## Thursday, January 07, 2016

### Shape dynamics and antirelativistic crackpottery in general

Crackpots may be classified to categories (or given time stamps) according to the first important discovery in physics that they hate. The closer this discovery is to the present, the more likely it is for the crackpots to impress many other people. The older this discovery is, the more visible the inadequacy of the crackpot should become to a larger portion of the public. For example, people who say that the Earth is at the center of the Universe don't enjoy too much support from the public (so far).

In 2006, the mass media began to hype anti-string crackpots (their time stamp is about 1974 – when string theory was shown to imply GR) as if they were on par with the real top physicists (if not better). To sling mud at some of the most valuable insights that the mankind has found is bad enough by itself. But because string theory is so perfectly continuously connected to the rest of physics and its history, it seemed obvious to me that the culture of physics hatred would gradually grow and extend to ever older pillars of physics.

The journalists would spend the following years by increasingly hostile attacks against things like quantum mechanics and celebrated the people who question facts settled at least since 1927. Right now, we may be entering the era in which it's considered "OK" for the mass media to hype anti-relativity crackpots.

Yesterday, the U.S. public TV channel PBS/NOVA published a text titled
A Radical Reinterpretation of Einstein’s Theory.
This is a rather ambitious title – which is either a very unlikely revolution or complete bunk.

The point is that relativity is such a clear theory with well-defined physical implications that there is nothing to "interpret" about it. (To pretend that there is a whole layer of physics dealing with "interpretations" is at least as silly as in the context of "interpretations" of quantum mechanics.)

One may use different kinds of notation to write down the quantitative formalism underlying relativity. But relativity isn't a bunch of regulations and commandments about which notation or conventions you should like. It is an existentially important physical theory that actually tells you something about the physical phenomena and patterns they exhibit – independently of any particular notation, language, or system of conventions.

At the end, the PBS article promotes a would-be research direction known as (or culminating as) the so-called "shape dynamics". Let me pick Flavio Mercati's tutorial as a definition of the theory – or, more precisely, a representative description of the fallacies or muddy thinking that is associated with the term "shape dynamics".

Now, let me return to relativity. It has two parts, the 1905 special theory of relativity and the 1915 general theory of relativity. They changed our understanding of space and time – and everything in it. Special relativity is built on two postulates:
1. principle of relativity: the laws of physics have the same form in all inertial systems (those linked to observers in the state of uniform motion relatively to other inertial observers)
2. constancy of speed of light: the speed of light in the vacuum is always 299,792,458 m/s regardless of any motion of the source and receiver
The postulates imply that the space and time get mixed, one may define the Minkowskian 4D "distance" between any two events, and the laws of physics must enjoy the Lorentz (and Poincaré) symmetry which organizes previously independent quantities into "multiplets"; and seriously constraints the laws of physics that is possible. These constraints also imply – independently of a particular chosen microscopic theory – certain kinds of behavior which become self-evident once the speeds approach the speed of light.

Similarly, general relativity assumes that
1. phenomena in small enough patches of the spacetime obey laws compatible with special relativity
2. principle of equivalence: the gravitational forces are locally indistinguishable from fictitious forces (inertia, centrifugal force etc.)
These two assumptions imply that it's possible to define the metric tensor on the spacetime, the metric tensor decides how you should transform your coordinates to locally reproduce special relativity, and in the presence of gravitational fields, the special relativity is most easily reproduced in freely falling frames. On the contrary, the presence of mass curves the spacetime and one may derive how (Einstein's equations hold at long distances).

Einstein has introduced a new powerful kind of thinking. One may start with some general observations that are not "quite guaranteed" and they tell us a lot. With enough thinking, we may derive lots of consequences. String theorists are using this ability of mathematics to greatly amplify our empirical knowledge a lot.

Now, what is shape dynamics (SD)?

Already in the abstract, Mercati says it's a theory in which GR's "relativity of simultaneity" is replaced by the "gauge symmetry under spatial conformal transformations". SD basically "undoes" the spacetime and forces you to treat each slice at $$t={\rm const}$$ separately from others. At the end, you may see that it's some intrinsically non-relativistic field theory given by a Hamiltonian and lots of first-class and second-class constraints. At a given moment, they play with the conformal or Weyl symmetry a lot.

Games of this kind are said to be a "radical interpretation of relativity" by the PBS. But it is not a "radical interpretation of relativity". It is just a plain and full-fledged rejection of its assumptions, methods, and results. It's a denial of relativity as a clever system of ideas. To suggest otherwise means to completely misunderstand what relativity is all about; or to intentionally deceive others about its meaning.

