“You’re making it quite clear that you’re devoted to doing exactly what I find problematic: misleading and confusing people about the status of string unification by refusing to distinguish between two completely different technical issues.”
So I stand accused by Peter Woit, in his latest comments on Tuesday’s post.
Dear readers, you are now the jury, and I stand by your opinion. I do not want to mislead you — indeed, the purpose of this website is to be a reliable, trustworthy source of information about high-energy physics for the public — and if I have misled you, I will correct the error.
If you look at Tuesday’s post, you will notice that at the start I stated (abridged here, but you can look back at the full text)
String theory has several applications, and you need to keep them straight. Let me mention two.
- Application number 1: this is the one you’ve heard about. String theory is a candidate (and only a candidate) for a “theory of everything” — …[which] really means is “a theory of all of nature’s particles, forces and space-time”.
- Application number 2: String theory can serve as a tool. You can use its mathematics, and/or the physical insights that you can gain by thinking about and calculating how strings behave, to solve or partially solve problems in other subjects. (Here’s an example.)
I carefully distinguished these two things, because the first is highly controversial, and the second — well, it should be much less controversial. And also because I don’t work on the first, and I work occasionally on the second, when it proves helpful to the physics I’m interested in. String theory sits in my toolbox, ready for use if needed.
Then I went on to mention that if string theory in its vanilla form were true in Application Number 1, then you would be able to make predictions for how particles would scatter that are characteristic of their being strings — although no one in the next century or maybe millenium is likely to be able to carry out such experiments. Now, I thought this was also non-controversial, and made it as an off-hand comment; but Woit complains that this is highly misleading, and also that I’m misleading you on purpose.
He’s wrong that I’m misleading you on purpose, but he’s right that there is a risk of being misled and that the situation is indeed complicated. So I added a note at the end of the post emphasizing the importance of the qualifier “in its vanilla form”, and that there’s no guarantee at all that string theory, even if it were true, wouldn’t be in ginger passionfruit soybean flavor, in which case the predictions would be different. Apparently this wasn’t enough for Woit; I am still accused.
Personally, I have never thought string theory was likely to predict the particles and forces of nature in a unique way. I am not surprised there’s a huge landscape of possibilities; I’m only surprised it seems so… conventional. In my opinion, any sufficiently complicated quantum field theory or quantum gravity theory will likely have a landscape. And so, in this sense, string theory is very unlikely to ever make predictions for exactly what particles and fields we will find in nature… these details will likely depend on the early history of the universe and on accidents of history that we are not going to learn about from the theory itself. On this point, most high-energy physicists seem to be agreed right now.
Question for readers: Do you feel misled, by what I wrote Tuesday, into thinking that I believe that string theory currently makes, or is likely to make, unique and specific predictions about nature?
If you do, then I screwed up, and I’ll correct the error.
Now I’d like to ask you another question.
In his comments to Tuesday’s post, Woit said that his “short-hand claim `string theory makes no predictions‘ is obviously a simplification of a very complicated situation, one that has been exploited for decades by string theorists making bogus claims for predictions.” [boldface mine]
Question: When Woit says “string theory makes no predictions“, and “string theorists making bogus claims for predictions“, do you think he means only Application Number 1, which is what he called “string unification”?
Or do you think he means Application Number 2 as well? Am I, because I have string theory in my toolbox and I use it occasionally, accused by Woit of being a “string theorist making bogus claims for predictions”? Or am I not, in fact, accused?
In particular, let me requote the accusation he levels at me:
“…misleading and confusing people about the status of string unification by refusing to distinguish between two completely different technical issues.“
Question: Is Woit, in your opinion, “misleading and confusing people about the status of string theory as a whole by failing to distinguish between two completely different applications of the theory“?