What is Brane theory?
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Brane cosmology is a protoscience motivated by, but not rigorously derived from, superstring theory and M-theory. The idea is to solve problems in cosmology using speculative particle physics theories and in turn use cosmological observations to motivate ideas in string theory.\n\nThe central idea is that our visible, four-dimensional universe is entirely restricted to a brane inside a higher-dimensional space, called the bulk. The additional dimensions may be taken to be compact, in which case the observed universe contains the extra dimensions, and then no reference to the bulk is appropriate in this context. In the bulk model, other branes may be moving through this bulk. Interactions with the bulk, and possibly with other branes, can influence our brane and thus introduce effects not seen in more standard cosmological models.\n\nAs one of its attractive features, the model can "explain" the weakness of gravity relative to the other fundamental forces of nature. In the brane picture, the other three forces (electromagnetism and the weak and strong nuclear forces) are localised on the brane, but gravity has no such constraint and so much of its attractive power "leaks" into the bulk. As a consequence, the force of gravity should appear significantly stronger on small (sub-millimetre) scales, where less gravitational force has "leaked". Various experiments are currently underway to test this. For example, in a particle accelerator, if a graviton were to be discovered and then observed to suddenly disappear, it might be assumed that the graviton "leaked" into the bulk.\n\nThe Randall-Sundrum, pre-big bang, ekpyrotic and cyclic scenarios are particular models of brane cosmology which have attracted a considerable amount of attention.\n\nThe theory hypothesises that the origin of the big bang could have occurred when two parallel branes touched.
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String theory is a model of fundamental physics whose building blocks are one-dimensional extended objects (strings) rather than the zero-dimensional points (particles) that are the basis of the Standard Model of particle physics. For this reason, string theories are able to avoid problems associated with the presence of pointlike particles in a physical theory. Studies of string theories have revealed that they require not just strings, but also higher-dimensional objects.\n\nThe basic idea is that the fundamental constituents of reality are strings of energy of the Planck length (about 10-35 m) which vibrate at resonant specific frequencies[1]. Another key claim of the theory is that no measurable differences can be detected between strings that wrap around dimensions smaller than themselves and those that move along larger dimensions (i.e., physical processes in a dimension of size R match those in a dimension of size 1/R). Singularities are avoided because the observed consequences of "big crunches" never reach zero size. In fact, should the universe begin a "big crunch" sort of process, string theory dictates that the universe could never be smaller than the size of a string, at which point it would actually begin expanding.\n\nInterest in string theory is driven largely by the hope that it will prove to be a theory of everything. It is a possible solution of the quantum gravity problem, and in addition to gravity it can naturally describe interactions similar to electromagnetism and the other forces of nature. Superstring theories include fermions, the building blocks of matter, and incorporate supersymmetry. It is not yet known whether string theory will be able to describe a universe with the precise collection of forces and matter that is observed, nor how much freedom to choose those details that the theory will allow. String theory as a whole has not yet made falsifiable predictions that would allow it to be experimentally tested, though various special corners of the theory are accessible to planned observations and experiments. Hence critics of string theory occasionally remark that the theory "... is not even wrong," quoting a quip attributed to Wolfgang Pauli.\n\nWork on string theory has led to advances in mathematics, mainly in algebraic geometry. String theory has also led to other theories, supersymmetric gauge theories, which will be tested at the new Large Hadron Collider experiment.
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dimensions used to explain the behavior of strings and subatomic particles in String Theory.\n\nbut to give you a basic understanding of what another dimension can be like, think about this for a moment, we live in a world limited to and guided by four dimensions, now they are \n1:up/down \n2:left/right \n3:backwards/forward\n4:time\nnow go outside take a look at an electrical feeder cable, from the ground it looks like a solid line, but if you get closer to it you'll notice that there is a line wrapping around the wire where the wire is braided, now imagine if you are an ant crawling on the wire, these braids will be a dimension to you, because you have to follow their path otherwise you'll fall off. that's a perfect example of what another dimension besides the four that you are familiar with can be like. now in string theory, in order to explain the very complex movements and behavior of the strings and of other subatomic particles, mathematics will include those  additional dimensions in the theory, the only problem is that its very hard to understand much less visualize these additional dimensions, because they can be extremely complex and twisted around all over the place.\n\nthe new M-theory includes as many as 11+1(that's 11 space dimensions and one of time)dimensions.
