Lawrence Krauss has an essay in today’s New York Times about science, religion and string theory, covering much the same material discussed here in a recent posting. There are postings about this from Mark Trodden at Cosmic Variance and Lubos Motl on his blog. In comments at Cosmic Variance, Lubos tries to make the rather bizarre claim that the status of the theory of evolution is much the same as that of string theory. I don’t notice any string theorists writing in there to tell him that he is full of it.

Meanwhile, in the real world, the Kansas Board of Education has voted to change the definition of science. Krauss has been very involved in this controversy in recent years, fighting the good fight against Intelligent Design and Creationism. I suspect he’s all too aware of the danger posed by string theorists like Lubos intent on muddying the waters about the question of what is solid, testable science, and what isn’t.

**Update**: Over at Cosmic Variance, see some of the reaction Krauss is getting to his criticisms of string theory.

String theory is no different from religion, except that while religion finds many practical applications in civilized society, string theory has none.

String theory is based on blind faith.

And not only blind faith, but tenured snarkiness, taxes, and vast student loans.

But nevertheless, the renaissance that takes us beyond postmodernism to truth’s beauty will yet be.

Peter:

There are something in parallel between the theory of evolution (TOE) and that of Super String Theory (SST). Both, in my opinion, are not falsifiable.

But there is a huge difference. TOE is unfalsifiable because it is the result of pure logic. Just like mathmatics, you know 1+2=3 is absolutely correct, but you can’t design an experiment to test to see if 1+2=3 is true or not. Because the possibility it’s wrong simply do noit exist.

TOE is pure logic. Natural Selection Rule and Survival of the Fittest. They come from logic and nothing more than logic. How could you refute that. How could you possibly design an experiment that could potentially defy logic. Fitness of a spiece is defined as the likelihood how it will survive. So of course a better fitting spiece has a better chance of surviving and spreading offsprings. It can not be falsified by any experiment, but it is correct by logic.

On another hand, SST is un-falsifiable because it has no relevance whatsoever with the reality world. There is no connection whatsoever so there is no way any experiment can be proposed to prove or disprove it. So SST is at the completely opposite end, the wrong end, of un-falsifiability.

Quantoken

I think Krauss put his finger on a very important issue. I have a feeling that some parts of theoretical physics were hijacked by formal mathematicians who place mathematical “beauty” above sober observable reality. I am not even talking about strings. For better or for worse, this started 100 years

ago with the invention of spacetime. This idea quickly became a favorite toy of mathematicians.

Think about many different ways you can play with the spacetime: you can bend it, twist it, “foam” it,

tear it apart. You can apply numerous branches of

mathematics to it: differential geometry, topology, … What if you add some extra dimensions? Oh! The joy is endless! There is just one thing you cannot do with the spacetime. You cannot observe it!

This seems to contradict one important lesson we learned from quantum mechanics. This lesson says: “never ask questions about something that you do not (can not) observe.” If you want to get a verifiable answer from your theory, then specify the experimental conditions and the measuring apparatus. You can say: I have an electron gun at point A, a two-slit screen at point B, and a photographic plate at point C. Then the theory would correctly predict what is the image on the photographic plate. If you don’t want to get into trouble, never ask which slit the electron passed through. This question has no counterpart in your experimental design.

Now back to the spacetime. I don’t think there is

experimental apparatus that can measure spacetime curvature or topology, or whatever.

All these “properties” are hidden, or maybe even non-existent.

I think there should be a very very high threshold for introducing non-observable concepts in physics. Wouldn’t it be much safer to limit the vocabulary of physics to things that we can directly observe: like electrons, photons, protons, their positions, momenta, spins, wave functions, etc.

I see a tendency to move away from this basic stuff to some esoteric high-dimensional never-observable purely mathematical rather speculative things. Some may say that the logic of science led us there. I am not sure. I have a suspicion that pursuit of pure “mathematical beauty” played a part in misleading us there. Sorry for harsh words directed to mathematicians, but this tendency worries me a lot.

Eugene.

Although it may sound strange, Quantoken is quite clearly closer to the truth than Peter Woit. The very evolutionary framework or the string theory framework are not falsifiable by a single experiment.

