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String theory - what do strings look like?

  1. Mar 14, 2009 #1
    I've watched a few documentaries about string theory, read about it, heard people talk about it. But I cannot visually grasp what the heck strings look like.

    Physicists (maybe not all of them but the ones I only hear) like to say stuff like that if you pluck a guitar string you get a certain note from a certain frequency, and if you pluck a string on a different fret you get a different frequency, etc. And everything in nature is made from all these different notes. The universe is a symphony and the laws of physics are harmonies in that symphonies.

    OK, I'm not a musician or a scientist. But many years ago I was in band in junior high. I also think I can match anyone's skills at turning on the TV and watching a show on parallel universes. This explanation is pathetic.

    How long are the strings? How wide? Are they actually string-shaped? Are they straight or narrow or curly or coiled or something else? Are they actually vibrating and sending off frequencies? Can their vibrations change? How do they vibrate, or how are their frequencies assigned in the first place? Do strings themselves compose matter or just the frequencies? Do they just float around? Do they stick to other objects? Do they stick to each other? Do they repel? Do they create a force? Do they respond to force? Do a trillion million gazillion of them make a proton or something? On and on and on.

    The analogy is driving me nuts. I compare it to trying to visualize the curvature of spacetime. Just about every demonstration of that goes like this: The sun sits in the middle of a proverbial rubber sheet, thus creating a depression in the sheet, and that depression represents the gravity drawing the earth toward the sun, etc. Yeah OK, great - you just told me about gravity by using gravity.

    How the hell do these people get PhDs?

    Someone around here posted a link that, for the first time for my eyes, explains spacetime curvature correctly. Don't remember who it was, sorry. But I kept the link, so thanks a trillion million gazillion, forgotten poster:
    http://www.adamtoons.de/physics/gravitation.swf
     
  2. jcsd
  3. Mar 14, 2009 #2

    cristo

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    By performing original research in the field. The ability to do so is not related to the ability to describe a highly mathematical theory to someone who does not understand mathematics. It's like trying to explain something to someone that doesn't understand English. Physicists try to do so, but will often come across people who not only require the subject to be dumbed down for them, but then complain that the analogies used are not detailed enough. Well, duh!
     
  4. Mar 14, 2009 #3
  5. Mar 14, 2009 #4

    malawi_glenn

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    how do you know if it is good when you can't compare it with the real deal?

    ColonelTravis: What if strings CAN NOT be visualized?

    The talk about gravity making a depression in a 2D sheet in 3D space is just an analogy. The depression around the sun will induce the earth to get close to the sun since the earth will follow the shortest path in space time. Now in reality this is done in 4dimensions and that can't be visualized. Earth follows geodesics, the shortest path. So I think you missed the point of that analogy.
     
  6. Mar 14, 2009 #5
    I'm glad I'm not the only person who is bothered by this explanation.
     
  7. Mar 14, 2009 #6

    jtbell

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    Search for "rubber sheet" in the relativity forum here and you'll find a lot of the physicists here are unhappy with that analogy, too.
     
  8. Mar 14, 2009 #7

    DaveC426913

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    At the risk of sounding trite (but I'm not trying to be trite), try reading a book on the subject. This is a big subject - videos are necessarily limited and short. They're not going to go into how strings vibrate within the 5-dimensions of Calabi-Yau manifolds.

    I highly recommend Brian Greene's The Elegant Universe. It will give you all the answers you need.

    BTW, even without a formal background in science or math it is possible to get your head around Brian Greene's ideas - though you may have to apply a softener to your skull-bones to accomodate all the brain-stretching.
     
  9. Mar 17, 2009 #8
    Brian Greene - King of The Rubber Sheeters. Yes, I've got Elegant Universe. Easy read, horrible analogies. Writes Greene halfway through the book: "But don't let the name fool you: Unlike an ordinary piece of string, which is itself composed of molecules and atoms, the strings of string theory are purported to lie deeply within the heart of matter. The theory proposes that they are ultramicroscopic ingredients making up the particles out of which atoms themselves are made. The strings of string theory are so small—on average they are about as long as the Planck length—that they appear pointlike even when examined with our most powerful equipment. "

    When you read Elegant Universe, you discover that fundamental strings are absolutely nothing like violin strings or shoe strings or any other strings humans are familiar with. But for some reason Brian Greene writes several hundred pages on how you should think they are. He may be one of the smartest guys on the planet, but I have no clue why he is thought of as one of the best explainers of the physical world to normal people.

    I've got string books by Polchinski, Susskind, Smolin, Kaku, the Beckers - math equations out the ying-yang, which I cannot follow, but they have string diagrams that resemble nothing found in The Elegant Universe. In fact, some of them are tubes. Greene talks about loops a great deal. A loop may be composed of string, but a string is not necessarily a loop, and a loop isn't a tube. How any of these things compose matter is still a mystery to me, but at least it's a mystery to everyone else.

    Science education has been going down the drain for a long time, and I will be the first to admit that I am indeed in that sewer system. But it used to not be that way for me, I loved science in school and I want to know more. These string people are not helping.
     
  10. Mar 18, 2009 #9

    Fra

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    Hopefully, before you starting reading such a book, you have some own questions on what the world is like. After all string theory is not established scientific knowledge in the ordinary sense. It's rather a speculative idea or proto-theory that may or may not answer some of the open questions in physics.

    Some lists of open questions
    http://math.ucr.edu/home/baez/physics/General/open_questions.html
    http://en.wikipedia.org/wiki/Unsolved_problems_in_physics

    I think before you start reading up on possible answers, one should appreciate and accept some of the open questions. What can we with resonable confidence say that we "know", and is established science, what are the "open question", and what are the current lines of speculation with regards to these open questions? Here string theory is one speculation, among several. Maybe if you read it like that, you will not expect more than is reasonable.

    I think the honest scenario is that there is alot of things noone knows. And alot of people are researching answers. String theory is one branch of such research.

    I think a plain 3D visualisation is the wrong level of understanding string theory. It's somehow an abstraction of the microstructure of matter, whose degrees of freedom are assumed to mathematically be like a string in a background space, and this microstructure can then be excited and have different states, and the tendency for excitation is given by a string action, which is a physicists mathematical measure of how likely certain paths or modes are. The hope is that this microstructure, can encode all forces in nature.

    This is all a conjecture, and the implications, and confirmations of predictions emerging from this picture is still in progress. Noone knows if this is correct. So what is presented is a line of reasoning, not a confirmed fact.

    Edit: String theorists of course argues that string theory is the, so far BEST candidate for a future theory, but set aside that such rating is a matter of who you ask, it's nevertheless IMHO still only a kind of conjectured reasoning.

    As I see it, some of these popularizations are not just educating the public, it may well also I think contain elements of selling their own ideas.

    There are string researchers that have "popularization work" on their agenda, and I suspect there is a dual motive for that.

    /Fredrik
     
    Last edited: Mar 18, 2009
  11. Mar 18, 2009 #10

    apeiron

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    Do you face a similar issue imagining electrons and protons as little balls? And they would be equally much an unreal but perhaps useful mental starting point for thinking about these things. You start by thinking, oh an electron is a little ball, then have to gradually learn the ways it is not really.
     
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