What is the Uncertainty Principle? What is the Wave/Particle Duality? Part 1. What is Quantum Tunneling? What is a Neutrino? Theory of Everything (intro) The Higgs Boson, Part I. How Quantum Suicide Works". A man sits down before a gun, which is pointed at his head. This is no ordinary gun; it's rigged to a machine that measures the spin of a quantum particle. Each time the trigger is pulled, the spin of the quantum particle -- or quark -- is measured. Depending on the measurement, the gun will either fire, or it won't. If the quantum particle is measured as spinning in a clockwise motion, the gun will fire. Nervously, the man takes a breath and pulls the trigger. Go back in time to the beginning of the experiment. But, wait.
This thought experiment is called quantum suicide. Symphony of Science.