They’re much more fundamental approaches to broad classes of questions that are supported by very general arguments – such as the billion-year-long history of Earth and life and/or the existence of gravity in the quantum world. In the case of string theory the arguments are much more mathematical in nature, but the basic reasons are very similar.

There is a belief system that is primary. It underlies another layer of insights which are viewed as technical details to be answered in the future. It is true about evolution much like about string theory.

Any particular experiment designed to falsify either evolution as such or string theory as such – before the exact vacuum etc. is localized – could only result in the modification of some subtle technical features of these theories. Only very unrealistic people claim that there exists a single experiment whose result would convince everyone in science that the whole Darwinian picture of species is wrong.

Something similar holds for string theory because we don’t have the complete picture either: the absence of SUSY at the LHC won’t kill string theory (although it may convince many to work on other problems) – and some people in fact claim today that SUSY is not a prediction of string theory.

Let me not go into details but string theory as such is a much more robust framework than SUSY at 1 TeV which is a mere quantitative technicality.

Peter’s celebration of Krauss’ anti-religious activity sounds like a prayer itself. Krauss may have obtained the right binary answer to the question whether creationism is wrong, but as far as his texts in the New York Times and elsewhere can indicate, his reasons are misguided. The reason why a theory in science is wrong is definitely not that the theory is too counter-intuitive for a layman or that it uses too complex maths or that the religious people may like the theory, and whoever thinks that these are the reasons that decide about the truth in science is confused about very basic features of the scientific method.

Also, I find Peter’s suggestion that biology of the early life forms is more rigorous or more scientific or more well-established than theoretical high-energy physics to be rather absurd. We’re continuing the same physics whose insights have been tested with the accuracy of 13 decimal places – the only difference is that we focus on harder questions that are also less accessible to cheap experiments.

At any rate, theoretical physics is more rigorous and reliable than biology – especially theoretical physics that follows from well tested frameworks. This includes the Bekenstein-Hawking entropy mentioned at Cosmic Variance and used as a non-trivial check of self-consistency of the theories of quantum gravity. Of course that the physicists are much more certain about the magnitude of the entropy of large black holes than the biologists can ever be sure about the hierarchy of very early life forms on Earth. If you disagree, Peter, are you just joking or are you serious?

I think that Eugene’s example is excellent. There are simply people around who deny not only spacetime curvature – something that has been tested in several different types of experiments (they deny it because the theory behind it normally involves differential geometry that they hate) – but even the spacetime itself. They have problems with special relativity from 1905 whose 100th anniversary we just celebrated.

Our colleagues like Lawrence Krauss and Peter Woit are qualitatively similar; the difference is merely quantitative. Maybe they don’t deny the insights made by Einstein in 1905, but they almost definitely deny all insights in theoretical high energy physics made after 1975. Because they don’t understand it and they don’t want to understand it.

Even if a majority of the population on Earth does not care about relativity, there are still people who care, and there is a subset of people who care about even more advanced questions, and so forth. What Peter Woit and Lawrence Krauss are doing is nothing else than a gigantic anti-scientific crusade. They want to destroy whole branches of science just because they personally find the questions and the concepts considered as solutions to be too difficult and too abstract.

Hi Lubos,

I was comparing string theory to the theory of evolution, not theoretical high energy physics to the theory of evolution. String theory is not equivalent to theoretical high energy physics, much as you wish that to be true.

You’re really out of your gourd to compare string theory and the theory of evolution. Sure, scientific theories are generally frameworks that can’t be easily falsified by a single experimental result. But the framework of the theory of evolution does something the string theory framework can’t do: it makes lots of testable predictions, ones that have been tested and come out as predicted. Wasting my time by arguing about this is against my personal religious convictions, as is responding to your foolish belief that people who have a problem with string theory just don’t understand it.

quantoken, I will repeat for you here a post I made on the Mark’s thread over at cosmic variance.

The theory that all organisms evolved is in no way the same postion as string theory. Microevolution, the prerequisite for the theories of speciation and common being general among all species, has actually been observed in the lab as well as selection pressures and other things. Corresponding things in string theory strings, compactified dimmensions, and susy have not been observed. Furthermore direct evidence that doesn’t depend on the observation of microevolution exist.

http://www.talkorigins.org/faqs/comdesc/

String theory meanwhile has not been subjected to any tests.

