# Why physics SE is much more inactive compared to MSE?

I'm a mathematical physics student and learning mathematics(algebraic geometry, complex geometry etc.) and theoretical physics (CFT, string theory, supersymmetry etc.) in the meanwhile.

I found an interesting phenomenon: students learning math are much more active than those laerning physics on line. Take myself as an example, I discuss math problems with schoolmates in online groups everyday, but I even don't know an online group about physics.

[edit: If you think it's a bias, ask yourself: do you discuss with your classmates about physics problems everyday online? And the frequency?

To math problems, my answer is yes, I do. Believe it or not. Maybe it's related to the difference between math and physics. ]

Is that because the difference between different physics branches is so large that people studying different areas of physics don't understand what others are doing?

[Edit: Maybe I shoule restrict it to pure math and physics. For a math student, no matter what field he's going to study, he' about to learn analysis(real, complex, fuctional analysis at least), algebra(linear algebra and modern algebra at least), geometry(analytic, differential geometry at least), and different backgrounds are more and more needed in math studies. But as far as I'm concerned, for a physics student, after learning classical and analytical mechanics, electrodynamics, quantum dynamics and statistical dynamics, they're doing different things. ]

And is that why Physics SE is more inactive than MSE?

In addition, the first question in MSE is asked in Mar 27 '10, for PSE is Aug 24 '10, but now MSE has $$1040$$k questions while PSE has $$132$$k.

Also, math sutdies maybe require more multi-subject backgrounds. For example, if you major in PDE, you may require lots of knowledge ahout manifold since we're more concerned about PDEs on Riemann manifolds. And algebraic geometry is gradually becoming the basic demand for all pure math students. But for physics, there's a huge gap between theoretical and experimental physics, and theoretical physics studies a lot of different things (although they might be the same thing or have some ingerent corrspondence at a very high level, like mirror symmetry, AdS/CFT corrspondence, M-theory etc.)

• Try comparing physics to math here: meta.stackexchange.com/q/321318. You could also compare math.meta.stackexchange.com/q/29577 to physics.meta.stackexchange.com/q/10958 The closing stats tell you a lot about the way the communities function differently, though that doesn't give you a complete answer. – Chair Jan 10 at 12:49
• I'm curious why the comments under this post were wiped with the post being less than 2 days old. Many Meta posts are significantly older and still have all of their comments (neglecting off-topic threads and ones not following the "be nice" policy, though my recollection is that this thread was not in that vein). – Kyle Kanos Jan 12 at 14:19
• @KyleKanos Do you know why a lot of comments were wiped? – Andrews Jan 12 at 23:31
• @Andrews I suspect someone flagged them for moderator attention & they deleted them. This often happens with comments, but not usually after such a short time between posting & deletion. – Kyle Kanos Jan 12 at 23:33
• "If you think it's a bias, ask yourself: do you discuss with your classmates about physics problems everyday online? And the frequency?" It all depended on what we were doing. In high school, I talked about math more because we had advanced math classes offered to us, but our physics was straightforward. Not a lot to discuss. In university, we would usually talk about physics, not pure math, since mechanical engineering was pretty heavy on physics. It all depended on what we were studying. – JMac Jan 15 at 17:44
• @Andrews Actually, I'm a physics & mathematics (double major) student, and this exactly the what I observed in my departments too. In mathematics department, students - assistants - professor, we discuss lots of problems and issues, however, in the physics department, if you don't know student who really digs up every bit of question that s/he comes up with, you basically hardly talk any physics at all. (In fact, I have a friend in physics dept. even one of us wakes up for pee at night, so in that sense, this might be an issue of both communities on encouraging the students to think and argue) – onurcanbektas Jan 22 at 8:10
• @onurcanbektas Ah! Finally meet someone like me :) (shaking hands) – Andrews Jan 23 at 7:57
• I work for a bank and talk physics with pretty much everyone there, physicists and mathematicians alike. I strongly suspect that any perceived lack of communication is due primarily to the person you see in the mirror. – Kyle Kanos Jan 23 at 15:41
• I'm going to comment with an answer that I can't quite fully form - easy math problems are more interesting then easy physics problems, and are therefore more accessible to more people. Thinking about like, proofs of the Pythagorean theorem compared to, for instance, projectile motion. The opposite might be true at the top end - compare K-theory to string theory. – levitopher Jan 29 at 16:52

Is that because the difference between different physics branches is so large that people studying different areas of physics don't understand what others are doing?

I don't think that's right. The branches of mathematics are of comparable magnitude. But I guess it depends on what definition of "large" you're using? Maybe you could dig up some statistics about the number of living mathematicians and physicists, and compare them? Anyway, these are my two conjectures as for why Math SE has more activity than Physics SE:

1. We close homework and exercises more often than Mathematics SE: On Physics SE we mainly deal with physics concepts rather than problem-solving. We have a rather high bar for homework-and-exercises. It's the opposite on Mathematics SE. There can be an unlimited number of mathematics problems, whereas physics concepts are limited (leaving aside the research front).

@knzhou: It's because we close homework. Looking at the Math.SE homepage right now, they would have half as much activity if they didn't allow calculus and high school level questions.

Sounds true to me.

1. On Mathematics SE, the number of users who regularly ask mathematics questions is strictly greater than the number of mathematics students and mathematicians who regularly ask mathematics questions: Most STEM subjects, excluding mathematics itself, depend on mathematics. For instance, physics, engineering, and computer science students often have mathematics questions which are better suited for Mathematics SE. On the other hand, the topics which mathematics students study is generally restricted to the scope of Mathematics SE. You won't find many mathematics students asking physics or engineering or CS questions.

Unlike you, I don't believe mathematics students are intrinsically more active online, compared to physics students. As for:

I found an interesting phenomenon: students learning math are much more active than those laerning physics on line. Take myself as an example, I discuss math problems with schoolmates in online groups everyday, but I even don't know an online group about physics.

...that smells of sampling bias, just as @KyleKanos says:

(...) arguments of the form "I see X exists but I don't about Y existing. Why isn't there Y?" tend to have the issue of sampling bias.

Nevertheless, these are conjectures, not proofs. I'll leave the burden of data collection and statistics to others. ;)

• It's disappointing to see that my comment stating that was deleted after such an extremely short time frame, but I am glad it was captured permanently beforehand. – Kyle Kanos Jan 11 at 18:30
• +1. Math.SE is overrun with do-my-homework questions. I've learned that if I post a question there, I have to give a detailed description of how it came up, so that it's explicit that it's not homework. Otherwise the default is guilty-until-proven-innocent, and I get nasty, snarky comments to the effect that I should look up the material in my textbook. What makes physics.SE livable for me as a professional-level physicist is that we have the homework-and-exercises tag, which I can use to filter out all the do-my-homework questions. – Ben Crowell Jan 20 at 15:47
• @BenCrowell Indeed. Interestingly it's also possible to completely hide all questions having a specific tag. – Blue Jan 20 at 15:51