I enjoyed the recent Blogging Heads dialogue between John Horgan and George Johnson, in part because I could follow the whole thing without falling asleep. But the comments about string theory were really over the top and kind of disturbing. I enjoyed Lee Smolin's jeremiad against string theory, The Trouble With Physics,1 but at least he acknowledged that his own camp was in a definite minority. In the exchange Horgan deems string theory "pseudoscience" and analogizes it to theology. You'd expect the author of The End of Science and The Undiscovered Mind: How the Human Brain Defies Replication, Medication, and Explanation to pull no punches. Horgan is a Pyrrho for our age, but he makes himself a caricature with such statements, credibility is given to proportionate statements, not bombastic ones. Later on in the discussion Horgan dismisses the Christian theism of Simon Conway Morris, a prominent paleontologist, as medieval superstition, so the association he makes between theology and string theory seems particularly a rank insult coming from him. Theology is the reasoned analysis of the idea of God. Clearly string theory does not address the same content as theology (i.e., God), so Horgan must be suggesting that the methods of string theorists are like those of theologians. I think not. If string theory is like theology, then so is most of higher mathematics which remains obscure to the eye of the non-specialist. The problem with string theory is its lacks of plain empirical falsifiability, or at least the perception of such. But, one assumes that the physicists who work in this area operate with some modicum of mathematical rigor which can be open to analysis and critique, to a far greater extent then the circumlocutions around a priori truths which are the hallmark of consensus theology. Of course, Sean Carroll has a post up which addresses the major points. Science and scientists are mostly wrong at any given time (at least to the infinitely precise level of description), there's no shame in that. Perhaps the whole field of string theory is wrongheaded, but that doesn't make them shamans or quacks, it simply means that the corrective functions of science have not come to the fore. Yet. Though we sin the faith lives on and we shall be redeemed!
Addendum: Let me be less cryptic about my contentions regarding theology: I believe that this "science" is fundamentally one which will always confirm the revealed truths of the sponsoring faith. That is, I do not believe that the verbal logic employed by theologians is really very rigorous, and so social consensus and pressure, as well as individual bias, will load the die. Christians will find their theology compelling, Muslims will be enraptured by their kalam, while Eastern philosophers will admire their metaphysical insights. I believe theology is powerfully "canalized" by culture. I believe science is less canalized, while I believe mathematics is the least canalized of all. String theory may not be good (or correct) science, but it is not canalized by the surrounding culture in the way theology is (though there is likely certainly a cultural mass psychology at work within the culture of theoretical physics).
1 - Obviously I can't follow the details of the physics so I wasn't convinced of Smolin's characterization of string theory in the specifics vs. quantum loop gravity, rather, his sketch of the way science works was, I think, often quite accurate in its highlighting of the flaws in the culture.
The recent expansion of loud imbeciles like Horgan, Woit, and many others is stunning.
They misunderstand the very basic facts about theoretical physics - that it is a systematic method to derive facts and predictions about the real world by mathematically processing insights from experiments made in the past.
It has been so roughly since the age of Isaac Newton and string theory hasn't changed anything about it whatsoever. Most theoretical physics Nobel prizes were given for theoretical or mathematical analyses and insights about phenomena that have been known for decades or centuries before the theorist made his discovery.
This includes revolutionary Nobel or Nobel-scale discoveries of Einstein, Pauli, 't Hooft, Veltman, Dirac and dozens of others. The whole theoretical physics is theoretical, by definition.
Thinking that theorists' work must be connected to experiments done today, yesterday, or tomorrow is a proof that the given person has absolutely no idea what science means and has farmers' ideas how science works.
I find it stunning that someone would publicly support John Horgan, a lunatic who predicted the "End of Science" ten years ago. This guy's intelligence and knowledge is way closer to the chimpanzees than theoretical physicists.
