Have added my book review of string theory book by expert string theorist to my page http://members.lycos.co.uk/nigelbryancook/discussion.htm:
WARPED PASSAGES by Dr Lisa Randall
(Allen Lane, London, 2005, 500 pp.)
Summary: this book is a nice discussion of the Standard Model, electroweak unification, the vitality of the Higgs field mechanism to electroweak theory, supersymmetry in the Standard Model to allow unification of all fundamental forces apart from gravity at high energy, the role of the Calabi-Tau manifold (in 10 dimensional string theory in which 6 dimensions are rolled up in such a way that the parity-violating weak force is explained in the standard model while supersymmetry is preserved), and Witten’s proof in 1995 that 10-D strongly coupled superstring theory is equivalent to 11-D weak supergravity speculation. Lisa explains that extra-dimensional strings are treated in some ways as real physical entities, having tension which determines the resonate frequency. The more tension, the more energy the string requires to oscillate, so gravity can be forced to work.
On the down side, the string size is assumed to be the Planck length, about 10^-35 metre, which is equivalent to an energy of 10^19 GeV. Lisa admits on page 295 that ‘even if string theory is correct, we are unlikely to find the many additional particles it predicts. The energy of current experiments is sixteen orders of magnitude too low. … because the string length is so tiny and the string tension is so high, we won’t see any evidence to support string theory at the energies achievable in accelerators, even if the string description is correct.’
At the end of the book, Lisa summarises what to me are even bigger problems, the fact that not only are these speculations impossible to test convincingly, they are also extremely vague because there are many variations of the extra-dimensional theories. She remarks on page 456: ‘We now know that extra-dimensional setups can come in any number of shapes and sizes. They could have warped extra dimensions, or they could have extra large dimensions; they might contain one brane or two branes; they might contain particles in the bulk and other particles confined to branes. … Which, if any, of these ideas describes the real world? We’ll have to wait …’
Bearing in mind that the energies to test the theories are sixteen orders of magnitude higher than we can achieve even if we copy Hitler’s technological methods and allow the Third World to starve to build earth-stradling particle accelerators, hell will freeze over before string theorists get anywhere.
I feel inclined to review Lisa Randall’s book, Warped Passages, in considerable depth here, because it is a sort of answer to Dr Roger Penrose’s Road to Reality which I reviewed somewhere on my website a few months ago. (I was surprised to learn recently that Penrose has given help to Peter Woit for finding a publisher in Britain for Woit’s book Not Even Wrong. Penrose is locked into twister theory, which is less well understood in mainstream physics than string theory. Twister theory is abstract mathematics resulting in a picture of a particle that looks like a rotating vortex. However, physically what are the lines that Penrose draws in the vortex? It would be nice to take the twister as a gravitationally confined slab of electromagnetic field energy, but these mathematicians have the knack of steering clear of the ‘crackpot’ idea of modelling reality.)
Lisa’s dust jacket contains a black and white picture of her, unsmiling and sultry, in a black dress. She is ‘the first tenured woman in the Princeton physics department and the first tenured woman theorist at MIT and Harvard’ (quoted from the publisher’s blurb below the picture). Below each chapter title are crazy lyrics from pop songs, to send out the message that string theorists can be groovy. You get the idea that Warped Passages is going to be a less lady like, or rougher, ride than the elegant sophistication of certain other writers.
Page 6 reveals the author’s motivation: ‘A tiny magnet can lift a paper clip, even though all the mass of the Earth is pulling it in the opposite direction. Why is gravity so defenceless against the small tug of a tiny magnet? In standard three-dimensional particle physics, the weakness of gravity is a huge problem [the ‘hierarchy problem’, the differences in the strengths of the fundamental forces]. But extra dimensions might provide an answer.’
I agree with her up to this point. But Lisa then goes on to explain that in Einstein’s general relativity, the spacetime fabric is warped by matter and energy to cause gravitational forces, and that she (and her collaborator, Raman Sundrum) had a pet theory in 1999 that ‘an invisible extra dimension can stretch out to infinity, provided that it is suitably distorted in a curved spacetime… (Not all physicists immediately accepted our proposal. But my non-physicist friends were more quickly convinced I was on to something…)’
The publisher’s blurb states: ‘Her work has attracted enormous interest and is some of the best cited in all of science.’ (A bit like saying that Hitler can’t be politically wrong, because Mein Kampf was a best seller and so many people can’t all be wrong. If something is popular, it must be correct. That’s all.)
Because the spectra of fascism had arisen so quickly, I was suspicious, checking Lisa’s index for Dr Luboš Motl. Sure enough, he is cited on page 152, in the context of Vladimir I. Lenin. Lisa writes that Lenin used the electron as a metaphor in his book Materialism and Empirio-Criticism. Lenin stated that the ‘electron is inexhaustible’, because of the its wave-particle duality (or whatever problem in electron physics that Lenin perceived at the time); but Lisa responds that the electron is really simple, with just a few properties, and she says in parenthesis that: ‘(The Czech anti-Communist string theorist Luboš Motl quipped that this is not the only difference between his and Lenin’s perspectives.)’
Other parts of the book reveal how surreal craziness starts. She admits in the preface: ‘When I was a little girl, I loved the play and intellectual games in math problems or in books like Alice in Wonderland.’ So we know why Lisa tries to copy Alice by going through the looking glass into the world of extra dimensions. (Lisa: beware of the big white rabbit following you, it looks very hungry!)
On page 17, she quotes from another inspiring book: ‘In Roald Dahl’s Charlie and the Chocolate Factory, Willy Wonka introduced visitors to his "Wonkavator." In his words, "An elevator can only go up and down, but a Wonkavator goes sideways and slandways and longways and backways and frontways and squareways …".’ After reading this, I went back to page vii where she wrote that other popular books ‘often seemed condescending to readers…’. The big white rabbit is a real menace!
By page 20 she has explained that a straight line has one dimension, a flat surface two dimensions, and a cube has three dimensions. On page 23 there is a nice picture of a three-dimensional rabbit dancing in front of a projection lamp to throw the image that looks just like a human hand on a two-dimensional screen. Unlike Penrose, she produces no mathematical equations (except in the mathematical notes at the end of the book). One think she shares in common with Penrose is the idea that climate change should be speeded up, which is why her book is about as thick as Road to Reality, requiring almost a rainforest in pulped trees (it uses thicker sheets of paper to make up the bulk, despite having only half as many sheets as Penrose).
In chapter 2, Lisa recounts the story of the Kaluza-Klein theory. In 1919, Theodor Kaluza wrote a paper that put 5 dimensions instead of 4 into the metric of general relativity, obtaining electromagnetism. Einstein had to referee the paper, and held it up two years, wanting to know what physical significance a fifth dimension could have. It was published in 1921. In 1926 the answer came from Oskar Klein, who suggested the extra dimension was unseen normally because it was rolled up into a small (sub-atomic sized) circle, forming the fundamental particles of matter. (All this was abstract unification mathematics, not mathematical physics: there were no testable predictions. The Klein unification just showed that electromagnetism and general relativity could be united by an extra dimension, it did not allow general relativity (gravity) to predict how strong the electric force was. All you could get out was what you had already put into general relativity in the form of the constants ‘c’ and ‘G’. Lisa does not mention these problems with the Kaluza-Klein theory.)
Chapter 3 is headed ‘exclusive passages’ and is about branes, explaining that in 1995 Joe Polchinski ‘established that they were essential to string theory.’ Branes (short for membranes) are domains with ‘fewer dimensions that the full higher-dimensional space that surrounds or borders it.’ In fact, therefore, a 4-dimensional spacetime is simply a ‘brane’ on the 5-dimensional spacetime.
Chapter 4, ‘approaches to theoretical physics’, contrasts two approaches of doing physics: building a theory on experimental facts (physics phenomenology), versus speculating and testing the theory by experiment (Popperian physics). Lisa says candidly: ‘The choice could also be phrased as "Old Einstein vs. Young Einstein".’ She then launches into a discussion of string theory, saying that it seems the only way to consistently unify quantum mechanics and general relativity. Actually, this is quite convincing, and vaguely correct, although her personal suggestion on how to bring gravity into quantum mechanics is actually wrong.
The later chapters improve markedly. I was surprised to find that this book makes a real effort to avoid glossing over some of the problems in the standard model that other books ignore.
Bosons (such as photons with spin 1) have integer spin, while fermions (such as electrons with spin ½) have half-integer spin. The ‘boson’ group name is named after Satyendra Bose who developed Bose-Einstein statistics, while the ‘fermion’ group is named after Enrico Fermi who built the first nuclear reactor and developed Fermi-Dirac statistics. The spin determines whether the statistics of a gas of the particles obey Bose-Einstein or Fermi-Dirac statistics. (Ordinary gases obey, of course, Maxwell-Boltzmann statistics.)
