Thursday, December 24, 2015

String theory is as much science as other pillars of science

Siegel's criticism of string theory is fully analogous to a criticism of heliocentrism

The Munich workshop has unsurprisingly encouraged the anti-string jihadists to stage a bunch of "string theory is not science" terrorist attacks across the world. Ethan Siegel has embarrassed himself several times in the past but he added one more "essay" with a not too original title
Why String Theory Is Not Science.
He starts by listing 5 stages of the scientific method – in my words: observations, formulation of a hypothesis, validation or refutation, extension to a full-fledged theory, search for new phenomena and jump to 2 or 3. Well, that's what string theory has been doing in all those papers, too.

The only thing that the non-experts such as Siegel don't understand (or pretend to misunderstand) is that theoretical arguments plus experiments that have been done a long time ago are sufficient to falsify an overwhelming majority of the theories that one may design to describe the quantum gravity or the unification of forces etc. A new careful theoretical analysis of well-known "old" experimental data is often as useful as new experimental data. In particular, the reconciliation of general relativity and quantum mechanics is an extremely constrained problem that basically has just one solution – every solution of the combo of constraints is an aspect of string theory. That's why string theory has been able to achieve such incredible progress in recent decades.

Theorists have to rely on the theoretical arguments and the existing experiments because we're not drowning in experimental results that would quantify the Planck scale physics or something like that. This is not a fault of the theorists (especially not string theorists); it's how Nature works. And if someone should be blamed for not bringing us the experimental miracles, it's the experimenters, not the theorists.

Siegel picks heliocentrism as a great scientific theory because it explained new phenomena including Jupiter's moons, phases of Venus and Mars in different seasons, periodicities of comets. It may sound like a great talking point except that it's completely misleading.

The fact is that geocentrism is capable of describing everything that heliocentrism may describe. Just replace all heliocentric coordinates \(\vec R_i\) of the \(i\)-th celestial body by\[

\vec R_i \to \vec R_i + \vec R_{\rm Sun}- \vec R_{\rm Earth}

\] and apply this transformation to the dynamical laws governing the accelerations as well. You get a new theory in which the Earth constantly sits at the origin. (You may also get rid of the Earth's spin by switching to a rotating coordinate system.) However, the fundamental laws governing the motion of the planets will contain special terms related to the "Earth" which will make these geocentric laws "less simple" than the heliocentric laws. This is the only reason why people prefer the heliocentric coordinates in the Newtonian physics. There is no full-fledged falsification of the "geocentric paradigm" and in fact, general relativity encourages us to say that all coordinate systems – including heliocentric and geocentric systems – are equally good starting points to formulate the laws of physics. (The fictitious forces that you need in a geocentric system of coordinates are interpreted by general relativity as a special form of the gravitational field – they follow from some "not so simple" configuration of the metric tensor that nevertheless obeys Einstein's equations.)

The case of string theory is analogous to the heliocentric theory – while quantum field theory is analogous to the geocentric description. Just like in geocentric coordinates, one may describe pretty much anything using the formalism of quantum field theory. However, the formalism becomes increasingly contrived as we move towards the description of quantum gravity and similar complicated things. To describe an increasing number of increasingly accurate observations, we have to add an increasing number of counterterms and/or new fields with unspecified properties to the quantum field theory (their number may grow indefinitely). The theory – effective field theory of gravity – becomes unpredictive at the Planck scale. That's analogous to demanding special corrections in the equations that protect the special status of the Earth in a geocentric description of the world. Just like the geocentric paradigm, the effective quantum field theory framework may be extended to deal with any phenomenon we will realistically observe. But people who actually study the content of the theories still see that much like the heliocentric description, the string theory description of the phenomena is the less contrived and more predictive one among the two. It's the only one among the two that is capable of becoming a full consistent theory of all phenomena, not just the observed phenomena beneath a threshold, and that's why they say that string theory is the right framework to deal with those phenomena.

My hip [I got from God] is like a wardrobe, Ewa Farna's Czech variation of All About That Bass (also: small girl, chipmunks), a 1.2-billion-views song that has been praised for its perceived anti-feminism and natural self-respect. Feminists boldly claim that Meghan Trainor has plagiarized them because the feminists have copyrighted fat female buttocks. See also her Dear Future Husband (0.2 billion, lyrics) to understand why feminists and Hollywood inkspillers go ballistic and say that she returned us back by five generations (she would surely deserve a Nobel prize in peace if this were the case!). While she wants the husband to treat her like a lady, she does the chores in the video (1950s style), something that true feminists never do. ;-)

In science, one may falsify specific enough models; and fundamentally wrong frameworks (e.g. classical physics may be falsified by a few experiments that force us to switch to quantum mechanics). But promising enough frameworks that have worked well for a long enough time cannot really be falsified. People are abandoning them because their description of certain phenomena becomes contrived and there exists a more natural description that replaces them.