Time for an argument from authority. If you want to compare string theory with pseudoscience, postmodernism or theology (pick your bogeyman, as Sean Carroll suggests), you have to content with Alan Sokal. Who knows more about the ways postmodernism has gone wrong?
On page five of the paper I linked above, Sokal says,
The original has lots of footnotes which I won't try to reproduce here, along with a picture.
In watching Feynman's Messenger Lectures — the ones which were made into The Character of Physical Law — it struck me that his description of particle physics in the early 1960s sounded an awful lot like a description of quantum gravity today. There was the same sort of thrashing about: propose an idea based on a symmetry principle, find that it doesn't apply to all particles or all interactions, and then justify yourself by saying, "That interaction must be particularly sensitive to the broken symmetry!" Feynman aptly compares this situation to psychology — but, he says, it's what we gotta do to make progress.
I have a great big rant brewing about how this whole String Wars: The Popper Menace nonsense tells us much more about the media than about the scientific community, let alone the Universe itself. . . expect bile and vitriol.
I recall that John Horgan's name came up on ScienceBlogs once before, when he tried to list the Ten Worst Science Books. Over at Pharyngula, PZ agreed with Horgan's choices, at least for the books which PZ had read, but a good many of us dug into Horgan's choices in the comments. For example, "poke" said the following:
Several people also defended Brian Greene's The Elegant Universe, saying that it explained currently known and established science pretty well. Of course, most everybody commenting at Pharyngula is smart and honest enough to say that they're not in a position to judge string theory, and they also chimed in with the observation that Horgan probably isn't qualified either. I wrote the following on Horgan's blog and re-posted it for the Pharyngulans.
From the original post:
OK, I have to call this a gross mischaracterization. Leprechauns were not invented by applying the concepts of quantum mechanics to the motion of wiggly objects defined to obey special relativity. Both quantum mechanics and special relativity are bodies of knowledge in which we have extremely high levels of confidence, assuming we discuss them within their range of applicability. No shrunken Celtic gods arose in the enchanted forest because someone combined two very good ideas to build a structure for generating more ideas.
Leprechauns do not respect energy conservation or Lorentz invariance. Leprechauns do not reliably reproduce known features of the universe — gravity and electromagnetism both fall out of string theory, when one considers closed and open strings respectively — while tantalizing us with the difficulty of getting the rest of the details exactly right. Leprechauns never gave a physicist tools for understanding quark-gluon plasmas, never blessed a mathematician with a result in knot theory and never let students understand non-Abelian gauge theories in terms of overlapping Dirichlet branes.
The AdS/CFT correspondence ain't no lucky charms.
that it is a systematic method to derive facts and predictions about the real world by mathematically processing insights from experiments made in the past.
yes, i believe this is an important point. science draws upon the past to shoot into the future. of course, theory has traditionally needed experiment to make course corrections because navigators are fallible....
Which is why every grad student I've met who works in string theory would give their eyeteeth for a theorem which makes a prediction testable by experiment. It's also why a good many theorists have devoted considerable energy to investigating the AdS/CFT correspondence (an area unjustly neglected in most popular discussions of this issue). For that matter, the experimentalists I've worked with, neutrino types mostly, are just as willing to consider a prediction from some stringy model as they are from anything else (e.g., a suggestion that large extra dimensions might be observable at Super-Kamiokande). So what if we can't design a single experiment, or a short list of experiments, which could knock down the whole mathematical behemoth? Show me the single experiment, in a lab or with a telescope, which can knock down Newtonian mechanics!
In my experience, at least in physics, I think we're switching from theory that tries to explain experiments done in the past to theory that tries to predict the results of future experiments. This has happened as experiment has gotten more complicated, expensive, and larger in scale (consider the current generation of colliders) and theorists have gotten better computational tools. Great theory was derived from experiment in the recent past - QM, QED, General Relativity, etc, etc, and it still is, of course. But I work in cosmology, and at least in this field, it seems like theorists spend a lot of their time saying, "based on what we've seen in the past, you should probably be looking at these energies at these scales for this thing".
Either one can come first. It's a team effort. I think a lot of the skepticism with string theory mostly boils down not to it being bad work, but that there are people saying, hey, you're getting too far ahead of experiment. And you're not taking any risks because you know you won't be shown right or wrong in your lifetime.
Just an observation.
For those who are wondering why there's a controversy over string theory and how it is being pursued, see the first comment and note that Lubos Motl is a tenure-track faculty member at Harvard (ex-Junior Fellow), and his endorsement appears prominently on two out of three of the very recent textbooks on the subject.
Technically, any observation that yields results incompatible with Newtonian mechanics can be considered to "knock it down". But of course such a well-established model requires multiple incompatibilities before we're justified in concluding that it's lacking.
String Theory is not a well-established model. It is a set of hypotheses that was designed to be compatible with existing data but that cannot make predictions that we can confirm or refute through any current experiment. In our attempts to use it to understand the world, it's not science. It's lovely mathematics, I am given to understand.
Imagine if all the hundreds of millions in tax, tuition, and foundation dollars were divided evenly amongst competing theories.
Over the past three years, Peter Woit has run an amazing blog, but unfortunately there are no new postulates to be found on it regarding physics. There are thousands of posts pertaining to Lubos, but I could find no posts pertaining to new theories based up simple elegance and beauty, underlying physical reality.
As each one of the following pages contains multiple refrences to Lubos, the result is thousands of posts pertaining to Lubos, at the expense of advancing physics:
http://www.google.com/search?hl=en&safe=off&q=lubos+site%3Awww.math.col…
At any rate, I decided to help Woit out--let's see if he allows comments pertaining to discussions of new theories, rooted in logic and reason--here's the thread:
http://www.math.columbia.edu/~woit/wordpress/?p=542#comments
Hello All,
I recently counted the references to Lubos on Peter Woit's blog, and they number in the thousands, culiminating in the above comment, linking to a video of Lubos which has not all that much to do with physics:
http://video.google.com/videoplay?docid=706444693144627950&q=lubos+motl
Indeed, it is entertaining, but I am hoping that as we move forward, we can move away from the snarky insiderism and postmodern performance art, and towards discussing physical theories rooted in logic and reason, such as Moving Dimensions Theory, which unifies disparate physical phenomena with a simple postulate: "The fourth dimension is expanding relative to the three spatial dimensions. "
This simple postulate offers a physical model underlying and unifiying:
RELATIVITY:
1) length contraction
2) time dilation
3) the equivalence of mass and energy
4) the constant velocity of light
5) the independence of the speed of light from the velocity of the source
QUANTUMN MECHANICS
1) action at a distance
2) wave-particle duality
3) interference phenomena
4) EPR paradox
THERMODYNAMICS
1) Time's arrow
2) Entropy
STRING THEORY'S MANY DIMENSIONS / KALUZA/KLEIN THEORY
1) a fourth expanding dimension can be interepreted as many dimensions, each time it expands
THE UNITY OF THE DUALITIES
1) wave/particle duality
2) time/space duality
3) energy/mass duality
4) E/B duality
GENERAL RELATIVITY
1) Gravitational redshift
2) Gravity waves
3) Gravitation attraction
THE SPACE-TIME BACKGROUND
1) quantum foam
2) the smearing of space and time at small distances
3) Hawking's imaginary time
PARADOXES
1) MDT explains away Godel's Block Universe
2) MDT unfreezes time
3) Resolves Zeno's Paradox
ONE GETS ALL OF THIS FROM A SIMPLE POSTULATE:
The fourth dimension is expanding relative to the three spatial dimensions in a sphereically symmetric manner, in units of the Planck length, at the rate of c.
