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

Strings: Big and small

  1. Dec 27, 2004 #1
    In a recent article in New Scientist Mag they are making claims of possible evidence of strings. Though I read the "The Elegant Universe" by Brian Greene and I once wrote to Greene with a question (his e mail address is on the web), I have pretty much looked the other way from strings because they seemed unprovable.
    In the article in News Scientist Mag on page 32 it says:

    "Contrary to what we used to think, fundamental strings need not be ultra-tiny," says Tom Kibble...

    I find this fascinating that strings might be seen in both the microscopic and macroscopic world.

    How long has this idea been known and is this true and well known? I don't remember reading about it Greene's book.
    Thanks, Robert
  2. jcsd
  3. Dec 27, 2004 #2


    User Avatar
    Gold Member

    Strings are strictly conjecture at this point and motivated more by the fact that the math of strings seems to pull together math already found elsewhere in QM than by any independent physical evidence.

    The notion that there could be two phenomena called strings is just a product of the lexicon.

    String theory is generally thought of as a description of something more fundamental than the standard model of QM. Hence, one would expect strings to be smaller than fundamental QM particles (quarks, electrons, photons, gluons, etc.) in some sense, or at least, on the same scale. Thus, on string arising from string theory should be macroscopic. Of course, there is considerable room for variation between the atomic scale of the Standard Model and the Plank Scale preferred by many string theorists.
  4. Dec 27, 2004 #3
    Well i just got that book for Christmas, and I remember reading in the preface or one of those things that comes before the actual book him saying that most of the information in the book is still as legitmate today as when he first wrote the book. One thing he did mention as possibly being changed is the sizes of the hidden dimensions may not be as small as first thought, which could maybe mean that the strings also are not as small as once thought, but I'm not too sure about that.
  5. Dec 27, 2004 #4
    strings could possibly strech...

    one way of looking for them today may be using the telescope... since strings if they exist would have been around in the begninning of the universe then they would have streched with the universe to marcoscopic size. Also if you remember in the book brian greene discusses the possiblitiy of strings streching to the size of a universe... watch the nova program it focuses a lot on this.
  6. Dec 27, 2004 #5
    To Tom

    I see what you are saying about stretching. Fascinating indeed. When is the Nova program? (I will check the PPS website)

    Furthermore I would like to say that we are pratically neighbors. I checked your profile earlier in the day and found that you live in Southwestern Michigan. Though at the time of posting my profile I was living closer to Chicago, I now live in Valparaiso, In. Not too far from you :smile:

    Tom: Never mind I found it

    The Elegant Universe: Welcome to the 11th Dimension—December 28 at 8 pm
    Eleven dimensions, parallel universes, and a world made out of strings. It's not science fiction, it's string theory. Go to the Web site
    Last edited: Dec 27, 2004
  7. Dec 27, 2004 #6
    I own the dvd of the show...
    also there are links to it streamed and a place you can download it if you search the forums.
  8. Dec 28, 2004 #7
    I don't know alot about string theory. It seems to me that alot of strange phenomena seem "possible" by interpretation of the math. Hence the field of theoretical mathematics. It all seems to be based on the assumption that math exactly describes the physical world. To me math explains more than the physical universe. i.e. many of the phenomena described by math just don't exist in the real universe. Think of genotype and phenotype. Though a genotype may exist the manifestation of this, the phenotype subset is smaller. I think the major mistaken assumption is that there is a negative number system. It sounds intuitive that there should be one because of symmetry around zero and math certainly supports it but it just doesn't seem to exist in the real world. Where has anyone seen a negative flower? How on earth can i have 30 real flowers by having negative six bunches of five negative flowers??? If we take negative numbers out of any mathematics that describes our universe do we still have strings? Don't come back by saying what about the charge of an electron. We have arbitarily assigned a negative value to it.
  9. Dec 28, 2004 #8


    User Avatar
    Gold Member

    I have heard of people who have a problem with imaginary numbers (i.e. square roots of negative numbers). You are the first person I've ever encounted who has had a problem with the concept of a negative number itself.

    Negative numbers are common place occurences in our world. You seem to be having problems assigning meaning to them, but it really isn't so hard.

    For example, suppose that you run a flower stand. You sell seventy bunches. Then six bunches are returned. The returned bunches could equally well be described as negative six sales.

    Often positive is used for credits and negative is used for debits. For example, if you make five withdrawals from an ATM of $40 each, you have -200 in the bank. But suppose that you reverse those transaction since a thief rather than you made them. Then you have -5*-40=+$200 in the bank as a result.

    And, lots of numbers are arbitrary and flow from a coordinate system. For example, it may be -7 degrees out. Zero is just an arbitrary location, but you need the math of negative numbers to get the right locations. Positive and negative aren't much different than East or West.

    If you have such a fundamental difficulty understanding basic mathematics, you need to head over to the math section of Physics Forums before trying to tackle string theory.
  10. Dec 28, 2004 #9


    User Avatar

    negative numbers

    Ignore O.

    You would like topos theory. In category theory, the natural numbers
    appear 'more fundamentally' than the integers.

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook