Two days ago, Nature published a rant by an average physicist and a physicist who really sucks titled
Scientific method: Defend the integrity of physics (by George Ellis, Joe Silk)Similar offensive, intimidating rants love to use the word "defend". It reminded me of "Science defends itself against The Skeptical Environmentalist" in Scientific American (2002).
It's a usual tirade about "falsification" by people who couldn't make it to the top of science by doing real technical work so they decided to spit on the top scientists and collect points among the stupid, science-hating part of the populace by misleading populist texts without any valid technical content.
Let me be somewhat more specific about the reasons why I consider this text (and its authors) to be crap or worse.
The subtitle says
Attempts to exempt speculative theories of the Universe from experimental verification undermine science, argue George Ellis and Joe Silk.However, the text talks (primarily) about theories like string theory and inflationary cosmology which are in no way "speculative". Even if they turn out to be incorrect, which is very unlikely, they are absolutely nontrivial, serious, and viable theories proposed to describe large classes of phenomena – all phenomena in Nature, in the case of string theory.
No physics PhD wants to exempt these theories from experimental verification. It's just a technical fact that the experimental verification is hard and it is probably impossible to build experiments that could "settle" the question about the validity of the theories in any foreseeable future.
This is not an intrinsic disadvantage of these theories; it is a likely fact about the relationship between the theories and the current state of technology as of 2014.
This year, debates in physics circles took a worrying turn. Faced with difficulties in applying fundamental theories to the observed Universe, some researchers called for a change in how theoretical physics is done.It's only a change relatively to what some semi-educated people who don't follow science in detail think that science is. Nothing has ever changed about the scientific method as such. At most, some issues that have always affected the scientists' search for the right theories were articulated more explicitly than before.
They began to argue — explicitly — that if a theory is sufficiently elegant and explanatory, it need not be tested experimentally, breaking with centuries of philosophical tradition of defining scientific knowledge as empirical.The question whether a given theory is elegant and/or explanatory has always been, is, and always will be an argument that helps to decide about the probability that the theory is correct. Straight falsification may achieve a higher degree of certainty – and it's still true, as it always has been, that falsification kills a theory. But if a theory is not killed by falsification yet, it is alive. And the surviving theories that are alive are undoubtedly competing, and have always been competing, by their elegance and explanatory power (and the degree of unification). It can't be otherwise. It could have never been otherwise.
Newton's theory of gravity didn't really predict any new observable phenomena for the motion of the planets – relatively to Kepler's laws – that could be tested at that time, with the available accuracy. The unification of the terrestrial and celestial gravity was a hypothesis – Ellis and Silk would call it a speculation. But the theory was known to be on the right track by Newton because it nontrivially worked. His ability to describe the motion of the Moon and the motion of an apple by the same inverse square law couldn't have been a coincidence and he knew that. That's why it was accepted, well before corrections and deviations from Kepler's laws were calculated and verified.
We must notice that Newton's theory – and the same holds in all examples you may think of – wasn't even correct. We know that it was non-relativistic and non-quantum, among other things. So wasn't it a mistake that it was studied and accepted? No, it wasn't a mistake. It was accepted because it was a viable, non-falsified provisional theory, a provisional theory that was better than any other viable competitor. It was better because all other competing theories (like those with more complicated formulae for the force) were less elegant.
Special relativity was elegant and had the unifying and explanatory power so it was accepted including its predictions about time dilation and length contraction that was only going to be validated much later. General relativity was known by Einstein to be the right relativistic theory of gravity because it was the only conceivable elegant reconciliation of special relativity and the equivalence principle. At that time, the Mercury perihelion precession was the only piece of "really empirical" evidence (except for "old" evidence that was already used in or explained by previous theories) that it could be right, and it could have had many other explanations. One extra – not quite sharp – verification of the bending light during a solar eclipse was rightfully enough for The New York Times to announce that general relativity had been validated and Einstein became the #1 world's scientific celebrity. The gravitational red shift and clear observations of black holes only came after Einstein died, much like the modern evidence supporting the big bang theory.
String theory is known to be almost certainly right because it's the most elegant, explanatory, consistent, and unifying reconciliation of general relativity and quantum field theory. This is a positive claim but it is perhaps more accurate to present the difference between string theory and quantum field theory – a competing theory to describe particle physics – in a negative way: Quantum field theory has been falsified as a description of all phenomena in Nature because its standard combination with gravity is mathematically inconsistent (non-renormalizable etc.).
That's why quantum field theory has been falsified and it has to be replaced by a different theory. String theory is the only known viable candidate. So the main problem with the babblers who try to question this step is their denial of the power of falsification.
