I am asking this question based on my recent experience as a physics major at a well-known school of science and engineering. My basic question is,

Why does the field of physics (at least at an undergraduate level) seem to be exclusively concerned about the "really small" scale and "really large" scale phenomena, and virtually nothing in between?

Background: I began college with a certain idea of what I thought physics was all about, the things I may end up studying, and boy was I wrong. To explain, I thought I would be learning about more "tangible" things, like things on the human scale. Examples of this might be fluid flow, acoustics, combustion/heat transfer, high speed collisions (not between particles), etc. I believe this first impression of physics was due to my experience in classes like Physics 101, where basic concepts like friction, kinetic and potential energy, spring systems, circular motion, and so on, were taught.

As the years went by, I very much lost sight of those expectations, learning mostly about quantum mechanics, solid state physics, electricity/magnetism, and relativity. I understand the practicality and usefulness of these topics in our modern world. What I am curious about is, why is the human-scale phenomena almost completely neglected in the undergraduate physics education? Or is this not true of other physics programs? I can not accept the answer that my friends have given, which is along the lines of "there is no interesting phenomena at that scale"... this just seems mislead.

So in summary, I am wondering if anyone has a reasonable explanation for why the "human-scale" (in between planetary and microscale) phenomena seems to be completely neglected at the undergraduate physics level.

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    $\begingroup$ Almost every physics experiment is an applied physics problem on the human scale. If you decide to be an experimentalist, you will be doing mostly mesoscopic physics for the rest of your career. The thing is... YOU are expected to pick up those skills on your own. We don't have time to teach them in class. If you can't do that, you won't be enjoying "mesoscopic physics" even a bit. $\endgroup$ – CuriousOne May 3 '16 at 23:32
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    $\begingroup$ There are exceptions to "there are no interesting phenomena at that scale", for instance nonlinear dynamics (chaotic systems) and biophysics. But they are not a typical part of "generic background" that an undergraduate "should" get. If you are interested you have to actively seek people who are experts on those. $\endgroup$ – Conifold May 4 '16 at 1:56
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    $\begingroup$ @CuriousOne There is a difference between cramming highly differentiated courses down someone's throat, and providing enough skills and opportunities to learn the rest as needed. I am just observing that an undergraduate course devoid of practical (experimental, meso scale) physics seems to prepare one insufficiently for professional life as a physicist. But maybe that's where Masters and above degrees come in. If you didn't lose your audience in the meantime. $\endgroup$ – Floris May 4 '16 at 2:33
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    $\begingroup$ I feel obliged to point out that the only reason you were taught those basic Physics 101 concepts in a physics class is because they are easy, intuitive examples to which you can apply the simplest differential equations. Unfortunately students are never told this, and many like you come away thinking advanced physics will be similar to introductory courses. The reality is those topics are a holding pattern while your math education catches up, giving you at best just a glimpse of some important physical principles. $\endgroup$ – user10851 May 4 '16 at 7:37
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    $\begingroup$ @Merkh if its any consolation many physics undergraduates (myself included) feel the same way as you. Before University and during the first year (Physics 101) I loved physics as it taught me how the world works. By the time I was half way through the second year it had basically turned into very hard maths and I was unable to connect what I was studying to the world around me. Luckily I was also interested in computing and had options to specialise. Now I have a decent career in IT. $\endgroup$ – Qwerky May 4 '16 at 14:43

Most of the "intermediate scale" problems were "solved" long ago, and are now mostly the domain of engineering: application of physics to real world problems. I put "solved" in quotes: "real world" solutions require that you don't make all the simplifying assumptions that make many problems "solvable" - this is no such thing as a spherical cow. Nonlinearity, instability, turbulence, chaos... all these things conspire to make a full analysis of real world problems really, really hard: while there are physical principles that apply, you need to open a bigger tool box to really get a handle. The result, as David Hammen pointed out, is the emergence of many subspecialties: not the stuff of undergraduate physics courses, but very much the path to many professional careers.

That leaves the more interesting, "esoteric" stuff as the material at the frontier; this is where research is happening, and that becomes the material that the lecturers (most of whom are researchers) find most interesting.

In the end, the macroscopic phenomena are mostly a manifestation of the microscopic mechanisms underlying them. So to understand heat capacity, conductivity, or almost any macroscopic phenomenon, you are quickly looking for explanations on the microscopic level. It all comes from a desire to figure out "how it works", rather than "how to make it work". The former is physics, the latter engineering.

