The Sphere

Morning. Polly woke up under a tarp. Someone had moved it during the night. She had not noticed. The bridge smelled of coffee. The engines were running.

Out on deck, the submersible sat under bright lights. The crew were already at work.

A man with grey hair was crouched beside the submersible. He held a small torch in his mouth. He had two screwdrivers in his pocket. He worked slowly.

Polly hopped closer. The man glanced at her. He did not seem surprised. "Visitor's deck is over there," he said, pointing at a stack of crates. Then he went back to his work.

He was checking the titanium pressure sphere. This is the part of the submersible where the pilot sits. It is a ball one and a half metres across, with walls nine centimetres thick.

Polly tilted her head. "Why is it a ball?" she asked. The man did not look up. "Because pressure is equal from every direction down there. A ball spreads the load evenly. A box would crumple."

The viewports were thick. Each one was made of acrylic, not glass. Acrylic gives a little under pressure and then comes back. Glass would just crack.

The man checked the seals around each viewport. He told Polly the seals were tested in a tank on shore, at full ocean depth, before the submersible ever left the dock.

"How long can the pilot stay down?" Polly asked. "Life support for ninety-six hours. Dive cycle is about ten," he said.

Polly watched his hands. They were rough and careful. There were maybe twenty people in the world who built one of these. Two of them were on this ship.

The man closed the panel. "It is one of two craft in the world rated to full ocean depth," he said, almost to himself. He patted the sphere as he walked away.

Polly stayed a while. She looked at the line where the two halves of the sphere met. Nine centimetres of titanium. Eleven hundred atmospheres of pressure. Just metal and bolts and a tiny round window into the deepest place on Earth.