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Which branch of physics is the most fundamental one?

  1. Aug 9, 2009 #1
    I'm still undergraduate and want to explore various branches of physics. I just feel that I like theory more and that's it. However I'm curious which branch of theoretical physics allows you to explore fundamental aspects of universe. I've heard that String Theory, QG, HEP etc. only sound sexy and not always lead to interesting reaserch. That's why I'm asking for honest opinion - which branch of theoretical physics is really fundamental and interesting as a reaserch field?
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  3. Aug 9, 2009 #2


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    Particle Physics.

    Think LHC
  4. Aug 9, 2009 #3


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    What do you mean by fundamental?
  5. Aug 9, 2009 #4
    particle physics is a dying branch. most of the theory is all worked out. I would say that the most fundamental you can get is working on the interface between quantum mechanics and gravity. that being said, many years and careers have been wasted on this.
  6. Aug 9, 2009 #5
    QFT is pretty fundamental...and it leads to jobs (condensed matter physics being a good example)
  7. Aug 9, 2009 #6
    But people who do field theoretic condensed matter are in CONDENSED MATTER. Not, "fundamental" physics (i.e. qft/string/LQG etc.)
  8. Aug 9, 2009 #7
    try getting an academic job after writing a thesis on string theory. All I was saying was that QFT is fundamental. Once you know it, you can pursue more fundamental theories within the QFT framework... or you can work in a field that already uses QFT.
    Last edited: Aug 9, 2009
  9. Aug 9, 2009 #8


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    Fundamental physics seeks to find a uniform basis for an understanding of nature. For a long time, it was hoped that Newtonian mechanics based on particles and forces could be such a basis. For example, the then phenomenological theory of Thermodynamics based on concepts like temperature, entropy etc. was explained within the framework of Newtonian mechanics as the behavior of large numbers of particles, i.e. the statistical mechanics of particles. Then came Electrodynamics with it's concept of 'field'. Newton of course tried to explain light in terms of particles and forces, but it was gradually recognized that this was not possible in any natural way. At the same time, atomic phenomena were being investigated, and it was realized that Newton's scheme could no longer be considered a basis for physics. The search for a new basis began, and continues to this day. The frontier of current research to find such a uniform basis is the search for quantum gravity. 'Fundamental' of course does not mean 'most important'. There are many extremely rich and interesting phenomena to study at a higher level, like the science of materials based on quantum principles etc.
    Last edited: Aug 9, 2009
  10. Aug 9, 2009 #9
    I mean the one that tries to answer questions about true nature of universe, structure of matter, energy, gravitation etc. I also wonder which (if it's possible) branch allows you for freedom and imagination useing. I mean being "doomed" to only one way of thinking and exploring it with pure math only which has nth in common with physics doesn't seem to be fun.
  11. Aug 9, 2009 #10


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    Many people (probably most) who are just beginning their study of physics want to understand the 'true nature of the universe' or the 'fundamental structure of reality'. There's nothing wrong with this of course, but I'd just like to point out that your ideas about what 'truth' is, and what physics itself is will change as you learn more about it, and some of your previous expectations of physics will seem naive.

    Physics is built on the most primary concept of all: experience. It tries to find order in experience. Our belief that this search is worthwhile is based on success alone. There is no a priori reason to believe that experience should be comprehensible in this sense. As Einstein famously said, the most incomprehensible thing about Nature is its comprehensibility. Physics is a natural evolution of everyday thought. We intuitively use a lot of physics everyday. For example, we order our visual experience in a mathematical structure called Euclidean 3-space (the ordinary three dimensional space with distance given by Pythagoras' formula). This is probably the oldest example of a physical theory, consisting of the mathematical structure E3, together with a map of our experience into this structure (done intuitively) (all theories of physics are of this form: mathematical structure + map of experience into it). This theory makes available various concepts and constructs like 'distance', 'point', 'line', 'angle', 'rigid body' etc., and gives these things various properties which must be checked against experience to test the theory.