The first problem with Mercati's "replacement" is that the "relativity of simultaneity" isn't a postulate or axiom of relativity. It is an unavoidable derived consequence of the postulates. One may be interested in this question or not interested in this question (whether the simultaneity is absolute or relative). One may emphasize or suppress this question. But the point is that we may talk about it and once we do, relativity gives an unequivocal answer: different observers must differ in their notion of simultaneity of two events. Otherwise the equivalence of the observers (principle of relativity) must be violated; or (like in Newton's theory) the speed of light will depend on the motion of sources and/or observers.

As long as you talk about a relativistic theory, you simply cannot "replace" the relativity of simultaneity because it is a true and important fact that can't be "revoked" within relativity. You may describe this fact in different words but this is pure linguistics. The statement about observations done by observers in various states of motion consists of operationally well-defined words so you should better learn this language. If you do it and if you're intelligent enough, you will agree that the evidence shows that the principle is at least very accurately approximately true, and most likely, it is exactly true. You can't "weaken" the fact by some words or "interpretations". If you start to gradually twist and distort your words and after a while, you're not sure whether the statement about the relativity of simultaneity is right, you're just exposing your muddy thinking. You're lubricating your body, your face, and your brain by greasy šit. By relativizing the relativistic claims about the relativity of simultaneity, you are just showing that your brain hasn't done enough work to even understand the questions that relativity was designed to handle, let alone to fully understand them (and the answers) or even to extend them in much more far-reaching theories.

These people switch to a preferred ad hoc slicing of the spacetime. They are conceptually returning to the Lorentz-style pre-relativistic theories that tried to explain the Morley-Michelson experiment and other things. If such theories produce Lorentz-invariant physics, it is an unbelievable coincidence – or a result of a huge fine-tuning – because there is no reason in their postulates for the consequences of the Lorentz symmetry to hold. At the same moment, there's nothing conceptually new – ordinary GR may be and has been described in the Hamiltonian, space-time-asymmetric, language, too.

So these men are not "reinterpreting relativity". Instead, they have completely missed and misunderstood this advance in physics – its axioms, its derivations, and its conclusions (and relativity is composed of these three things). They're trying to return back to 1904 or further. They work and think in the old and outdated non-relativistic framework.

Similar comments apply to their discussion of gravitational phenomena. SD is said to have evolved from Julian Barbour's obsession with the "resuscitation of Mach's principle". But you know, the progress in physics has shown that Mach's principle wasn't really right and there's no reason why it should have been. It has encouraged Einstein to think about the right questions but couldn't have been used as an axiom of his valid theory (GR). If gravitational waves happen to be discovered ;-), we will have the most direct disproof of Mach's principle. Mach said that in the empty space, nothing can happen. But the empty space with gravitational waves will have demonstrably differed from the empty space without them.

They use some field theory formalism with the 3 spatial and 1 temporal dimension "carefully separated". But if this separation is important for their "framework", their theory simply implies that the spatial and temporal dimensions shouldn't be mixed and the Lorentz symmetry is fundamentally wrong. If a theory obeys the Lorentz symmetry, it can often use a description in which the space-time symmetries refuse to be manifest. But they must still be there and the proponent of the theory can't actively say that "one shouldn't" think about the unified spacetime continuum.

Their formalism is ugly, too. All the first-class and especially second-class constraints are annoying, unnecessary, and the need to use them usually indicates that something is seriously wrong with the theory.

The symmetries that they use – the conformal symmetries acting on the spatial dimensions only – are not natural in any way. Unlike the Lorentz symmetry which "really holds", the spatial-only (or full-spacetime, for that matter) conformal symmetry doesn't hold in the Universe around us (we will get to their bizarrely wrong claims about the scale momentarily). Also, there is nothing original about their theory. The focus on theories that separate the space and time again may be said to be nothing else than plagiarism or a derivative reaction to the Hořava-Lifshitz fad started in late 2008 and in 2009.

But I want to discuss some aspects of the PBS article in the rest of this blog post.
...Barbour, 78, is an independent physicist who contemplates the cosmos from ... a thatched-roof country house some twenty miles north of Oxford. He is perhaps best know[n] for his 1999 book The End of Time: in which he argues that time is an illusion.
You know, it's a problem for an idea about physics if it is best known from a popular book, as in Barbour's case. This indicates (and it's often true) that the content is only good enough for the laymen while the experts may see that it's wrong or vacuous or otherwise worthless.
...and Barbour has made a point of inviting a handful of bright young physicists to join him...
It's unfortunate for journalists who don't have a clue about physics to invent their own ratings. There exists no objective reason to think that there have been any bright people among the people invited to that cottage.
It could, of course, be a dead end, as most bold new ideas in physics are.
It's a dead end but the sentence above says something else about the wrong attitude adopted by that the PBS writer (and probably also the "bright" physicists he is hyping). You know, good physicists simply avoid publishing – or otherwise sharing – ideas that are known to be wrong or are at a very high risk that they will be shown wrong. Because of this carefulness, most bold new ideas that get out there from the brains of the good physicists are actually not dead ends.

