In detail

Schrödinger's cat: what's it all about?


It was created in 1935, making its comeback at the latest in the popular series "The Big Bang Theory": Schrödinger's cat. Founded as a thought experiment by the physicist and Nobel laureate Erwin Schrödinger, it appears again and again in the everyday media today. But what is the famous cat all about? Not quite the box Erwin Schrödinger had in mind in 1935, but similar - Shutterstock / Dalibor Valek

Yes, cats had cult potential even before the Internet was invented. But Schrödinger proves not only that. Behind Schrödinger's cat is a thought experiment that is supposed to prove that the transfer of laws of quantum mechanics to our everyday world is nonsensical.

Schrödinger's cat: the experimental setup

Erwin Schrödinger asks whether a cat is alive or not - it's about the condition of the cat inside a hidden box, which could also be a kind of deadly trap. Don't worry: it's just a thought experiment. No animal was harmed by Erwin Schrödinger's hands. The answer can be anticipated at this point: the cat is both alive and dead. That’s not possible. Right! But let's best go step by step by looking at the experimental setup:

• A cat comes into an invisible box for an hour.
• The box also contains an unstable atomic nucleus, which is likely to disintegrate within a certain period of time, as well as a Geiger counter with a hammer and a bottle of hydrocyanic acid.
• If the atomic nucleus decays, the Geiger counter strikes due to the radioactive radiation and triggers the hammer.
• Option 1: The hammer could fall on the bottle of poison, causing the cat to die.
• Option 2: If the unstable atomic nucleus does not decay, the Geiger counter would remain inactive and the hammer would not smash the bottle with hydrocyanic acid. The cat would live.

Why do cats love tight boxes and boxes?

Many cat owners know it: you bring a new cat toy, unpack it and the cat ...

That's what Schrödinger's cat is all about

The question of the condition of Schrödinger's cat serves to show in the form of a paradox that quantum mechanical laws are not so easy to match with the laws of our everyday world:

Objects in the microcosm fall within the realm of quantum mechanics. Individual atoms, for example, such as the radioactive atoms in Schrödinger's crate, have the property of not adopting a fixed state and, for example, being able to be in two places at the same time if we are not observing them. This is normal for the atoms and even necessary. Only when we take a look at the atoms are they in a constant state.

In the macrocosm, our everyday environment, this looks different. A house, for example, has fixed properties. Once built, it is always on one side of the street and cannot be on the other side of the street at the same time. It is similar with living things. Animals like Schrödinger's cat cannot be dead or alive at the same time, but always have one of these existential states.

That means… ?

For the thought experiment, this means that as long as we don't observe the atomic nucleus in the hidden box, it has decayed and not decayed at the same time - an admittedly difficult idea from our macrocosmic point of view. This means that the Geiger counter strikes and does not strike, the hammer falls and does not fall, the poison is released and is not released and the cat is alive and dead. The latter does not work, however, because the cat, as part of the macrocosm, must either be one or the other and cannot be both at the same time. So micro and macro cosmos are not so easy to bring together. It is not known why Erwin Schrödinger chose a cat as an example. After all, this is why his proof finds contemplation.

Do you have any questions? The following video illustrates the experiment again: