For those who know what string theory is all about, you can skip the following. The real question is at the end: ''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.'' My perspective of the whole situation is that two sides are in an oxymoronic battle: In respect to accepting the theory, the following is evaluated: 1. The string theorists say ''we are damned if we don't.'' 2. The non-theorists of strings say ''we are damned if we do.'' Reiku :m: Please Register or Log in to view the hidden image!
Con: To date there has been no verifiable test. Neutral: Loop quantum gravity is an alternative, which has the same problem (no good test).
Pro: It has helped in the investigation of high energy physics Con: It can only work in a spacetime which exceeds Einsteins and Minkowski's predictions.
Actually, instead of making such a huge list of pros and cons, why don't we examine the pros and cons individually. Deal?
Deal... But, this ratio-like configurate keeps things in perspective, but have it this way thy wishes.
Read more See also http://www.sciforums.com/showthread.php?t=58845 http://www.sciforums.com/showthread.php?t=74061
Title: Testing String Theory with CMB Authors: Renata Kallosh, Andrei Linde Future detection/non-detection of tensor modes from inflation in CMB observations presents a unique way to test certain features of string theory. Current limit on the ratio of tensor to scalar perturbations, r=T/S, is r < 0.3, future detection may take place for r > 10^{-2}-10^{-3}. At present all known string theory inflation models predict tensor modes well below the level of detection. Therefore a possible experimental discovery of tensor modes may present a challenge to string cosmology. The strongest bound on r in string inflation follows from the observation that in most of the models based on the KKLT construction, the value of the Hubble constant H during inflation must be smaller than the gravitino mass. For the gravitino mass in the usual range, m_{3/2} < O(1) TeV, this leads to an extremely strong bound r < 10^-24. A discovery of tensor perturbations with r > 10^-3 would imply that the gravitinos in this class of models are superheavy, m_{3/2} > 10^13 GeV. This would have important implications for particle phenomenology based on string theory. Read more (128kb, PDF)
I dunno, what all these string theories are all about (here's many of them without fixed list of postulates, so they can predict everything) - but the basic asumptions, i.e. the existence of strings (i.e. the highly compactified density fluctuations of inertial environment) and the hidden dimensions proposal follows from AWT by simple and natural way - so I've no problem with this and every evidence of strings can be considered as an evidence of Aether theory itself. The another thing is, the math formalism of dual theories (like the QM and SR, which the string theory is based on) doesn't enable to derive certain unambiguous solution by rigorous way. For example, if from quantum mechanics follows the value of cosmological constant by many orders of magnitude lower, then from general relativity by rigorous way - then every rigorous quantum field theory, which claims, it can derive the general relativity from quantum mechanics by rigorous way has an obvious problem here - it cannot be possible to consider the both at the same time... ;-) Currently the string theory predicts the value of cosmological constant, which differs by more then forty orders of magnitude from observed values. From this dilemma the existence of 10E+500 possible solutions of string theory follows and it's evident, the basic formal paradigm (blind combining of relativity and QM equations without deeper understanding of subject) should be changed. The above doesn't mean, in some particular cases the string theory cannot supply relevant result (like at the case of virtually every theory) - but my understanding is, for example the Heim's theory is proposing a much more effective formal approach in practical cases.
I want everyone to note what Zeph said: ''It is to predict everything'' Due to the Uncertainty Principle, and underlining rule of Copenhagen Interpretation, you cannot know everything. Zeph has answered the question.
The true is, you just cannot observe/describe everything by using the single paradigm/approach/theory/way of energy spreading, whatever... But you can understand a substantial part of Universe by combination of different approaches at the same moment. Even the tendency to describe the Universe by deterministic, causual way (by language of math) CAN introduce an unwanted bias into our perceiving of chaotic nature of Universe. On the other hand, our tendency to observe it as pure chaotic CAN introduce an unwanted bias into our perceiving of its highly organized nature by the same way. I consider the chaos as a dual side of complexity. Even our animal pets are perceiving our conscious behavior as a highly random and chaotic, because it's affected by many influences from hidden dimensions, which they cannot realize. Your dog doesn't knows, you're sitting at home or buying the textbooks, because you're in love or you're learning the physics for examines. What he can see is just the fact, you're sitting at home or buing something by random, chaotic way. By the same way, the particles undulating perfectly in many hidden dimensions behaves randomly from our local perspective. If we want to understand the Universe, we should remain unbiased in our prejudices and experience, which effectivelly means, in our description of Universe we should consider all mankind experience at the same moment. We can develop the complex and abstract theories, but we shouldn't remember, they're just a certain slices/perspectives of reality. The fact, the reality appears complex doesn't means, such complexity cannot be driven by the very simple (if any) principles.
Yes i agree. We can know only what is eventful that we can know. And there is of course, the added tint of God.