We disagree. As the philosopher of science Karl Popper argued: a theory must be falsifiable to be scientific.It is completely irrelevant whether two not so good physicists disagree with something – science evolves according to the evidence – and it is even more irrelevant what a philosopher of science said. What a philosopher of science such as Popper said is always partly right, mostly wrong, and it is always unusable as a firm foundation to do serious science. If Popper had really misunderstood why the ability of a theory to explain something in a more unified way increases its probability that such a scientific theory is right, his understanding of physics was defective and a low-brow cult of personality can't change anything about this obvious fact.
Chief among the 'elegance will suffice' advocates are some string theorists. Because string theory is supposedly the 'only game in town' capable of unifying the four fundamental forces, they believe that it must contain a grain of truth even though it relies on extra dimensions that we can never observe.They completely misrepresent that status of string theory. String theory is not "supposedly" the only game in town. It is the only game in town. And it doesn't contain just a "grain" of truth. It contains the whole truth. Due to its basic mathematical properties, it cannot be just another approximation that has to be deformed to obtain the right theory. It must be the right theory exactly.
We may lack the ability to extract all the predictions of everything in any environment, even in principle, but we may still demonstrate that string theory's equations of motion are equivalent to consistency conditions and any deformation of its rules would render the theory inconsistent – a feature that Einstein used to dream about well before others (although he had no chance to find the right theory, essentially assuming that his rigid "unified theory of everything" would be a classical field theory).
These two "writers" use a wording "even though it relies on extra dimensions" trying to mislead the reader into believing that there is something a priori wrong about extra dimensions. There is nothing wrong about extra dimensions. Theories with extra dimensions and theories without extra dimensions must be considered fairly as competitors and the evidence going in both directions must be carefully compared. Extra dimensions can't be observed, at least not with the existing gadgets, but the absence of these dimensions can't be observed, either. So any "a priori" favoring of one answer and suppression of the other answer proves that the person doing so is simply lacking scientific integrity.
String theory predicts the total number of dimensions because it is really rigid and it has been shown that compactified vacua are as consistent and good solutions to string theory's equations as the decompactified ones. And rather soon, people realized that this new feature that string theory "forced us" to introduce in physics, the compactified dimensions, is a virtue because the topological and other features of this compactification encode the apparently complex patterns in the spectrum of particle species.
Some cosmologists, too, are seeking to abandon experimental verification of grand hypotheses that invoke imperceptible domains such as the kaleidoscopic multiverse (comprising myriad universes), the 'many worlds' version of quantum reality (in which observations spawn parallel branches of reality) and pre-Big Bang concepts.All these concepts are accessible to the scientific tests even though the tests that may be done now are inevitably indirect and never fully settle the question about the correctness. But the evidence supporting inflationary cosmology is extremely powerful, the evidence that the inflation is eternal is very strong, and in that case, the multiverse is almost inevitably created.
Proposals how the existence of the multiverse could affect the observed parameters of Nature exists and they are not unique, they are very inelegant, and they are the key reasons why no one can be too confident about these matters. Many of the proposals may be shown to be almost certainly wrong. But what's important is that one may discuss all these possibilities scientifically – by analyzing the logical and mathematical implications of these hypotheses and by comparisons of these implications with the empirical data.
These unprovable hypotheses are quite different from those that relate directly to the real world and that are testable through observations — such as the standard model of particle physics and the existence of dark matter and dark energy.This claim is complete rubbish, too. String theory requires "slightly" more sophisticated and elegant mathematics than the Standard Model but from a qualitative viewpoint, it is a physical theory of the very same type as quantum field theory – and string theory's vacua are particular candidate theories of the very same qualitative type as the Standard Model.
The whole idea that string theory is something qualitatively different is a delusion of the laymen who don't have the slightest idea what they are talking about, and it's unfortunate to see that these two not so good physicists belong among these uninformed laymen.
String theory and quantum field theory are two competing theories to describe Nature around us. Because all the experiments are consistent with the framework of quantum field theory (and even the subset of the "nice enough" quantum field theories that may follow from string theory and that string theory seems to cover finely enough), both quantum field theory and string theory are compatible with all the tests done by particle physics experiments. But one may say that quantum field theory is falsified because it's incompatible with gravity. That's if we demand some rigor in the predictions. If we don't demand much rigor, we may say that quantum field theory – with Einstein's general relativity added into the effective field theory – is OK for the description of all doable experiments including gravity. However, we know that this union has problems so it is surely less elegant than string theory, a reconciliation that has no problem of a similar kind.
The idea that the Standard Model is epistemically "better" than string theory is the same kind of unscientific superstition as the idea that the Jews are basically not human beings. They're theories of the same kind. All known formulations of string theory are ultimately based on "some" quantum field theory – either in the spacetime, or in the world sheet, or the boundary of the spacetime, or some auxiliary space – and the holography has shown that as very general frameworks, quantum field theory and string theory are really equivalent. They are inseparable. Everyone who wants to master the insights known as "quantum field theory" well enough must also learn some "string theory" and vice versa.
