In 1927, Werner Heisenberg declared it impossible to measure both the velocity and location of any subatomic particle. The explanation seemed simple enough: the light needed to see a subatomic particle gave the tiny mote more energy and knocked it somewhere else before the photons showing where it had been reached the observer's eye. Heisenberg called this the Uncertainty Principle. And Einstein didn't like it. He came up with all kinds of clever experiments to disprove it.

In a thought experiment, Einstein filled a box on a scale with a radioactive substance that emitted radiation randomly. The shutter of the box opened and quickly shut, timed by a precise clock, so that some radiation escaped. In this way, he determined with accuracy the time the energy got out and how much the box weighed before and after. His famous E = MC2 equivalence of mass and energy allowed him to calculate exactly how much energy was left in the box. Ta-da! He had measured both the location and the velocity of the escaping radiation and had disproved the Uncertainty Princple!

But he was wrong. His own theory of relativity proved him wrong. Once the energy left the box, the box got lighter and rose slightly on the measuring scale. That altered the position of the clock and immediately put the box in a different reference frame. Einstein's principle of relativity insists that a set of measurements depends on an observer's particular frame of reference, and so the clock's measurement of time was different before and after the energy escaped - and that resulted in an inevitable margin of error. Experiments verified, in fact, that the imprecision equaled the specific uncertainty predicted by Heisenberg's equation!

Like it or not, Einstein had to accept that, on a fundamental level, the physical universe does not have a definite form but exists as uncertainty - a reality of probabilities, potentials, and pure chance. That is why he said, "I cannot believe that God would choose to play dice with the universe."

Neils Bohr, a fellow quantum physicist responded, "Einstein, don't tell God what to do."