[Yahya A.Sharif (OP)]

I understand physics. Can someone tell me how to expand my physics knowledge by knowing quantum mechanics? from where should I start?

[Bored chemist]

This is as good a place to start as any.
https://www.khanacademy.org/

[paul cotter]

Yahya, I commend your interest in expanding your physics knowledge. A lot of contributors post on topics they have no understanding of with the absolute certainty that is only available to the truly ignorant. Unless one understands conventional physics there is no hope of any coherent new concepts being developed. Quantum theory is a particularly difficult subject-much of it is counterintuitive. I have no more than a basic knowledge of physics and would not attempt to explain quantum theory to anyone. Relativity is another counterintuitive theory and here I might just be able to explain the basics of special relativity but not so with general relativity. A quote attributed to a physicist( I can't remember who it was ) was "if you think you understand quantum theory you haven't been paying attention", or words to that effect. I hope this does not discourage you.

[HaelSturm]

 Depending on your previous knowledge and the depth of understanding you desire, there are a number of different ways you could approach learning more about quantum mechanics. If you are new to the subject, a good place to start might be with an introductory book or online course that will give you a basic understanding of the key concepts. Once you have a foundation to work from, you could then move on to more advanced texts or tutorials. Alternatively, if you are already familiar with the basics of quantum mechanics, you might want to focus on a specific area that interests you. For example, you could study the mathematical principles underlying quantum theory, or learn about the experimental techniques used to test its predictions. Whichever route you choose, expanding your knowledge of quantum mechanics is sure to be a rewarding experience.
Good luck

[Yahya A.Sharif (OP)]

Unless one understands conventional physics there is no hope of any coherent new concepts being developed.

I invent theories in classical physics. How Newton invented a true gravity equation although he has no quantum physics background ? This equation sill works and is independent of general relativity. I can invent something like a gravity equation by observing the gravity force and how the distance between the masses and values of the masses affect the force without knowing Quantum mechanics " I am not comparing myself to Newton but that is possible if I have his mind and still Newton do not know quantum mechanics "
This great true theory is purely classical.
https://www.thenakedscientists.com/forum/index.php?topic=84458.0

[alancalverd]

Newton did what physicists do: constructed a mathematical model that matched and then predicted actual observations. Nothing to do with quantum mechanics - and quantum gravitation still remains an undemonstrated hypothesis.

The best introduction to quantum mechanics I think is to follow its historical derivation via Planck's explanation of black-body radiation and the photoelectric effect, then to consider how line spectra can occur. This will at least put some "visual"  framework in your mind. The conceptual difficulty I found was incorporating Schrodinger's wave mechanics into my thinking but it gets clearer if you approach it from the point of view of stereochemistry (why are molecules the shape they are, and wobbly?).  Whatever you do, don't get sidetracked by Schrodinger's cat or anything that smells of philosophy or psychology - it's just physics, chemistry and mathematics.

[Niko43Gold]

I don't really know physics but quantum physics it's so fun to learn about because it's so unique and fun.

[Origin]

I understand physics.

You actually don't understand basic physics.  You don't know some of the very basics such as the conservation of energy.  I would recommend getting a good base of understanding of the easy stuff before trying to tackle the really hard stuff.

[Colin2B]

……quantum physics it's so fun to learn about because it's so unique and fun.

It is also one of the most misunderstood and poorly explained in the popular press.
It depends on your definition of fun!

[Zer0]

I've seen some fun & interesting documentaries on YouTube.

I'd recommend watching them for fun & understanding.

Keywords are " Jim Al Khalili Quantum Physics ".

His documentaries are Simply Fascinating.
Have Fun!

[Eternal Student]

Hi.

   Looks like you've had some reasonable advice already.   You need to have studied Mathematics to about the equivalent of a UK  "A" level before you try and seriously start learning some Quantum Mechanics.   You may need to push that understanding a further and learn a little more about differential equations as you go through the course.   If you don't have the equiavlent of an A level in mathematics  then I would start by learning that first.  Without the Mathematics you will be limited to the "Pop Sci" version of Quantum Mechanics  (QM) -  for example watching some general access documentaries about Quantum Physics.

    I'm always keen to try and access the same resources that university students would have.   That pretty much guarantees that you would be exposed to the same sort of thing as someone who could reasonably call themselves professionally educated in that topic.

    There are some old University lectures available on YouTube  given by  prof.  Leonard Susskind.   Sadly the video quality is not high - this was made about 16 years ago when sharing university lectures to the general public was a new and cutting edge thing.   
   The website  URL is given in a quote box to prevent the forum software from automatically embedding the actual YT video in here:

https://www.youtube.com/watch?v=2h1E3YJMKfA

    and find the rest of the lecture course with sensible search terms    (e.g.  just type the title and add "lecture 2"  etc.).    These are roughly 1st year University courses.

    There are also some slightly newer videos on QM  from prof. Susskind but the lectures are at an even more advanced level   (let's say roughly the equivalent of a UK University course for the final year of study).   

https://www.youtube.com/watch?v=8mi0PoPvLvs

   

M.I.T.  have decicded not to be left behind in the race to make their lectures available to the general public.    Their version of a lecture course is available here:

https://www.youtube.com/watch?v=lZ3bPUKo5zc

   I haven't seen many of the lecture courses prvided by M.I.T. so I can't be sure they are as good  BUT  you would have thought they were good.

    There are probably other University lectures now made available online.  (In my opinion, EVERY university should be doing this by now.  However, many of them continue to keep their lectures private and will only release that material to students that pay the annual fees for the University.   This is a separate issue and has been discussed in another thread).

     The lecture courses I have found and mentioned above were studied by students over one full semester  with about  1 lecture per week,  of about 1.5 hours each   x  12 weeks    and would have included doing some work on your own at home to build and improve your understanding.   You should expect to spend a similar amount of time yourself.   You won't have the problem sheets with all the examples set out for you to try at home BUT you should still look through your own lecture notes and start asking yourself questions about it.   See if you can reproduce or remember how to prove some bits from more simple results etc.  Set yourself examples and practical problems and see if you can solve them etc.   Like most bits of Science or Mathematics, you MUST practice it yourself, simply listening to someone lecture is not good enough.   It is much harder to solve a problem from scratch, entirely on your own, rather than to just follow along with what someone else is doing  BUT you will learn more when you work on your own examples.

   Overall, expect to spend several weeks learning this stuff.     These lecture courses usually give a recommendation for a textbook.   If and when you think you're really interested then try and get that book or arrange for your local library to get in it in for you to borrow etc.   You can be fairly sure that the lecturer has done most of the hard work for you and identified a book that is useful out of all the others on the topic that may be  too advanced  or too difficult to understand,  too simple, extremely inaccurate  or  suffer from some other problem.

Best Wishes.

[MikeFontenot]

I understand physics. Can someone tell me how to expand my physics knowledge by knowing quantum mechanics? from where should I start?

The best explanation of QM that I've seen is in Penrose's book "Shadows of the Mind".