But Barbour and his "bright" colleagues – along with the inkspillers who hype their activities – don't have any quality standards, filters, or just plain human conscience which is why most (almost all) of their ideas are wrong or at least dead ends. But this doesn't mean that the same comment holds in all of physics. It simply doesn't. It doesn't mean that it's just okay for a physicist to be sloppy and talk rubbish most of the time. It's not okay. Physicists of different quality levels differ in the percentage of rubbish that they publish (or even say to the journalists) and the comment that "most ideas people bring are rubbish anyway" only holds for the lousy physicists similar to the "bright" chaps on Barbour's cottage.
Or it could be the next great revolution in our conception of the cosmos.
At least 4 almost equivalent hyping sentences of this kind follow. Now: How can someone say something like that? SD would be at most a very awkward formalism to write the same physics, a formalism that fails to be sufficiently concise which is why it also produces serious doubts about whether it is actually equivalent to relativity. But these folks haven't found – and haven't even proposed – any big ideas, big assumptions, observations, patterns, derivations, previously uncalculable results, or other conclusions. So what could be the "beef" of the next great revolution in physics?

There is absolutely nothing intriguing let alone revolutionary going on here. Where does the inkspiller take so much arrogance to write all these big words?

Incidentally, if they had an equivalent formalism to describe dynamics of GR with an unusual gauge symmetry, it would be a bit nontrivial thing but not yet an intriguing one. Gauge symmetries are redundancies which means that because of the incorporation of unphysical degrees of freedom, the descriptions involving gauge symmetries are non-minimal ones – in some sense, they violate Occam's razor, if you wish. This is a potential vice which is only justified if there are some benefits. The normal Maxwell, Yang-Mills, and diffeomorphism gauge symmetries are great because they allow us to write the theories in terms of fields (gauge potentials, metric tensors) that are organized as spacetime vectors or a tensor and those make the Lorentz symmetry of the theory manifest (very easy to check) for that reason. The shape dynamics guys' new "gauge symmetry" almost always doesn't bring us any advantage of this kind (e.g. a manifest physical symmetry) at this point which is why it's just an awkward, unjustified complication of the formalism.
“We’re trying to re-evaluate the basic assumptions of Einstein’s theory of relativity—in particular, what it has to say about gravity,” Gryb says. “It’s a shift in what we view as the fundamental elements of reality.”
I wrote the basic assumptions of special and general relativity above. If someone fundamentally or sharply disagrees with those axioms and their consequences, he is simply denying (not "interpreting") relativity. There is nothing in between. 3+1 is either equal to 4 or not. There is no "new revolutionary interpretation" answer in between Yes and No. You may say words in between Yes and No but it just means you're vague. Relativity and other theories are so valuable partly because they allow us to make comprehensible, sharp, and guaranteed claims. To replace relativity with a vague theory where Yes and No get blurred is surely a negative change.

"Fundamental elements of reality" may sound like an impressive phrase but at a certain level, it may also be a completely physically vacuous one, a kind of language that is only good for cheesy commercials, not in serious research. Physics isn't about assigning big and bigger adjectives to concepts. Physics is about separating true and false propositions about Nature. What is the "fundamental element of reality" ultimately isn't an operationally well-defined question. But despite this fact, some ideas and concepts are important in various theories. The spacetime, the Lorentz symmetry, the equivalence principle etc. are surely fundamental features of special and general relativity. Which of them is more fundamental? Well, this one or that one, maybe, blah blah blah, we don't always know. But the propositions about them are true and this is what matters.

