What is "Theoretical Physics" ?

[timo]

I just read another of those posts where someone said he's a layman with interest in ... and Theoretical Physics. I have a vague idea why people are interested in that and for the most part I'd advice them to rethink their interest - but that's not what I am going to ask about. Another instance I met the term and was a little puzzled was on Wikipedia where I wrote that the Einstein notation is mostly used in relativistic physics and someone "corrected" me and wrote "theoretical physics", instead.

 

My question is

What does "Theoretical Physics" mean to you?

 

As a matter of fact, I don't really know what it is to me. Generally, I tend to think of it more as a method than a field. But for throwing some points into the discussion here's a few thoughts and possible definitions:

 

• I spoke out against the "Modern and Theoretical Physics" section of this forum on some occasions, the main reason being that apparently no one knows what the title means. The best answer I got was "it means the things written below the title", which is "Atomic structure, nuclear physics, etc.", presumably meaning to include particle physics. Well, there certainly is no reason to consider those fields the most modern ones in the sense of "new". I see no reason why those fields should be more theoretical or abstract than others, but I do think there is the tendency to assume that the more away from everyday length-scales a field of physics is, the more "theoretical" it is.
  
• I do know that some website named "Wikipedia" (often incorrectly referred to as "Wiki") exists. I do disagree with the major definition of both the English and the German Wikipedia saying: "Theoretical physics is a branch of physics which employs mathematical models and abstractions of physics in an attempt to explain natural phenomena.". That is, in my eyes, bollocks: Employing mathematical models and abstractions to explain and predict natural phenomena is a definition for all physics, irrespective of the adjective before the term.
  
• One natural definition would be that theoretical physics is what is left from physics after you take away comparing to experiment or the transfer of physics to actual applications, i.e. physics for those who don't know how to use a screwdriver. Perhaps theoretical physics is also less interested in particular experiment but more in classes of (possible) experiments, i.e. some abstraction layer over the actual work that needs to be done?
  
• In principle, I happily embrace the "perhaps one cannot fully distinguish theoretical physics from other physics"-compromise. In practice, that does not reflect reality: The term is readily used among laymen and professionals in a manner pretending it had a rather precise meaning, for example in the statement "I am interested in Theoretical Physics".
  

 

Don't be shy to offer an opinion even if your actual physics education is limited to having read a popular science book - or not even that. In fact, that views on the field/technique/whatever might be the most interesting for me. But please note that since I am interested in your opinions there's little point in quoting me Wikipedia articles (unless you wrote them, of course).

Edited March 19, 2010 by timo
Added another example where I met the term without really beign able to put a finger on the meaning.

[Cap'n Refsmmat]

In the uses of the term that I've heard, theoretical physics is often presented as the natural opposite of experimental physics. You get the impression of professors standing around chalkboards using math to come up with ideas, rather than technicians in a lab using reality.

[ajb]

I would say that it "is the building of mathematical models of natural phenomena and preforming calculations within these models that can in principle be tested against experiment/observation".

 

I don't know if I have defined theoretical physics or rather presented the ethos and philosophy of theoretical physics.

 

Removing the connection with experiment and observation is closer to mathematical physics. Here one is more interested in the mathematical constructions and methods needed in theoretical physics. It is much more like mathematics than physics.

Edited March 19, 2010 by ajb

[Icefire]

My guess is that theoretical physics is fomulas or whatever* that are derived using assumptions as to how the universe works that have not been proven.

 

 

*(yeah, REALLY scentific sounding )

[Klaynos]

I would say it's the development of predictions using analytical methods. It's a part of the process of doing physics, not really a subject itself.

 

We used to have theoretical physics degree programs, where the masters projects were purely predictive, all about writing codes and the core modules included more mathematical subjects such as relativistic relativity, analytical dynamics etc...

[Royston]

I agree with the second bullet point, in that all physics is theoretical (but that extends to every other branch of science.) I've never really given it much thought, to the meaning of the term.

 

I've always stuck it in the category of 'what is yet to be tested', but that doesn't make sense with afterthought...I guess it's indicative about the perception of physics more than anything else, that such a category should exist, i.e over theoretical biology et.c

[Cap'n Refsmmat]

I spoke out against the "Modern and Theoretical Physics" section of this forum on some occasions, the main reason being that apparently no one knows what the title means. The best answer I got was "it means the things written below the title", which is "Atomic structure, nuclear physics, etc.", presumably meaning to include particle physics. Well, there certainly is no reason to consider those fields the most modern ones in the sense of "new". I see no reason why those fields should be more theoretical or abstract than others, but I do think there is the tendency to assume that the more away from everyday length-scales a field of physics is, the more "theoretical" it is.

