IT'S NOT JUST ANOTHER CAT!

It is customary to help your friends to connect to your home WiFi network. My friends often get amused when they find that my SSID is named, "Schrödinger's cat," leading to some interesting discussions.

Erwin Schrödinger has made several groundbreaking contributions to quantum physics. Yet, he is most famously known for something else - a thought experiment involving a cat. Imagine a cat enclosed in a box (let's discuss the details later; for now, let us just imagine a cat enclosed in a box) - until someone opens the box, the cat can be thought of as both alive and dead. Once the box is opened, the cat will be found to be either alive or dead. Simple, right? 

If it were that simple, Erwin Schrödinger would not deserve credit. It is just a reasonable thought! However, the significance lies in the phrase "the cat can be thought of as BOTH alive AND dead." Yes, at the same time! 

But how? Why? 

I am not a physicist and I often struggle to understand this concept, let alone explain it to my friends who are connecting to my WiFi network. Maybe a little background of this thought experiment would be useful. 

Copenhagen interpretation 

From our high school science classes, we have understood that all matter (living and non-living) is made up of atoms - the fundamental building blocks. We are also familiar with the structure of atoms as protons and neutrons packed up tightly in the core (nucleus) and the electrons revolving around the nucleus in specific orbits like planets revolving around the Sun. This is an easy-to-understand "planetary model" of the atomic structure. However, this model is not perfect. 

We commonly think of electrons as tiny round particles. A "particle" will have a specific position and velocity. When scientists tried to define these properties they were not only held in surprise but the results shook the very basics of the classical physical laws. The results implied that an electron can be present anywhere in its orbit and in more than one places in an orbit at the same time. It behaves like a wave. A wave has frequency and amplitude but not a position. 

But when an electron is observed, it will be sighted at any one place. What the scientists say is - when you observe, the wave function of the electron collapses and it behaves like a particle. Without actually observing the electron, the electron can be thought of as being present at every position throughout its orbit with a certain probability. Yet, when you observe, it is present at only one point in its orbit. Therefore, without observing, you can only deduce the probability of finding an electron at any given point in its orbit. This is in contrast to how accurately we can predict the position of the Moon for the next hundreds of years. If Moon were to behave like an electron, there is a "chance" that every day could be a full moon day! 

This existence of an electron at multiple places at the same time (when not observed) is known as "Quantum superposition." The act of observing somehow affects the electron and the probabilities will vanish, giving a "random" position to it at that time. This is known as "wave function collapse." Albert Einstein didn't like this uncertainty and is known to have said, "God doesn't play dice with the universe." 

I know it is strange and something difficult to imagine. It is not just us, even physicists find it challenging to understand this strange but true phenomenon (popularly known as the Copenhagen interpretation). 

Schrödinger's thought experiment

Schrödinger came up with a thought experiment to illustrate the weirdness of the "Copenhagen interpretation" of quantum mechanics. In simple words, Schrödinger imagined a cat enclosed in a box which contains a sealed container of poisonous gases. The container is set up in such a way that it will break open if there is a decay of a radioactive atom. According to the Copenhagen interpretation, until the system is observed, the radioactive atom is in a state of superposition of decayed/non-decayed - the sealed container of poisonous gases is in a state of superposition of intact/broken - and therefore, the cat is in a state of superposition of dead/alive!! Once you open the box (when the system is observed), there is a wave function collapse and the radioactive atom is either decayed OR not decayed - the container is either intact OR broken and therefore the cat is EITHER dead OR alive. 

Not just another cat

Without going to the details of the quantum physics on which this thought experiment had a tremendous impact, Schrödinger's cat has often provoked an intellectual discussion with my friends. The Copenhagen interpretation of the quantum mechanics seems weird because it implies that two mutually exclusive events can co-occur. It is like tossing a coin and getting both heads and tails at the same time. 

That seems odd because of the physical nature of the outcome. If you were to apply this phenomenon to non-physical entities such as good/bad, happy/sad, pleasant/unpleasant, etc., this phenomenon doesn't seem so odd after all. Instead of a cat, imagine a person who you haven't met. Before you talk to him, you can think of them as BOTH good AND bad. It is by interacting with them that you will begin to think of them as either good or bad. Now, don't you think that your interaction with that person somehow affected the behavior of that person? Absolutely! In reality, a person is often an admixture of BOTH good AND bad qualities. It is we who interact with them and brand them as EITHER good OR bad, forgetting the fact that we were judging them by the circumstances. 

Schrödinger's cat, thus, fuelled an interest in me to explore the world of quantum physics and in the process made me stumble upon a fascinating book that drew parallelisms between the modern physics and Eastern philosophies - "The Tao of Physics" by Fritjof Capra. The book helped me understand how the whole Universe is connected and all distinctions are meager arbitrary. We distinguish objects, people, and our experiences because we rely too much on our sense organs. 

"Quantum theory thus reveals a basic oneness of the universe. ... This means that the classical ideal of an objective description of nature is no longer valid. The Cartesian partition between I and the world, between the observer and the observed, cannot be made when dealing with atomic matter. In atomic physics, we can never speak about nature without, at the same time, speaking about ourselves."
-Fritjof Capra, The Tao of Physics, Chapter 4 (The New Physics)

"Here is a hint of aspects deep within the world of physics, and yet unattainable by the methods of physics. And, moreover, we have found that, where science has progressed the farthest, the mind has but regained from nature that which the mind has put into nature. We have found a strange footprint on the shores of the unknown. We have devised profound theories, one after another, to account for its origin. At last, we have succeeded in reconstructing the creature that made the footprint. And lo! it is our own."
-Sir Arthur Stanley Eddington in 'Space, Time and Gravitation'

Yet there are people who transcend these physical boundaries (through a lifetime commitment, they perform Sadhanas), and thus, they experience something very effortlessly which a quantum physicist struggles to even understand. 

Schrödinger's cat is helping me find such people.