The only other possibility is for you to say that they are false but then you are not doing relativity. You are promoting or pushing an alternative system of ideas – one that will face huge problems because it won't be able to explain what relativity explains so amazingly.
Gryb, 33, is a tall and athletic figure; he’s affable and good-humored.
It makes you wonder why you have never learned that the Šmoits are short, non-sporty, boring, whining, and stuttering. Maybe a certain kind of people only deserve "good press" while others only deserve "bad press"?
His PhD supervisor was Lee Smolin, one of Perimeter’s superstar scientists.
LOL, what a pedigree. Smolin is a crackpot, not a scientist, let alone a superstar scientist.
Smolin, like Barbour, is known for his outside-the-box ideas...
Outside-the-box ideas are those that string theorists propose whenever they spark a new minirevolution. Smolin's ideas are not "outside-the-box"; they are said to be idiotic.
...and has been a vocal critic of string theory...
Is that supposed to be an explanation why Smolin has been called a "superstar scientist"? Every idiot is capable of vocally criticizing string theory and most idiots are actually doing so.
Sure, [Gryb] could work on problems where the questions are well defined and the strategies clearly mapped, slowly adding to what we know about the universe.
Jesus Christ, this offensive šit just drives me up the wall. Good scientists simply have to shape their vague ideas to a form where they become at least partially if not completely well-defined – otherwise their ideas have nothing to do with science or rational reasoning in general.

And when they do so successfully, they are slowly adding to the mankind's knowledge of the Universe. Even Einstein has described his most important results - both theories of relativity – as a minor refinement of Newton's and Maxwell's theories. One may use more self-confident words, too. But every advance is building on some previous ones. Some insights end up being more dramatic than others but in general, advances in physics form a continuum.

It is nothing else than a complete disrespect for science to suggest that it's not exciting to be gradually shifting what we know about the Universe. Incidentally, I am ready to make a bet that the "sure" sentence above is just wrong and Gryb surely could not do the kind of serious science that the inkspiller despises. What he's saying is just like "Anička Dajdou could sing boring songs with the correct melodies like Dido or Meghan Trainor". Except that she couldn't: she's tone-deaf. In the same way, Gryb and others are physics-deaf. They write papers about garbage not because they have transcended the "ordinary" top researchers in physics – but because they can't do better.
There’s no shame in that; it’s what most physicists do.
It's not right to say that "there is no shame in that". Instead, it is fascinating to gradually shift the mankind's knowledge about the Universe. Physics is fascinating. Also, it's untrue that "it's what most physicists do". Instead, it's what all physicists do. If someone isn't working to gradually shift what we know about the Universe, he isn't doing physics research.
Instead, like Barbour and Smolin, he focuses on the very foundations of physics—space, time, gravity.
Sorry, it's the string theorists who primarily focus on the foundations of space, time, and gravity. They differ from crackpots like Gryb or Smolin by their ideas', arguments', and calculations' making sense and by their propositions' being "well-defined", if I use the PBS journalist's own words; and by avoiding hugely immodest words (such as those above), especially in cases when they would be unjustified (like in the case of shape dynamics). String theorists are also vastly more innovative, creative, and original than the crackpots who just keep on combining the notions from 110-year-old papers by Lorentz and others in various random ways, hoping that a permutation will lead to a revolution comparable to relativity even if they don't understand relativity.

Long paragraphs describe the fact that relativity isn't scale-invariant. But these long paragraphs are futile because at the end, it turns out that neither the journalist nor the crackpots understand what the scale invariance – and even the measurement of lengths – actually is.
“Absolute size is something that seems to be built into Einstein’s theory of relativity,” says Gryb. “But it’s something that actually we don’t see. If I want to measure the length of something, I’m always comparing it against a meter stick. It’s the comparison that’s important.”
This "interpretation" is complete bullšit, too.

The fact that we may compare the elephant to an omnipresent meter stick (or, more accurately, to the wavelength of some atomic radiation that is used to define one second and therefore one meter, too) proves that we do see the absolute size of the elephant. The seeing/measuring of the elephant's length and the comparison of the elephant to the meter stick (or another unit of length) are exactly equivalent or synonymous. To measure the length means to compare the length to some unit or prototype. It just cannot mean anything else!

The meter stick or the wavelength are just units in which the length must be expressed. The only question is whether there exist fixed objects that are guaranteed to have the same length everywhere. In our world, the answer is Yes and this answer is exactly equivalent to the statements that Nature has a preferred scale; or fails to obey the symmetry of scale invariance.

So now, a huge portion of their crackpottery is about this misunderstanding of the notion of the "length" and "scale" and "measurement". They want to believe – even though it's nonsense – that the measurement of the length may mean something else than a comparison to a unit such as the meter stick. It's clear that they don't have any other meaning of the measurement but they incorporate the wrong assumption into the foundations of their muddy thinking, anyway. From that very early moment, they lose the ability to distinguish scale-invariant and scale-variant physics. Their muddy thinking about the lengths is getting mixed with the rest of their greasy šit.
Perhaps the best way to understand what Gryb is saying is to imagine that we double the size of everything in the universe. But wait: If we double the size of everything, then we’re also doubling the size of the yardsticks—which means the actual measurements we make don’t change.
Holy cow, he is a complete idiot. I understood these things about units when I was 7. This "bright" chap is still clueless when he's above 30 years old. The length is a dimensionful quantity. If you double the numerical size of all lengths in the world, it means nothing else than to reduce the length of your unit (e.g. the meter) to one-half of the original value. This operation would be unphysical – a mere change of conventions.