This means that every point in three dimnesional space is always expanding into a fourth dimensional sphere with a radius of the plank length. A photon is matter caught on the surface of this quantized expansion, and thus energy is quantized. The expansion of the fourth dimension occurs at the rate of c, and thus the velocity of all photons is c.
Check out the t-shirt with a simple proof of MDT:
http://www.cafepress.com/autumnrangers.72464949
"The only way to stay stationary in the fourth dimension is to move at the speed of light through the three spatial dimensions. Ergo the fourth dimension is expanding at the rate of c relative to the three spatial dimenions."
How sad it is that when truth stares modern physicists in the face, they must close their eyes so as to get a postdoc or raise more funds for String Theory.
Moving Dimensions Theory is in complete agreement with all
experimental tests and phenomena associated with special and general relativity. MDT is in complete agreement with all physical phenomena as predicted by quantum mechanics and demonstrated in extensive experiments. The genius and novelty of MDT is that it presents a common physical model which shows that phenomena from both relativity and quantum mechanics derive from the same fundamental physical reality.
Nowhere does String Theory nor Loop Quantum Gravity account for quantum entanglement nor relativistic time dilation. MDT shows these derive from the same underlying physical reality. Nowhere does ST nor LQG account for wave-particle duality nor relativistic length contraction. MDT shows these derive from the same underlying physical reality. Nowhere does ST nor LQG account for the constant speed of light, nor the independence of the speed of light on the velocity of the source, nor entropy, nor time's arrow. MDT shows these derive from the same underlying physical reality. Nowhere does String Theory nor
Loop Quantum Gravity resolve the paradox of Godel's Block Universe which troubled Eisntein. MDT resolves this paradox.
Simply put, MDT replaces the contemporary none-theories with a physical theory, complete with a simple postulate that unifies formerly disparate phenomena within a simple context.
THE GENERAL POSTULATE OF DYNAMIC DIMENSIONS THEORY
The fourth dimension is expanding relative to the three spatial dimensions.
If at first the idea is not absurd, then there is no hope for it.
-Albert Einstein
http://physicsmathforums.com/showthread.php?t=2381
"...Most theoretical physics Nobel prizes were given for theoretical or mathematical analyses and insights about phenomena that have been known for decades or centuries before the theorist made his discovery.
"This includes revolutionary Nobel or Nobel-scale discoveries of Einstein, Pauli, 't Hooft, Veltman, Dirac and dozens of others. ..." - Assistant Professor Lubos Motl
Einstein won the Nobel Prize for the equation of the photoelectric effect, which made checkable predictions?
Edison and others had noticed the photoelectric effect qualitatively, but Einstein worked out that to release electrons there's a certain threshold energy needed (the work function of electrons on the surface of the metal cathode), and he was able to work out the speed at which electrons would be emitted by a hot cathode with electrons being hit by photons and knocked off. Before Einstein, this had not been worked on and no predictions were possible.
The predictions Einstein made were not merely ad hoc "post-dictions". The photoelectric effect is important for example in the attenuation of X-rays and gamma rays (although for gamma rays the cross-sections for Compton effect and pair-production are generally larger). There is no analogy to string theory there: no landscape of uncheckable ad hoc models!
Pauli came up with the exclusion principle on the basis of experimental evidence that electrons (known then to have a magnetic moment) don't all pair up with the same spin and other quantum numbers: the electrons are well separated and in general the intrinsic magnetic moments and thus spins of electrons cancel out.
Pauli's other great prediction, the neutrino, was again based on data. Beta particles have a continuous spectrum (unlike the line spectra of gamma rays). The total energy emitted in every beta decay is typically 1/3rd of the total energy emitted. The total energy emitted is known from the difference in mass between the beta active nuclide and its decay product. Hence, 2/3rds of the energy in beta decay is being lost somehow. Bohr and Heisenberg argued that this proves that the conservation of energy is subject to the indeterminancy principle, but Pauli argued that the simplest explanation was that a new charge-less particle was being emitted in beta decays that normally couldn't be detected. Fermi worked out the theory, then invented a nuclear reactor, which produces enough neutrinos to check the theory. There is no analogy to string theory there: no landscape of uncheckable ad hoc models!
