wave-particle duality
What is light? Sometimes it seems wave-like and sometimes particle like. See how Einstein applied his theory of relativity to the problem, predicted that photons have no mass and laid the foundations for quantum mechanics.
Quantum mechanics is the physics of the extremely small. With something so far outside our everyday experience it's not surprising to find mathematics at the heart of it all. But at the quantum scale nothing in life is certain... Peter Landshoff explains.
