Can someone clearly and simply explain quantum physics?

Question

I'd just like a clear definition of what it is, as im a little confused on the subject.

Answer 1

its based on the quantum theory: that certain properties occur only in discrete amounts.

Answer 2

Quantum physics aims to explain various phenomena we are observing in small (a few particle) systems. Since one of these properties is that position and momentum can't be measured simultaneously, the state of a particle must be described by another "set of variables".

In fact, quantum mechanics (this term is used often interchangeably with the quantum physics, but see below) goes deep into mathematics and describes the state of a particle by some special subset of some special vector space. It then must tell how this state evolves in time and what results can give various measurements done on the particle. So its main part is linear algebra and functional calculus—one must be quite good at these to understand all the concepts used by QM (not only to be able to rant about them).

One problem of quantum mechanics is it gets much more complicated than classical physics when it comes to more than one particle. The mathematics gets MUCH worse very fast—we say the complexity is growing exponentially. This makes it impossible to use QM for describing macroscopic physical systems.

The other problem is that its applicability is limited on the other side too—for explaining high energy and sub-particle phenomena, quantum field theory must be used instead. However, the term "quantum physics" is sometimes used to cover all things "quantum", so this would be not really a problem.

You can't expect an introduction to quantum physics that would allow you to compute, say, the energy levels of an electron in hydrogen atom, without getting all the basics in linear algebra, electromagnetism, Lebesgue measure calculus, special functions and maybe a few other fields.

I hope this helps anyway.

P.S. It's NOT true that "quantum" is the same as "quantized". For example, position, momentum or time are never quantized in the scope of this theory. Some particles, for example free particles, have their possible energies continuous. Sometimes energy is discrete, but not really in integer multiplies of some "quantum". This is just one result of quantum theory.

Answer 3

No.

No one can clearly and simply explain quantum physics.

That is sort of like asking someone to clearly and simply explain all of mathematics or chemistry or biology.  No one can clearly and simply explain biology.

Now, if you have a question about an aspect of a certain piece of the vast physical science covered by quantum physics, perhaps someone could take a shot at answering it.

Quantum physics includes all the physics that is on such a small scale that the interactions are often quantized rather than continuous.  For example, a steel ball can be at 30 degrees or 300 degrees or every temperature in between, heated smoothly from one temperature to the other, existing for a moment at every temperature along the way.

An atom however can only have a few, discrete, quantum energy states.  When it goes from one to state to the other it does not have any in between energy position.  One instant it is one, the next it is the other, it cannot be in between.

Quantum physics describes and predicts many situations at the quantum level that are not intuitive to most people because we don't have much quantum experience in our lives.  Can something be a particle and a wave?  Can a coin be flipped (or a cat maybe poisoned) and the result wait indefinitely for somebody to observe before it is resolved?

Finally, there is no person who clearly and simply understands all of quantum physics to explain it to us.

Answer 4

"simply and clearly" and quantum mechanics is a contradiction.

on the other hand, "confused" and quantum mechanics is normal. Even the experts are confused and cannot explain it clearly.

Answer 5

I don't think that's even possible, even many of the leaders in the field of quantum mechanics and particle physics are confused, some of whom are considered to be the Einsteins of our time, quantum mechanics is a very confusing and extremely long topic to discuss, it's particles are strange and behave in completely random ways, and the more accurate readings we try to make the less reliable they are. However if you would like to know more about quantum mechanics there are several books that may help you, I personally would recommend The Elegant UNiverse by Brian Greene as it describes and explains very plain and clearly not only quantum mechanics and particle physics, but also general and special relativity ( Einstein's works on physics to do with gravity, space and time) but also a new " Theory" in physics called string theory that is supposedly able to unite the physics of the small and the physics of the large.  

            As to what a definition of Quantum Mechanics is it is the study and research of extremely small particles making up atoms or being on that scale, such as electrons, protons, and neutrons, but also quarks, gluons, neutrinos ect.