Editing Schrödinger's cat (section)

== Thought experiment ==
[[File:Schroedinger cat.jpg|thumb|upright=1.2|A life-size cat figure in the garden of Huttenstrasse 9, Zurich, where [[Erwin Schrödinger]] lived from 1921 to 1926. Depending on the light conditions, the figure appears to be either a live cat or a dead one.]]

Schrödinger wrote:<ref name="Schrodinger1935" /><ref>{{cite journal|last1=Trimmer|first1=John D.|title=The Present Situation in Quantum Mechanics: A Translation of Schrödinger's "Cat Paradox" Paper|journal=Proceedings of the American Philosophical Society|date=1980|volume=124|issue=5|pages=323–338|jstor=986572}} The English translation here is based on the German original, not on the inaccurate version in this source's translation of the entire article:
[https://archive.today/20121204184041/http://www.tuhh.de/rzt/rzt/it/QM/cat.html#sect5 Schrödinger: "The Present Situation in Quantum Mechanics." 5. Are the Variables Really Blurred?]</ref>

{{Blockquote|
One can contrive even completely burlesque [farcical] cases. A cat is put in a steel chamber along with the following infernal device (which must be secured against direct interference by the cat): in a [[Geiger counter]], there is a tiny amount of radioactive substance, so tiny that in the course of an hour one of the atoms will perhaps decay, but also, with equal probability, that none of them will; if it does happen, the counter tube will discharge and through a relay release a hammer that will shatter a small flask of [[hydrocyanic acid]]. If one has left this entire system to itself for an hour, one would tell oneself that the cat is still alive if no atom has [[radioactive decay|decayed]] in the meantime. Even a single atomic decay would have poisoned it. The [[wave function|psi-function]] of the entire system would express this by having in it the living and dead cat (pardon the expression) mixed or spread out in equal parts.

It is typical of these cases that an indeterminacy originally restricted to the atomic domain turns into a sensually observable [macroscopic] indeterminacy, which can then be resolved by direct observation. This prevents us from so naïvely accepting a "blurred model" as representative of reality. Per se, it would not embody anything unclear or contradictory. There is a difference between a shaky or out-of-focus photograph and a snapshot of clouds and fog banks.}}

Schrödinger developed his famous [[thought experiment]] in correspondence with Einstein. He suggested this 'quite ridiculous case' to illustrate his conclusion that the wave function cannot represent reality.<ref name=BaggottStory>{{Cite book |last=Baggott |first=J. E. |title=The quantum story: a history in 40 moments |date=2013 |publisher=Oxford Univ. Press |isbn=978-0-19-965597-7 |edition=Impression: 3 |location=Oxford}}</ref>{{rp|p=153|q='I am long past the stage where I thought that one can consider the <math>\psi</math>-function as somehow a direct description of reality'}} 
The wave function description of the complete cat system implies that the reality of the cat mixes the living and dead cat.<ref name=BaggottStory/>{{rp|154}} Einstein was impressed by the ability of the thought experiment to highlight these issues. In a letter to Schrödinger dated 1950, he wrote:<ref name=BaggottStory/>{{rp|157}}
{{Blockquote|You are the only contemporary physicist, besides [[Max von Laue|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 gun powder + 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.<ref>{{cite journal|title=Induction and Scientific Realism: Einstein versus van Fraassen Part Three: Einstein, Aim-Oriented Empiricism and the Discovery of Special and General Relativity|first=Nicholas|last=Maxwell|date=1 January 1993|volume=44|issue=2|pages=275–305|doi=10.1093/bjps/44.2.275|jstor=687649|journal=The British Journal for the Philosophy of Science}}</ref>}}
Note that the charge of gunpowder is not mentioned in Schrödinger's setup, which uses a Geiger counter as an amplifier and hydrocyanic poison instead of gunpowder. The gunpowder had been mentioned in Einstein's original suggestion to Schrödinger 15 years before, and Einstein carried it forward to the present discussion.<ref name="Stanford1" />