However, distances in the Universe may also double in the physical sense, e.g. when the Universe is expanding. We may really squeeze a greater number of atoms in between two galaxies when the Universe is older (more expanded). Some (dimensionless) ratios change when the Universe is expanding which is why the expansion is a physical change, not just a change of some conventions.

Our definitions of the units – like one second and one meter which is 1/299,792,458 of a light second – are such that they are equal to a fixed numerical multiple of certain wavelengths (or periods) of some particular radiation between particular states of particular atomic species. The number defining the numerical multiple is fixed by definition. So you can't double it. The wavelength of the radiation cannot double because by definition, the wavelength is a particular numerical multiple of one meter. (You could change the definitions of one meter etc., but the resulting "theory" would be physically equivalent and you would only introduce chaos.)

Up to the irrelevant factor, the wavelength is our meter stick, a fundamental object needed whenever you discuss lengths and distances. To say that it doubles is as meaningless as to talk about the doubling of the number $$1$$ or $$\pi$$. The number $$1$$ just can't double because it would be replaced by a completely different number, $$2$$. The number $$1$$ is the only nonzero number that squares to itself; $$2$$ doesn't obey this condition. So there's no symmetry in between them as long as multiplication is allowed; there's no legitimate justification of a confusion that mixes the numbers $$1$$ and $$2$$. To be uncertain about the difference between $$1$$ and $$2$$ means to be a hopeless moron. Exactly the same thing holds for the people who are confused about the "doubling of one meter".
This suggests that “size” isn’t real in any absolute sense; it’s not an objective quantity.
It doesn't. This conclusion is completely wrong and shows that the "bright" guy has smoked drugs way too much and he got lost in some elementary facts about the definition of units and the dependence of some statements on the choice of units. If the scale invariance is broken in a Universe, and it is broken in our Universe, then the absolute size is unavoidably an absolute quantity.
With shape dynamics, says Gryb, “we’re taking this very simple idea and trying to push it as far as we can.
If you're really denying that the size is absolute and that the scale invariance is broken, then your theoretical framework directly contradicts the empirical data because our Universe obviously isn't scale-invariant.
And what we realized—which was a surprise to me, actually—is that you can have relativity of scale and reproduce a theory of gravity which is equivalent to Einstein’s theory—but you have to abandon the notion of relative time.”
One can't ever "reproduce" relativity by denying the relative time because the "coincidences" we derive from the Lorentz symmetry, a principle underlying relativity, cannot be derived from anything else. So if a theory denies the relative time or any other major axiom or conclusion of relativity, then it predicts that the patterns we normally derive from the Lorentz symmetry are infinitely unlikely to occur.
Does this mean that Einstein was wrong about time being relative? Surely we’re not heading back to Isaac Newton’s notion of absolute space and time? Gryb assures me that we’re not. “We’re not going all the way back to Newton,” Gryb says.
Sorry, you obviously are. The lie that you are not returning to the 17th century is a lie designed to pretend that your "theories" are less stupid than they are. The problem is that even rather average people may figure out that your "theories" building upon the absolute time seem to belong to the same class as those in the 17th century and you are therefore less advanced than Einstein – you can't even understand something he found 100+ years ago, let alone discover something comparably important.
Newton had imagined that space was laced with invisible grid-lines...
Except that Newton and his theory have recognized Galileo's principle of relativity so the position of the origin of the grid/coordinates at one moment didn't specify its position at another moment.
But Mach saw that this was wishful thinking. In real life, there are no grid lines and no universal clock.
Sorry but this is an example of a totally scientifically irrational thinking. Newton's theory assumes a certain structure in the space and time (the word "grid" is a bit misleading because of the Galilean relativity and spatial and temporal translation invariance, but OK, it is some kind of a grid). But the key point is that Newton's theory agrees with the observations up to some moment and this agreement is what strengthens or validates all required Newton's assumptions, too.

The agreement with the empirical data simply must matter (and, in real physics, does matter) for our confidence in the theory's assumptions. It's deeply ironic that this simple point – that science ultimately revolves around the empirical data – is completely denied by the "colleagues" and likes of Lee Smolin who is sometimes visualized as a guy who cares about the empirical verification more than others do.