't Hooft and Veltmann showed that Yang-Mills quantum field theories - which successfully describe particle physics in the standard model - are renormalizable. There is no analogy to string theory there: no landscape of uncheckable ad hoc models!
Dirac predicted antimatter, including its properties. There is no analogy to string theory there: no landscape of uncheckable ad hoc models!
"Leprechauns were not invented by applying the concepts of quantum mechanics to the motion of wiggly objects defined to obey special relativity. Both quantum mechanics and special relativity are bodies of knowledge in which we have extremely high levels of confidence, assuming we discuss them within their range of applicability." - Blake Stacey.
That's just it: special relativity won't hold at the Planck scale. Firstly, gravity becomes strong at the Planck scale, and strong gravity invalidates the constant velocity of light (gravity makes light bend).
It's significant that special relativity assumes that the velocity of light is constant, i.e., it assumes that light cannot curve (a change in direction involves a change of velocity, a vector; it's not the same as changing speed).
General relativity is entirely different to special relativity. Special relativity is just that, a special case which actually exists nowhere in the real universe. It's just an approximation because light is never really moving with constant velocity where there are masses around.
'The special theory of relativity ... does not extend to non-uniform motion ... The laws of physics must be of such a nature that they apply to systems of reference in any kind of motion. Along this road we arrive at an extension of the postulate of relativity... The general laws of nature are to be expressed by equations which hold good for all systems of co-ordinates, that is, are co-variant with respect to any substitutions whatever (generally co-variant). ...' - Albert Einstein, 'The Foundation of the General Theory of Relativity', Annalen der Physik, v49, 1916.
String theorists are confused over background independence. Really, general relativity is background independent: the metric is always the solution to the field equation, and can vary in form, depending on the assumptions used because the shape of spacetime (the type and amount of curvature) depends on the mass distribution, cc value, etc. The weak field solutions like the Schwarzschild metric have a simple relationship to the FitzGerald-Lorentz transformation. Just change v^2 to the 2GM/r, and you get the Schwarzschild metric from the FitzGerald-Lorentz transformation, and this is on the basis of the energy equivalence of kinetic and gravitational potential energy:
E = (1/2)mv^2 = GMm/r, hence v^2 = 2GM/r.
Hence gamma = (1 - v^2 / c^2)^{1/2} becomes gamma = (1 - 2GM/ rc^2)^{1/2}, which is the contraction and time dilation form of the Schwarzschild metric.
Einstein's equivalence principle between inertial and gravitational mass in general relativity when combined with his equivalence between mass and energy in special relativity, implies that the inertial energy equivalent of a mass (E = 1/2 mv^2) is equivalent to the gravitational potential energy of that mass with respect to the surrounding universe (i.e., the amount of energy released per mass m if the universe collapsed, E = GMm/r, where r the effective size scale of the collapse). So there are reasons why the nature of the universe is probably simpler than the mainstream suspects:
'It always bothers me that, according to the laws as we understand them today, it takes a computing machine an infinite number of logical operations to figure out what goes on in no matter how tiny a region of space, and no matter how tiny a region of time. How can all that be going on in that tiny space? Why should it take an infinite amount of logic to figure out what one tiny piece of spacetime is going to do? So I have often made the hypothesis that ultimately physics will not require a mathematical statement, that in the end the machinery will be revealed, and the laws will turn out to be simple, like the chequer board with all its apparent complexities.'
- R. P. Feynman, Character of Physical Law, November 1964 Cornell Lectures, broadcast and published in 1965 by BBC, pp. 57-8.
In addition to the gravitational field problem for string scales, special relativity doesn't apply at the Planck scale because that's supposed to be a grain size in the vacuum irrespective of Lorentz contraction.
