A mix of numbers with an 'imaginary' part, known for a century, turned out to be the key linking the predictable world of billiard balls and the misty quantum realm. New mathematics shows: both are just different settings on one cosmic dial.
🎯 The Hamilton-Jacobi equation, created in the 1830s for billiards and planets, was already quantum in form. Erwin Schrödinger said that all he had to do was 'see' the resemblance and give classical quantities a complex character—and his famous equation was born.