Books on String Theory

Discussion in 'Physics & Math' started by Reiku, Oct 30, 2007.

  1. Reiku Banned Banned

    Messages:
    11,238
    Does anyone here know any goods books on string theory?

    I never studied it at college, so my knowledge on it is very limited.

    Reiku :m:
     
    Last edited: Oct 30, 2007
  2. Google AdSense Guest Advertisement



    to hide all adverts.
  3. Orleander OH JOY!!!! Valued Senior Member

    Messages:
    25,817
    I thought string theory was dead.
     
  4. Google AdSense Guest Advertisement



    to hide all adverts.
  5. Reiku Banned Banned

    Messages:
    11,238
    Nearly. Not yet though.
     
  6. Google AdSense Guest Advertisement



    to hide all adverts.
  7. Zakariya04 and it was Valued Senior Member

    Messages:
    6,045
    hey reiku

    what is this string theory???

    ~~~~~~
    cheers
    zak
     
  8. sniffy Banned Banned

    Messages:
    2,945
    Ask Ben The Man he makes a living from it.
     
  9. Zakariya04 and it was Valued Senior Member

    Messages:
    6,045
    hey benthe Man
    As per sniffy's direction

    pls elaborate in basic english what this string theory is about

    ~~~~~~~
    cheers
    zak
     
  10. Reiku Banned Banned

    Messages:
    11,238
    Zak...

    From what i understand of string theory, is of the following.

    Until the 'string theory' came about, it was thought that matter existed as tiny little 'pointlike' units, like a grain of sand on a beach. This idea has been challenged. Superstring theory is a mathematical insert, describing all fundamental particles as tiny strings vibrating at different frequencies, and correctfully predicts the work of the forces between particles, (especially gravity and the strong force). Strings come in two distinctive forms: Open strings and closed strings. Open strings make up fundamental matter, whilst closed strings move throughout different universes.

    Open strings have two endpoints, and closed strings are envisioned as tiny loops. The two types of string play different roles, yielding two different spectra. For a quick reference, one of the closed strings is the elusive graviton, and one of the open strings make up the photon. Because open strings have two endpoints, they can inexorably join with other strings forming a closed string. Strings can split and combine, describing particles emitting or absorbing other particles.

    The theory states that our universe has 11 dimensions in space, but 7 of these dimensions are undetectable so far, because they are curled up into the smallest space possible called the 'Planck length.' However, physicists Nima-Hamed, Savas Dimopoulos and Gia Dvali have brought forward new ideas how to probe these dimensions using gravity. This makes sense, since according to theory, gravity travels freely between dimensions.

    We see three spatial dimensions everyday and are aware of a 4th dimension of time. We know our universe has three dimensions for sure, not only because of the apparent shape of an object, but also because of the 'inverse square law of gravity,' which allows the force between two masses to decrease as the square of the distance, represented as 'r', between them. You can imagine the distance 'r' and the gravitational field strength as being radiated through a 3-dimensional sphere enclosing a mass. The surface area of the sphere increases as the square of the distance 'r^2' and the strength of the field is distributed in proportion.

    Thus, in a 4-dimensional space, similarly the surface area of the 4-dimensional sphere would emit a field that gives away with the cube of the distance 'r^3'. Therefore, adding extra dimensions, as string theory does, would mean that the gravitational field would decrease with a corresponding increase in the power of 'r'.

    Even though we have not detected these extra dimensions in spacetime, the recent lab results show us that we can probe space to a distance of 200 micrometers. Theory suggests a visible dimension curled up to about 100 micrometers - so you can imagine, we are half way there. The smallest surface around the mass where we can experimentally measure the gravitational field, would enclose the extra dimension searched for, and they would have no effect on gravity at larger distances. There is even a theory that there is a baby universe curled up into the sixth dimension of space, see 'the theory of hyperspace.' It is these hypothetical 'larger scale dimensions' that fits in neatly with the so-called 'brane theory,' or also known as 'membrane theory,' which is an extension to a multi-dimensional string theory.

    'M-theory' stands for many expressions, such as magic, mother, mystery and of course, membrane theory. The 'm' itself however, has been attacked, by scientists calling it the 'moron' theory. M-theory added an extra dimension onto the existing dimensions of string theory - before M-theory; string theory was a '1-brane theory'. It was the realization in the mid 1990's that the string theory itself could be extended to allow higher dimensional objects.