If it is "completely neglected", you are either expected to come in with a very full bag of tricks - or you are indeed being somewhat short-changed. I know I learnt a lot of "classical" physics as an undergraduate - plenty of stuff that had not been covered in high school. As an example, Landau and Lifshitz volume 1 - "Mechanics" - certainly goes far beyond the high school level. It was one of the texts we studied in university, and it was challenging!

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    $\begingroup$ Right - the problems are solved but you don't know the solutions yet! Incidentally - do you know the Feynman lecture series? Again about 1/3 "world scale" physics. And accessible enough that you could study it on your own if you feel you are missing out. $\endgroup$ – Floris May 3 '16 at 23:50
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    $\begingroup$ @Merkh: While I agree with Floris... one warning... theoretical physics is the explanation of how to set up problems, it rarely has the solution in canned form. Even Newtonian physics is still very much an active discipline with regards to the solution spaces. Do not, for a second, think that you can solve even a slightly non-trivial problem with what you can find in these books. $\endgroup$ – CuriousOne May 3 '16 at 23:56
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    $\begingroup$ Gone with the winds of non-integrability? $\endgroup$ – CuriousOne May 4 '16 at 1:48
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    $\begingroup$ @Merkh: The subjects are not neglected. They are taught and practised daily in engineering. The things you mention in your question are all entire fields of engineering by themselves. Fluid flow: aerodynamics (technically fluid dynamics but the most active and funded researchers tend to be aerodynamicists), acoustics: audio engineering, combustion: thermodynamics, collisions: mechanics. There are indeed open questions in engineering that are studied by physicists. They are just not as popular as the modern stuff. $\endgroup$ – slebetman May 4 '16 at 3:30
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    $\begingroup$ I'd argue that rather than saying human-scale problems are solved, I'll say the remaining problems are hard; there are lots of issues at human-scale physics that there isn't a solution to. Researchers find most interesting problems that are hard enough that we don't know the solution yet, yet easy enough that they can make progress on them. So researchers move to fertile new ground (often opened up by new technology, like colliders or telescopes or perfect sphere or particle detectors), where new information could provide new "easy" yet important papers to write. $\endgroup$ – Yakk May 4 '16 at 14:58

In almost every technical field, one of the key goals of an undergraduate degree is to prepare one to work as a professional in that field. Working as a professional physicist pretty much means having a PhD in physics. The key focus of an undergraduate physics degree is to prepare students to enter a graduate school program in physics. Excluding biophysicists, medical physicists, fluid mechanists, aerodynamicists, and other offsprings of physics, professional physicists tend to work in the field of the very, very small, or the very very large.

I'm going to disagree with comments and answers that denigrate engineering and other offshoots of physics as working on "solved problems." These are not solved problems. It's more that physics got too big in the 19th and 20th century. Parts of what were physics split off to become disciplines in and of themselves. Physics proper (what professional physicists do) has come to focus on the very, very small and very, very large. So that's what they teach you in undergraduate schools.

  • $\begingroup$ Fair and thoughtful points. I have expanded my first paragraph. I certainly did not intend to denigrate. $\endgroup$ – Floris May 10 '16 at 0:20

The problem is that many "human scale" phenomena are terribly difficult to treat: friction, fluid dynamics, vorticity, heat transfer... Even if they are ubiquitous in our everyday lives, these things are really difficult (and sometimes impossible!) to treat analytically.

Just think about friction: the microscopic mechanisms behind this force that rules our everyday life is incredibly complicated, thus we are forced to make use of simplified, empirical relations to describe it.

Another example is thunderstorms: today, we still don't have a decent theory to explain how clouds can accumulate such a humongous amount of electrical charge in such a short period of time. And lighting! Even the microscopic mechanism behind lightning is largely unknown. And not for lack of trying!

Think about it: we can solve exactly the harmonic oscillator, the ideal gas, the hydrogen atom, the 2d Ising model, the Schwarzschild black hole...but, what else? Truth is, we can only solve exactly a small number of systems!

Small systems can be relatively easy to solve because of the small number of degrees of freedom, while when we work with large systems (for example in astrophysics) we can ignore the enormous number of "small" degrees of freedom. But when we talk about the so-called mesoscopic (in-between) scale, things can get really messy!


protected by Qmechanic May 4 '16 at 8:28

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