As we see it, theoretical physics risks becoming a no-man's-land between mathematics, physics and philosophy that does not truly meet the requirements of any.String theory has nothing to do with philosophy. It is not building on philosophy – although, like all scientific theories, it may have an impact on the philosophical thought. String theory is a physical theory that uses lots of advanced mathematics – which is why many mathematicians have a lot to say to string theorists – but the deep links between physics and mathematics, and the flows of ideas between the disciplines in both directions, have been around since the birth of physics and they were getting stronger.
Newton had to invent calculus to write down his theories. Physics forced mathematics to deal with partial differential equations (field theory), extend the knowledge of differential geometry (general relativity), Hilbert spaces (quantum mechanics), representations of groups (quantum mechanics, quantum field theory), and so on, and so on. Theoretical physics which has always been the brain-driven leg – and the only brain-driven leg – of physics has been partly rooted in the realm of mathematics since the birth of physics. It is something to be proud about. And because of this intense flow of ideas through theoretical physics, attempts to strictly separate mathematics and physics have always been partly or mostly artificial.
To demonize this overlap between physics and mathematics – by calling theoretical physics a "no man's land that doesn't meet the requirements of either discipline" – means to totally and fundamentally misunderstand both. One may argue that theoretical physics has been recognized as a more prestigious discipline of science than "general physics" and "mathematics" themselves – theoretical physicists (Einstein, Feynman, Hawking...) have surely become more famous and more celebrated gurus than other physicists and mathematicians – so the suggestions that theoretical physics is a no man's land between two big empires is silly. It is a tail wagging the dog.
The issue of testability has been lurking for a decade. String theory and multiverse theory have been criticized in popular books [1, 2, 3] and articles, including some by one of us (G.E.) .An important detail cleverly omitted in the formulation above is that like these two inkspillers, virtually all people who have ever criticized string theory are spherical stinky šitheads – they are stinky šitheads from all perspectives. I may give an exemption to Sheldon Glashow – he hasn't participated in this falsifiability hysteria business for decades – and maybe another good man but I would have big trouble to find out who is the third.
In March, theorist Paul Steinhardt wrote  in this journal that the theory of inflationary cosmology is no longer scientific because it is so flexible that it can accommodate any observational result.The third man to get an exemption would surely not be Paul Steinhardt.
Theorist and philosopher Richard Dawid and cosmologist Sean Carroll have countered those criticisms with a philosophical case to weaken the testability requirement for fundamental physics. We applaud the fact that Dawid, Carroll and other physicists have brought the problem out into the open.It's a misinterpretation of Dawid (and especially of the reality of physics and its history) to say that the status of falsifiability has suddenly weakened. Falsification has always been, is, and always will be a sufficient condition needed to kill a candidate theory. And scientific theories must be in principle falsifiable. But that doesn't mean that it must actually be possible to promise a falsification test within a lifetime, or in 5 years, or by Christmas, depending on the stupidity of the "falsifiability cop". And it doesn't mean that straight and completed falsification is the only thing that directs the scientific research in one way or another.
Such a condition has never existed in science. That's why the atomic theory has always been viable in science, even though it was neither established nor falsified for thousands of years. You just can't change these rules of the game. You can't eliminate a theory by disliking it, by becoming a spherical stinky šithead, and by writing a low-brow rant directed to the bottom of the human population that claims that the theory must be wrong, otherwise it would have been falsified by now.
Theories can't be declared wrong by their being viable. Every theory that hasn't been falsified yet remains a competitor. And the competitors are not equally likely. There are other features that distinguish them. A more consistent, more unifying, more rigid theory is more likely than the inconsistent, not quite consistent, not unifying, full of ad hoc assumptions containing, fine-tuned, contrived theories. This is not just some rule that came out of nowhere. One may show why it is so by Bayesian inference. Elegant theories – which directly follow from a smaller, more concise list of assumptions – are less likely to agree with the empirical data a priori. So if they are found to agree, their a posteriori probability increases more because they have passed a more nontrivial test than the inelegant theories that may be adjusted.
The misinterpretation about the "revolution in falsifiability" is praised by these two men because they find it helpful to spread their fraudulent argument.
But the drastic step that they are advocating needs careful debate. This battle for the heart and soul of physics is opening up at a time when scientific results — in topics from climate change to the theory of evolution — are being questioned by some politicians and religious fundamentalists.Theory of evolution has been opposed by Christians for 150 years. It's just a dramatic and nonsensical talking point if someone says that we are living at a special moment in this debate between biology and religion.
