What every physicist should know about string theory | Hacker News Reader

What every physicist should know about string theory

physicstoday.scitation.org

44 pointspaulpauper47 comments

What I find most interesting about these articles showing up on Hacker News is how discussion of abstruse details irrelevant to the bulk of progress in physics or mathematics gets almost all the air time.

Compare the number of articles on string theory and physics beyond the standard model to those on exotic materials, advances in turbulence, orbital mechanics, modern elasticity, solar system formation, or foundations of quantum mechanics. Is it that there is no tradition of popular writing that makes people think that they have any insight beyond the wall of knowledge necessary to understand these fields?

String theory and things similar to it evolved to be as intellectually interesting as possible. Normally you have a mixture of humdrum "experiment theory" and exciting abstractions, but without the humdrum experiments to motivate all the humdrum calculations only the most attractive parts get studied. As a result, string theory is 99% mind-blowing, while the rest of the items on the list are 1% mind-blowing and 99% "numerical simulation of heat transfer in a honeycomb lattice." Nobody would ever write a boring string theory paper because there is no possible motivation for doing so. This is not to say that string theorists are somehow neglecting a duty, just that there is almost certainly a vast mine of untapped results that are not presently being worked on because there is little motivation for them.

One thousands years from now when humanity is building star-bridges out of beyond-standard-model particles, I guarantee that there will be a Journal of Taychon Engineering whose articles never make it on PBS.

Seems to me one solution would be for you and others who think like you to regularly post links on HN to articles on these topics you believe are being unjustly neglected.

... and see them being completely ignored. (That was the whole point, I think.)

Where are the articles on Boyce–Codd normal form, Java bytecode, SOLID etc..

This is still a 'social' network.

I don't think I've heard of BCNF for a while, thanks for the mention. I doubt anyone uses more than 1NF. I've posted it here: https://news.ycombinator.com/item?id=19140206

I would be concerned if an engineer I worked with put forward a DB design that wasn’t normalized to 3NF without a really good reason. Designs that are 1NF but not 3NF are generally either hyper-optimized (better have a really good reason) or just bad. It’s not hard to get a DB into 3NF.

I remember having to learn how to normalize my data a lot when I was learning SQL, because the only tools available for use in my environment was a good ole' tool called Microsoft Access & VBA.

String theory is the buzziest of science buzzwords.

It's just the wrong audience altogether.

Peter Woit's critique of this article: http://www.math.columbia.edu/~woit/wordpress/?p=8068.

I've never found that Peter Woit's critiques of string theory match up very well to the reality of what string theorists are doing.

Woit's critiques are of string theory as an extension of the Standard Model. But most string theorists are not working on string theory trying to get predictions about current energy frontiers. Rather, they are working on understanding the mathematical structure of string theory and seeing what it can teach us about analogous mathematical structures in quantum field theory. (A now classic example: The first calculable models of 4-dimensional confinement came out of string theory.)

And here is an answer to that critique: https://motls.blogspot.com/2015/11/first-quantized-formulati...

Should be called string hypothesis.

I would accept theory as the right word. A mathematical structure that has been assembled for testing is generally referred by practitioners to as a model or, if there is a collection of models and mathematics linking them, a theory.

Unfortunately, a fully fleshed out theory with centuries of matching experimental data is still called a theory.

I think that is more of a namespace collision than anything else.

Even in mathematics, there are different definitions of "theory". One is that a theory is a body of knowledge, like set theory or automata theory. This is where I would group string theory as well.

Another definition from mathematical logic is that a theory is a set of axioms and deduction rules. Fascinatingly, those have in common with scientific theories that they can (if sufficiently complex) only ever be falsified, not verified.

I believe the point (excuse the pun) is that it may well be a mathematical theory but it's not (yet?) a scientific one.

Did any physics enthusiasts read this paper? https://arxiv.org/abs/1001.0785

"Every" is a bit rich, considering we're likely 100s of years from testing it directly.

It isn’t clear that any amount of time would lead to it being falsifiable.

It has to agree with every prior measurement in Quantum Mechanics and Relativity. That, in itself, is impressive.

It's not so impressive if all you're doing is generalizing frameworks or cherry-picking the subsets that happen to agree with experiment. You have to show something new.

For example, (going from memory here, so don't quote me), your basic (Von Neumann's?) formulation of quantum mechanics was basically a generalization of Newtonian physics that specified an unreasonable number of non-real possibilities, and you can only recover meaningful results by taking Newtonian physics as an axiom a la the 'classical limit'. This would have just been mathematical over-complication had it not been for the fact that this model predicted things that differed from Newton physics in measurable ways.

So to reiterate, if your theory is unfalsifiable, it is not impressive that it agrees with every measurement. All you'd have achieved is restating what is already known in a language nobody wants to use.

It also has developed some interesting mathematical tools and perspectives, but as a TOE I think the growing skepticism is warranted. The worst outcome of course being that M-Theory is accurate, but untestable. It would be a bitter irony for humanity if our best theory required a galactic-scale collider to test it!

It would be a bitter irony for humanity if our best theory required a galactic-scale collider to test it!

Doesn't that also mean that (in such a hypothetical situation) our best theory says that our previously best theories will give accurate predictions up until the point at which we observe something equivalent to a galactic-scale collider? If so, that doesn't sound so bad to me.

The trouble is that strings is more of a framework for physics to fit in to (like quantum mechanics) than it is a physical theory. There isn't a specific list of string particles, just like there isn't a list of Schrodinger equation particles. You have to add in whatever particles you discover, and then the theory tells you how they move.

On the bright side, if there was a single particle that didn't move like a string, string theory would be falsified. On the dim side, it's difficult for anything to not move like a string, because string theory is so powerful as a framework that you can get it to make just about anything consistent. What you really want in physics is a brittle framework that only allows you to slot in a few different behaviors.

It's kind of funny because programmers want the opposite thing that physicists do. When your client asks for a behavior that you have painted yourself into a corner against ever implementing your software has been "falsified," an expensive disaster that you work very hard in advance to prevent! If you made universes for a living, strings would be an ideal framework.

We just need to make contact with a hyper-dimensional sentience who can give us the low down on how everything works.

I don’t think most PhD physicists know what a diffeomorphism is.

I very much doubt that. I certainly learned it in a physics undergraduate degree.

Ok, let me guess without looking it up... A diffeomorphism is a smooth map that lets you switch coordinate systems.

(I sure hope that's not wrong.)

Pretty close. It's a smooth map with smooth inverse. If you've chosen chosen coordinates, it will transform them for you.

I think most physicists probably have a reasonable intuitive idea what a diffeomorphism is, since most have probably learned something about relativity.

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