Lacuna and William Switch On a Light the Hard Way

“The book stays,” Lacuna said.

William held the cardboard ramp steady. “The marble could land directly on the light.”

“The book turns a nudge into a decisive press.”

“It also turns four things that can go wrong into five.”

Lacuna balanced the paperback on its lower edge, just beyond the ramp. Ahead of it sat the battery light, its broad button waiting beneath the book’s intended fall. Behind it: one marble, a slope, and a short procession of dominoes. An entire table enlisted to do the work of a finger.

“Better?” William asked. “Or merely longer?”

“Let’s obtain evidence.”

Lacuna checked the gaps once more, then pushed the first domino.

Click-click-click.

Both leaned forward. William’s hands hovered safely clear. The marble rolled down the cardboard with a dry little rumble, struck the paperback, and stopped.

The book remained upright.

Neither breathed.

Then it tipped—slowly enough to make them both negotiate with gravity—and slapped the button.

Warm light spread across the table.

William let out a breath. “We could have switched that on ages ago.”

“Yes,” Lacuna said, watching the fallen book. “But we wouldn’t have watched.”