What is Quantum Physics in simple?

[Cookie_1993]

hi!

is quantum physics that difficult to understand?
because i had read the explanations given in the internet but couldnt get any proper explanation.

thankz in advance!
(ps. please explain quantum in simple)

[G01]

Quantum Physics is considered conceptually difficult because it is not based off of any of our previous knowledge of the universe.

Asking us to explain the whole of quantum theory to you in simple terms is a lot to ask. It covers a vast ammount of material, enough that trying to cover it in a post on a message board would accomplish hardly anything.

I guess my point is that, if you looking for an explanation of quantum physics based off of previously held notions and experiences you have in the world, your not going to find it. Quantum Physics just cannot be explained in classical terms because it just isn't classical.

I suggest finding a book, many people here can give good reccomendations, and going from there. I read the small book, "Introducing Quantum Theory" while I was still in high school. It was non-mathmatical and gave decent description of the history and developement of the theory. Looking back on it now as someone who knows more physics, I think it was a decent place to start.



EDIT: Also, you may end up seeing stuff that says "Quantum Physics says this, says that,etc." Alot of crackpots try to use Quantum Physics to support everything from psychic readings to the belief that we can change things around us by thinking. This is all crap and has nothing to do with Quantum Physics. If you come across anything like this, be VERY skeptical. Also, do not use the movie "What the Bleep Do We Know?" as a source of information on quantum physics. It falls into the above category. In fact, it may be the epitome of the above category!

[tim_lou]

I don't think quantum mechanics is THAT difficult and abstract as people (specially crackpot "physicists" as G01 mentioned) claim.

just know some algebra and differential equation and accept the Schrodinger's equation and you are all set.
Quantum mechanics is very axiomatic (depends on how you learn it). If you know the mathematics, then things will become intuitive. For instance, the uncertainty principle is simply the Cauchy-Schwartz (a mathematical theorem) and nothing more that that. (it's not like a particle flies in something bizarre dimension then comes back from the future and destroy the world... no, it is a mathematical theorem, and nothing more than that)


take a look a griffith's book and the whole idea of quantum mechanics will become demysticified.

edit: very often, the internet just make things more confusing that it actually is. Grab a book (Griffith's introduction to quantum mechanics) and all your questions will become clear.

[G01]

I don't think quantum mechanics is THAT difficult and abstract as people (specially crackpot "physicists" as G01 mentioned) claim.

just know some algebra and differential equation and accept the Schrodinger's equation and you are all set.
Quantum mechanics is very axiomatic (depends on how you learn it). If you know the mathematics, then things will become intuitive. For instance, the uncertainty principle is simply the Cauchy-Schwartz (a mathematical theorem) and nothing more that that. (it's not like a particle flies in something bizarre dimension then comes back from the future and destroy the world... no, it is a mathematical theorem, and nothing more than that)


take a look a griffith's book and the whole idea of quantum mechanics will become demysticified.

edit: very often, the internet just make things more confusing that it actually is. Grab a book (Griffith's introduction to quantum mechanics) and all your questions will become clear.

I agree. If you have knowledge of calculus and differential equations, I also Reccomend Griffiths "Intro to Quantum Mechanics" as a good book.

[cesiumfrog]

Aye, Griffiths' is surely the most "readable" undergraduate QM textbook.

[Cookie_1993]

whats the name of this book?

[Loren Booda]

Some concepts to consider in quantum mechanics:

The correspondence principle correlates macroscopic with microscopic physics.

There is (the Heisenberg uncertainty principle) a minimum product (~h, the Planck constant) for the uncertainties of energy and time, or position and momentum.

Quantum mechanics applies best at small distances and high energies.

(Sub)atomic matter and energy both display wavelike and particle-like qualities.

(Sub)atomic states embody Planck constant discreteness.

Space(time) is believed to become foam-like on microscopic scales.

Observable outcomes on quanta are affected by measurement itself.

Schroedinger's equation expresses conservation of energy for wave dynamics.

Probability is calculated by integrating the wavefunction (a solution to Schroedinger's equation) over the variable in question.

Macroscopic tests of quantum mechanics include Josephson junction superconductivity.

[G01]

whats the name of this book?

Introduction to Quantum Mechanics by David J. Griffiths

[Cookie_1993]

thank you!!

[G01]

The Book does require knowledge of Calculus and Differential Equations, just in case your not up on the math, and want to do the problems.

[malawi_glenn]

Niels Bohr said once:

If you think you have understand quantum mechanics, you have not understand quantum mechanics.

=P

[Cookie_1993]

Niels Bohr said once:

If you think you have understand quantum mechanics, you have not understand quantum mechanics.

=P

what did neil bohr mean by that?

[malawi_glenn]

what did neil bohr mean by that?

that what "DrWatson" said, that reading books like the one he recomend, you will understand QM. We can not understand QM in intuitive way.

At what level do you study physics yourself?

[chroot]

You can completely understand the theory, in the sense of being able to solve problems, analyze experiments and derive the correct predictions, and so on. Many people (tens or hundreds of thousands) understand the theory in this way.

