Six weeks ago, I linked to a PBS video Why string theory is right. As expected, they also released the twin video,
Why string theory is wrong (PBS video at YouTube)I have listened to those 19 minutes rather carefully and I am pretty sure that the video doesn't contain any glimpse of evidence or an answer to the question "why string theory is wrong". For this reason, I must agree with Niki that PBS has simply chosen a clickbait title.
Just to be sure, this blog post does include an answer to the question in my title: one such answer may be seen in the previous paragraph.
Another reason why this is a clickbait title is that the two videos, "right" and "wrong", don't differ much. Both offer the viewers some fast sketches of structures and insights of string theory, along with some incoherent critical fog, and the proportion of the scientific content and the stupid fog is about the same in both videos.
The comments, to be discussed at the end of this text, make it pretty clear that an overwhelming majority of the people who open the YouTube page only see the title and not much more.
In the new video, we see a sequence of factoids and overly fast explanations of things like the Weyl symmetry, the Weyl symmetry on the world sheet, T-duality, (less detailed) S-duality, five versions of string theory, M-theory, Calabi-Yau manifolds. And near the beginning, we see some sketch of the old Kaluza-Klein theory.
This Matt tries to talk about science. But literally everything is a little bit wrong. One incorrect prediction that is cited – perhaps the closest point to an explanation "why string theory is wrong" – is a prediction of the oldest Kaluza-Klein theory that the charged elementary particles should weigh some 5 kilograms. Clearly, this isn't a prediction of full-blown string theory so it doesn't really count.
But it isn't even really an unavoidable prediction of the Kaluza-Klein theory in the modern sense. We do use the Kaluza-Klein theory as a theory with any number of extra dimensions such that the compact manifold has any isometry group \(G\). That isometry group becomes – generically non-Abelian – gauge symmetry of the effective four-dimensional theory. Oscar Klein himself came extremely close to the Kaluza-Klein version of the electroweak theory, including an \(SU(2)\) factor, in the late 1930s.
There are too many assertions in the video that are wrong and I don't think it makes sense to spend the time and enumerate them. Just one example that just shocked me. At some point, we learn that M-theory was perhaps discovered because string theory "didn't work" in ten dimensions so Witten just added another dimension to fix it. This has absolutely nothing to do with the reality. The ten-dimensional string theory worked great and it still does – the heterotic \(E_8\times E_8\) theory is arguably still the most precise description of the real world we find in string theory.
M-theory wasn't invented for any phenomenological reasons at all – it took some time before models almost as realistic as the heterotic string theory were found in M-theory. (Quite generally, the laymen are always tend to think that everything is about phenomenology, making some easily observable predictions right away – but physics simply doesn't work like that.) And there was nothing ad hoc about the addition of the 11th dimension. This dimension was completely derived. When we go to strong coupling, type IIA string theory (as shown by Witten) as well as the heterotic \(E_8\times E_8\) string theory (as shown by Hořava and Witten) simply develops a new dimension (whose topology is a circle or a line interval, respectively). Everyone who believes that the 11th dimension (or the previous ten) are a product of the human arbitrariness or exuberance is a fudging moron.
It's similar at most moments. The narrator can say about 4 sentences that are right and somewhat informative but the fifth one is complete nonsense. He constantly makes stuff up and it is not surprising that almost everything that he makes up is bullšit. You can't really "guess" difficult physics insights in this way. At least no particular crackpots are quoted by their name.
What's frustrating is the comparison with similar videos that were produced some 15 years ago. You know, the very same PBS channel hired Brian Greene as a host of the filmed version of his books, The Elegant Universe and The Fabric of the Cosmos (NOVA). There were no mistakes – surely mistakes of the staggering type as I mentioned in previous two paragraphs. The budget was several million.
Almost all the informative or technical comments from the "Why string theory is wrong" video may be found in the 15-year-old PBS series. The added value of the PBS YouTube video are all the made up ludicrous comments that sound negative because it has become fashionable to parrot ludicrous negative statements about the cutting-edge scientific research.
Fifteen years ago, I was actually thinking how the presentation of science (among more important things, of course) would get transformed e.g. in the following 15 years. The PBS videos at YouTube must be considered an answer because no better movies about these topics have been made for years – and it is arguably politically or economically infeasible in the current epoch to make such things any longer. I hadn't envisioned such a shocking deterioration of the quality, not even in my wildest nightmares.
And now the comments, the actual tragedy of the commons. YouTube wasn't really running those 15 years ago, at least not in the current proportions, so I can't be sure what the comment sections would look like 15 years ago. But I would have surely imagined nothing like what we see under the fresh PBS video. These people are just fudging unbelievably complete worthless crap. There are nominally over 1,000 comments over there right now and, after I have read hundreds of them, I still believe that there is not a single one that would indicate some interest of a commenter in physics or knowledge about physics – interest or knowledge that would reach at least the level of the popular sketches in this video.
The most upvoted comment says:
Evariste Galois: PBS Space Time: "Why String Theory is wrong" ... John Henry Schwarz is typingHow can this comment get 411 upvotes? WTF? The second most beloved comment, with 268 upvotes, is from the same "guy":
Evariste Galois: The dislikes are from bots created by Edward WittenWell, I am sure that they won't believe me but I am not a bot created by Edward Witten but I have "disliked" the video. Both of the dumb comments above have a greater number of upvotes than the number of downvotes of even the main video. And it goes on and on and on. Another comment with over 100 upvotes:
maf: this comment section in a nutshell: (insert name of a string theorist) is triggered)Well, this prediction has been shown completely wrong, hasn't it? There is not a single comment by a string theorist – or anyone who would be even capable of understanding and writing anything positive about the theory itself. Someone responded to this comment – he had made the same prediction and at least noticed that it was completely wrong:
GigawingsVideo: To be fair I was expecting string theory supporters to start frothing in their mouth and typing angry commentToo bad. The number of people who know something about string theory to even defend it is some 3 million times smaller than the number of heavily limited folks such as those who have created the comment section. So you would need roughly 3 million comments for the first comment of the predict type to emerge.
No, this is not funny. I am really terrified how much the society around pop science has degenerated. For decades, I haven't expected a string theorist – not even a graduate student – to have the balls to appear in such comment sections. I am the only one in this part of the mental world who has any balls. But what about some intelligent teenagers, those who are interested in science and who could potentially become theoretical physicists in a few years? Don't you expect such folks to be numerous among the viewers of similar videos? I think that if YouTube had existed when I was a teenager, my inspiring comments would be everywhere. ;-) Where are the counterparts of the hypothetical myself?
There aren't any. The scenario in the "Idiocracy" movie has always been possible but we're approaching it so much more quickly than the movie envisioned. At the current rate, the mankind will be intellectually equivalent to "Idiocracy" sometime around 2050. There aren't any "string supporters" in such comment sections today and there won't be any string theorists in 2050. We will be fortunate if there will be people who know something about the Newtonian mechanics. The faster rate of the mankind's intellectual rottening must mean that it is not just the negative biological selection, as hoped in the movie. Even the people whose DNA could do better end up being morphed to hopeless morons such as the commenters under the PBS video – some epigenetics and/or societal pressures must contribute the bulk of the effect. People aren't spanked for not doing a proper science homework so they just turn to superficial trolls – it's probably unavoidable.