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

String's mass

  1. Jan 4, 2005 #1


    User Avatar

    Do physicists have any idea how much a string or brane would mass?
  2. jcsd
  3. Jan 5, 2005 #2
    Hi Mk.

    I am not a science advisor but I have asked myself this question, so I'll tell you what I think and one of the high hats can correct me if I am seriously off course.

    First, physicists as a general class do not believe in strings and branes. The whole topic is very theoretical. Scientists like to be able to measure things and strings and branes, so far, have never been observed, much less measured. Most of the experimental work on strings and branes has been in the realm of pure mathematics. Wikipedia lists string theory as a protoscience, which means I suppose that it may or may not actually turn out to be scientific.

    I have seen some work on calculating the tension in strings, and the conclusion was that it must be immense. So the energy in the strings must be immense, so the strings must have immense mass. This actually turns out to be one of the problems with string theory, since such immense mass is not actually observed to have an effect on, say, the gravitational force between objects.

    Physics mostly is concerned with events in three dimensions of space and one dimension of time. String theory seems to require eleven dimensions, and perhaps the gravity bleeds off into the other dimensions, or something.

    If you are interested in physics, you should first learn classical physics, which covers pretty much everything that happens in our universe, except for black holes and the big bang. Then you should learn about relitivity, which is also part of the classical world. When you have a grasp of these, you can begin to understand the relitivistic arguments which lead to singularities, objects which probably cannot exist in classical and relitivistic physics, and yet they have to exist or the physics is wrong.

    While you are studying relitivistic physics you should also learn something about quantum physics. The quantum mechanical model, also known as the standard model of particle physics, is one of the finest achievements of human thought and engineering. Unfortunately it conflicts in several particulars with relitivity.

    Loop Quantum Gravity (LQG) is one attempt to unify the standard model with relitivity. There are also other approaches.

    Your question indicates a level of curiosity and interest, and possibly insight, which would serve you well in the study of any science. With this question, you are prying at one of the locks on our understanding of the Universe. Picking those locks is a hobby for many of us and a career for a lucky few. If you want to make a career of it, you need the right tools, which would be a solid basis in classical and quantum physics, with all the math you can absorb along the way.

    Good luck to you. I hope you will find better questions, and that if you find any answers, you will share them with the rest of us.

    Be well,

  4. Jan 5, 2005 #3


    User Avatar

    Yes, I totally understand it is all in theory, I find your comments on learning about a string's immense mass perplexing. Is this a major problem in string theory? It seems it would be, unless you mean comparatively, to what you would envision, strings being sooo much smaller than a proton, about 0.00000000000000000000000000000000000001 (1^-37) inches, a duodecillianth of an inch.

    I'm not sure about gravity bleeding off into other dimensions, it bleeds into other p-branes, though I don't know about dimensions, and most of them are near Planck length.

    Wow! I find that wikipedia lists string/superstring theory of a protoscience amazing! And is it a science? Sure the math is reproduceable, but there are no observations of anything! Are there?
  5. Jan 5, 2005 #4
    Hi Mk

    I am just a student here myself so I don't want to sound as if I actually know anything. But it was such an interesting question. At first I assumed you were a beginner but now I see that you are somewhat advanced, probably more advanced than I am in some areas. Heck, I don't know, maybe I should be asking you questions instead of trying to answer them.

    Anyway, yes, strings are incredibly tiny, on the order of the Planck length, about 10^-33 cm. I don't use inches any more because of the way they clutter up equations with conversion factors. So if they are so tiny, how can they support all those complex vibrations? Think of a piece of wire. You can bend a coat hanger pretty easily. But cut off an inch long piece and try to bend it. That is more difficult, requires more force, due to shorter leverage arm. Make it shorter and bending becomes even more difficult.

    Vibration is a kind of bending. If the complex vibrations required to make particles are confined to so small a length, the energy required to force the bending must be very great. Great energy equals great mass, so the strings must have great mass. I didn't make this up, I read it somewhere, but no longer have the link at hand. Perhaps I could find it again with some searching.

    Anyway, that is a line of reasoning which seems to have application to your question.

    Then, again, how many of them go into making up a particle? Is one tiny string vibrating all alone there in an isolated space? I have imagined not, but this is another unanswered question for me. I imagine that the strings make up a lattice work of some kind, and that each string is an element in the lattice, and that there must be zillions of them in a space the size of a proton, but this is only a conceptual model which has been waiting on evidence, or at least on confirmation or denial according to some as yet unexplored line of reasoning. So if there are gadzillions of them, and if their masses are additive, then observed masses of particles should be much higher than they seem to be.

    As for the dimensional bleeding, that is an argument which seeks to explain why gravity is so much weaker than the other forces. Try this link to the current issue of Nature:


    Here is a relevant quote, (for educational purposes only of course)
    " in 1998, Arkani-Hamed and his colleagues published calculations showing that some of these extra dimensions might be as large as a millimetre (N. Arkani-Hamed, S. Dimopoulos and G. Dvali Phys. Lett. B 429, 263–272; 1998). Such large dimensions, they argued, have escaped detection because everything we know — except for gravity — is confined to the three dimensions of space and one of time. But gravity, they think, might be able to seep into these extra dimensions. This would explain why it seems so weak to us. And, as a result, unexpected variations in gravity could allow researchers to detect the hidden dimensions."

