Why the tooth fairy is important for theoretical physics (opens in new tab)

In this Universe, our intuition isn’t always a good guide for how reality actually works. The deterministic laws that describe reality so well in our everyday experience no longer apply to a variety of quantum systems: from radioactively decaying atoms to determining which of two slits an electron passes through. The simple addition of velocities that works in our conventional experience, like throwing a baseball from a moving train, requires replacement by a more complex rule when you approa...