Concerning "climate change", I must say: Wow. Those who actually understand the climate science know that the theory that the Earth is expecting some dramatic or catastrophic evolution of the climate in coming decades has been basically falsified. But even those who are still unaware of this fact must know that the theory about the dangerous "climate change" isn't making any predictions that are also not made by theories of the climate that imply that everything is fine – except for predictions that have already been falsified and are being falsified on a daily basis. Like Jehovah's Witnesses, the cataclysm is moved into the future by a few years every time the prediction is humiliated by the reality – which contains almost no significant change of the climate. Some people want to say that the rate of warming is 3-5 times faster than what the scientific calculations suggest and it will soon be catastrophic. Many of these doomsday claims will only be ruled out after these people will have collected all of their salaries and pensions – and, what is worse, no one seems to care even when the predictions are actually falsified and humiliated by the real-world data that haven't shown any significant climate change for 2 decades.
To advocate "climate change" (the hysterical ideology) in the same article that criticizes string theory and inflationary cosmology for their "unfalsifiability" is a sign of dishonesty and arrogance so breathtaking that I am really terrified by it.
Potential damage to public confidence in science and to the nature of fundamental physics needs to be contained by deeper dialogue between scientists and philosophers.What damages science is the public promotion of claims about science that are either demonstrably wrong, or at least are not backed by the adequate amount of evidence. For example, claims that science has something to do with the environmentalist activists' claims that the Earth is facing a dangerous climate change, undoubtedly cripples the credibility of science among the public.
Demagogic articles about "unfalsifiability" of the pillars of state-of-the-art physics damage the credibility of science, too. They are especially dangerous because at least one of the authors of this rant in Nature has a PhD and there are many ordinary people who can't even realize that people with a PhD may be totally dishonest and deluded jerks who have no idea what they are talking about and who don't find it hard to lie directly to your face. Some of the listeners may even treat this junk seriously.
Then they talk about their (partly correct) ideas about what string theory is, what supersymmetry is, and what Dawid argues about the probability of the concepts and their accessibility via logical arguments and experiments.
Dawid equates confirmation with the increase of the probability that a theory is true or viable. But that increase of probability can be purely theoretical.A confirmation that wasn't guaranteed to occur independently of the theory is always increasing the probability that a hypothesis is true. This is called the Bayesian inference. This principle has always been used – whether it was explicitly articulated or not – it is inevitably used now, and it will always be used as long as science remains science.
The increase of the probability of a hypothesis is always theoretical. And in science, it always ultimately boils down to the empirical data. The only difference between various situations is a quantitative one: in some cases, the empirical data are connected with the claims about the validity almost directly, in others, there has to be a long chain of indirect derivations and calculations in between.
Because “no-one has found a good alternative” and “theories without alternatives tended to be viable in the past”, he reasons that string theory should be taken to be valid.You may say that one-half of the relevant researchers, almost all the string theorists, say that it is really the only possible theory of the relevant phenomena. The other half, the less informed ones, if I have to avoid the term "idiots", say it is not. A sociological estimate might be that it is 50-50 that it is the only possibility which is still a good reason why some people study it.
In our opinion, this is moving the goalposts.
But even if string theory were not the only possibility, it is the only known possibility and it is simply not possible to study a theory that we know nothing about. Are these two individuals really incapable of understanding this simple point?
In our opinion, this is moving the goalposts. Instead of belief in a scientific theory increasing when observational evidence arises to support it, he suggests that theoretical discoveries bolster belief. But conclusions arising logically from mathematics need not apply to the real world.No, on the contrary, these two idiots are moving the goalposts. Throughout the history of science, people were accepting the principle of the scientific method which says that a hypothesis remains viable up to the point when it is falsified. You simply can't revert this rule. You can't demand theories to be first proven. Science never proves theories. Science only falsifies theories – you may say that like many legal systems, the scientific method respects the presumption of innocence – and string theory has so far passed all the tests.
Experiments have proved many beautiful and simple theories wrong, from the steady-state theory of cosmology to the SU(5) Grand Unified Theory of particle physics, which aimed to unify the electroweak force and the strong force.Steady-state cosmology has never been beautiful and SU(5) non-SUSY Grand Unified Theory is the simplest grand unified theory but not the most beautiful one. They are not using state-of-the-art scientists' measures to estimate the beauty of a theory.
But if the grand unified theory with the smallest spectrum and the smallest group is falsified, it doesn't mean that the paradigm or the class of grand unified theories has been eliminated. It surely has not and due to its natural embedding in string theory, string theory also makes it comparably likely to 50% that grand unification is a genuine feature of an effective field theory exactly describing Nature. Even this string-theory-based argument related to a hypothesis of a simpler type, the grand unification, is a relevant one and affects the probability that grand unification is right – even if we are not quite 100% sure whether string theory is right and which vacua it prefers.
