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

Theory that everything is composed of 'string'

  1. Apr 6, 2003 #1
    In the search for the ultimate particle that all matter is made of scientists once thought that it was the atom and then protons and neutrons etc. Now the theory that everything is composed of 'string' has come along and not everyone agrees with it.

    Does it not seem obvious that all matter is made of a 1-dimensional object (such as string) because if it was not then surely the multi-dimensional object could theroticaly be broken down?
    Last edited by a moderator: Feb 4, 2013
  2. jcsd
  3. Apr 6, 2003 #2


    User Avatar
    Science Advisor

    Nothing is obvious! Before string theory, the fundamental particles (leptons, quarks) were thought of as points, recognizing this leads to problems when you get too close.
  4. Apr 7, 2003 #3
    Exactly. I realize that string theorists believe this is almost the TOE and that they are thiiiiis close to completing it. History, however, dictates that quite the opposite is true. Who is to say what may be discovered -theoretically or not- in the future. Strings (or branes) may be found to be composed of even smaller than plank length particles. only time will tell

  5. Apr 7, 2003 #4
    What are branes? Hawking tried to explain them in the universe in a nutshell but I did not understand.
  6. Apr 7, 2003 #5
    The n-dimensional equivalent of strings. Points are 0-d objects; strings 1-d object; n-branes are n-dimensional objects. I like to think of 2-branes as little flapping sheets, sorta like a flag.
  7. Apr 7, 2003 #6
    Not sure that I understand. Are they just dimensions then and if so why not just call them that?
  8. Apr 7, 2003 #7


    User Avatar

    Strings are not dimensions, though the only have one dimension. Branes are the same - they are fundemental objects with 0 to 10 dimensions.
  9. Apr 9, 2003 #8
    Do you mean 10 space and 1 time, or 10 dimensions total? Would it be somehow possible that there is a fundamental building block of time? thatd be crazy...sorry im kinda...hmmmmm 'out of it' right now :wink:
    Last edited by a moderator: Apr 9, 2003
  10. Apr 9, 2003 #9
    Reality and mathematic models are not equivalent in my opinion. The superstring theory seems more and more to illustrate this point as physicists develop new math continually to complete it. I can't really say I understand any of the math, but it is impossible for to picture a 10 dimensional universe. The fascinating thing to me about the string theory is that it deals with the quantum foam problem by saying that you can divide space no further once you have reached a minimum of Planck Length.
  11. Apr 9, 2003 #10

    The quantum undulations, which, due to their complexity shall never be able to be expressed mathematically, have been 'smoothed' out by string theory. The theory introduces the concept of supersymmetry, which when implemented does not describe the undulations but rather allows string theorists to work around them. These superpartner particles are said to have the exact mass, but opposite charge and spin of their partners. However, to this day none of these particles have been experimentally detected. This is somewhat of a mystery because they would certainly be large enough for our accelerators to detect given their size and mass.

    I believe in Geneva they are constucting the Large Hadron Collider which will be completed within the decade. This collider is supposed to be able to detect these partners which thus far have remained unseen by us. But why are they unseen? If they have the same mass just opposite spin and charge from the particles we witness today, then why havent we observed them in our current accelerators?

  12. Apr 9, 2003 #11
    I'm at a loss at whether to believe in existence of any matter that exists in less than 3 dimensions. With the wave function, we can say that the object can and will exist in 3 or more dimensions at one time.

    It's difficult to comprehend something that has length but has no width whatsoever. No matter how close the width of the particle approaches 0, it will never do so, because then the particle will cease to exist and so will the length of the particle, which is its only dimension. I must say that it will most likely be the smallest possible width of any quantum particle, which just may be the base of all measurement.

    Also, if we have a 5th or higher dimensional particle, the string of the particle would be spinning into the 5th or respective dimension, would it not? But nevertheless, the very center of the string exists in all dimensions, as it has no spin.

    I had an idea once, that photons may be 5th dimensional matter, based on the Kaluza-Klein theory; but all we can observe is the very center of the string, or even a spinning electron that possesses no spin that we can observe in any dimension. Being that the string is the base of matter itself, the center of the string, that we can detect only due to the particles dissasociation of the electron in this case with any other subatomic particle, with the only one to have a spin. But if we dig deeper into the photon, if it is an electron in the 5th, perhaps we can detect another spinning string, or the center of which.
  13. Apr 9, 2003 #12
    When one explores the quantum level, by definition that observer interferes with the nature of the object. Such interference may not only affect observables included in the Heisenberg uncertainty principle, but also the (spacetime) geometry of the underlying structure. Particles could have a fractal nature whose nonlinearity corresponds to general relativity, but changes dimensionality depending on the scale probed.
  14. Apr 9, 2003 #13
    Wait, so if we suppose that I had superpowerful 20/1 x 10^-20 vision, that I could see a subatomic particle, and measure it, somehow, that the size would change relative from measuring it while observing it at 20/20 vision? I would expect the scale you're viewing it to change, but the unit of measurement to reamin the same through any conversions.
  15. Apr 9, 2003 #14
    Not so much the size, but structure and dimensionality. As a crude example, magnify a "2-D" piece of paper until one sees its "1-D" fibrous nature, then again to its atomic "3-D" nature, and still again to the "0-D" nature of its point-like electrons. This might continue indefinitely, as others have suggested. The progression of dimensionality with scale thus transforms seemingly at random, and possibly without limit.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook