Monday, August 12, 2013

Shroedinger's cat

Today is Erwin Shroedinger's 126th birthday. I've read the blurb on Wikipedia explaining the thought paradox of Shroedinger's cat, that the cat can be both dead and alive, until it is observed to be one or the other.
"Our intuition says that no observer can be in a mixture of states—yet the cat, it seems from the thought experiment, can be such a mixture. Is the cat required to be an observer, or does its existence in a single well-defined classical state require another external observer? Each alternative seemed absurd to Albert Einstein, who was impressed by the ability of the thought experiment to highlight these issues. In a letter to Schrödinger dated 1950, he wrote:
You are the only contemporary physicist, besides Laue, who sees that one cannot get around the assumption of reality, if only one is honest. Most of them simply do not see what sort of risky game they are playing with reality—reality as something independent of what is experimentally established. Their interpretation is, however, refuted most elegantly by your system of radioactive atom + amplifier + charge of gunpowder + cat in a box, in which the psi-function of the system contains both the cat alive and blown to bits. Nobody really doubts that the presence or absence of the cat is something independent of the act of observation."
Someone should have reported Shroedinger for cruelty to cats. Yet I guess it's a sort of compliment; Shroedinger's super-subtle cat gets to explain a concept in the observation of phenomena, while Pavlov's dumb dogs just have to salivate on demand.

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