What's the simplest way to explain quantum mechanics? - by Alexei Voronin and by Assistant - Quora Question Review

This document contains a review of the answer by Alexei Voronin and by Assistant on the question in Quora: "What's the simplest way to explain quantum mechanics?"
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Contents

• 1. Answer Review by Alexei Voronin
• 2. Answer Review by Assistant

Reflection

• Reflection 1 - Question Review

1. Answer Review by Alexei Voronin

The word “explanation” means reduction of some new facts to the already known. And word “simple” could be a synonym to word “short”. The shortest way to make such a reduction of quantum physics phenomena to everyday common sense is to say that all we believed were regid bodies are in fact waves. After saying this magic phrase you should make a pause and enjoy an effect produced by your words. You should also add that the very important fact which is the cornerstone of quantum physics is that there is no way to completely reduce quantum behavior to the world of macroscopic bodies. One has to accept it; and this is a way physics does it job. It accepts basic facts from experiment and use these few facts as principles to explain all other things. The basic fact is: all particles manifest wave properties. Rigid body is an illusion. But you could give much more detailed explanation why waves “pretend” to look like rigid bodies in our everyday macroscopic world. Optics gives the best background for that. You can see a ray of a laser pointer in a dark room (due to reflections from dust in the air). It looks like a strait line, it does not change its form when you move it, it looks like rigid rode. However if you point it on a thin glass (it could be a bulb, made of thin glass) under grazing angle you could see reflections on the wall which look like bright and dark strips. It is interference of light, a phenomenon of pure wave nature. Thus you can realize that under certain conditions a set of waves could look like waves or could mimic a rigid body behaviour. It depends on a ratio of two spatial scales, namely a wave-length of a wave and a size of a physical system, which detects it. All particles are waves, like photons, but in macroscopic world the waves “pretend” to look like rigid bodies, just because the ratio of these scales is very small. And here is another crucial question which is important for “explanation” of quantum physics. This is a question how can we practically describe the world of waves if we are made of macroscopic objects, where wave behaviour is hidden. The answer is: a) all we could do is to use measurements done by our macroscopic devices as a fundament for description of the world b) such measurements would produce huge unavoidable effect on microscopic particles-waves. Quantum physics is a way to encorporate the unavoidable effect of measurement of a microscopic wave-particle by macroscopic device into a theory, that could predict future outcome of some experiment. All difficulties of “understanding” quantum physics are here. We used to believe that we could measure the position of a bullet by means of a photodetector as many times as we need to reconstruct its trajectory. Each such measurement does negligible effect on bullet trajectory, so our procedure is meaningful as well as classical mechanics methods to predict trajectory. In quantum world each measurement would drastically change the properties of a microscopic bullet, thus trajectory has no sense any more. The “magic” wave-function is a way in which we describe a behaviour of a quantum particle, obtained as a result of multiple measurements. But now it could have a sense of probability distribution only. After “explaining” all this “simple” things you could give your companion a book of Landau, Lifshitz v.3 and say that “technical” details are there.

2. Answer Review by Assistant

Quantum mechanics is a branch of physics that deals with the behavior of very small particles, such as atoms and subatomic particles. At this scale, the classical laws of physics don't apply, and instead, we use quantum mechanics to describe how these particles behave. One of the key principles of quantum mechanics is superposition, which means that particles can exist in multiple states at the same time until they are observed. Another important concept is quantization, which says that certain properties of particles, like energy levels, can only take on discrete values. The famous Schrödinger's cat thought experiment illustrates a strange aspect of quantum mechanics: a cat in a box can be both alive and dead at the same time until someone opens the box and observes it. Overall, quantum mechanics is a complex and fascinating field that has led to many technological advancements, such as quantum computing and cryptography. It challenges our classical intuition but provides a powerful framework for understanding the behavior of particles at the smallest scales.

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