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What is the difference between special and general theory ?

  1. Jun 20, 2011 #1
    what is the difference between general theory and special theory of relativity :redface:?
  2. jcsd
  3. Jun 20, 2011 #2


    Staff: Mentor

    The Einstein Field Equation.
  4. Jun 20, 2011 #3
    can you Explain more ? i need to learn
  5. Jun 20, 2011 #4


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    This may be too technical of an answer,but in special relativity, the geometry of space-time is Lorentzian and globally flat.

    In general relativity, the geometry of space-time is still Lorentzian, but it's no longer globally flat. The geometry of space-time is locally flat if you consider a small enough region, just as the surface of the Earth is locally flat (within some specified accuracy) if one considers a small enough piece of land. "Locally flat" doesn't mean the curvature dissapears, it just means that you can ignore it for practical purposes like surveying.

    GR also has Einstein's field equations, which relate the curvature of space-time to the matter and energy present.

    If you need or want a defintion of "Lorentzian" geometry, just ask, though it might be helpful to have some idea of the level at which you want the answer.
  6. Jun 20, 2011 #5
    really i need definition of lorentzian geometry and
    what is the meaning of globally and locally because i'm not good at English
  7. Jun 20, 2011 #6


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    The special theory is a theory without gravity.

    The general theory of relativity is a theory of gravity (and I have no idea why it is called "general relativity" instead of "Einstein's theory of gravity").
  8. Jun 20, 2011 #7
    so general theory discuses the relation between space time and gravity
    and special discuses the space time relation
    so G theory more difficult than special
    so i will focus special
  9. Jun 20, 2011 #8


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    The general theory simply says spacetime is gravity. Since mass generates gravity, gravity is changed by moving masses, which means that spacetime is curved.

    Yes, it's good to start with the special theory. There spacetime is flat and unchanging, since there is no gravity.
  10. Jun 20, 2011 #9

    before i start in spacial Explain how mass generates gravity ? how are you Concluded that mean
    spacetime curved by moving masses?
  11. Jun 20, 2011 #10


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    Gravity is the force of attraction between masses. We think of a mass generating the gravitational field, which acts on another mass, attracting it to the first mass.

    Now, what do we mean by spacetime? We mean something that we measure by rulers and clocks. If our ruler has mass, it will be attracted by other masses, and will be bent, so spacetime will appear curved in the presence of gravity.
  12. Jun 20, 2011 #11
    good i think i will begin by special theory ? although i think general theory is more interesting
  13. Jun 20, 2011 #12


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    Yes. Definitely start with the special theory. It is a bad idea to start with the general theory. Mastering the special theory is the best way to start understanding the general theory:)
  14. Jun 21, 2011 #13
    i heard that michlson experiment helps Einstien to begin in the theory of special
    what is this Experiment ? and HOw it helped him ?
  15. Jun 21, 2011 #14


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    This is the stage where you really want to get a book. You're not going to be able to learn SR by asking people questions on web forums. Some special relativity books that I like are (from easiest to hardest):

    Takeuchi, An Illustrated Guide to Relativity
    Mermin, It's About Time: Understanding Einstein's Relativity
    Taylor and Wheeler, Spacetime Physics
  16. Jun 21, 2011 #15
    okay i need easy book or some books
    Last edited: Jun 21, 2011
  17. Jun 21, 2011 #16
    and I love discuses with people now i thin k they will help me ..:smile:
  18. Jun 21, 2011 #17


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    Well, yes, folks here WILL help you but I think Ben's point in saying that now is the time you need a book is that by JUST asking questions here, you will jump around too much. Get a book and read the whole thing through so that you get ALL of the aspects.

    As you are reading, if you have questions then of course it is a good idea to ask them here.

    Good luck.
  19. Jun 21, 2011 #18
    okay thank can you give link for simple book of relativity special ...:smile::redface:
  20. Jun 21, 2011 #19


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    I suggest that you look up the books Ben listed on-line (Amazon will probably have reviews of them) and see if one of them would be right for your level of understanding of math. Doing that will lead you to other titles that you might want to explore to see if they are right for you.
  21. Jun 21, 2011 #20

    i will do when i finish my Exams i will search for find good book
    thank you :smile:
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