Subject: Zeno's paradox
https://www.scientificamerican...

Solved with calculus (yes, we can outrun tortoises).

For thousands of years, scholars pondered the question of how anything can move in our world. The problem seemed to have been solved—until the development of quantum mechanics

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According to quantum mechanical theory, quantum objects, such as an electron or a molecule, cannot change or move while they are being observed. They behave like an actor with extreme stage fright who freezes, as it were, under the penetrating gaze of the audience.

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How can the basic building blocks of our world move and change? What exactly is a measurement? And what does an observation mean for a quantum system?