    The introduction of string theory introduces branes which are 'spatially extended objects'. The variable 'p' is for the spatial dimension of a particle; thus 0-brane means a zero dimensional particle. A 1-brane is a string and a 2-brane is a 'membrane' ect. ect. Membrane-theory brought with it an extra dimension of space, and the 'fundamental string', or 'F-string' became a 2-dimensional membrane, called a 'supermembrane.' Membrane-theory has brought other new and bizarre ideas to physics, such as the 'Holographic Principle.'

    Plato, the Greek philosopher (427bc - 347bc), wrote a series of dialogues which summarized many things he had learned from his great teacher Socrates, who was executed in the year 399bc. One famous dialogue was called the 'Allegory of the Cave.' It describes a disturbing picture where people are chained to the ground inside of a cave, circling a fire, which cast their shadows on the walls of the cave. However, one escapes the prison, and went out into the light of the day and see's his true reality. When he returns to the captives inside of the cave, he tells them about the deception, but they all mock him for talking absurdities.

    In 1993, a Dutch theorist and physicist G. t' Hooft put forward a rather bold proposal, using Plato's Allegory of the Cave. The theory became to be called the Holographic Principle. The idea arose based on two assumptions;

    The first says that all the information contained in some region of space can be represented as a Hologram - it is ultimately a theory that exists on the boundary of that region of space. The second assertion is that the theory on the boundary be allowed at least one degree of 'Planck area.'

    The Planck area is a very small 'square' measurement which has a side length equal to that of the Planck length, which is 1.6 x 10^-33 centimeters. Moving on, the principle suggests a strange reality, where everything physical in our universe is nothing more than shadows on a wall! M-Theory predicts that our 4-dimensional continuum is just the boundary of a larger space. If we could move away from this wall, this apparent restriction of reality, we would be moving into the 5th-dimension which is curled up into a space smaller than a infinitesimal size of a superstring. Move around in the dimension and you would start to shrink to the size of superstring and then back to normal size! Even if one moved into the fifth dimension, you would end up where you had started. The theory of the fifth dimension was named after its inventor Oskar Klein, 'Kaluza-Klein Theory'. The Allegory of the Cave, one might say, was the first hypothetical assumption that reality as we know it was built up of much more unseen phenomenon, such as dimensions.

    String theory has come under considerable attack by many physicists, especially within the last twenty years; prominent critics involve Philip Anderson, Sheldon Glashow, Lawrance Krauss and Peter Woit. The main problem, is that string theory is not testable, and is thus not falsifiable. It is in essence, a very safe theory: Though, if nothing experimental can arise from it within the next couple of decades, it will most probably fade into the past.
     
  11. Gondolin Hell hath no fury like squid Registered Senior Member

    Messages:
    709
    I personally enjoyed The Elegant Universe and Fabric of the Cosmos by Brian Greene. One accompanies the other, no matter which one you read first. Search for them on Amazon. He also explains things very well, which I also like.
     
  12. Zakariya04 and it was Valued Senior Member

    Messages:
    6,045
    errr thanks Reiku

    I'm sorry mate but could you jsyt not sum it up in like a 3 or 4 line paragaph??? its just that i know i will loose the will to live if i read all that lot
    LOL
    ~~~~~~~~

    Cheers
    zak
     
  13. Reiku Banned Banned

    Messages:
    11,238
    Brian Green is amazing. Fred Hoyle is better.
     
  14. James R Just this guy, you know? Staff Member

    Messages:
    39,397
    About the only popular books I've read on it have been Brian Greene's The Elegant Universe and Michio Kaku's book Hyperspace. Both are ok, although both tend to lose the required detail to really understand string theory quite quickly. (Of course, they aren't really attempting to explain the theory, but just to give the flavour of what it is all about.)
     
  15. Reiku Banned Banned

    Messages:
    11,238
    I've heard of hyperspace. I might get that. Cheers.
     
  16. Donnal Registered Member

    Messages:
    638
    yeah brian green he does talk shows and been on television
     
  17. Gondolin Hell hath no fury like squid Registered Senior Member

    Messages:
    709
    He did a two part special on Nova. They followed his books. Pretty good program.
     
  18. superstring01 Moderator

    Messages:
    12,110
    Loved' em!

    ~String
     

Share This Page