In particular, fermions like electrons obey the Pauli exclusion principle that states that in an atom each electron must have a different set of quantum numbers. The reason behind this principle is clearly related to the magnetic moment of the electron. When you put two magnets in the same place, they pair up with opposite poles adjacent, so if one magnet has its North Pole pointing upwards, the other magnet (attracted to the first) will end with its South Pole pointing upwards. This causes each electron in a pair of adjacent electrons in an atom to have different spin states. As you add more electrons to an atom, more shells get filled up, so you physically cannot have any two electrons with the same set of quantum numbers. So it appears that the Pauli exclusion principle is powered by magnetism, which keeps the electrons apart and acts as a repulsive force to prevent the atom being compressed easily.
Lisa points out that the electromagnetic force is mediated by the photon, which is the carrier or ‘gauge boson’ of the force. The use of the term ‘gauge’ in this context is ‘because of a tangential analogy to railway gauges that tell you the distance between the rails – a term that was far more familiar a hundred years ago’ Lisa says (she is an expert on railways as well as string). Gluons would be the ‘gauge bosons’ for the strong nuclear force, and gravitons for the gravitational force. For the weak nuclear force there are three gauge bosons, positive, negative and neutrally charged. The positive gauge boson is symbolised W+ (shortened from ‘weak + charged’), the negative is W-, and the neutral is Z (shortened from ‘zero charged’). Weak forces are complex since they violate parity symmetry, so a left-hand spinning particle obeying the weak force does not behave like the mirror image of a right-hand spinning particle. This investigated theoretically by C.N. Yang and T.D. Lee and experimentally proved by C.S. Wu in 1957. Lisa says that the male physicists Yang and Lee who suggested the experiment won a Nobel Prize, but the female physicist Wu who actually did the experiment didn’t.
Quarks and leptons (like electrons) can spin either one way or another. This is like the option of the planet earth either spinning towards the east (spinning anticlockwise as seen looking down on the North Pole) as it does, or spinning the opposite way. Because the weak force is responsible for beta radioactivity, where a neutron decays into a proton (by emission of an electron and an antineutrino, as predicted in 1930 by Wolfgang Pauli from energy conservation issues with the spectra of beta particle energies), it allows a downquark in a neutron to change into an upquark. Pauli however did not succeed in generating much interest in the neutrino, since when Enrico Fermi wrote about in a letter sent to the journal Nature in 1933, the paper was rejected as containing ‘speculations too remote to be of interest to the reader.’ Nevertheless, neutrinos were detected from a nuclear reactor in 1956.
Lisa explains that in the Standard Model of fundamental particle physics, gauge bosons do not have mass (these people mean that the gauge bosons have light velocity and by special relativity this implies they have zero rest mass, or their transit masses would be infinite), but the carriers of the weak force turn out to have mass. In order to explain this difference, the ‘Higgs mechanism’ is used to give weak gauge bosons their mass.
Chapter 10 in Warped Passages is ‘The Origin of Elementary Particle Masses: Spontaneous Symmetry Breaking and the Higgs Mechanism’. Peter Higgs proposed the mechanism for mass in 1964. Lisa says: ‘Without the Higgs mechanism, all elementary particles [according to the Standard Model] would be massless; the Standard Model with massive particles but without the Higgs mechanism would make nonsensical predictions at high energies.’
The reason that weak force gauge bosons have to have non-zero mass is that they are short-ranged. If they had no rest mass, then like light and electromagnetic forces they would have infinite range, decreasing only by the inverse-square law due to geometrical divergence. To get a short-range requires a borrowing of energy according to the uncertainty principle, whereby the maximum force range is inversely proportional to the mass-energy of the gauge boson. Another option is that Higgs bosons in the fabric of spacetime obstruct the weak force gauge bosons from travelling long distances but not short distances.
The Higgs field boson is too heavy to have been created in high energy experiments to date, which is why it has not been discovered, according to Lisa. However, if the Higgs boson is the cause of inertial mass, then we are feeling them everytime we have to overcome inertia to move, and by Einstein’s equivalence principle, inertial mass is the same as gravitational mass. The Higgs field is the ether of the vacuum of space, and inertia arises by the physical mechanism whereby the Higgs field obstructs the motion of fundamental particles.
