Galileo's Ship — Below Deck
Water drips into a bowl, a fish swims, butterflies drift — and nothing inside the cabin can tell you whether the ship is tied up at the quay or making fourteen metres a second. Run the same experiments in a sailing cabin and its moored twin side by side, then let the swell get up and watch every instrument in the room give the secret away.
Como usar esta simulação
- Compare Galileo's cabin at a steady 6.0 m/s against its moored twin
- Press Full sail at 14 m/s to confirm the speed itself never shows up
- Press The swell gets up to give the cabin an acceleration of 2.5 m/s²
- Switch between the below-deck view and the whole-ship view to see both descriptions
O que observar
- Every drop lands in the bowl whether the ship is moored or at full sail
- The fish and the butterflies behave identically in both cabins
- From outside the ship the drop clearly travels forward; from inside it falls straight down
- Doubling the steady speed changes nothing at all inside the cabin
- The instant the swell adds acceleration, the drops miss and the frame gives itself away
A física por trás
Two frames moving at constant velocity relative to one another are equivalent for mechanics: accelerations are identical in both, so every force law gives the same predictions and no experiment inside can distinguish them. A drop released in the cabin already carries the ship's horizontal velocity and keeps it, so it lands at the same spot on the deck whether the ship moves or not. The equivalence fails the moment the frame accelerates — a swell gives the cabin an acceleration a₀, and objects then depart from where they should land by exactly that amount.