On the other hand, quantum mechanics is so unintuitive that many people, even after learning the theory intimately, still have trouble accepting that the universe really behaves that way. Quantum mechanics is very difficult to appreciate from the perspective of human experience -- unlike the motion of billiard balls, which clearly makes "sense" to anyone who studies it.

- Warren

[Cookie_1993]

hm... i dont exactly know the level of physics i am at present i mean i dont know what it is called

[Cookie_1993]

so QM explaines how the universe behaves.....
does it also state something about the behaviour of atoms and electrons?
i had read something about that once..

[chroot]

Quantum mechanics is essentially the study of how very small things "move," if they can be said to move at all in the usual sense. Quantum mechanics does indeed have the power to describe how electrons behave inside atoms. The canoncial system studied in basic quantum mechanics classes is the hydrogen atom: a proton and an electron together in a bound system.

Quantum electrodynamics is a physical theory, based on quantum mechanics, which describes the interactions of light and matter.

- Warren

[G01]

To help us understand the level of physics you are at answer these questions:

Can you do general physics problems, such as ones from a standard college general physics text, or do you study more of the qualitative aspect of the material?

If you can do general physics problems, how far along are you? Have you completed a general physics course? Can you do problems beyond general physics, such as problems in Modern Physics?

What level of math have you studied up to?

These will help people judge the level you are at, and recommend the best study material.

[ice109]

Niels Bohr said once:

If you think you have understand quantum mechanics, you have not understand quantum mechanics.

=P

actually richard feynmann said that

[Cookie_1993]

thank you!!!

[vanesch]

hi!

is quantum physics that difficult to understand?
because i had read the explanations given in the internet but couldnt get any proper explanation.

thankz in advance!


As others pointed out in this thread, the formal theory of quantum mechanics can be learned. It is pretty mathematical, and in fact, there are even serious problems if one wants to be absolutely rigorous and wants to go beyond the finite-number-of-non-relativistic-particles-in-a-potential model. The mathematical artillery is much heavier than introductory classical mechanics, and beyond a certain point of sophistication, even not established rigorously.

However, what is "difficult" to understand is the physical meaning of quantum theory. People disagree since its origins (in the middle of the 1920ies) of what is physically meant with what - a situation unheard of in classical physics where the link between formal elements and "things out there" is so intuitively obvious that it is even never discussed.

That said, if you limit yourself to the mathematical formalism (without delving too deep into matters of rigor), and you limit yourself to those aspects of the formalism which are clearly identifiable with physical quantities (often "outcomes of measurement"), then you have a powerful and pragmatic machinery which is "up and running", in the sense that you can calculate a lot of things, and compare it successfully with experiment. That's essentially what has been done for the last 80 years.

In order to delve deeper into the difficulties (technical, but mainly conceptual) of quantum theory, which is what some people refer to when talking about "quantum mechanics is difficult/incomprehensible", you have *at least* to master the above pragmatical approach. Moreover, you will have to arm yourself with some philosophy.

[Aidan130791]

If you really want an unmathematical layperson's explanation to get you going, I suggest reading 'In search of schrodinger's cat' by John Gribbin. After you have a feel for the theory, perhaps you could have a crack at the maths.

[G01]

If you really want an unmathematical layperson's explanation to get you going, I suggest reading 'In search of schrodinger's cat' by John Gribbin. After you have a feel for the theory, perhaps you could have a crack at the maths.

Before I started formally studying physics, I read "Introducing Quantum Theory." I forget the author, but it does explain quantum physics in a nice, not too mathematical way. It won't make you a master of the theory, but it's a good start if your interested but don't have much mathematical background.

EDIT: I just realized I already said this in my first post in this thread a while back. Sorry! Can't hurt to reinforce it though.:smile:

[Aidan130791]

Before I started formally studying physics, I read "Introducing Quantum Theory." I forget the author, but it does explain quantum physics in a nice, not too mathematical way. It won't make you a master of the theory, but it's a good start if your interested but don't have much mathematical background.

EDIT: I just realized I already said this in my first post in this thread a while back. Sorry! Can't hurt to reinforce it though.:smile:

If it's the one by David Griffiths, then that was my first semi-mathematical intro to quantum physics. But there are so many books called that, so it might not be the same one.

[G01]

If it's the one by David Griffiths, then that was my first semi-mathematical intro to quantum physics. But there are so many books called that, so it might not be the same one.

The one by Griffith's I have used and like it as well, though it wasn't the one I was talking about in this case.

The one I was thinking of is a popular science book. It's small and non-mathematical. It's not a textbook. It have a quasi-comic book style look to it. It explains the history and development of quantum theory. It worked well for me, though it definitely doesn't prepare you well for a course in the subject, it's good for the casual reader. The only problem is that it is a popular science book. You have to watch out for those PS books that are crackpottish, but I'm pretty sure this one is ok. All it is is pretty much an overview of the history of quantum theory. It should be OK.

If the OP has the background in Differential Equations and Calculus, then I definitely recommend Griffith's though.

[Aidan130791]

I think I know the one. Slightly cartoonish and has drawings of all the original quantum physicists (schrodinger, dirac, etc) on a a page near the beginning?

Popular science books are fun to read when the maths gets boring in real textbooks, most aren't crackpot-ish and you can usually tell by the title anyway.