Schrödinger’s Cat Is Simultaneously Both Alive and Dead
Schrödinger’s cat and the Many- World interpretation of Quantum Mechanics
Quantum mechanics is weird. There have been several interpretations of this weird and somehow absurd theory of physics. In this story, I shall share two of the most widely talked about interpretations of quantum mechanics and why some of the most significant theories in modern physics and cosmology require the theory of multiple universes.
Well, science is not about belief, it’s about observation and evidence. Let me explain an interesting scientific thought experiment conducted by one of the most accomplished theoretical physicists of all time. Erwin Schrödinger conducted this thought experiment with the objective to prove or disprove the Copenhagen Interpretation of Quantum mechanics. Now to understand the Copenhagen interpretation, let’s first understand what quantum mechanics is all about. The quantum theory deals with the atomic and sub-atomic particles and their interactions. It also deals with the study of various fields like electromagnetic fields, or the Higgs fields. But the most important thing to understand about the phenomenon associated with the quantum world is that they are probabilistic.
We associate the properties of a quantum particle in a given quantum system with something called a wave function. According to quantum theory, the measurement of any quantum state or particle affects the state itself. It’s much like saying that the observation of the phenomenon actually affects the phenomenon itself. Consider this example, if you are an alien, and you come to the planet earth totally unaware of the phases of the moon. If you are not observing the moon, the moon could be at any phase, it could be a full moon, a new moon, a waxing crescent, or any other phase. The moon is in the state of what we call a ‘superposition’ in quantum mechanics. When you observe the moon, all the possible probabilities get collapsed into one single state. Now try to apply the same idea to the particles and their interactions in a quantum state. This is known as the Copenhagen Interpretation of quantum mechanics. It was first provided by Werner Heisenberg and Neils Bohr in the 1920s.
Now let’s get back to Schrödinger’s thought experiment. Erwin Schrödinger proposed a thought experiment in 1935 in order to demonstrate the problem with the Copenhagen interpretation. A living cat is kept inside a box with a Geiger counter, a radioactive source, a hammer, and a flask of poison. At any point in time, the decay of the radioactive source can trigger the hammer, break the flask and kill the cat. Now since the cat is not observed by an outside observer and the box is closed, the cat is either dead or alive, but not simultaneously dead and alive. Now the real question here is, when exactly does the quantum superposition collapse. In order to resolve this paradox, Hugh Everett came up with another interpretation known as the Many-worlds interpretation. His 1957 doctoral thesis was about this monumental theory where he stated that there exists a universal wave function which is the only possible outcome of a quantum phenomenon. It means that all the possible outcomes are actually true in their own realities or their own universes. This solves the Schrodinger’s cat paradox because according to the Many-Worlds interpretation the cat is simultaneously both alive and dead, but in different realities or different universes. These realities do not merge or interact with each other until the phenomenon is observed by an external observer.
There’s an interesting paradox associated with time travel. The idea of time is not as easy or straightforward as it sounds. Although, ironically, time is always unidirectional. Anyway, the paradox is called the grandfather paradox. Imagine you travel back in time to kill your grandfather before he got married. That alters the future incidents and happenings thereby not leading to your grandfather’s marriage, hence your father was never born, and neither were you, which raises the question: how did you go back in the time if you were not born in the first place?
There is a weird but promising solution to the paradox which doesn’t alter the universal fact that time is unidirectional. The idea is when you become able to go back in time you do not go back in time to your own reality. You kill your grandfather in a different dimension of time of a different reality or universe, thereby killing him, but in the present, you still stay alive (in another reality or universe). In other words, the incidents take place in multiple realities, or multiple arrows of time, where the reality of killing the grandfather doesn’t alter with the reality of you being alive. This suggests that there could an infinite number of universes with infinite arrows of time and hence infinite possibilities.
Think of the beginning of everything. The only accepted theory about the beginning of the universe is the big bang theory provided by Fr. Georges Lemaitre. We know that the universe was condensed into a space-time singularity that started to expand at an instantaneous time. Everything else after that is explainable and has been well verified through observations. What we do not know, however, is where did that singularity come from. Well, there are several speculations regarding this. Many cosmologists believe that the big bang is actually an interaction between two or more universes. It happens when either two universes collide or one universe gets fragmented into two or more baby universes. This, again demands the theory of multiple universes.
There are several instances in modern physics and cosmology where the theory of multiple universes is required and totally makes sense, theoretically and logically. Maybe there are multiple universes and our comprehension is to just understand the universe that we live in and the laws of physics that work in our universe. Maybe other universes have a different set of laws that work differently than ours. So far, this is something that is a matter of pure speculation as it is highly unlikely to prove experimentally with the technology we have today. But we as curious beings and the students of the universe never say ‘it is impossible to prove or disprove it’ we say ‘we just haven’t been able to do it, so far.’
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