To be clear, the Higgs field exists everywhere as the spacetime fabric or ether. It stops the weak gauge bosons within a short distance, and provides the masses of quarks and leptons by the mechanism of their bouncing off the virtual charges of the Higgs field. Because the weak force has a maximum range of 10^-18 metre, the energy-time version of the Heisenberg uncertainty principle (assuming light speed force mediation, so that time multiplied by speed of light equals this maximum distance) tells us the energy of the weak force mediator – it is 250 GeV, equivalent to 10^-24 kilogram.
This energy, 250 GeV, is close to the observed mass-energy of the weak gauge bosons (W-, W+, and Z). It is also the energy of the Higgs bosons. The weak force symmetry (which exists for energies above 250 GeV) breaks spontaneously at 250 GeV, because of the Higgs mechanism. Below 250 GeV, there is no weak force symmetry because particles have masses since they are mired in the Higgs field which causes inertia. Above 250 GeV, particles become effectively massless, simply because they then have more energy than the Higgs bosons. (By analogy, it is possible to move through syrup if you have enough energy to overcome the sticky binding forces holding together the syrup molecules, but you get stuck after a short distance if you don’t have enough energy!)
Electroweak theory was developed by Sheldon Glashow, Steven Weinberg and Abdus Salam. They showed that early in the big bang, there were three weak gauge bosons and a neutral boson, and that the photon which now exists is a combination of two of the original gauge bosons purely because this avoids being stopped by the weak charge of the vacuum; other combinations are stopped so the photon exists uniquely by the filtering out of other weak gauge bosons. Because the photon does not interact with the weak charge of the vacuum, it only interacts with electric charges. The vacuum is composed of weak charge, but not electric charge, so the photon can penetrate any distance of vacuum without attenuation. This is why electric forces are only subject to geometrical dispersion (inverse-square law).
These developments in the 1960s led to the Standard Model of fundamental particles. In this model, the strong nuclear, weak nuclear and electromagnetic forces all become similar at around 10^14 GeV, but beyond that they differ again, with electromagnetic force becoming stronger than the strong and weak forces. In 1974, Howard Georgi and Sheldon Glashow suggested a way to unify all three forces into a single superforce at an energy at 10^16 GeV. This ‘grand unified theory’ of all forces apart from gravity has the three forces unified above 10^16 GeV but separated into three separate forces at lower energies. The way they did this was by ‘supersymmetry’, doubling the particles of the Standard Model, so that each fundamental particle has a supersymmetric partner. The energy of 10^16 GeV is beyond testing on this planet and in this galaxy, so the only useful prediction they could make was that the proton should decay with a half-life somewhat smaller than has already been ruled out by experiment.
Edward Witten developed the current mainstream superstring model, which has 10/11 dimensions with 6/7 rolled up into strings. The history of string theory begins in the 1920s with the Kaluza-Klein theory as I’ve already explained above. Kaluza showed that adding a fifth dimension to general relativity units gravity and electromagnetism tensors, while Klein showed that the fifth dimension could remain invisible to us as a rolled up string. In the late 1960s, it was shown that the strings could vibrate and represent fundamental particle energies. In 1985, Philip Candelas, Gary Horowitz, Andy Strominger and Edward Witten suggested that 10-D string theory with the 6 extra dimensions curled up into a Calabi-Yau manifold would model the standard model, preserving supersymmetry and yet giving rise to an observable 4-D spacetime in which there is the right amount of difference between left and right handed interactions to account for the parity-violating weak force. This ‘breakthrough’ speculative invention was called ‘superstrings’ and led to the enormous increase in research in string theory.
Finally, in March 1995, Edward Witten proved that 10-D strongly coupled superstring theory is equivalent to 11-D weakly coupled supergravity. Apparently because it was presented in March, Witten named this new 10/11-D mathematics ‘M-theory’.
Witten then made the misleading claim that ‘string theory predicts gravity’:
‘String theory has the remarkable property of predicting gravity’: false claim by Edward Witten in the April 1996 issue of Physics Today, repudiated by Roger Penrose on page 896 of his book Road to Reality, 2004: ‘in addition to the dimensionality issue, the string theory approach is (so far, in almost all respects) restricted to being merely a perturbation theory’. String theory does not predict for the strength constant of gravity, G!
This means that my work on gravitational force mechanism which does predict gravity correctly is suppressed: http://members.lycos.co.uk/nigelbryancook