    Arkani-Hamed is at Harvard and I am sure a google search would turn up more.

    P-branes, as far as I can remember, are a generalization of a membrane....meaning a kind of surface. The simplest surface would be a Euclidian flat plane, a 2-brane. By extension of this concept, a 1-brane would be an edge, a 3-brane a volume, and a p-brane would be the generalized term for branes of any dimension.

    Actually, I am not sure what mass is at all. Some work has been done, also reported in this week's Nature, showing that in some conditions the charge of an electron and the mass of an electron may actually become spatially distinct entities. This is referred to as "Splitting an electron" and is, again, a theory derived mathematically, altho I think I remember that it comes from studies of condensed matter and superconduction.

    It could be, so I have imagined, that strings do not have mass at all, but that mass is a property that belongs to larger scales. At the smallest scales, for example in a black hole where space and time themselves become compressed, mass seems to go to infinity. This is an unsatisfactory result. If mass is a large scale phenomena, maybe as time and space are condensed, they fall below the regions where mass has an effective presense. Just a thought, pure speculation.

    Anyway, thanks for the stimulating ideas.

    Be well,

    Last edited by a moderator: Jan 5, 2005
  6. Jan 8, 2005 #5


    User Avatar

    I love your thoughts!
    Well, the wire analogy was good, but think of a piece of paper, if you cut it smaller and smaller, it doesn't get more difficult to bend.

    Actually point particles are known to string theory as being 1 string, and I think the proton is made of a jazillion strings.

    Of course Nature isn't quite a physics journal, I read the article and am thinking if by the hidden dimensions they mean huge p-branes, p-branes highly resemble other dimensions, you can't see, feel, hear or anything them, though gravity does flow between them.

    It could be, so I have imagined, that strings do not have mass at all, but that mass is a property that belongs to larger scales. At the smallest scales, for example in a black hole where space and time themselves become compressed, mass seems to go to infinity. This is an unsatisfactory result. If mass is a large scale phenomena, maybe as time and space are condensed, they fall below the regions where mass has an effective presense. Just a thought, pure speculation.[/quote]

    Maybe if the higgs boson is real, it doesn't effect strings, because its "bigger," some sort of quanity I mean by bigger.

    Thanks for the stimulating ideas as well.

    Be well,

    Any experts are welcome.

    Why "nightcleaner?" Are you a janitor? :biggrin:
  7. Jan 8, 2005 #6
    Thank you Mk.

    Actually I do maintenance in restaurants for trade. It keeps me alive in a simple style, and gives me plenty of time to read and think. I work at night because I have to tear down a lot of the kitchen equipment to clean and repair as needed. I make a pretty big mess but get it cleaned up by morning.

    I have a university degree in biology and a certificate to teach in secondary education but never got on well in rigid structured environments. I do better working by myself and have gotten accustomed to it. I spend much more time by myself than I do with other people. I like people and they mostly seem to like me, but I don't pretend to understand them and mostly they don't understand me either. I am something of a fondly tolerated curiosity to most of my friends and aquaintences.

    Anyway tonight I was reading Linus Pauling, General Chemistry, and he has a good discussion of electron capture and release in the photoelectric effect, using Einstein's equations. He doesn't talk about any structural events in terms of how the electrons and photons interact, but he does verify my memory about the photon energy going entirely into the resulting kinetic energy of the liberated electron. He goes over the equations rather thoroughly and supplies several problems with solutions, for example calculation of the velocity of an electron accelerated in a voltage field. He has some discussion of xray diffraction by crystals, showing a geometric relationship between the spaceing of the atoms and the wavelength of the light, but he only discusses it in terms of simple optical reflection, very much like Snell's law in college physics. He does not use the path integral method of Feynman, which I found a little dissapointing, but then it is a text in general chemistry, and I suppose path integrals are a bit much to expect college freshmen to appreciate.

    I noticed in some of your other posts that your math seems rather more advanced than mine. What is your current line of study?

    be well,

  8. Jan 8, 2005 #7


    User Avatar
    Staff Emeritus
    Gold Member
    Dearly Missed

    AFAIK Pauling wrote the first edition of this book in the 1930s, long before Feynmann developed his path integral approach. The book was a blockbuster at the time, the first Chemistry text based on quantum mechanics. Pauling of course is the one who developed the quantum theory of the chemical bond.
  9. Jan 8, 2005 #8
    Hi selfAdjoint

    I didn't mean I was dissappointed in the book....just in my own failure to find what I was looking for at that moment. Surely not Pauling's fault. Anyway my edition, an inexpensive paperback by Dover, has copywrite 1947, 1950, 1970, and I am very pleased by the thoroughness of the treatment. As I said, I especially like the way he presents the formulae and uses them in meaningful examples. I've been reading it for a week now and the review is stimulating, and I am learning things I didn't learn in University, where the text I used was written for the mathematically disinclined.

    Thanks for the update. Hope you are well,

Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: String's mass
  1. The mass of strings (Replies: 2)