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In theoretical physics, a supergravity theory is a field theory combining supersymmetry and general relativity.\n\nOne of these supergravities, the 11-dimensional theory, generated considerable excitement as the first potential candidate for the theory of everything. This excitement was built on four pillars, two of which have now been largely discredited:\n\n    * Werner Nahm showed that 11 dimensions was the largest number of dimensions consistent with a single graviton, and that a theory with more dimensions would also have particles with spins greater than 2. These problems are avoided in 12 dimensions if two of these dimensions are timelike, as has been often emphasized by Itzhak Bars.\n\n    * Shortly afterwards, Ed Witten showed that 11 was the smallest number of dimensions that was big enough to contain the gauge groups of the Standard Model, namely SU(3) for the strong interactions and SU(2) times U(1) for the electroweak interactions. Today many techniques exist to embed the standard model gauge group in supergravity in any number of dimensions. For example, in the mid and late 1980s one often used the obligatory gauge symmetry in type I and heterotic string theories. In type II string theory they could also be obtained by compactifying on certain Calabi-Yau's. Today one may also use D-branes to engineer gauge symmetries.\n\n    * In 1978, Eugene Cremmer, Bernard Julia and Joel Scherk (CJS) of the Ecole Normale Superieure found the classical action for an 11-dimensional supergravity theory. This remains today the only known classical 11-dimensional theory with local supersymmetry and no fields of spin higher than two. Quantum-mechanically, inequivalent 11-dimensional theories are known which reduce to the CJS theory in the classical limit, that is when one imposes the classical equations of motion. For example, in the mid 1980s Bernard de Wit and Hermann Nicolai found an alternate theory in D=11 Supergravity with Local SU(8) Invariance. This theory, while not manifestly Lorentz-invariant, is in many ways superior to the CJS theory in that, for example, it dimensionally-reduces to the 4-dimensional theory without recourse to the classical equations of motion.\n\n    * In 1980, Peter G. O. Freund and M. A. Rubin showed that compactification from 11 dimensions preserving all the SUSY generators could occur in two ways, leaving only 4 or 7 macroscopic dimensions (the other 7 or 4 being compact). Unfortunately, the noncompact dimensions have to form an anti de Sitter space. Today it is understood that there are many possible compactifications, but that the Freund-Rubin compactifications are invariant under all of the supersymmetry transformations that preserve the action.\n\nThus, the first two results appeared to establish 11 dimensions uniquely, the third result appeared to specify the theory, and the last result explained why the observed universe appears to be four-dimensional.\n\nMany of the details of the theory were fleshed out by Peter van Nieuwenhuizen, Sergio Ferrara and Daniel Z. Freedman.
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consult the below link...very brief...http://en.wikipedia.org/wiki/String_theory
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ok this is a video and ther is also a book on it called the eligant universe by brian greene. http://www.pbs.org/wgbh/nova/elegant/program.html\nthis will help explain theory and the science needed to understand string theory it is good.
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String theory suggests that when you travel back in time you actually travel into another dimension so theoritically speaking, you would be bringing back yourself from another dimension. But, I don't think you could even get back to your own dimension.
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STRING THEORY, is one of the theories of modern sciences where it states that every thing in this universe is made of strings. The visual and other evidence of differences in objects is how the strings are. For example, longer strings mean more red color (this is a hypothetical example.) \nString Theory was predicted to give solutions to lot of problems in modern Physics. It has not ben proved yet, thus is not a complete true science yet.
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I might be able to answer more fully if you reword your question and put some thought into exactly what it is you're looking for.  For example, string theory predicts extra dimensions beyond the four we experience.  Is that it?  Or are you referring to the Branes explanation, where there are extra dimensions as well as additional universes removed from our own?  Get some additional details and I'll edit.
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its actualy String-theory that proposes the existance of many other universes. the theory proposes a so called "Landscape of probabilities" with probabilities of as many as 10 to power of 500 universes, and with that many probabilities it is very likely that some of them will be similar to or just like our own universe.\n\nif you would like to know more about this facsinating subject, i would suggest this book http://www.amazon.com/gp/product/0316155799/104-3626905-5554311?v=glance&n=283155\nits a great and easy to understand book.
