Why Quantum mechanics is weird ?
Sub-atomic partiple's behaviours are strange and deviate from reality that human cannot comprehend. In the quantum world, sub-atomic matters become fuzzy and unreal, matters can be in different places at the same time, it appears that matters can pop in and out of space simultaneously, an electron can travel in wave motion but when they are being observed the wave would collapse to motion in a straight line. However, there are mathematical equations to describe their behaviours. Hence there is a quote.....
“if you think you understand quantum mechanics, then you don't”
The above is a famous quote from physicist Richard Feynman, his quote seemed to be derived out of frustration of the deviation of quantum mechanics from human intuition. Experiments has proved the prediction of quantum mechanics theories is true but it is hard for humans to understand why it is like that. Scientists are amazed by the fact that quantum mechanics is not deterministic but probabilistic. Sub-atomic particle like an electron can be in any location at the same time in an electron cloud. What is mind boggling about quantum mechanics is that an electron can be dispersed throughout space with a probability function. There is a much higher probability that an electron will be in place within its orbit around an atom’s nucleus, but it can be any other place with lower probability.
An electron can be both a wave or particle. Scientists proved this by a double slit experiment below. When the experiment is performed without human observation an electron behaves like a wave it goes through both slits at the same time and interfere with itself to form a pattern on the wall (see left picture below), but when detectors are placed beside the slits to observe which one it went through, the wave collapsed to a particle and went through only one slit at a time (see right picture below) to form two lines on the wall. Scientists are confused by the mystery of the behaviour.
Scientists are amazed by the weirdness that the electrons appeared to be sentient and know when to be a wave or particle. Also, it can be observed that an electron can go through slit 1 or 2 at the same time. That’s is not possible in the real world that we know because matter can only be exist in one location at a time.
This nature of quantum mechanics suggest that our moon may not be there if we don’t look at it, because atoms of the moon can be dispersed in space in a probability function. Only when you look at it, all atoms of the moon would collapse to one location in the sky.
Applications of the weirdness
The absurd prediction of quantum mechanics baffled scientists but there were numerous experiments to prove that quantum weirdness exists and can be replicated. Yet it is the weirdness nature of quantum mechanics that makes quantum computing and quantum communication possible.
Quantum computing - A classical bit has only 0 or 1 status, a quantum bit can be 0 and 1 at the same time, quantum bits hold much more information and allow parallel computation or perform tasks simultaneously in quantum computing.
Quantum communication - The wave and particle duality of the particles makes hack proof quantum communication possible, because when hackers interfere the flow of particles (eg photons) in a communication line, the wave nature of photons would collapse and alert the management of the communication line.