Mach's (or his mindless followers') mere claim that "this was a wishful thinking" isn't backed by any evidence. We may fail to see the "Newton's grid" but the agreement of Newton's theory with the observations is evidence that this grid exists. At the end, Newton's theory wasn't quite right but the exact same reasoning may be applied to general relativity which continues to be right.

We don't see gravitational waves in the empty space by our naked eyes. But that does not mean that they don't exist. We have seen them indirectly (the 1993 Nobel prize in physics) and LIGO/VIRGO may have seen them as well. The boss of LIGO Washington said, in a recent video, that so far "there has been no official reliable announcement of a discovery". Note that they probably need to produce a bit contrived sentences now to avoid outright lies LOL; all the words "official", "reliable", and "announcement" are needed to avoid straight lies, we think. A mindless follower of Mach could also say that it's a "wishful thinking that there exist gravitational waves" in the empty space – because we don't see them. Except that they do exist. They unavoidably follow from a theory that has passed tons of empirical tests – which is how we know that the philosophers' preconceptions and hostile comments about a "wishful thinking" are just wrong.
“What happens in the real universe is that everything is moving relative to everything else,” Barbour says. It is the set of relative positions that matters. Only that, Mach concluded, can serve as a foundation for physics. Einstein, as a youngster, was deeply influenced by Mach’s thinking. Now Barbour, too, was hooked—and he’s devoted his life to expanding on Mach’s ideas.
But as I just said in different words, Mach's claims were ultimately wrong. The rotational and acceleration motion is absolute in GR, the most accurate non-quantum theory of gravity we have. After all, we know that the spacetime is filled with a new grid – the Einsteinian grid, the metric tensor field. This new grid may be written down in infinitely many coordinate systems but the coordinate redefinitions aren't enough to bring every form of the new grid to a universal standardized form. The new grid – the spacetime geometry – may get and generally does get curved. And it may oscillate, like in the gravitational waves.

A commenter who is a successful particle phenomenologist has recently mentioned – semi-jokingly – that the LIGO discovery of the gravitational waves will/would be used as a confirmation of string theory. Well, it's a semi-joke because we don't need the full string theory to predict and calculate the gravitational waves. On the other hand, it is not quite trivial for everyone working on foundations of space and time to acknowledge that gravitational waves exist. These nut jobs still want to preserve Mach's principle. It's possible that if you asked them whether gravitational waves exist, they will answer No.
Barbour isn’t alone. “Julian’s interpretation of Mach’s ideas are at the bedrock of what we’re doing,” Gryb says.
LOL, the walking (or swimming) probably isn't easy if you have to be satisfied with this greasy šit as your bedrock.
Imagine dividing space-time up into billions upon billions of little patches. Within each patch, shape dynamics and general relativity tell the same story, Gryb says. But glue them all together, and a new kind of structure can emerge.
If the laws of physics – whatever they are – obey locality, the scenario described above is simply impossible because the laws governing the small patches imply unique predictions for the union of these patches, too. This simple principle may be said to be the "justification of reductionism". When we understand the microscopic behavior of the world, we understand the behavior of large objects and regions, too. After all, the very general relativity and its Riemannian geometry may be said to be a "general enough methodology how to glue the small special-relativity-like patches".
...example: Möbius strip...
The Möbius strip differs by some "global" topological properties from other manifolds – in particular, it is an unorientable manifold. A "global" theory should be able to say whether such unorientable etc. topologies are allowed. But a point is that a sufficiently well-defined theory may extract this information from the local dynamics, anyway. For example, it is trivial to show that our 4D spacetime cannot take the shape of an unorientable manifold because the local dynamics isn't left-right-symmetric. So the laws of physics governing the "mirrored" Universe aren't the same ones as those that govern our world which is why it's not possible to glue the spacetime patches in the way we need to produce the Möbius strip.

Quite generally, if the local physics is exactly left-right-symmetric, the unorientable manifolds must be allowed. In quantum gravity, it's a nearly established lore that all symmetries must be "local" – this is conceptually said to be analogous to the equivalence principle. So if there is an exact symmetry, it's a gauged one, and you're therefore allowed to produce manifolds that are closed or "periodic" up to the transformations by these symmetries (e.g. unorientable spacetime manifolds).

But even if we ignore this "modern" wisdom about the local character of symmetries (I am sure that the Barbour-like folks don't have the slightest clue about these findings), and if we assume that theories could differ "globally" but agree "locally", it's important to realize that all the successful tests of GR so far are "local" in character. So empirically, we have no reasons to prefer one theory over another. If someone constructs a theory that agrees with GR locally but not globally, he can't say that his theory is more likely to be true than GR.

