Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

How do theoretical physicists know so much?

  1. Jan 9, 2014 #1
    I'm a PhD student in theoretical physics, and I am just amazed by how much physicists working in my field actually know. I am currently studying QFT and plan on going a bit deeper into General Relativity afterwards, but look at people like Rovelli or Susskind (just two names that came to my mind). I mean they know QFT , Statistical Physics, General Relativity, LOTS of mathemathics, and they mix up concepts in all of them, looking like they are at ease with everything they do.
    My question is....when the heck did they manage to find the time to cover that amount of material? I mean QFT (with Chromodynamics and GSW) , studied thoroughly, should take you at least a year...if not more. And GR takes about as much, if you go beyond the introductory stuff...
    Am I ok to feel like I have a hell of a lot to learn, even as a 1st year PhD student?
  2. jcsd
  3. Jan 9, 2014 #2


    User Avatar
    Gold Member

    They all work like dogs.
  4. Jan 9, 2014 #3


    User Avatar
    Science Advisor

    It's only natural to feel this way so don't worry bud. Indeed Rovelli has a formidable amount of expertise in thermodynamics, stat mech, GR, and QFT and whenever I read a paper of his (e.g. his paper on general relativistic stat mech: http://arxiv.org/pdf/1209.0065v2.pdf) I think to myself "how in the world does this guy know so freaking much?!" but it isn't really a mystery. They have a lot of experience and hard work and time under their belt. You on the other hand are a 1st year PhD student so of course you have a lot to learn when compared to legends like Rovelli. What PhD student doesn't?
  5. Jan 9, 2014 #4
    Yeah, but I mean... it's freakin' awsome reading them and seeing how they solve one problem in QFT using GR or Statistical Physics arguments, and so on. Another question, related to the first...after you finish studying something, do you remember how to do the derivations? For example, could you derive the feynman propagator from the ground up, just with a piece of paper and a pen? Is it normal, even for a researcher not to remember complete proofs, but just the essential steps, and what they mean? I found that no matter how many times I go over something, after a while, I need my notes, in order to redo the proofs.
  6. Jan 9, 2014 #5


    User Avatar
    Science Advisor

    I especially love it when a physicist uses purely physical arguments to arrive at a mathematical result. It's extremely elegant even if it lacks "mathematical rigor".

    Not usually no, not if it's a mathematical derivation.

    After seeing it once I could probably outline the main steps i.e. why we need a time ordering operator for the transition amplitude, what kinds of contours to choose in order to re-express the transition amplitude after plugging in the appropriate field etc. but there's very little chance I could derive it ground up step-by-step in detail.

    But more importantly, is it necessary to be able to do that? What insight will be imparted by rote memorization of steps in a mathematical derivation? In my experience: none.

    I can't speak for researchers since I'm a student myself but I too have a need to redo proofs if some time has passed from when I first saw the proofs; sometimes it can be quite annoying because I have to keep flipping back to pages in books. Regardless, I think your statement "just the essential steps, and what they mean" is what's really important in the end, not the individual steps that can always be looked up whenever needed.
  7. Jan 9, 2014 #6
    Few reasons:

    One, those guys are some of the best out there - on that alone you shouldn't really compare yourself to them. That's like comparing yourself to olympic athletes and feeling bad you can't compete with them.

    Two, they have decades of experience and hard work as mentioned, you (and myself since I'm also a 1st year) have maybe one year of real physics experience.

    Three, they really love what they do, and physics is their life. For me, I enjoy physics (most of the time) but it's not something I put all my time/energy into, and I don't ever expect to be like those guys.
  8. Jan 9, 2014 #7


    User Avatar
    Science Advisor
    Homework Helper

    Plus, quite likely they didn't learn most of their "modern physics" from books and lectures. They learned it by hanging out with the people who were inventing it.

    Susskind was born in 1940, Rovelli in 1956. On that timescale, first year PhD students are still wet-behind-the-ears kiddies.
  9. Jan 13, 2014 #8


    User Avatar
    Science Advisor

    Dirac, apparently, could not remember Poisson brackets. He had to look them up in the library.

    His breakthrough came during one of his habitual long Sunday walks in the countryside – “the idea first came in a flash – out of the blue . . . [that] there seemed to be a close similarity between a Poisson bracket of two quantities and their commutator.” But he only “had some vague recollections” about Poisson brackets, and had to wait “impatiently through the night” until the libraries opened, whereupon “I looked up Poisson brackets . . . and found that they were just what I needed.”
  10. Jan 13, 2014 #9


    User Avatar
    Science Advisor

    And so Goldstein was born.
  11. Jan 13, 2014 #10


    User Avatar
    Science Advisor

  12. Jan 14, 2014 #11


    User Avatar
    Science Advisor

    One can learn a lot during several decades, provided one has acquired a good study technique. I.e., actually reproduce the calculations one sees sketched in journal papers, rather than just reading them.

    A wise man once told me: "much of a scientific career consists of reproducing what others have done". My own learning curve certainly accelerated when I started accepting and applying that wisdom.

    If, at the end of each year, you don't feel like there's even more to learn than at the same time last year, then you're not studying/researching effectively. :biggrin:
  13. Jan 18, 2014 #12
    A question arises after your post Qubix. Whether current system of education in universities produce such guys which one know many things out of their professional field of study?Doesn't the growing importance of paper and citations make an expert collapse to his narrow area of research and do not study and think about other branches?
  14. Jan 18, 2014 #13
    I have read your posts and am really astonished by the fact that a person of your age can learn this much. From your earlier posts, I came to a conclusion that you have read math books and lot of physics at same time. How could you keep yourself motivated in the process?
  15. Feb 19, 2014 #14
    Take Heart. My abilities are very modest compared to Susskind and Rovelli, and I am as old as Rovelli. I was a first year PhD student 35 years ago. I now realize how much I still had to learn. You will learn too.

    I also agree with the other poster. They all work like dogs.
  16. Feb 20, 2014 #15
    I once read an article on good pianists. Top pianists all spend some crazy thousands of hours playing their pianos, and they accumulate far more hours playing than their lesser colleagues of the same age. Edison is credited with the saying "a genius is 10% inspiration, 90% perspiration" - I may be misquoting the percentages, but that does not change much: to excel at something, one must invest a lot of hard work into it.
  17. Feb 20, 2014 #16

    Ben Niehoff

    User Avatar
    Science Advisor
    Gold Member

    This, pretty much.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook