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Explained: The physics behind #TheSchrödingerCat going up or down

world Updated: Apr 11, 2015 12:51 IST
HT Correspondent
HT Correspondent
Hindustan Times


The hashtag #TheSchrödingerCat has been trending since a photo of a cat triggered a debate in the virtual world on whether the feline was going up or down a flight of stairs.

But what is Schrödinger’s cat? It is the name of a hypothetical experiment devised by physicist Erwin Schrödinger in 1935 to illustrate the nature of tiny particles like electrons and atoms. The experiment showed that wave particles can’t be governed by the general laws that govern the motion of a ball or person or car.

With the experiment, Schrödinger reflected on the limitations in the ‘Copenhagen interpretation’ of quantum mechanics, which states that a particle exists in all states at once until observed.

In Schrödinger’s experiment, a cat is placed in a sealed box with a radioactive sample, a Geiger counter (a device used for measuring ionizing radiation) and a bottle of poison. If the Geiger counter detects that the radioactive material has decayed, it will trigger the smashing of the bottle of poison and the cat will die.

The analysis stands that if we go by the Copenhagen interpretation, then the radioactive material can have simultaneously decayed and not decayed in the sealed environment. So, the cat too is both alive and dead until the box is opened.

Physics professor Eric Martell has explained the paradox thus: "If you put the cat in the box, and if there's no way of saying what the cat is doing, you have to treat it as if it's doing all of the possible things—being living and dead—at the same time. If you try to make predictions and you assume you know the status of the cat, you're [probably] going to be wrong. If, on the other hand, you assume it's in a combination of all of the possible states that it can be, you'll be correct."

But when the box is opened, one would get to immediately know the status of the cat — either it is alive or dead — thus resulting in the death of the hypothesis that it was in both states.

The idea of this paradox ultimately developed into the concept of wave functions — something that describes all of the possible states that particles can have, including properties like energy, momentum and position.

Read: #TheSchrödingerCat is out! But is it going up or down?