In fact, I would argue that we should be so open-minded about these issues that the very term "general relativity" should include all the variations of it that may differ by the allowed global constraints. For example, if the local physics were left-right-symmetric (in the world around us, it is not), we could have both GR that allows or forbids unorientable manifolds. With this sensible open-minded convention (which most physicists arguably agree with right now, anyway), it is wrong to say that "their new theory disagrees with GR". Instead, it's just GR with some specific choice of allowed globally boundary conditions or topological constraints.
So while shape dynamics may recreate Einstein’s theory on a small scale, the big-picture view of space and time may be novel.
Again, the new realizations imply that this statement is almost certainly incorrect – and in fact, just the opposite of this statement (local physics uniquely determines global physics) is one of the valuable gems that the general research of quantum gravity (not necessarily dependent on any stringy formalism) has led to.
But the picture of black holes in shape dynamics is more radical than that. “It looks like black holes—in shape dynamics—are qualitatively different from what happens in general relativity,” Gryb says.
It's a particular example of the general wrong claim above. It is not possible to avoid black holes – defined by the event horizons – and not even the singularities in a theory that locally coincides with GR. Why? Simply because the existence of the event horizons and singularities may be proven (see e.g. the singularity theorems) purely from the local behavior of the spacetime in various spacetime patches.
But beyond the horizon, the story changes dramatically.
It is not possible for physics to abruptly change beyond the horizon because the event horizon is a hypersurface in a totally ordinary smooth portion of the spacetime – and the precise location of the event horizon isn't even known at a given moment (the place of the horizon may only be retroactively drawn in the future when the full evolution of the spacetime and the causal structure resulting from it becomes clear).
You can think of the black hole as a wormhole into that new space, Gryb says.
That's just nonsense (Mercati, Section 12.1). The interior of the star was a 3D ball at the beginning so there must be a way to slice the interior spacetime after the observer falls in in the topologically identical way, too. The area of the spheres near the center of the stars was small and there's no way for it to suddenly get inverted and become infinite (this confusion of theirs almost certainly depends on the fact that they don't understand that the proper lengths may be measured in an absolute way).

It's very hard to seriously discuss any of these things. These folks really work hard to avoid any spacetime so all pictures of "wormholes" are 3D pictures that assume a universal preferred time coordinate.

But the black holes are situations in which the mixing of the space and time becomes extreme and extremely important; in the presence of black holes, the idea that there is a preferred universal time coordinate becomes as wrong as you want and the time coordinates natural for different questions (e.g. observers who fall in at different moments) may differ to a basically unlimited extent. If you simply deny the mixing, you can't possibly understand let alone predict what's happening near the black hole event horizon, let alone beneath it. Their theory is fundamentally non-relativistic which means that it is simply completely inadequate for the discussion of physics near the event horizons – for a discussion of black holes. Any attempt to turn this self-evident defect of their ideas into a virtue is totally demagogic.
“If we can make definite predictions for this [new features of the Hawking radiation], then it might provide a way to test our scenario against general relativity.”

Such tests are “just wild fantasies” at the moment, Gryb admits...
"Wild fantasies" is way too generous. These people disagree with the fact that it's even possible to measure the absolute lengths of objects and that the two-spheres inside the black holes are smaller than those outside. How can they talk about testing and predicting new features of the Hawking radiation? Their retarded mental system isn't even compatible with the existence of gravitational waves and other things. They haven't even learned to pronounce the word "quantum" let alone incorporate quantum mechanics into their framework (as Steinhardt has complained).
The physicists that I spoke with—the few who have been following what the shape dynamics crew have been up to—are understandably cautious. This new picture of black holes is interesting, of course, but the critical question is whether it can be tested.
It is not the critical question. It can be tested and, like astrology, it's been tested many centuries ago. The problem is that all the tests show a clear "fail" result, something that the crackpots and the inkspillers who promote them don't give a damn about.

