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A strange tale of a Cat (Schrödinger's cat)

In my earlier blog, I mentioned that quantum world is crazy. In this blog I will give an example of that. Initially, when quantum physics came along many of the renowned physicists of that era did not like it. Infact, even Albert Einstein thought that quantum physics was not correct. Why didn’t they like it? Well, the answer is that there is something known as uncertainty in quantum physics (Heisenberg’s Uncertainty principle) which says one cannot determine with complete precision the mass (momentum) and velocity of a particle simultaneously. And this fact does not deal with how good instruments we have. There is a fundamental limit beyond which we cannot measure with complete precision the mass and velocity of a particle simultaneously.
THIS WAS THE PROBLEM!!
Because physics which was known up till that point of time to describe dynamics of particle i.e. Newtonian mechanics or even Einstein’s General theory of Relativity are completely “deterministic” i.e. if we know the state of a particle at one point of time(position and velocity) then we can determine with complete accuracy the state of the particle at any point of time in the past and future upto infinity. So, there is no uncertainty in classical mechanics. But, in quantum mechanics everything is chance and associated with probability i.e, if you know the state of the particle at any point of time there is no way you can predict the future states with complete accuracy. The best you can do is to calculate the probability for the particle to be in one state or others at anytime in future.

This made Einstein very upset. Infact, he quoted “God does not play dice” to say that the fate of anything in this universe must be uniquely determined and it should certainly not be governed by probability. Thus, according to him quantum physics must have been wrong.
Now, physically if we try to think that why there is an uncertainly associated with particles in the quantum domain? The answer would we : it has been seen that in the quantum domain particles behave like waves. A fact that was first mathematically described by Louis De Broglie. And, finally it was Schrödinger whose wave equation described the quantam state of any particle at any time(t) given the boundary conditions. Now, Schrödinger’s wave equation is a 2nd order differential equation. But, Schrödinger himself was not convinced with the ideas of quantum physics and he devised an experiment to show the absurdity of qunatam mechanics when applied to real world objects like cat. Yes, the experiment is known as Schrödinger’s cat.

The experimental setup contained a thick box made of lead. Inside the box there is a cat, a giger counter, a glass which contains cyanide capsule and a radioactive element. Now, radioactivity is a quantum phenomenon so there is a probability that the radioactive element will decay or not decay.If it decays then the Giger counter will catch its vibration and this will initiate the glass to break.Then the cyanide gas realeases and the cat will die. Now, if the radioactive element does’nt decay then no such things happen and the cat remains alive.So, the cat can be either dead or alive.

Now, comes the catch!!

There is another state for the cat which comes from superposition principle. Schrödinger’s wave equation is a 2nd order differential equation where superposition can be applied.

Let me describe what is meant by superposition ..

Let us take a 2nd order equation:- x^2 -7x +10=0.
If we solve it then the solution would be either x=5 or x=2. But had it been a 2nd order differential equation then any linear combination of the solutions like 5+2 i.e. x=7 would have also been a solution which is in short the principle of superposition. Now, since Schrödinger’s wave equation is a 2nd order differential equation we can apply the superposition principle.And, this principle when applied to our experiment there emerges another state for the cat which is : “The cat is dead and alive simultaneously” until the box is opened, which is absurd. Hence, quantam world is crazy!! But experiment after experiment has proved that quantam physics is correct and hence we see that nature works in strange ways at various domains.Quantam physics has shown to us that reality indeed is stranger than fiction!!

Reality is more than what meets the eye

I have always wondered what is real and what is unreal?Physics is a part of science whose basic objective is to study the physical properties of objects and to explain them. But to study those properties of objects,which exists in nature, we have to take the help of abstract symbols of mathematics like imaginary numbers, negative numbers etc.What does these implies in real world?Well, why do we have to take the help of "imaginary" numbers to describe our "real" world objects and their phenomenon.It seems a little weird isn't it? Well the answer is that nature is far more richer than what meets the eye.Let us take a simple case. The maximum mass that we can estimate is say 100 kg(without any instrument)with only our senses and the smallest mass is say 100 gms. But nature works in a much more wider range than that of our senses and thus the intuitions that we have about nature in general if we try to apply that to every domain of nature, that would certainly be wrong. In fact,the domain of nature which is astronomical is explained by Einstein's General theory of Relativity which is somewhat different than the world around us and the physics which is used to explain the domain which is extremely small is known as Quantum physics which is totally insane to say the least. Quantum world is totally crazy.Well,I would try to explain each of these domains in details in my next blogs.Thank you!!