    The next big development in physics came with Newton, which is a theory for understanding the phenomenon of motion. It builds on E3 by introducing the concepts of 'point particle', 'force', 'mass' etc. Newtonian mechanics is still quite close to everyday human experience and intuition, so it is difficult for us to appreciate that these concepts are not derived inductively from experience, but are invented by us in a creative process in our search for order and pattern in experience. For example, the idea of 'force' is not needed, and doesn't exist as a fundamental concept in other formulations such as Lagrange's mechanics. So a question like, "is gravity truly a force?" has no meaning. The only possible meaning that one can give to this is within the context of some theoretical description of the phenomenon of gravity as it presents itself to our experience. It is a force in Newtonian physics, it is a term in the Lagrangian function in Lagrangian mechanics, it is a tensor field in general relativity etc.
    Last edited: Aug 9, 2009
  12. Aug 10, 2009 #11
    I am fully aware of that fact. I have never said that I have certain plan for my future. I hated physics in high school, chose EE and when changed to physics though that I like experiments more so I know that everything can change. However I got interested in physics because of my desire to know "truth" and it happened to be similar to my interests. If there were gods in this world I would never bother studying it and choose being priest instead. I see "fundamental" physics as one of many options and want to know more about it.
    However asking about it's nature isn't that bad. I know that math isn't a tool that human invented but it exsists within nature. However it's easy to forget about it and use it as a tool. What's more we can't use "true" math but only an image which can easly distort reality. You can prove ******** which is "correct in math terms". You can try to know sth useing many ways however it's easly to forget about your goal and focus on a way only. I am not experienced but I've seen many ppl who were so deep in "math-tool" stuff that they forgot about it's true meaning. They forgot that "force" and "tensor field" describes the same thing and that different way can give you more information but it's still nature, not "math-tool" object. What's more there is a difference between mathematical and theoretical physics and useing imagination is also important. What I'm trying to say - it's good when you can look at sth from many points of view and that's it.
  13. Aug 10, 2009 #12
    Well firstly I'd like to point out that math IS a construction of humans and not something that exists. It is an internally consistent abstract framework. The world around is NOT a 3D-Euclidian space but to first approximation it can be MODELED as one. Holding 3 beans in your hand is no more THE NUMBER 3 then pushing to piles of beans together is the OPERATION addition.

    Now that that's out of the way, all theoretical physics is math (the THEORY is a mathematical theory and thus if one studies the theory/expands it, one is doing math). There are EXPERIMENTAL particle physicists who work on the colliders and such and THEORETICAL particle physicists who work with pen and paper and computers. Any new "perspective" one takes is still going to be expressed mathematically. Therefore, if you want to do "fundamental" you will learn lots and lots of math. (In fact if you do any field of physics you're still going to do lots and lots of math)

    Furthermore, every physics major and their cousins dog came into the field after reading a book like Elegant Universe or A Brief History of Time and wants to do string theory or quantum gravity (I know I did). However, in reality very few of these physics majors go on to do that. Now part of that is because these fields are very competitive but also it's hugely due to the fact that as these majors go through their studies they start to realize that either string/QG doesn't sound as appealing as they originally thought or that they found another field they like much better.

    In fact many people get the impression from the popular science community that MOST physicists do "fundamental" when in reality the biggest field of physics is CONDENSED MATTER.