If the LHC and colliders of the future fail to find evidence of the graviton, will Standard Modelers and Stringers still search for it?

On TOE. Natural Selection and Survival of the Fittest exist obviously enough, but Darwin’s insight is that these phenomena are the ONLY mechanisms behind the differentiation of species.

So it is falsifiable. If you proved that, say, species bifurcate because endoparasites diddle with their germ lines – for their own benefit, not their hosts, that would disprove Darwin by making Selection irrelevant.

(and don’t laugh at the example; the endoparasites in your body get away with tons of weird shit we don’t even know about).

Lubos,

it is not correct to say that “spacetime curvature … has been tested in several different types of experiments.” As far as I know, curvaturemeters have not been invented yet. What have been measured are observable effects with real physical systems, like planet Mercury, or light rays passing near the Sun, or binary pulsar systems. Spacetime curvature is a theoretical tool that our current model of gravity employs to explain these effects.

There is no theorem stating that GR is the only possible theory that can explain these effects.

Surely, GR is very beautiful mathematically. Surely, no other successful theory has been suggested yet. But I think we should better keep an open mind and try to avoid as much as possible those non-observable theoretical ingredients Krauss was talking about.

I think it is important to keep an open mind, because, in my opinion, quantum gravity project was a complete failure so far. In order to make it right, we should exercise discipline and logic, and try not to be distracted by beautiful, but physically empty, mathematical ideas.

I don’t hate differential geometry or algebraic topology. To the contrary, I find them very enjoyable. I am just not sure what is their place in physics.

If (keeping the discipline of logic and an open mind) we rewind 100 years back and analyze foundations of special relativity, we may find that

4D Minkowski space-time unification does not follow from two Einstein’s postulates (which are based on solid observations, of course) by straight logic. In fact, the idea of Minkowski spacetime is an additional postulate.

Moving some 20 years closer to our times we may discover that this idea is in a deep contradiction with basic quantum mechanics where position is an observable described by 3 Hermitian operators, and time is a numerical parameter. This just does not work well with the 4D spacetime unification. That’s where the seeds of modern quantum gravity controversy were planted. In my humble opinion.

I am convinced that this controversy will not be solved until we make a deliberate choice between sober reality-based formalism of quantum mechanics where each component has a directly measurable counterpart in the real world and abstract non-observable (but mathematically so sweet!) postulate of the 4D spacetime unification.

Note that rejecting the 4D spacetime does not require us to reject the principle of relativity or the Poincare group properties of transformations between inertial observers. These two ideas have overwhelming support in experiments.

Eugene.

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While I get some people are pissed at string theory, people outside the community (physicists in neighboring disciplines, like me) have I think a pretty accurate idea of what string theory is. It’s a set of mathematical ideas, with some intriguing analogies, that a number of very smart people have worked on for more than twenty years.

Back in the day, string theory made some big claims. It still makes some big claims, but it tends to make them in the New York Times these days, and not in serious journals.

There are competitors to string theory. Even some of the great string theory gurus have taken up research into those areas.

Today, string theory is in trouble. It has provided no significant input into other areas of physics in a long time. All of its predictions are either trivial (fundamental Lorentz invariance, which may yet be hidden) or ambiguous (different versions say different things.) Sexy things like string cosmology may be “inspired” by string theory, but in practice are mostly statements in classical GR with a dose of field theory and a perhaps a nod to Hawking radiation.

Fields in trouble are not new for Science. Science will survive despite the occasional ideologue.

That’s how we see it. IMO, Krauss should not be saying silly things about Intelligent Design and science. ID is, intellectually, somewhere up there with Dick Cheney’s 2001 napkin theory of Iraq.

“There are simply people around who deny not only spacetime curvature – something that has been tested in several different types of experiments (they deny it because the theory behind it normally involves differential geometry that they hate) – but even the spacetime itself. They have problems with special relativity from 1905 whose 100th anniversary we just celebrated.” – Luboš Motl

Luboš, the spacetime curvature is physically required to keep Pi intact when the contraction term of GR reduces the radial distance around mass without affecting transverse distance, circumference. One way to account for this reduction of radius while circumference isn’t reduced is to say spacetime is curved by the fourth dimension.

