Quantum Mechanics was developed over 80 years ago and it brought us the computers, microchip technology, semiconductor industry and laser technologies. Despite how successful quantum mechanics has been over the last century, we as physicists are still struggling with understanding the theory and coming up with logical explanations of why it works the way it does.
Unlike classical mechanics, quantum mechanics cannot talk about an electron having a precise position or a fixed velocity. The only way we can describe the electron is using a wave function to represent the superposition state of the electron and we assign a number which when we square it, gives us the probability of finding that electron when we look for it. When we are not looking at the electrons, their existence become meaningless.We cannot even think they exist at all until we look for them and wave functions are all we have to work with. This is indeed very strange and physicists such as Albert Einstein was really bother by it and he claimed quantum mechanics was incomplete. However, time after time, quantum mechanics has surpassed every single test there is over the last 80 years and it is by far the best theory we have to describe how the fundamental particles behave at the subatomic level bringing us all the innovative modern technologies of today.
But as of now, we are still struggling to understand the quantum interpretations of various phenomena that we observed and famous physicist like Schrodinger constructed a paradox ( cat in a box) to explain the quantum superposition state where the cat is both dead and alive at the same time until we open the box, which then the wave function collapses and the cat becomes either dead or alive. But how does the wave function collapse? Are wave functions real? Or are they just mathematical tools for physicists to get an answer but without any real contexts or existence? So there are still lots of questions we don’t have answers for despite the fact that quantum mechanics has been very successful and finding an underlying mechanism in quantum physics will be a major accomplishment in the future and only then we may have a chance to discover gravity within quantum mechanics in order to get a better understanding of how the universe originated at the very beginning.