Even though the geocentric paradigm has always been closer to people's direct observations – they live on the Earth while the Sun is just another light bulb on the celestial sphere – it is true that when we get rid of the obsession with our everyday lives, the soil that we walk on etc., we see that the heliocentric system connected with one of the particular light bulbs on the celestial sphere leads to a more natural and coherent description of the motion of objects in the Solar System. The heliocentric system brings lots of unnecessary complications for someone who just wants to understand the walking on the Earth and similar things. But it's simply needed for a more general spectrum of physical phenomena. The number of astronauts who "really need" a non-terrestrial system of coordinates is tiny but unlike the anti-string jihadists, the geocentrists have mostly gone extinct, anyway.

Analogously, quantum field theory may be more convenient to describe low-energy phenomena such as those that we can achieve with the existing colliders. Those experiments are analogous to the walking on the Earth which is nicely captured by a geocentric theory. But once we realize that our anthropocentric perspective (one connected with the Earth's surface and/or with the low-energy fields) is neither "all of science" nor the "fundamental pillar of science", we may find out that a heliocentric theory, and similarly string theory, is superior, more natural, more predictive, and simply more compatible with the phenomena that take place beyond the everyday life experience.

Ethan Siegel's criticism of string theory is therefore totally analogous to a criticism of heliocentrism. People just walk on the Earth so we don't need to downgrade the Earth or use non-terrestrial reference frames. In a similar way, he says, people don't do experiments at Planck energies so we don't need string theory. Except that it is in principle possible to leave the Earth; and it is in principle possible to achieve Planckian energies. So a better theory has to have some explanations and predictions for those situations and pretty much the pure thought is enough to figure out that heliocentrism and string theory are superior in this extended domain of phenomena.

In another section of his tirade, Siegel tries to suggest that it's wrong to use the term "string theory" for string theory because it's not a physical theory, just a mathematical theory such as set theory. Well, string theory has been named string theory because strings seemed to play an important role in it; and because it was and is a physical theory exactly in the same sense as e.g. quantum field theory. So physicists have just used exactly the same terminology.

The differences between quantum field theory and string theory are just technical differences. String theory works a little bit differently, more coherently, than quantum field theory in the spacetime. But both systems of ideas are frameworks that are not relevant for particular observations unless extra information (about the field content and interactions in QFT; and about the compactification in string theory) is specified. And when the extra information is specified in a viable way, both frameworks agree with all the observations that the mankind has ever done. When it comes to predictions, the two frameworks primarily differ in the predictions of "extreme" experiments that haven't been done. In the Planckian regime, string theory predicts something that makes sense; quantum field theory makes no coherent predictions at all. So in the "easy" experiments, the two frameworks are tied; in a more general domain of conceivable experiments, string theory can only do better, not worse, than quantum field theory.

This point has always been obvious to particle physicists and even in these discussions with the laymen, it's been done very clearly for more than a decade. If Ethan Siegel hasn't been capable of understanding this point that the "falsifiability" status of quantum field theory and string theory is exactly the same, then he is a hopelessly retarded imbecile. If he has understood it but he keeps on repeating the nonsense about string theory being less science than QFT or other important theories in physics, then he is a dishonest crook.

Siegel parrots all the misunderstandings about the untestability of all the phenomena – all physical phenomena in string theory are testable in the scientific sense – and refers to some of his fellow crackpots as if they were authorities. Then he tries to claim that a rose is a tulip or something like that – I have no idea what this childish segment is supposed to mean. He adds lots of other incredible idiocies such as:
What’s interesting about string theory is that when it was first proposed, it was called the string hypothesis, as it was recognized this idea hadn’t yet risen to the status of a full-fledged theory.
This is just complete nonsense. String theory has never been called "string hypothesis", not for one day. The word "string hypothesis" was recently used for some much more specific conjectures about the stringy behavior of systems outside particle physics etc. But string theory was born in 1968 when Veneziano found the amplitude. It was realized that this kind of an amplitude may be predicted from models that were named the "dual models" where the duality referred to the duality between the \(s\)- and \(t\)- channels.These days, when we're overwhelmed by many dualities that are more important, we use the term "world sheet duality" for that old duality that string theory was named after for a few years. You may check that the term dual models was used up to 1976 or so.

