If you follow the pop culture, you must have already heard this term at least once. For those who haven’t, Schrödinger’s cat isn’t about some pet Cat. It is a thought experiment performed (or rather, thought) by Erwin Schrödinger. The experiment later went on to become a popular term for many pop culture references, internet jokes, memes and even T-Shirts. But, what is this experiment really about? What was Erwin Schrödinger trying to prove by putting an innocent imaginary cat in a complicated situation of life and death? Let’s find out.
Before we move to the actual experiment, let’s first know why Schrodinger thought of the experiment in the first place. This has to do with the Copenhagen interpretation of quantum physics. What is it? Well, it basically says that according to Quantum Theory, all the matter exists in two forms particle and wave. Now, as for the bigger objects such as cats, the wave properties cannot be observed as their wavelengths are very negligible. But, for objects like atoms or electrons, the particle and wave duality can be observed and they do show properties of both waves and particles. The Copenhagen interpretation says that if every matter exhibits the dual nature then, any physical properties such as length, speed or even position of that object cannot be definitely determined as a wave does not have a single position but many positions along its wavelength. So, it stated that any particle exhibits in all states unless an observation is done. So, basically it said that a particle can be at all the positions along the wavelength unless an observation is made. Once an observation is made, the position of particle on the wavelength for that particular observation is determined. Similarly, for all the other physical properties. I know it sounds absurd but, it’s quantum mechanics it can’t get any more simple. This theory does apply to the atoms and electrons as they don’t follow Newton’s laws of physics which are generally followed by larger objects. Many physicists were not in the agreement with this interpretation proposed by Neil Bohr including Albert Einstein (and we can see the reason). Erwin Schrödinger was one of them. So, he thought of the famous cat experiment.
The experiment was somewhat like this. Schrödinger thought of a cat inside a closed steel box. The steel box also contains a Radioactive material, a Geiger counter and a bottle of poison. The apparatus was made such that once the radioactive material decays even a single atom, the Geiger counter will detect it and it will trigger a relay which in turn will smash the bottle of poison which will kill the cat. Also, the rate at which the radioactive material will start decaying is unknown and it is assumed to start decaying at any random time. Another assumption is that once steel box is closed there is no way of knowing what is happening inside unless you open the box. Now, the twist, as per the Copenhagen Interpretation, the Radioactive material is in state of decay as well as stable both at the same time. Which means the Geiger will detect and not detect the decay in turn both killing and not killing the cat unless we observe it. So, basically, the famous statement – “The Cat is both dead and alive at the same time until we open the box.” But, common sense tells us this is not possible. Thus, Schrödinger wanted to disprove the Copenhagen interpretation when applied to real world objects.
Why there is so much more to this genius thought experiment is that it gave rise to a series of other mind-bending theories. One of such theories is the theory of Multiverse. The theory suggests that when the steel box is closed and the status of cat is not observed, the cat is indeed both dead and alive but, in two different universes or in two different realities. When the box is opened, one of the realities takes physical form and thus we can see if the cat is dead or alive.
Even if Schrödinger was able to disprove the Copenhagen interpretation for everyday objects, it is still considered as one of the most important theories in quantum physics and is still considered true at least for subatomic particles. But now we know that there is so much more to this Cat than the internet jokes and Schrödinger didn’t actually say that the cat is both dead and alive at the same time, he said it can’t be.