The idea that preconceived truths about the world can be inferred beyond established facts (inductivism) was overturned by Popper and other twentieth-century philosophers.The only "preconceived truth" here is the preconceived "truth" promoted by these two "authors" that there must be something wrong about string theory, inflationary cosmology, extra dimensions, grand unification, supersymmetry, or multiverse.
We cannot know that there are no alternative theories. We may not have found them yet.We can't be 100% certain but we may still collect – and we have collected – evidence that strengthens or weakens the proposition that there are no alternative theories. And be sure about it, the proposition that there are no other consistent theories in quantum gravity in \(d\geq 4\) than those that fit within superstring/M-theory has strengthened considerably. The arguments are, for obvious reasons, incomprehensible to the non-experts, but they exist and they make the claim almost as clear as the claim that \[
11111 \times 11111 = 123454321
\] even though this is only obvious to sufficiently math-literate folks, too. But even if we assume that string theory is not the only consistent theory of quantum gravity, we simply cannot study a different theory that has never been spotted, or that has never shown any signs to be promising.
Or the premise might be wrong. There may be no need for an overarching theory of four fundamental forces and particles if gravity, an effect of space-time curvature, differs from the strong, weak and electromagnetic forces that govern particles.For most people, there has never been any need to look for any unifying theory of anything. One could have always said that different objects and different phenomena in Nature are just different and there is no need to unify them, interpolate them, or look for overarching theories. They may be remembered one-by-one.
Only curious enough people have been looking for theories of Nature and they soon realized that the proposition by the primitive people I just mentioned – virtually identical to Ellis' and Silk's claim – is just plain idiotic. That's why they figured out that animals and plants have common ancestors, gravity is the same on Earth and in the Solar System, everything is made of the same atoms, electricity and magnetism morph into each other when we change the reference frame, electromagnetism and the weak interactions are unified, all hadrons are made from quarks and gluons, temperature may always be linked with the energy per (atomic) degree of freedom, and so on, and so on. The "world is divided" alternative theories just didn't pass the tests – they were either internally inconsistent, or predicted wrong, experimentally falsified phenomena in the intermediate regions, or were just forgotten due to their inelegance before the relevant tests arrived. The Standard Model supplemented with general relativity in any other way than the string theoretical way is just inconsistent or infinitely ambiguous and unpredictive, at least for the prediction of Planck-energy collisions.
So it just can't be quite right. Non-curious people may not care but curious physicists do and those things obviously belong among the most important defects of the otherwise pretty and faithful scientific portrait of the world that people had before string theory which is why they focused and still focus so much attention on these questions.
And with its many variants, string theory is not even well defined: in our view, it is a promissory note that there might be such a unified theory.The evidence is virtually rocksolid that string theory is a unique, absolutely robust theory that cannot be deformed and whose behavior in various corners of the parameter space agrees with the content of tens of thousands of papers written about the subject.
The "variants" have been known not to be "variants" but different solutions of the same theory for 20 years – since the Duality Revolution of the mid 1990s – and only complete losers could have failed to notice this fact by 2014. (Joe Polchinski will release a new semipopular introduction to dualities tomorrow.) It's spectacularly sick if such losers who obviously don't know anything about string theory try to impress some readers with their opinions on whether string theory, something they are not familiar with at all, is well-defined. It is well-defined even though we can only write down the complete form of the "definition" in a subset of the superselection sectors.
Some physicists consider that the multiverse has no challenger as an explanation of many otherwise bizarre coincidences.The multiverse is likely to be predicted by the correct theory of Nature, but the anthropic method to use the multiverse to say something about parameters of Nature remains a set of vague proposals.
Unlike string theory which is backed up by thousands or tens of thousands of high-precision and nearly mathematically rigorous papers to calculate diverse kinds of physical observables, the anthropic reasoning remains an inelegant preliminary guesswork with lots of poetic words and a small number of equations.
But it's true that it's the only known explanation of e.g. why the cosmological constant is so tiny that is embedded into a theoretical framework compatible with everything else we know. The apparent (and, I think, probably eternal) inability of the "anthropic principle" to provide us with sharp formulae make the situation vastly less convincing than the situation of string theory. But that doesn't change the fact that this "anthropic explanation" of the small cosmological constant is the only complete enough, "ready to be used" possibility, and that's why a substantial amount of activity is going in this direction. I say it despite the fact that I think it is a wrong direction. Because this proposal is much more concrete and developed than my conceivable alternatives, I respect that it makes sense for many papers to build on the working hypothesis that the small cosmological constant was selected "anthropically" from a huge number of options at the beginning – and from a shortlist of small enough values that are compatible with the existence of stars (or life).