 

Hmm. Given the current organization of the Physics forum, and the difficulty of rearranging thousands of old Physics threads, what do you think would be the best name? Is there a better title we can give the various Physics subforums?

[StringJunky]

Hmm. Given the current organization of the Physics forum, and the difficulty of rearranging thousands of old Physics threads, what do you think would be the best name? Is there a better title we can give the various Physics subforums?

 

With respect to people not versed in Physics...when they think of Theoretical Physics they probably really mean 'Novel' Physics.as in untried, untested or speculative.

 

One additional subforum you don't have that might be useful is Applied Physics:

 

Applied physics is a general term for physics which is intended for a particular technological or practical use.

 

In my uninformed opinion, Modern and Theoretical Physics is basically meaningless....the other subforums cover it.

[Hendrix]

Einstein would be the father of modern & theoretical physics, would he not? There by modern & theorectical physics would simply be post-Einstein or Einsteinian physics. It's era more so than content, which the 'modern' suggests.

[ajb]

Einstein would be the father of modern & theoretical physics, would he not?

 

For me the farther would be Newton. I think he was the first to apply mathematics to physics in way we would recognise today. He also was in the same way the farther of mathematical physics as he needed to develop the mathematics itself for this application.

[StringJunky]

For me the farther would be Newton. I think he was the first to apply mathematics to physics in way we would recognise today. He also was in the same way the farther of mathematical physics as he needed to develop the mathematics itself for this application.

 

Do you not think think Modern and Theoretical Physics is the umbrella term for the rest and should in fact be the forum header and not a subforum?...it seems to cover everything.

[timo]

Thanks for the replies so far. I'll probably comment on them as soon as I can spare the time to consider them and formulate a reply/statement. Until then, further comments and discussion are highly welcome. This thread is not supposed to be about the forum organization on sfn but more towards the question what people in general (or in particular) do consider "theoretical physics" to be.

[ajb]

Do you not think think Modern and Theoretical Physics is the umbrella term for the rest and should in fact be the forum header and not a subforum?...it seems to cover everything.

 

I am not sure how easy or useful a complete rearrange would be. It is also not really what the thread is about.

 

Modern and Theoretical physics covers just about everything. So your point is valid. And goes towards an answer to the opening question. Anything that is described in mathematical terms is theoretical physics.

[StringJunky]

]I am not sure how easy or useful a complete rearrange would be. It is also not really what the thread is about[/b].

 

Modern and Theoretical physics covers just about everything. So your point is valid. And goes towards an answer to the opening question. Anything that is described in mathematical terms is theoretical physics.

 

I take your point and you are right in the context of this whole thread but it was this bit I was addressing' date=' albeit unduly narrowly and I see now, in hindsight, not the OP's intention:

 

[i']I spoke out against the "Modern and Theoretical Physics" section of this forum on some occasions, the main reason being that apparently no one knows what the title means.[/i] (first bullet point).

[Mr Skeptic]

Theoretical physics is mathy and philosophical, where logical reasoning is used in lieu of experimentation. This may be to avoid time consuming and unnecessary experiments, but also is the only physics that can currently be done on certain topics dealing with things currently beyond our experimental capabilities.

[ajb]

... used in lieu of experimentation.

 

That is not the generic case. It is however true of particle physics where the theory is now well in advance of the experiments. This is no so much the case in condensed matter physics for example. The fractional Hall effect is a good example of experiment proceeding theory.

[Severian]

I agree with the sentiment that there really shouldn't be any separation between theoretical and experimental physics. After all, theory that is not testable is not physics at all, and an experiment needs a theoretical hypothesis to test otherwise it is just mucking about.

 

However, in modern times both theory and experiment have become so complicated that it is incredibly hard to understand both fully. Someone who focussed on the mathematical formalisms and the predictions that a theory makes may not have the time or inclination to figure out exactly how some sophisticated bit of kit, like a silicon vertex detector works. Similarly, the guy building the experiment, while he may understand the motivations and goals of the experiment, may not have the time nor inclination to understand the intricacies of the prediction itself and how it relates to the underlying theory.

 

So while I think it is a shame that we don't have Renaissance men who understand both, it is a reasonable level of specialisation in order to make advancement more efficient.