, didn’t even offer to help, though he surely must have seen Vanya bending under Miri’s weight. And while she slept, he stared out on the countryside and thought about relativity. He’d come so close. If only he could have solved the equations. But while he’d held his notebook, taken it everywhere with him since the eclipse, he had yet to work in it. But then he had a thought. Not about his equations, but about his sister. There might be another way to help her. He couldn’t remember the last time he’d seen her with a book or a journal.
“Miriam,” he said. “I need your help thinking through a problem. When Dima, Yuri, and I were hiding in the cave, after we stopped for coal, I imagined I was in a rocket, shooting upward—acceleration.” He waited for Miri to focus on him, but she continued to stare at the window, seemingly at nothing. He continued, “What if I wasn’t on a rocket, but rather in an elevator? Free fall, acceleration. They’re related. I know it. But how?” The train barreled forward louder than ever, echoing on snow. Miri said nothing, but Vanya knew she liked to puzzle through pieces that stumped him. Her mind was as sharp as anyone’s. Maybe if he could convince her to think it through with him, she’d come back. “Can you help?”
Miri kept her eyes toward the window, toward the snow. Why wouldn’t she respond? Hours passed with them sitting in silence. Vanya was about to give up hope, but then Miri turned to him.
“You’re thinking about it wrong,” she said. The first words she’d spoken in days. “In an elevator. If you’re going up, your feet are pressed to the floor. But if you’re not moving, your feet are also pressed to the floor. The force only gets lighter when the elevator is in free fall. If you closed your eyes at any point, how would you know whether the elevator is stopped or moving upward?” She lapsed back into silence. Or maybe it was Vanya who went quiet because he was stunned.
Yes, yes, she was right. She had a point. An obvious—brilliant point. It had been there in front of him the whole time, but it took Miri to see it. In an elevator, you wouldn’t feel any difference between gravity and acceleration. They are the same thing.
Gravity equals acceleration.
He pinched the skin on the bridge of his nose. And he thought. And thought it through. “Gravity and acceleration are the same,” Vanya whispered later, much later, when it was dark, when the rest of the train was asleep. “My God, Mirele. You’re right.” It was simple. Elegant. There was no question in his mind it was correct. Up to then, he’d been trying to balance gravity and acceleration, but he didn’t need to do that. Gravity not only bent space—it was equal to acceleration.
Would it solve his equations? He opened his notebook for the first time since the eclipse. “Mirele, you’re brilliant,” he said, and took out his pencil—and began to write.