That's just how science has to work. Of course that as long as something remains the only at least slightly well-defined proposal that makes sense, a significant amount of the related research activity is going to the research of it. If and when a better, complete enough explanation of the smallness of the cosmological constant emerges, it will partially or almost completely supersede the research within the anthropic framework.
A few paragraphs are dedicated to a struggle against a straw man called Sean Carroll. I am not going through this exchange because I would most likely vomit. My reasons are similar as the reasons why I don't like to watch films or sitcoms where everyone is an aßhole.
Some people have devised forms of multiverse theory that are susceptible to tests: physicist Leonard Susskind's version can be falsified if negative spatial curvature of the Universe is ever demonstrated. But such a finding would prove nothing about the many other versions.If an idea by Lenny makes one more prediction than other ideas, it's surely not the main reason why Lenny enjoys his fellow physicists' respect. The suggestion that it should be is just a hysteria of wild laymen who became obsessed with a silly slogan.
Sometimes it's hard to discriminate theories or answer questions. If someone can do it, great. But if no one can do it, then it is simply an open question. It is an open question for all scientists in the discipline and trying to criticize people or theories for the people's inability to answer certain questions – even though he can't do it, either – only proves that these people ceased to be members of the research community. They have turned to Al-Qaeda-like terrorists who are fighting against the scientific research and whose fame boils down to the (real or just perceived) failures of sciences and not successes.
Fundamentally, the multiverse explanation relies on string theory, which is as yet unverified, and on speculative mechanisms for realizing different physics in different sister universes. It is not, in our opinion, robust, let alone testable.The multiverse is probably not robust and tests of it may be impossible in practice but whether or not it exists may still be a physically meaningful question, specific enough theories of Nature may provide us with their answers to the question (and in these conceptual cosmological matters, it is always important what string theory seems to say or at least suggest), and what are the right answers may obviously be a topic of a large number of deep papers simply because people want to know the answer.
Even if the question seems "too hard for us at this moment", it may still be among the most sensible and realistic conceptual questions that we cannot answer yet.
Billions of [Everett's] universes — and of galaxies and copies of each of us — accumulate with no possibility of communication between them or of testing their reality. But if a duplicate self exists in every multiverse domain and there are infinitely many, which is the real 'me' that I experience now? Is any version of oneself preferred over any other? How could 'I' ever know what the 'true' nature of reality is if one self favours the multiverse and another does not?Everett's story has nothing to do with cosmology per se. By mixing it with cosmology, they again show that they have no idea what they are talking about.
In our view, cosmologists should heed mathematician David Hilbert's warning: although infinity is needed to complete mathematics, it occurs nowhere in the physical Universe.
This Many World Interpretation is really wrong but it is wrong because of arguments that are rooted in physics and involving the analysis of physical situations and predictions of the theory and its compatibility with other established principles of physics. When done correctly, one sees that this proposed theory doesn't really work.
But the reason why it's no good is certainly not that it predicts many worlds and many worlds of any form must be considered "bad". Preconceived conclusions like that are simply absolutely unacceptable in science. Many worlds of various kinds are a priori allowed and may be considered – much like it had to be considered that the Sun was just another star and there were many galaxies aside from ours. Only research that boils down to careful enough logical arguments and mathematical calculations rooted in the empirical data may decide whether many worlds of one type or another exist in Nature or not. Some types of many worlds may be true, many others are wrong.
David Hilbert's claim about infinity in physics is just wrong. Theories in physics may be regularized and everything may (perhaps) be put on a computer which has a finite number of states. But by doing it, one inevitably uses some approximations and these inaccuracies break symmetries and principles that are essential for the character of the physical law.
In the uncompromised version of the laws of physics, we deal with precisely continuous objects so many things are literally infinitesimal, but many other things may be infinitely large, too. Hilbert's thesis is exactly the kind of a "preconceived truth" that has no business to direct science.
It is absolutely crazy to try to introduce this cult of personality. What a mathematician said about physics 100 years ago can clearly not be used to filter the physical research in 2014. Even if the best mathematician who is alive now – probably string theorist Edward Witten, sorry – said something about the desired character of the physical law, it wouldn't have to be treated as a gift sent from God. And that's despite the fact that Witten knows much more than Hilbert did, especially about the kind of mathematics that is relevant for physics.
Witten's prophesies – like any other prophesies – are rather likely to fail by the year 2214 which is something that Witten is aware of and wisely and modestly tries to avoid similar long-term prophesies. Sometimes his silence is surely too excessive. If Hilbert (I mean his famous name) has survived having said similar wrong things, surely Witten could offer his (probably much more likely to be true) guesses more often, too.