The Planck scale doesn't get smaller when there is motion relative to the observer. People including Smolin have introduced "doubly special relativity" to resolve which is a break down of special relativity at the vacuum grain size such as the Planck scale (which is the size scale assumed for strings!!).
The fact that string theory is built on the assumption that special relativity applies to all scales is typical of the speculative, non-fact based nature of string theory.
All of the other non-empirical, yet uncheckable, assumptions put into string theory follow suite (7 extra dimensions to explain unobserved gravitons, 6 extra dimensions for unobserved speculative supersymmetric unification of forces at the planck scale which "explains", branes to explain that 10 dimensional superstring is a membrane surface effect on an 11 dimensional bulk, etc., etc.).
'... I do feel strongly that this is nonsense! ... I think all this superstring stuff is crazy and is in the wrong direction. ... I don't like it that they're not calculating anything. I don't like that they don't check their ideas. I don't like that for anything that disagrees with an experiment, they cook up an explanation - a fix-up to say "Well, it still might be true". For example, the theory requires ten dimensions. Well, maybe there's a way of wrapping up six of the dimensions. Yes, that's possible mathematically, but why not seven? ... In other words, there's no reason whatsoever in superstring theory that it isn't eight of the ten dimensions that get wrapped up ... So the fact that it might disagree with experiment is very tenuous, it doesn't produce anything; it has to be excused most of the time. ... All these numbers ... have no explanations in these string theories - absolutely none! ...' - Richard P. Feynman, in Davies & Brown, Superstrings, 1988, pages 194-195.
Peter,
Lubos also "prominently" endorsed the French edition of the Bogdanov's nonsensical book "Avant le Big Bang" (Before the Big Bang). Really surprising!
Caledonian:
The qualification in your second sentence is a most important one. For example:
The observation that Uranus was not where it was supposed to be, after all the tugs of one planet upon another were accounted for, was a result incompatible with Newtonian mechanics plus a hypothesis about the matter distribution of the Solar system. One could explain such a result by (a) saying that Newtonian mechanics is wrong, or (b) postulating some "dark matter" which interacts gravitationally via Newton's law. Further experiments are then necessary to tell these apart, and in this case, "dark matter" won out — we call the dark matter in question the planet Neptune.
The same thing happened again with the inner solar system, only this time it was Mercury not behaving the way Newtonian laws said it should. Searches for "dark matter" (an intra-Mercurial planet dubbed Vulcan) failed, and so this observation supports a non-Newtonian theory of gravity. Luckily for us, general relativity has support from other directions as well (gravitational redshifts measured by Moessbauer Effect, for example).
Creationists ask mockingly for "just one fossil" to prove that evolution happened. This is rather like demanding to see one single photograph which proves that a child was born, grew up, turned old and died. It's easy to imagine an individual photograph which greatly upsets a view of life ("Oh my God, Dad used to have hair!"), but if you're trying to test a theory which speaks of changes over time, you need observations which cover a period of time.
A set of ideas which do not connect to experimental observations do not constitute a scientific theory (or at least they don't yet). However, the idea that a "single experiment" can confirm or deny a scientific proposition is a straw Popper. And you know, after a while, I get tired of "discussions" about string theory which make grand philosophical claims completely disconnected from the way science actually operates. I'm not aiming this remark at you, Smolin, Woit or any other big names — it's just a general observation about what I see in blog comment threads and the like.
A single experiment can involve multiple observations. If a deviation in orbital paths is found, and no matter can be located to explain the deviation, then we'd be justified in doubting the accuracy of Newton's equations.
Your metapoint - that one experiment by itself doesn't give us enough data to justify conclusions - I quite agree with.
The problem with String Theory is not that it's beyond the scope of science, but that without the ability to experimentally confirm it, it's logically equivalent to every other explanation consistent with the data, yet it's being given far too much attention relative to the others and relative to being a mere hypothesis.