Why God plays dice

September 1998

"God does not play dice" Albert Einstein once said, expressing his contempt for the notion that the universe is governed by probability - an idea fundamental to quantum theory (see "Quantum uncertainty" in Issue No 5). Since then the undisputable successes of the quantum theory have convinced all but a handful of contemporary physicists that God does indeed play dice. The question some physicists are now asking is why does God play dice? What's the point? Popescu, a Cambridge physicist, believes he has the beginnings of an answer to this seemingly monumental question.

God plays dice

There's now no doubt that God plays dice, but why should our universe be probabilistic at all?

"Quantum entanglement" is the term used to describe the bizarre link that may develop between two or more particles, even when they are separated by cosmological distances. A photon may decay into an electron and a positron (the positron being the antiparticle of the electron). Electrons and positrons possess an observable quantity called spin, a kind of internal angular momentum, which when measured in some direction will either be "up" or "down". According to quantum mechanics, if one measures say the electron spin to be "up" in some direction, at that very instant the spin of the positron will be "down" in the same direction, no matter how far apart the particles. This poses a serious problem: according to relativity, no signal can travel faster than light, the "speed limit of the universe". Imagine it; we could measure the electron spin here on earth, and instantaneously the positron, which could be in another galaxy, would "know" which direction its spin should point. Weird.

Popescu believes he can resolve this apparent paradox between the two theories. He believes that God "plays dice" precisely to allow quantum theory and relativity theory to coexist.


Always question the premise

What did Einstein mean when he said, "... God does not play dice"?

Despite the endless repetition of this quote we should note that it is NOT A QUOTE. Einstein never said this, someone else did. Einstein generally spoke in German and was doing so in this case. This alledged quote is a subjective translation that has been refuted by experts who say, "it's not even wrong" :)

See Abraham Pais's "Subtle is the Lord ..." where he points this out and suggests several alternative translations all of which strike me as better and which never use the word "dice". Among the best is the one he uses in the very title of his well received Einstein biography.

Analyzing something he never said is, at best, troublesome.

- greg

Does God play dice

Einstein said “God doesn’t play dice” but much of mother nature can be emulated with a random number generator. Are there “Physics Foibles”? Numbers are the Supreme Court of science. What would Godel say?

God plays dice

There are Physics Foibles. A random number generator can duplicate some of natures events!!!!

"God does not play dice": why is this wrong?

Many phenomena exhibit probabilistic behaviours (e.g., election, human height), but this does not imply that someone is playing dice. Quantum uncertainty merely suggests that there is a limit in term of what we can measure. For those variables or their resolutions that we cannot measure, we can never be sure about the true casual relations among these variables, so we may HAVE TO (though not ideal) model many causal relations probabilistically (similar to playing a dice under some specific conditions). However, the sciences were never satisfied by probabilistic causal relations. Otherwise Newton’s laws would be some probabilistic causal relations. NASA would have to employ some fortune-tellers.

It is correct to recognise our limitation in modelling many phenomena using quantitative laws. It is wrong to generalise this to a statement that causal relations are merely some probabilities.

MC, Oxon