We agree with theoretical physicist Sabine Hossenfelder: post-empirical science is an oxymoron.Right. But it's these two men – and, to a large extent, also Sabine, among many others – who are making claims about such a post-empirical science. Natural science is always deriving the verdicts from the empirical data. However, the derivations are getting more complex and/or more indirect and the flow of "radically and conceptually new" empirical data is slowing down because the energy frontier and similar experimental frontiers have been pushed rather far where progress is not easy. Everything that is closer seems understood in principle (and often in practice). None of these trends implies that the scientific method is breaking down, however.
Yet numerous historical examples point to how, in the absence of adequate data, elegant and compelling ideas led researchers in the wrong direction, from Ptolemy's geocentric theories of the cosmos to Lord Kelvin's 'vortex theory' of the atom and Fred Hoyle's perpetual steady-state Universe.None of these theories was really elegant in the modern sense. But even some of these theories were legitimate theoretical frameworks to deal with the empirical data.
In particular, Ptolemy's geocentric model was just fine to describe a huge body of the planetary data and this model only differed from the modern one by a coordinate redefinition, by third-order corrections, and by the lacking deeper explanation. Ptolemy and his contemporaries – and 50+ other generations of thinkers – couldn't have done better. So it's really silly to present this as a mistake of Ptolemy and other ancient thinkers, a mistake that we could learn a lesson from.
No one was able to speed up science by 1500 years. Just get used to it, those are historical facts. If Copernicus' and Kepler's and Galileo's and Newton's discoveries were made in ancient Greece, we could have still complained about Tutankhamun's apparent inability to derive Newton's laws, or QED, for that matter. What's the point? Physicists can't really fairly compete with physicists who enjoy 1500 extra years of hindsight.
Kelvin's vortex atoms resemble some of my topological theories of particles I had when I was 14 or so. (I had neutrinos; electrons; protons as the only elementary particles, and they were topological defects, namely wormholes connecting pairs of filled genus zero, one, two surfaces in the space. That was my model of "all" elementary particles. It was probably hard for them to annihilate away LOL but I was extremely happy about it, especially because the possible \(\ZZ_3\) symmetry of the genus-two surface looked like an explanation why people say silly things about "three quarks", and of course that I was already planning what to do with the 1988 Nobel prize in physics, too.)
There were too many guesses that Kelvin couldn't have possibly believed to be guaranteed to be true, so the comparison with the rigid structure of string theory is inadequate. However, Kelvin was ahead of his time because these knot-theory-like models of the atoms were rather close to solitons that are used in quantum field theory today – and they may describe "some" particles, indeed. They are *the* most important visualization of the interior of the elementary particles – aside from their being elementary field excitations or strings. So this vortex theory wasn't the right theory of the atoms but it was a good idea that was largely recycled by physics much later. So I would have surely found it extremely counterproductive if someone were trying to discourage Kelvin when he was thinking about these things.
The steady-state cosmologies were always natural possibilities. The right cosmology is either steady state or not. It's silly to say that the steady-state ones were "prettier" than the big bang. The big bang unifies all matter – everything came from one point. It's more beautiful in the modern sense. It has to be because the truth is prettier. But again, the steady-state cosmologies may be seen as legitimate competitors of the big bang – that finally appeared when the space of simple enough GR-based possible cosmologies was finally mapped. And the big bang won. It would have been totally wrong to try to prevent the research on such alternative models. The victory of the big bang is great partly because it shows that the steady-state and other cosmologies are wrong.
No one could have been ever "sure" about the steady-state cosmological model in the same sense as we are (almost) certain about string theory. It totally lacked the uniqueness and rigidity string theory is famous for. One may partly say that the steady state model was attractive because it was simple. Things are not changing with time is simple. But the "deformation" in which things may change with time is mathematically consistent or possible so it must be considered. Only when it's falsified, if some lethal problem (internal or empirical or a combination) is found, it's eliminated from the list of competitors and it is dead. You can never speed up the death of the model! Or at least, you shouldn't.
The consequences of overclaiming the significance of certain theories are profound — the scientific method is at stake.The scientific method is under assault if someone claims that standard, tested criteria such as the uniqueness, consistency, universality, elegance, unification, and explanatory power don't matter. These things have always mattered, do matter, and will always matter.
To state that a theory is so good that its existence supplants the need for data and testing in our opinion risks misleading students and the public as to how science should be done and could open the door for pseudoscientists to claim that their ideas meet similar requirements.Once again, the theoretical properties of a theory have always affected the probability that a theory is right or on the right track – and therefore the amount of attention that a theory is getting. This realization became pretty clear in the 20th century and almost all the great theoretical physicists of the century understood that these internal theoretical features of theories matter. Einstein was talking about this elegance and rigidity all the time. Dirac liked to write that the physical laws has to have mathematical beauty as his main "equation" during his visits e.g. to Moscow. And I could continue with others, too.