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String Theory says there may be several more; up to 10 more dimensions, IIRC, but they can generally be ignored, in "real life".  This is because the extra 10 or so are tightly "wound up", so they act as if they are not there, most of the time.\n\nWords do not suffice to discuss String Theory; you need mathematics.  Howver, my maths skills are limited, so I just read the simplified verbal summaries.
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Because "String Theory" as a whole has not yet made falsifiable predictions that would allow it to be experimentally tested, though various special corners of the theory are accessible to planned observations and experiments.\n\nInterest in string theory is driven largely by the hope that it will prove to be a theory of everything. It is a possible solution of the quantum gravity problem, and in addition to gravity it can naturally describe interactions similar to electromagnetism and the other forces of nature. Superstring theories include fermions, the building blocks of matter, and incorporate supersymmetry. It is not yet known whether string theory will be able to describe a universe with the precise collection of forces and matter that is observed, nor how much freedom to choose those details that the theory will allow.
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Short answer it is meant to unify the supersting theories (which are of course aimed at answering the most fundamental question of the most elementary (sub)particles).\n\nLonger answer, there are dualities in the five "original" string theories. These dualities lead to the same pursuit as in the Grand Unification theory when people started thinking of more elegant theories. The M (or U) theory is basically the  grand unification of the five string theories. \n\nThe theory has a huge problem like the "originals", too many dimensions. Just as you can fit a polynomial of nth degree to any data, given enough dimensions you can explain any physical occurrence with almost any explanation this is why scientists are still dismissive of the M and String theories (except the guys who try to convince the rest)
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Its matter. But what is matter. String theory suggest that all matter is made up of vibrating string and the different vibrations causes different characteristics in matter.
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first of all 4 dimentions is true because there are 3 spacial dimentions and the 4th is time.\n\nand we dont know if superstring theory is true, it's still just an idea, and hasn't been proven, nor has any evidence been shown for it, we just like it because it can be used to explain certain things if it were true.  in string theory, there are 11 dimentions, its not crap, why dont you read "the elegant universe" by brian greene, or at least do some type of reading on it before you call it crap.  the dimentions are interwoven in our own universe, just like the 4 that are already proven.
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In the Standard Model, quarks, electrons and the like are considered to be pointlike. This gives problems at short distances where for instance the electromagnetic force between two of them becomes infinite.\n\nThe basic idea of stringtheory is that the fundamental constituents of matter are strings of a length of order of 10^35 m which vibrate at specific frequencies. However, the simplest string theories give more problems then they solve and consistent theories requires more then four dimensions. \n\nMembranes take the idea even further.  The particles are represented by vibrating surfaces and higher dimensional objects.
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String theory is a model of fundamental physics whose building blocks are one-dimensional extended objects (strings) rather than the zero-dimensional points (particles) that are the basis of the Standard Model of particle physics. For this reason, string theories are able to avoid problems associated with the presence of pointlike particles in theories of physics. Studies of string theories have revealed that they predict not just strings, but also higher-dimensional objects.\n\nThe basic idea is that the fundamental constituents of reality are strings of energy of the Planck length (about 10-35 m) which vibrate at resonant specific frequencies[1]. Another key claim of the theory is that no measurable differences can be detected between strings that wrap around dimensions smaller than themselves and those that move along larger dimensions (i.e., physical processes in a dimension of size R match those in a dimension of size 1/R). Singularities are avoided because the observed consequences of "big crunches" never reach zero size. In fact, should the universe begin a "big crunch" sort of process, string theory dictates that the universe could never be smaller than the size of a string, at which point it would actually begin expanding.\n\nInterest in string theory is driven largely by the hope that it will prove to be a theory of everything. It is a possible solution of the quantum gravity problem, and in addition to gravity it can naturally describe interactions similar to electromagnetism and the other forces of nature. Superstring theories include fermions, the building blocks of matter, and incorporate supersymmetry. It is not yet known whether string theory will be able to describe a universe with the precise collection of forces and matter that is observed, nor how much freedom to choose those details that the theory will allow. String theory as a whole has not yet made falsifiable predictions that would allow it to be experimentally tested, though various special corners of the theory are accessible to planned observations and experiments. Hence critics of string theory occasionally remark that the theory "... is not even wrong," quoting a quip attributed to Wolfgang Pauli.\n\nWork on string theory has led to advances in mathematics, mainly in algebraic geometry. String theory has also led to other theories, supersymmetric gauge theories, which will be tested at the new Large Hadron Collider experiment.