Dialogue Concerning the Two Chief World Systems

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1. 01

   If you are in a closed cabin on a smoothly moving ship, no experiment inside can tell you whether you are moving or standing still.

   Dialogue Concerning the Two Chief World Systems · 1632

   Uniform motion cannot be detected by experiments inside the system.

   Galileo asked readers to imagine tossing a ball or pouring water below deck on a perfectly smooth ship. Everything behaves exactly as it would on land. From this he drew the bold conclusion that Earth could be moving through space without us feeling it directly.

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