Pseudoscientists can make and do make – and have always been doing – similar claims and comparing their "ideas" to the best scientific theories. But unlike good scientists, they just didn't evaluate their "ideas" correctly and their claims about the virtues of their "ideas" are simply wrong. That's exactly true for the Mr Ellis' and Mr Silk's ideas about the early cosmology and quantum gravity, too. They are pseudoscientists, too, and like other pseudoscientists, they are of course trying to pretend that they are substantially better than (not only established top scientists and those from the textbooks but also) other pseudoscientists, but they are not. Like other crackpots, they claim to have found a problem with the conventional theories believed by the "big shots" except that if an expert reads their incoherent rants, like the rant in Nature, he sees that they haven't found a glimpse of anything that would be a problem according to the scientific criteria and the whole criticism is just an inconsistent stream of whining, misunderstandings of theories, stupidity, and prejudices.
All of their writing is a pile of trash.
What to do about it? Physicists, philosophers and other scientists should hammer out a new narrative for the scientific method that can deal with the scope of modern physics.Science is not an activity that is following "narratives". That's how science differs from politicians' speechwriters and filmmakers producing TV commercials, among others. Philosophers have no business to preach to the physicists – and scientists from other fields lack the expertise to say something relevant, too. After all, it is the case even of some people who do claim that they are members of the theoretical physics community, like Mr Ellis and Mr Silk, even though they are actually not.
What these two men propose is nothing else than an attempt to return science into the times of Galileo where scientifically incompetent (Church) officials were trying to restrict what conclusions scientists were allowed to reach – and perhaps even what they are allowed to investigate.
In our view, the issue boils down to clarifying one question: what potential observational or experimental evidence is there that would persuade you that the theory is wrong and lead you to abandoning it? If there is none, it is not a scientific theory.See e.g. these nine points about what would be enough to falsify string theory. I got 190 upvotes for that and it is actually my most upvoted answer (among 1,900+) on that server. ;-)
The ways how a theory can be falsified or superseded are exactly the same as they have always been. Find a lethal mistake in the mathematics, or some experimental falsification – probably one we are not realizing that it's possible now, because otherwise it would have already been done. Falsify one of the general principles that string theory includes, like special relativity or the equivalence principle. Or make more precise predictions about what matters so that even the not-so-demanding experimental tests may decide. In some cases, there will be loopholes but you will significantly transform the research in the field, anyway. It's not easy to falsify string theory because it has already passed lots of the relevant tests and others you may invent are usually not qualitatively new. But this "passing grade" is not a drawback; it is a virtue. It is a necessary condition that was needed for string theory's survival.
Or just find a more elegant or more explanatory theory that is also compatible with all the empirical constraints. Depending on the power of the new idea, a part or the whole research may be redirected to it.
These things – and they include lots of possibilities – are enough to "kill" string theory or a similar theory. On the other hand, arrogant pseudoscientific bullying by two aßholes or conferences of ignorant outsiders and "philosophers" organized to intimidate theoretical physicists are not enough and they won't move the research of legitimate researchers by a string length. Or the 11-dimensional Planck length, for that matter.
Such a case must be made in formal philosophical terms. A conference should be convened next year to take the first steps. People from both sides of the testability debate must be involved.Cutting-edge science doesn't depend on commandments by "philosophers" from either side of a philosphical confrontation who have no idea about the technical content of the cutting-edge theories. Make your intimidating conference as formal and as scary as you want but it will still fail to be capable of changing the fact that according to the competent researchers of quantum gravity, string theory is the only known consistent description of quantum gravity and there is enough evidence justifying a strong focus on that set of ideas.
In the meantime, journal editors and publishers could assign speculative work to other research categories — such as mathematical rather than physical cosmology — according to its potential testability. And the domination of some physics departments and institutes by such activities could be rethought.Should the cutting-edge theoretical physics be isolated as Jewish physics once again, and should these two mediocre not-so-Gentlemen become the new protectors of the Deutschphysik?
String theory is the most refined portion of the research of formal high-energy theoretical physics and inflationary cosmology is the most sensible theoretical framework that goes beyond the standard big bang cosmology. If these two men are incapable of learning these things and doing research in them, they should realize that it is their defect and not a defect of the top scientists that they are unable to get to the top.
The imprimatur of science should be awarded only to a theory that is testable. Only then can we defend science from attack.String theory and inflationary cosmology are testable but true scientists don't worship the word "testable" as if "more easily testable" always meant "better". It doesn't. There are much more important criteria, you know, namely whether the available evidence indicates or proves that a theory is right or wrong.
The easiest way for Mr Ellis and Mr Silk to defend science from attack is to flush themselves down the toilet where they undoubtedly belong.
And that's the memo.