What does the photograph show? Well, it shows a judgement written yesteryear Dirac himself.
In 1956, he bought an air ticket to Moscow. The original role of his trip was to write the of import judgement on a blackboard – well, it was the blackboard of Russian physicist Dmitry Ivanenko (1904-1994). On Oct 3rd, 1956, Dirac in conclusion wrote this of import sentence. Ivanenko together with his comrades appreciated the importance of the judgement together with so you lot tin nevertheless encounter the quote on that blackboard. If a janitor mistakenly erased it, Vladimir Putin would rightfully ship the janitor to a Gulag. ;-)
It's non difficult to encounter why Dirac is together with so naturally associated alongside the concept of beauty inwards theoretical physics. His contributions to physics possess got been beautiful. The derivation of the Fermi-Dirac statistics from the anticommuting fields is beautiful. The bra-ket formalism of quantum mechanics is beautiful. Most obviously, the Dirac equation\[
(i\gamma^\mu \partial_\mu - m) \Psi = 0
\] is beautiful. This quantum mechanical equation describing a spinning relativistic fermion generalized the previous equations – Schrödinger's or Pauli's equation – inwards a means that respects the Lorentz covariance together with to a greater extent than or less other (e.g. discrete) symmetries, that tin hold upwards expressed yesteryear a modest publish of characters (especially if you lot utilisation the "slashed" annotation for contractions alongside the gamma matrices), together with whose really existence was surprising.
Also, nosotros may tell that the equation is beautiful inwards the same feel equally a femme fatale: a brilliant plenty human is instantly charmed when he sees her or it for the start time. He wonders how he could possess got lived without knowing her or it. He wants to retrieve her or its shape together with curves because they seem to hold upwards perfect, they seem to agree together, in that location exists no elementary plenty (or sufficiently nearby) means to deform or adapt it that could hold upwards considered an improvement. Any alteration would brand her or it worse.
These are to a greater extent than or less informal reasons why the Dirac equation is pretty. Now, for a contemporary theoretical physicist, the Dirac equation is a rather footling thing together with so its "fundamental beauty" is beingness exaggerated. But the regulation that beauty matters holds to a greater extent than generally. Even when 1 considers to a greater extent than modern together with less footling insights inwards theoretical physics than the Dirac equation (such equally grand unification, supersymmetry, string theory equally a whole, together with lots of private aspects of string theory), it's nevertheless truthful that the of import ones are truthful inwards an analogous feel equally the Dirac equation.
Now, Sabine Hossenfelder wrote to a greater extent than or less other rant against theoretical physics, against string theory, together with particularly against beauty inwards physics. Her original thesis is:
Nature has no obligation to hold upwards pretty, that much is sure.Oh, really? Is it "sure" that Nature has no obligation to hold upwards pretty? Influenza A virus subtype H5N1 much to a greater extent than sure proffer is that her judgement to a higher house straight contradicts Dirac's quote on the Moscow State University blackboard that was reproduced inwards the really title. According to Dirac together with many others, Nature truly does possess got the obligation to hold upwards pretty. This declaration wasn't manifestly truthful a priori. But in that location be lots of evidence that the declaration truly is truthful a posteriori.
Beauty together with the truth aren't synonymous but in that location be totally rational reasons why a prettier candidate for the police of physics is to a greater extent than probable to hold upwards truthful than an uglier candidate. The beauty inwards the Yes/No feel – i.e. a qualitative belongings that "a femme fatale optimizes a sure quantity that measures her beauty quantitatively" – divides theories to 2 groups together with the right means to attain Bayesian reasoning is to assign comparable prior probabilities to qualitatively dissimilar hypotheses. In this sense, a "pretty" theory is equally probable a priori equally an ugly one, but because in that location are together with so many ways inwards which 1 may hold upwards ugly, the pretty theory ends upwards beingness special together with hence dramatically overrepresented according to the probabilistic distribution.
If you lot detect that a candidate theory has to a greater extent than or less symmetry or whatever other "special feature" that looks similar an aspect of beauty, the same regulation is nevertheless true. One can't plough whatever of these arguments into high-precision scientific discipline (at to the lowest degree today, nosotros don't know how to attain it) but the full general vague declaration has both rational reasons to hold upwards right – equally good equally lots of circumstantial, basically empirical evidence that it is truly true.
You tin reformulate the same declaration alongside to a greater extent than or less theological flavor, too. When God was creating the Universe, He needed to choice to a greater extent than or less laws of physics. He in all likelihood didn't attain that chore also hastily. Instead, He in all likelihood wanted skillful plenty laws – or the best laws according to to a greater extent than or less chore tender. The beauty of the proposed laws is at to the lowest degree a natural virtue that God could possess got preferred.
Now, Hossenfelder doesn't let on anything foreign virtually her inexpensive negation of Dirac's of import quote. Her "good friends" inwards quotation marks are shocked, we're told. Surely she doesn't hateful it, they say. But she does. She understands literally nothing virtually the of import lessons of 20th century physics, she has no innate aptitude (let lonely intuition) for theoretical physics whatsoever, but the political correctness that has run amok has encouraged worthless individuals from privileged groups such equally herself to precisely trash Paul Dirac, his quote, his equation, all other of import insights inwards modern theoretical physics – together with pretend to hold upwards of import at the same time.
I am truly annoyed yesteryear the politically right "good friends" (including to a greater extent than or less string theorists who possess got worked at the places where this mistaken physicist has pretended to work) who constantly bring upwards the illusion that she can't hateful what she says. She can't hold upwards this dumb, this dishonest, this ugly, this disgusting, together with and so on, tin she? Well, she sure enough is. If you lot weren't deliberately fooling yourself all the time, "good friends" of hers, you lot would encounter it almost immediately. If you lot hybridize to a greater extent than or less of the most deluded, dishonest, disgusting, together with stinky edifice blocks together with excrements from to a greater extent than or less of the most notorious jerks together with professional person crackpots – including Mr W*it together with Mr Sm*lin – together with if you lot mix these things alongside to a greater extent than or less extra distasteful stuff, what you lot halt upwards alongside is Sabine Hossenfelder.
The physical laws should possess got mathematical beauty – together with their vitriolic foes should hold upwards disgusting, lying, untalented likes of Sabine Hossenfelder. That's how the roles are divided inwards our Universe.
And that's the memo.