(Siegel includes a picture of hadrons that corresponds to the understanding of the meaning of string theory in the late 1960s. Sorry but such pictures have been outdated for quite some time. Siegel and his soulmates clearly want to believe that they can remain well-informed about the big picture of theoretical physics while outright rejecting or not watching 40 years worth of research at all but this ain't the case. With this attitude, you are guaranteed to gradually become a self-evident moron, a critical point that Siegel has already surpassed.)

In 1973 and especially 1974, the literature was already full of titles referring to "strings" because it was realized that the amplitudes and the physics of "dual models" follows from the dynamics of strings. In 1974, you could see numerous papers with "...theory of...string[s]" in the title. Ramond, Kaku, Kikkawa, Scherk.

The term "superstring theory" became standard in the early 1980s, thanks to papers by numerous Russian authors plus those by Green and Schwarz in particular (GS would talk about "dual string theory" as recently as in papers written in 1981 and published in 1982).

In the same years like 1982, the literature was already full of the shorter term "string theory". For example, Daniel Friedan wrote "Introduction To Polyakov's String Theory" in 1982. The term "string theory" was soon to mean what was previously called "superstring theory" – the true theory that is a viable contender is the supersymmetric version and one wants a short enough name for such an important theory.

You won't find any papers with string hypothesis in their title before 1985 and all the later papers with these words in the title mean something else than "all of string theory" by the "hypothesis".

So Siegel is just rewriting the history. These claims are pure lies. No credible physicist has ever agreed with the terminology and "classification of science" presented by these anti-string jihadists. No actual working particle theorist thinks that the word "theory" in "string theory" should be changed. (It's the word "string" that is perhaps kept because of some inertia.) These attacks on string theory are purely the hobby of a movement of crackpots and it's shameful if they pretend to be something else than they are.

Also, Siegel writes:
Even a physical state that arises as a consequence of an established theory, such as the multiverse, isn’t a scientific theory until we have a way to confirm or refute it; it’s only a hypothesis, even if it’s a good hypothesis.
Sorry but this "until" is complete nonsense. Saying that a theory only becomes a part of science once we have a way to confirm it is exactly as stupid as saying that Darwin's theory wasn't a theory until Charles Darwin was given a ticket for HMS Beagle. It surely doesn't matter for the status of an idea whether some human has been given some opportunity to do certain experiments or observations. The idea is the same and as long as one evaluates it by its merit and avoids the ad hominem fallacies, it is damn obvious that some people's ability to do certain experiments doesn't affect the status of the idea. The inability to obtain a ticket doesn't extinguish the true scientists' curiosity, either.

More generally, this obsession with the replacement of the word "theory" by the word "hypothesis" is 1) analogous to the creationists' attacks against Darwin's theory – both groups are convinced that by changing the words, one changes the probability that the theories are correct; 2) among rational people, this "cause of the jihad" is ludicrously unimportant because the words "hypothesis" and "theory" mean basically the same but the conventions have been set so that more specific sets of equations and formalism are called "theories" while "hypotheses" are one-sentence claims about certain results that may follow from some theories. To start to use the term "hypothesis" instead of "theory" in theories such as string theory (or perhaps the theory of inflation etc.) would mean to introduce havoc into the terminology of physics. But nothing would change about the substance, anyway. The substance in physics isn't about loaded terminology; it's about the evidence. Feel free to rename Darwin's theory to "Darwin's possibly lucky hunch"; competent folks will consider it a foundation of biology, anyway. This Siegel-style obsession with terminological reforms is a sign that his main focus isn't the scientific curiosity but the optimization of tools of propaganda.
When that day comes, we’ll all proudly welcome string theory into the fold as science.
Sorry but you are a bit too late. String theory was welcome into science in 1968 and it was welcome as the new pillar of science in 1984 or 1985. You must have slept for the recent 30 if not 47 years. We don't know all the answers to the questions whether string theory agrees with the phenomena beyond the verified ones at all, what it actually implies about the phenomena, and whether there is a deeper principle that unifies or "explains" the aspects of string theory that we already know. But the open status of questions is exactly why the scientific research is taking place. When no big questions like that will be opened anymore, it will be too late for doing original research. But even if and when all things are clear sometime in the future, there will always be people who will try to "undo" and "fight against" all the insights that will have been accumulated – just like what their predecessors are already doing today.

These aggressive semi-educated self-anointed populist "pundits" are just so annoying. The political correctness must be blamed for a big part of these decadent movements. If a naughty boy like that comes to the classroom and screams similar things, he should be spanked, spanked, and spanked.

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