This is equivalent to radial pressure from the spacetime fabric virtual radiation, causing the contraction in the same way as the FitzGerald-Lorentz contraction in the direction of motion. I’ve shown how each contraction is related to the other, on my home page.

If you are going to worship Einstein religiously, relativity is going to forever remain stuck in either 1905 or 1915. How are you going to prove it is a theory so special that it can’t be worked on any more? How are you going to defend it by saying it is so useful that nobody is allowed to use it? Differential geometry shouldn’t be used to simply cover up ignorance, nor should any other mathematical tool.

Speaking of curvature meters – we measure the curvature of space-time in exactly the same way as we can measure the curvature of earth – by observing and measuring the non-parallelism of geodesics.

While there is no theorem that General Relativity is the only theory that can explain all the things we observe, there is the Parametrized Post Newtonian formalism, which is a systematic set of corrections to Newtonian gravity with a number of free parameters. Any theory of gravity sets values for these parameters; these parameters are obtainable by experiment or observation; and as I understand it, GR is the only theory left standing.

Arun,

GR is not a scientific theory as Popper views such a thing, it is right because it ties up two empirical facts, Newtonian gravity (put in as the weak field/slow speed limit) and mass-energy conservation (the contraction term correction).

This is why GR is not a speculative Popper-type guessed theory. Einstein was not being arrogant when he said to a student in 1919 that it is right regardless of Eddington’s experimental result. GR is not fallible provided the two inputs, Newtonian gravity plus the mathematical compensation for energy conservation, are correct.

Since the two ‘arbitrary’ inputs are empirical facts at least within the solar system, GR is logically correct on that basis alone. You don’t need to test a mathematical prediction based entirely on empirically determined facts. Where Einstein ran into problems was in fiddling the basic field equation to give cosmological predictions, such as the cosmological constant fix to give a steady state universe. In addition there is the issue of whether gravity (thus the Newtonian G factor) is due to a mechanism like some kind of gauge boson pressure, which causes the contraction in gravitational fields, which is determined by the surrounding matter in the universe. Because rotational motion appears to be absolute with respect to the surrounding stars, ultimately there is empirical evidence for Mach’s principle over relativism. GR is, as Einstein recognised in his 1920 Leyden university inaugural lecture “Ether and relativity”, an absolute motion theory because it describes accelerations – which are and have always been absolute. Restricted or “special” relativity (SR) is incomplete. So much applauding is given to SR having only 2 postulates that people forget Einstein added a third postulate in GR in 1915, and GR is the universal theory.

As an analogy to GR, consider the heuristic interpretation of QFT, with virtual particles polarised around particle cores, forming a shielding veil which reduces the bare core charge by the 137 factor. In turning the maths of GR into a physical mechanism, you do the same thing, looking for a mechanism which fits the facts and then using the mechanism to make some testable predictions.

I completely agree Eugene!

Great physicists like Isaac Newton or R. Feynman understood perfectly the diference between physics (‘science’) and math. There is a current tendency in theoretical physics to use the pure mathematical formalism without a clear underlying physics.

Not only nobody has newer measured spacetime curvature. Even as i said in sci.physics.relativity and sci.physics.research time ago, in others theories as FTG or torsion gravity one verifies the same tests that GR with a

flat spacetime.Perhaps the most interesting of last days in this topic was my proof in spr of that in the nonrelativistic limit of GR, the metric of spacetime goes to (1 -1 -1 -1) and spacetime looks flat.

Some specialists like Carlip were rather sckeptic and initially did rather bold statements (as “your metric is wrong”, when is a recomended metric) but finally Carlip agreed with me own proof that in the nonrelativistic limit one can obtain zero connections and still there is Newtonian-like gravity: a = -grad(phi).

Obviously curvature, R_ab, R, or \gamma^i_{ab}, etc. of spacetime is zero in that limit, but gravity is not.

If A is cause of B, then elimination of A may eliminate B…

My emphasis on this is because this is one of keys on why until now GR has been not unified with other forces and quantized: the geometric view of gravity has been the great failure of 20th century physics.

String theorists just hereditated this geometric view and the result has been… 40 years…

Juan R.

Center for CANONICAL |SCIENCE)

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