Blogging Heads Science Saturday

Today’s “Science Saturday” on Bloggingheads features me and Sabine Hossenfelder, supposedly talking about What’s wrong with string theory. Actually, we both agreed that we were pretty tired of that topic, so tried to discuss some more interesting related issues we both have an interest in. Here’s a clip from the full thing, I promise to not start regularly embedding video in this blog:

I hope this thing came out all right. It was recorded a couple weeks ago, in a process involving no trouble on my end, but heroic efforts on Sabine’s. While Sabine had to set the whole thing up on her end, and ended up crouched in an attic since it was the only place she could get a connection of good enough quality, I just sat at my office chair and someone from Bloggingheads took care of everything. Unfortunately we couldn’t see each other while talking. I can’t really bear the thought of watching myself on video, so I guess I’ll never see exactly how this turned out, but I’m glad to see that the turtles on the bookcase behind me made it into the frame.

Sabine has her own posting about this here, and the full thing is here.

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60 Responses to Blogging Heads Science Saturday

  1. somebody says:

    “Claiming that the situation of QFT (which makes a huge number of non-trivial, verifiable predictions of high accuracy), and string theoy (which predicts absolutely nothing) are the same is just sophistry.”

    The entire conversation was about an idealized scenario IF we had model-building freedom in string theory. And there, sorry, I still stand by my claim.

    Incidentally, “sophistry” implies malicious misrepresentation. Lets avoid personal commentaries and attacks in discussions of physics, shall we? I just want to nip it in the bud because I have seen (as I am sure you have) this sort of thing degenerate into online foodfights.

    “QFT would be in the same situation as string theory if simple QFTs didn’t work, so you had to keep adding more fields and complexity, just to evade falsification, ..”

    The real reason why we are forced to complexities in string theory is because we are tied to certain kinds of models because of the technical tools we have for model-building. Its like trying to build a ladder, but only using forks. It is entirely unlike the situation in QFT where you have the freedom to build models following ideas, and not technical tools.

    Also, “simplicity” is an extremely slippery fish when you are only in the phase of trying to understand the (non-perturbative) principles of the theory. If we did not know about non-Abelian gauge symmetry of the Lagrangian description, there is no sense to saying that a QFT is “simple” because the gauge groups are. If somebody just gave you a bunch of rules for constructing messy scattering amplitudes, we would first have to come up with a (non-perturbative) Lagrangian description before even having a notion of “simplicity” of that description. This is EXACTLY the state in string theory. So it is really not clear to me what is the simplicity that we should expect from string theory at this stage.

    Again, if you notice, both these issues stem from the lack of understanding/control we have of string theory. I am entirely willing to give you that these are real problems, and not merely details, but if you give me those, I find no reason whatsoever why it is any less of a framework predictively than QFT. Besides, I know that it gives me many generic features of particles physics, I know that it has all the expected features of a quantum gravity including black holes (at least once we fix the asymptotic boundary), and that it seems to incoroporate and generalize the most successful ideas in physics like gauge symmetry, spacetime geometry etc. It seems crazy not to want to understand that structure.

  2. somebody says:


    If there is more than one model that fits data at low energies, it is no longer within the realm of science to want to distinguish them while doing only low energy experiments. What we call the standard model is merely a collective tag for all models that look like it at low energies. We can have more resolution in the space of theories only as we probe higher energies. The real problem with the low energy physics of today is that we know it has to fail being consistent at some scale because of gravity etc. So we know it cannot be the thing. If we understood string theory better, we could do UV complete model-building.

    To make any successful model, we need ingenuity and creativity like Weinberg and Salam had back in the day. I am saying that one way in which string theory could deliver (one of the more unlikely ways, actually), is by being such a PARADIGM in which one can exercise that creativity.

    There are many questions to ask here, and many string theorists would not be happy with this possible paradigm that I am suggesting here. But thats only because the ways in which truth is going to be realized in the future is vague speculation at this point. The only real way to find out is to work. My point was only that the blanket statements that people make about predictivity are often a result of confusing between preditivity with uniqueness. So I was demonstrating by a scenario that uniqueness and predictivity are entirely different beasts.

    I am kind of busy, so perhaps this message is not very clear.

  3. stranger than fiction says:

    The public opinion is relevant to the question what fields are generally of importance for our societies and how money should be invested to be as beneficial as possible, but the public never ‘votes’ on research funding on the specialist level. There is a reason why funding agencies have an elaborate referee process.

    Sure but what are you willing to pay back?

    String theorists paid back a little in the form of launching “The Elegant Universe” into popular culture and speculative articles and popular science books and TV shows on how string theory changes our view of the universe. I think that’s part of the role science has to play within a culture that believes in science and funds the creation of a particular world view and appreciates the scientific method.

    I’m not sure how this process can be avoided? Physics is not an auxiliary science that can hide itself into obscure academic discussions but the very foundation of the big picture. In that sense I also do understand physicists like Susskind who try to launch ideas that are compliant with our knowledge of the universe although they aren’t empirical. It is correct that they are used to avoid the capitulation of string theory where they arise from but in the absence of a stronger alternative they also avoid capitulation of fundamental research. It compromises empirism in favour for science as a belief system that lets research continue as it is. This is less ironic in the sense that we in fact know it is not true but it is paradox: it lets something work by virtually terminating it.

    Back to the public audience. You can’t avoid paying back and becoming criticized for poor gifts, but the public has also no alternative to take what you give them unless it wants to give up their faith in reason and embraces either scepticism ( postmodernism ) or old obscure gods.

  4. Sitting in the attic? Ha, all the better, that’s always a fun place to be curled up with a book, or in this case a cam. Great discussion. So much talk about string theory.

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  6. Daniel de França MTd2 says:

    Since this post is about videoblog, recently lubos made a post on Youtube concerning criticism of string theory. The tone is very light heart, I was really surprised.

  7. Daniel de França MTd2 says:

    Sorry about the post, I found it at , but I couldn’t refrain from posting here. It just shows the guy on a different light.

  8. Chris Oakley says:

    I saw Lubos’s YouTube effort and remained puzzled as to why he chose to post it. The only thing I can think of is that it is a coded message to his (alien) controllers, pleading for clemency following the initial failure of his campaign to subvert terrestrial science.

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  10. GC says:

    I don’t remember it adding multiple trackbacks here in the past like it did now, and I nearly always edit my posts after I publish them. Even now, I saw a few edits I’d like to make, but I’ll wait until later to see if does it again.

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