I don’t think I’ve ever seen a popular account of quantum entanglement that failed to mention Einstein’s “spooky action at a distance” quote. That’s not surprising, because quantum mechanics is a notoriously difficult subject to communicate to the non-specialist. It needs all the memorable sound-bites it can get... especially ones that a layperson can relate to. If you saw an experiment in which an electron in one location seemed to know what another electron somewhere else was doing, then the word “spooky” might well spring to mind.
Part of the appeal of the quote is that “spooky” is a colloquial word, rarely encountered in serious writing. It’s quite a recent coinage, as you can see from the Google Ngram chart below. “Spooky” was virtually unknown before the 20th century, and its usage only really took off in the 1970s and 80s. When Einstein used it in a letter to Max Born in 1947, the word was still quite novel (you can view the original context here – it’s on page 158 of the original, on the left-hand-side of page 90 of the scanned PDF).
Ngram stats for spukhafte (or spukhaft) are different from spooky – the word was at the peak of its popularity around 1947, and its usage has declined since then. This led me to wonder if “spukhaft” might have a slightly different meaning from “spooky”.
Spooky comes from “spook”, which is an informal, rather playful term for ghost. The German word Spuk also means ghost, but as you can see from the chart it’s been around longer. The word occurs in the first scene of Wagner’s Der Fliegende Holländer (mentioned a few weeks ago in Fortean Opera)... a gloomy Gothic tragedy, which isn’t the sort of place you’d expect to find a childishly jolly term like “spook”. The Norwegian sailors, on hearing eerie voices emanating from the Dutchman’s ship, say: “Welcher Sang! Ist es Spuk? Wie mich’s graust!”... which is rendered in the English version as “What a song! Are they ghosts? I’m filled with fear!”
If “Spuk” simply means ghost, with no cosy Halloween or Scooby-Doo overtones, that makes me wonder if “spukhaft” is better translated as “ghostly” rather than “spooky”. If so, it would place a somewhat different emphasis on the Einstein quote. If you say something is “spooky”, that’s not so much a description of the phenomenon itself, as your reaction to it – something is “spooky” if it makes you uneasy because you can’t explain it. On the other hand, if something is described as “ghostly”, that’s saying something about the phenomenon itself. It’s being labelled as supernatural, non-physical and possibly even irrational. For a scientist to refer to something in these terms is tantamount to saying it’s not real.
The closest idiomatic phrase I can think of would be “mystical action at a distance” rather than “spooky action at a distance”. If Einstein objected to “mystical action at a distance”, he wasn’t the first one. As I’ve mentioned before, this was the reason Galileo heaped ridicule on Kepler for his suggestion that the Moon was responsible for the Earth’s tides (see Galileo wasn’t always right...). Soon after Galileo’s time, Newton explained the tides—and the motion of the Moon and planets—as consequences of the gravitational inverse square law. On the face of it, this was nothing more or less than “action at a distance”, and many people objected to Newton’s theory on the metaphysical grounds that action at a distance was illogical and therefore impossible. Numerous mechanical explanations of gravitation were put forward to try to get around the need for action at a distance.
My understanding of the German language is only marginally better than non-existent, so I really don’t know what Einstein meant by spukhafte Fernwirkung. He might have meant “spooky action at a distance” in the sense that English-speakers would understand the term – i.e. that he found the concept unsettling, if not downright scary, because it was seemingly supernatural. But I’m not convinced the emotive overtone of the word “spooky” was intended at all. He may just have been saying “I don’t believe in it, because I don’t believe in the supernatural”.
Ultimately, it doesn’t matter what Einstein meant. “Spooky action at a distance”, as the phrase is commonly understood, is a perfect description of quantum entanglement. Wittingly or unwittingly, Einstein gave quantum physics one of its most accessible memes, right up there with Schrodinger’s Cat, the Many-Worlds Interpretation and the God Particle.