    So anyways, I'd say the best tact is to stay in physics and just explore as many disciplines as you can in your undergrad. Do some mathematical physics, as many quantums as you can, condensed matter/solid state, if your school offers it try modern optics, maybe an introduction to particle physics and general relativity and simply SEE WHAT YOU LIKE. That's probably the best way to do it. You really don't choose a "field" of physics until grad school (and even then there's usually room for switching). The first 3 years of a physics major are usually identical regardless of what field the person wants to work in because ALL physicists need to know statistical mechanics, quantum mechanics, thermodynamics, classical mechanics, optics and electrodynamics (and mathematical physics)
  14. Aug 10, 2009 #13
    I wish you read what I wrote before. It's last time I'm telling this - I am not planning my PhD now and I won't start doing this after reading this topic. I know how important math is and I like it. Oh and I've never read popular science or SF books about physics before. In reality I accidently got interested in physics because of solid-state physics labs during EE major. I found superconductivity fascinating and wanted to study it. So please don't tell that I did sth while I didn't. Putting everything aside - let's get back to the topic.
  15. Aug 10, 2009 #14
    Sure, I personally know many young people who obtained such positions during the last five years. Try getting a waiter position if you are a bad waiter. If you are a bad string theoretician, sure you'll not get a position. How is this relevant ?
  16. Aug 10, 2009 #15
    Well superconductivity is in condensed matter. Not "fundamental" physics.
  17. Aug 10, 2009 #16
    I know that. What I'm trying to say is that I'm interested in various topics - not only "fundamental" ones. I just want to gain information. Why fundamentals are more competitive than others? Which field leaves you more space for different methods of thinking? Which one isn't explored like HEP?
  18. Aug 10, 2009 #17
    There is a not so popular field, some people call it philosophy of science. It deals with very fundamental aspects, like various interpretations of quantum physics and stuff. This field certainly lets you explore "different methods of thinking". To get a flavor of this field start with exploring EPR experiment ;)
  19. Aug 10, 2009 #18
    Well like I said the biggest field in physics is condensed matter. Now of course I'm biased because that's where I'm currently focused but there are tons of very cool things like superconductors, superfluids, carbon nanotubes, Bose-Einstein Condensates, quasi-particles, etc. In particular I found the entire notion of Emergent Phenomena and specifically quasi-particles to be very fascinating. And there is very much a ton of work to be done in condensed both in terms of experimental and theory. In addition, feld theoretic techniques (a la quantum field theory), computational approaches, engineering and experiment all have their place and you can experiment with a whole lot of approaches and problems (although at some point you're going to have to narrow your focus/specialization, that's life). There are even "fundamental" theories/formulations that are done in condensed matter (to varying degrees of success) like string-net theory (not related to string theory).
  20. Aug 11, 2009 #19
    I was sure that in theoretical physics "thought experiments", questions, various ways of thinking etc. are as important as math. Do you really need to do sth so exotic and new discovery lacking like philosophy of physics?
    I am familiar with CM somehow so I have a general idea about working in this field. That's why I'm asking about fundamentals because I have no idea about them.
  21. Aug 11, 2009 #20
    Alright dude you really need to specify what you mean by fundamentals. To us that means string theory/LQG/GUT, etc. foundational physics which is usually done in cosmology and theoretical particle physics. Is this what you mean?
  22. Aug 11, 2009 #21
    Yes. I am asking about all that stuff. And because I have no idea about it and I won't because undergrad covers only basics of physics and reading popular science book isn't the same (so it's pointless to do so in that matter) and in my country you need to know what you want to do before going to grad school I want to know which one is the most "fundamental", which one isn't explored like HEP, which one allows you for many thought experiments and different methods etc, which one only sounds sexy and which one can provide interesting reaserch. I just want to know more about working in fields which may be interesting for me.
  23. Aug 11, 2009 #22
    Well I don't think you're going to find anyone in any of these fields that wouldn't claim their field is the best and all those fields are going to be extremely math heavy and light on thought experiments (all physics fields are). Think about all the physics thought experiments you can (I've got like 6 or 7) and think of all the mathematical results, symmetries, reformulations, etc. (Hundreds and hundreds). Thought experiments aren't really a big part of any work of physics. They certainly have their place but there is no "thought experiment" approach to physics. It simply doesn't exist.
  24. Aug 12, 2009 #23
    I know that theory is math-heavy. I don't mind this as long as there is a small space for different methods. I like math but I also like do various stuff when approaching the problem. During undergrad mathematical methods is the only one type of subjects that allows me for abstract thinking and imagination useing - rest (especially theoretical basics of experiments) is very analytical which tends to be boring. I hope that theoretical physics math is similar to that way. Anyway when it comes to fundamentals I am most interested in nature of dark matter and energy, gravitation and link between RT and QM. Which fields cover this subjects?
  25. Aug 12, 2009 #24
    Quantum cosmology.
  26. Aug 12, 2009 #25


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    I think it was Michio Kaku who said one in ten berkeley string theorist go on to faculty positions. Thats pretty alarming
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