The Longest Broom in the World

The assembly was over and the gym smelled like floor wax and folded chairs. Mr. Okafor was changing a light bulb high in the rafters, fifteen feet up, balanced on a ladder with a telescoping pole in his hands. The pole was long. Longer than anything Maya had ever seen anyone hold.

"Imagine if it were a mile long," Maya said. She was sitting on the stack of mats, swinging her feet. "You push this end. The other end moves. Instantly."

Soren stopped sweeping. "Not instantly."

"It's one solid thing. You push, it all moves. Like the whole pole is one piece."

"That's what I'm saying it can't be." He leaned the broom against the wall. He had a feeling in his stomach he got when something everyone agreed on was secretly wrong. "If you could push a mile-long pole and the far end jumped instantly, you'd be sending a message faster than light."

Maya frowned. "It's not a message. It's a pole."

"It's a message if someone's watching the far end."

Mr. Okafor, from the ladder, said, "You two want to make yourselves useful, hold this steady." He lowered the pole to them. It was aluminum, three sections, light. Maya took one end and Soren took the other and they stretched it out across the gym floor.

Maya pushed her end. "There. It moved."

"Did my end move at the same time?"

"Yes."

"Did it though?"

She stopped. That was the thing about Soren. He asked the question that turned the floor into a question. She looked down the silver length of the pole. "It looked like it."

"Twelve feet," Soren said. "Of course it looks like it. But there has to be a tiny delay. The push goes from atom to atom. Each one shoves the next one. That takes time."

"How much time?"

"I don't know." He picked up the pole and tapped one end against the floor. A sound came out the other end a beat later, a faint metallic ring traveling up to his hand. "That. That's the push. It travels as a wave. The same speed as sound in the metal."

Maya took the pole back and tapped it herself. She felt the ring arrive in her palm. She had felt it a hundred times before and never once thought it was the same thing as pushing. "So when I push the near end," she said slowly, "the far end doesn't know yet."

"Right. For a tiny moment the metal near your hand is squished. Compressed. And the squish travels down the pole like a wave before the far end feels anything."

Maya went still. "The pole bends."

"Not bends. Compresses. Just a little. There's no such thing as a perfectly stiff pole. There can't be. A perfectly stiff pole would pass the push along instantly and you'd beat light. So the universe doesn't allow it. Everything has to be a little squishy."

"Everything," Maya said.

"Everything. The pole. The floor. The ladder. Mr. Okafor."

From up in the rafters Mr. Okafor said, "Leave me out of it."

Maya was looking at the pole like it had changed into something else while she was holding it. "So a mile-long pole."

"You push it. The squish wave travels down it at the speed of sound in aluminum. Which is fast. But not light fast. The far end just sits there, not knowing, for ages, while the wave crawls toward it."

"How long is ages?"

Soren thought. He liked this part, the part where you could actually get a number. "Sound in aluminum is something like five kilometers a second. So a mile, that's a bit more than a kilometer and a half, the push would take, what, a third of a second to get there?"

"A third of a second," Maya repeated. She held up her end and stared at it. "I push. And for a third of a second the other end of my own pole hasn't happened yet."

"Hasn't found out yet."

Maya laughed, but it was not a funny laugh. It was the laugh she made when the world got bigger than she was ready for. "Soren. There is no such thing as one thing."

He went quiet.

"There isn't," she said, faster now. "This pole isn't one object. It's a crowd. Every atom shoving the next one, passing it along, and the message takes time to cross the crowd. We just call it a pole because it's small enough that we never notice the delay."

"The earth's a crowd," Soren said. "If you could push the planet from one side."

"The other side wouldn't feel it for ages." Maya was almost off the mats. "Nothing is solid. Solid is just slow."

"Solid is just a wave that gets where it's going fast enough that we can't catch it," Soren said, and he wanted his notebook badly, but his hands were full of pole.

Mr. Okafor came down the ladder. "You finished arguing?"

"We're not arguing," Maya said. "We agree. That's worse."

He took the pole from them and began to collapse it, section sliding into section with three soft metallic clicks. "Useful or not, I'm taking my broom back."

Maya watched the sections slide. Each one pushing into the next. "Mr. Okafor. When you push the top section down into the bottom one. Does the bottom one know right away?"

Mr. Okafor paused with the pole half-collapsed in his hands. He looked at the eleven-year-old looking at his broom like it was the strangest object in the universe. "It's a broom," he said.

"I know," Maya said. "That's the part that's getting me."

He slid the last section home. The click traveled up the metal and reached the floor, and Maya put her bare hand flat against the gym floor and waited to feel it arrive.