In an earlier post, we talked about the strange double life of light and wave-particle duality (read here). Today we move to another idea that is just as unsettling. But before we enter the quantum world, let us travel back to around 260 BCE.

You probably know the famous story of Archimedes and the golden crown. King Hiero of Syracuse suspected that his new crown was not made of pure gold. He wanted to know the truth but without melting, scratching, or damaging the crown in any way. The challenge was simple and impossible at the same time. Archimedes eventually found a clever method, but the real unsung hero in this story is the king himself for asking an ingenious question: Can we learn something about an object without disturbing it?