It was a bright Saturday morning, and seven-year-old Mia was learning to ride a bicycle in the park. Her father jogged along behind her, one hand on the back of the saddle, delivering a steady stream of encouragement that she was in no state to hear. All she could think about was the ground, which seemed remarkably far away and remarkably hard. "Don't let go!" she begged. "I won't," he promised. "I'm right behind you."
The bicycle swayed alarmingly from side to side, but somehow Mia kept pedaling, and by degrees the swaying settled into something like a line. The wind rushed past her ears, the path unrolled in front of her, and before she had quite decided to, she was laughing. After a long moment she shouted, "Papa, you're still holding, right?" Nobody answered, and it was this silence, rather than any sound, that made her risk a glance over her shoulder.
Her father was standing a long way back, in the middle of the path, waving both arms like someone trying to flag down a train. His hands were completely empty, and he was laughing so hard that he had to bend over. Mia wobbled but, to her own astonishment, stayed upright. She swung a wide circle around the pond and braked in front of him, breathless. "You let go!" she accused him. "Two minutes ago," he said, glowing with pride. Mia weighed this information for a moment, as though it were an offer of doubtful value. Then she turned the bicycle round. "Again," she said.