Several paragraphs talk about some random criticisms by random people – Paul Steinhardt is the most well-known one among them.
The answers he got during the workshop didn’t satisfy him. “Some people said, ‘The discipline is too young, so we don’t know yet. It might bring us something new.’ And my brain is thinking, ‘OK, good—come back when you’ve got that something.’ ”
Right. If someone has nothing that makes sense, why doesn't he simply shut up? Then we're told that a "new narrative" or "ontology" is good. This is just vague talk designed to impress those who care about pompous philosophers' buzzwords much more than they care about science. Show me the new physics principles or results or anything that makes sense in physics. The inkspiller compares the crackpots to the fathers of heliocentrism – what? Steinhardt says that the truly impressive heliocentric insights were only brought by Kepler, not yet by Copernicus. I agree with that. Copernicus was just a guy who was right about something that was supported by convincing evidence much later. It should have been right for the institutions to tolerate thinking within Copernicus' axioms but they were only proven later. (But I would still dare to say that even some accessible "essence" distilled from the future Kepler-Galileo-Newton insights should have been enough to see that the Copernican heliocentrism made more sense. However, I do admit that those arguments could have been too vague.)
The resistance to shape dynamics—like the skepticism that surrounds any new idea in physics—is par for the course.
It is not true that any new idea in physics is surrounded by skepticism. When an unknown patent clerk sent his relativity paper to a journal, editor Max Planck immediately saw it was correct, published it, and within a year or two, all genuinely world-class theoretical physicists were sure about it. (For example, all the people who would become founders of quantum mechanics – an independent breakthrough in physics – were certain about relativity.) The skepticism was confined to a bunch of crackpots complaining about "Jewish Physics". They were never the people who should have been listened to when it came to the foundations of physics. Like in the case of Smolin, the main "advantage" of these Nazi crackpots or subpar physicists who were simply not good enough to work on "foundations of physics" was that they were sufficiently connected to certain powerful political interests.
Even for those who find shape dynamics compelling, it may be risky to pursue it.
I don't think so. They are not putting anything valuable at risk because they have nothing valuable. They have no talent, they have no genuine education, intelligence, creativity, originality, anything of the sort. They're a bunch of politically connected mediocre parasites living a risk-free life while traveling between villas near Oxford and North America all the time and while pretending that they are physicists, if not revolutionary ones.
Most of those working on shape dynamics are young, and shape dynamics, at least for now, lies somewhat toward the fringes of mainstream physics—which means that junior researchers are taking a risk by pursuing it.
Again, no. The cause and effect are reverted in the sentence above relatively to the truth. The primary causal relationship is the following one: Junior researchers who work on this garbage work on it because they are not talented enough to see that it's garbage. The fact that they are considered untalented is just a result of an analysis of previous events. How they're considered is not the primary cause that could decide about the character of their careers. The primary cause that has decided about them was either that they simply didn't get penetrating enough brains from Mother Nature; or they haven't learned enough physics before it was probably too late.
“They said, ‘Look, I suggest you don’t [work on SD],’” he recalls. “Try something more down to earth.” Because of the vagaries of the job market for academic physicists, there’s pressure to steer clear of deep, foundational issues, Mercati says.
This is not true. There are people working on foundation issues. But they require a true breadth and depth from the researchers and not everyone is like Maldacena etc. What the senior collaborators told Mercati was that he was no Maldacena and he should have picked a more modest subfield where he has a chance to do something meaningful because when Mercati focuses on truly ambitious questions that exceed how far his brain can see, Mercati ends up with ill-defined or wrong junk which simply shouldn't be enough to feed someone as a physicist.
Pursue matters that are too esoteric and “you pay a price, career-wise.”
Someone may pay a price for working on too esoteric things but the PBS fails to mention that most people similar to Mercati who pay the career-wise price pay it not because they're doing esoteric things but because what they do is garbage. Shape dynamics surely is. Even the people who are completely sensibly eliminated – for meritocratic reasons – may continue to say how wonderful they are and most of the stupid journalists and stupid people may buy it. But it's not true in most cases and it can't be true for anyone doing SD because SD is garbage.
All of this leaves these young shape dynamics researchers poised uncomfortably on the knife-edge between excitement (a new paradigm!) and humility (we’re probably wrong).
If they know that they're probably wrong, they should draw some consequences. Let me express the same idea as a response to the following sentence, too:
In the end, Barbour, Gryb, Mercati, and their colleagues are taking the only route possible—they’re going where their equations lead them.
Sorry but if these people weren't junk, they would have a better route – try to find out whether some equations they have proposed are the right or wrong ones. If they pursued this better route, they could realize that they have no correct or promising equations and all and they could free their brains to try something correct or promising. But because these crackpots never pursue this route – trying to impartially find out whether some claim is right; trying to impartially compare the evidence for and against – they can never find out anything of value. They're just mindlessly following and parroting a couple of randomly found unimpressive guesses while having no mechanisms that could produce real progress.
“We’re saying something totally different from what everyone else is saying,” Gryb says toward the end of our interview. “Can it possibly be right?”
If the only notable feature of your propositions is that they differ from everyone else's propositions, the answer is almost certainly "it cannot be right". The only good reason to think that a specific enough proposal or idea is on the right track is the evidence and these individuals don't have any. There's a lot of evidence against their theory and the very attitudes to physics they represent – but they unfortunately do not care about the "negative" evidence at all.