Chapter 1 — The Ship That Did Not Sink

Iota stopped at the edge of the river walkway as a large cargo ship glided past in front of her. Its gray hull rose as tall as a two-story house, with its lower section sitting deep in the water. Yet the ship did not sink to the riverbed. It slid along the surface, slow and steady.

Walking beside her, Wong Nam paused as well and smoothed down the folded collar of Iota’s jacket.

“Is that ship made of iron?” Iota asked.

“Its hull is made of steel, and steel is a metal made from iron.”

Iota studied the vessel. Round portholes lined its side beside an iron doorway, and heavy cargo crates sat stacked high across its deck. The ship carried all of that weight while gliding calmly down the river.

“It must be terribly heavy,” Iota said. “Why doesn’t it sink?”

“Why do you think?”

Iota thought for a moment. “Maybe the steel they use for ships is lighter than ordinary iron. Lighter than a nail.”

Wong Nam did not call her guess right or wrong. “We have nails in the toolbox at home. Let us start by watching what happens to a nail.”

Once they got home, Wong Nam opened his toolbox and took out a single steel nail about as long as Iota’s index finger. Because its point was sharp, Wong Nam held onto it himself.

Iota fetched a small, clear plastic basin about the size of a soup bowl, filled it halfway with tap water, and set it on the table. Holding the nail horizontally above the water, Wong Nam let it go.

Plop. The nail dropped straight through the water. Clink. It hit the bottom of the basin.

Iota crouched down until her eyes were level with the side of the basin. The steel nail lay flat on the bottom, completely underwater and still.

“The nail sank right away,” Iota said. “And the ship did not, even though the ship is thousands of times heavier than one little nail.”

“So it cannot just be a matter of whether something is heavy or light,” Wong Nam said.

Iota pictured the gray ship on the river again. Its hull was wide and hollow, filled with open rooms inside, whereas the nail at the bottom of the basin was thin, narrow, and solid all the way through.

“Maybe it has to do with its shape,” Iota said. “A ship is wide and hollow, and a nail is thin and solid.”

“We can test that.”

Wong Nam lifted the nail out of the basin and dried it off on a dish cloth. Opening a small storage box, he took out a lump of modeling clay about the size of a table-tennis ball and handed it to Iota.

“We are going to use this exact lump twice,” Wong Nam said. “Nothing added, nothing taken away. The amount of clay stays identical.”

Iota rolled the clay between her palms until it formed a smooth, tight ball.

Would that little ball of clay float, or would it sink?