8 ms·
> Instead, at these scales, a new effective force emerges — the strong nuclear force, transmitted between nucleons by the exchange of pions. I'm admittedly ign
by version_five 3y ago
> Instead, at these scales, a new effective force emerges — the strong nuclear force, transmitted between nucleons by the exchange of pions.
I'm admittedly ignorant, but I'm not convinced that a lot of theoretical physics is basically curve fitting where you've got a model with enough flexibility that you can make it fit the data. String theory always seemed like an egregious version of this, I think it's less popular now.
I think that's why elegance goes a long way in theories: a simple and concise description is harder to overfit.
- comboy 3y agoYou may enjoy The Structure of Scientific Revolutions by Thomas Kuhn. Fantastic book.
- gumby 3y agoParticle physics is probably still stuck in the butterfly collecting phase, in which case “curve fitting” is not a criticism.
- iainmerrick 3y agoI think the "butterfly collecting phase" in particle physics was really the 40s and 50s, when a whole bunch of surprising new particles were discovered. Gell-Mann and other proposed a unifying principle in the 60s, and as far as I know that's been broadly successful and ultimately led to the standard model. https://en.wikipedia.org/wiki/Eightfold_way_(physics) https://en.wikipedia.org/wiki/Eightfold_way_(physics) We are not now discovering any new unexpected particles (or any theoretically expected ones, since the Higgs), which is a bit unfortunate in terms of giving theorists something to work with.
- dboreham 3y agoIt's entirely that.
- andreareina 3y agoThe standard model has a number of free parameters [1] but the results of calculations are pretty sensitive to them, and this is what predicted (not just explained post-hoc) the Higgs. It's not incorrect to say there's curve fitting involved, but it severely understates the magnitude of the achievement that is the standard model, and its success in explaining everything that underpins everyday life[2], as well as most things beyond that regime[3] [1] https://en.m.wikipedia.org/wiki/Standard_Model#Construction_of_the_Standard_Model_Lagrangian https://en.m.wikipedia.org/wiki/Standard_Model#Construction_... [2] https://www.preposterousuniverse.com/blog/2010/09/23/the-laws-underlying-the-physics-of-everyday-life-are-completely-understood/ https://www.preposterousuniverse.com/blog/2010/09/23/the-law... [3] https://physics.stackexchange.com/questions/128374/evidence-of-why-the-standard-model-is-a-successful-theory-of-particle-physics#:~:text=Perhaps%20the%20biggest%20success%20of,prediction%20of%20the%20Higgs%20Boson https://physics.stackexchange.com/questions/128374/evidence-....
- zmgsabst 3y agoThe standard model doesn’t explain GPS satellites.
- jfengel 3y agoBut relativity explains GPS. And the two theories together explain practically everything to insane levels of precision. The only time they go wrong is when they both operate at once, in a narrow range around black holes or the very earliest universe.
- lilgreenland 3y agoThey also go wrong with large scale phenomena like inflation, dark matter, and dark energy.
- azalemeth 3y agoThere's also the problem of fine tuning -- why is the fine structure constant roughly 1/137? If it were different from its current value by a tiny amount, the universe as we know it wouldn't exist. Is the anthropocentric principal the only explanation we have -- it has the value it has because it produces a universe in which we're able to observe it? And I guess less formally there's also the problem of complexity: condensed matter physics exists because trying to solve the standard model for a solid directly is both incredibly infeasible (think "cost of flipping bits in the calculation far extends that of all matter in the observable universe") and fails to capture the emergent phenomena in a natural way.
- willis936 3y agoWhat passes the bar for "elegant enough"? Why would laws of nature care about such human principles? And, most of all, why treat elegance as a guiding principle when all it has done is produce models incapable of being accurate outside a narrow range?
- JKCalhoun 3y agoHistorically, haven't the more "elegant" models been shown to be correct? The various explanations for planetary motion come to mind as an example.
- willis936 3y agoCorrect in a narrow range. Newton's elegance failed to accurately predict orbits of even our rather typical stellar system. Good for a start, but hardly something to strive for once we know better. So where do we go next? There is a real chance of artificially keeping ourselves in a local minimum if we don't seriously consider inelegant theories. It'd be neat if someone came up with an elegant theory that accurately described nature from quantum fields to stars. It'd also be neat if someone did that with an inelegant theory.
- vaidhy 3y agoNo.. In fact by the standards of the day, an circular orbit is more elegant. Think about circles within circles and the entire universe revolving around you. To some extent, models that made less assumptions tend to be more correct.. but I think those are few and far between. We are now trying to explain very small discrepancies (by human scale) and the models are necessarily more complex.
- JKCalhoun 3y agoI was thinking of the epicycle in fact. Kind of a hack, I think.
- dexwiz 3y agoElegance is matter of perspective. Epicycles are a very elegant way to explain planetary orbits from a geocentric view point, but they are very wrong.
- godelski 3y agoExperimental physics works a bit differently than most people think. While string theory was/is popular, very few hold it as certainty. From the very beginning the discussions around it were that it was a non-testable theory. While out-group conversations around physics are "physicists believe" in-group conversations are more "the leading theory is". Uncertainty is deeply ingrained in the study and the focus is more around making our knowledge less wrong rather than proving something correct/making our knowledge correct. Subtle, but notably different. It is the reason you always see quotes with qualifiers like "should" or "we think" and rarely certainty (easy to miss if you aren't looking). These distinctions matter when you create experiments and interpret results. They generally don't matter to the layman, since an authoritative answer is good enough. But they do matter if you need to do any form of evaluation, as essentially what I'm talking about is the importance of including error and uncertainty. Which btw, particle physics often has a uniquely tight bound: 5 sigma. You'll even notice CERN's blog post about 5 sigma has lots of qualifiers, does not suggest it claims certainty, how it isn't alone enough, and even references that there are good arguments for even higher bars. It's a different language than people are used to. https://home.cern/resources/faqs/five-sigma https://home.cern/resources/faqs/five-sigma
- jfengel 3y agoI don't get why the arguments are confined to string theory. The standard model plus general relativity are so good that any theory that resolves the conflict is necessarily only testable when you've got a stellar mass black hole in your lab. That could be a call to stop bothering with exploring the domain entirely as infeasible. But I don't understand why string theory gets singled out for finger waggling when any other theory must run into the same problem.
- godelski 3y agoNo serious physicist only considers String Theory. That's part of the point I was making. Really String Theory is only a guide used while we wait for something better and more testable to come along. Nothing is set in stone, they are just guides to being less wrong.
- akomtu 3y agoString theory looks like a good math framework to describe possible universes. Physics today is hindered by the obsessive idea that what we see around - the observable universe - is all there is, rather than just one of many possible worlds. This is the good old geocentric model on steroids. And this is why physicists are puzzled by the lucky combination of constants that define our world.
- evanb 3y agoThe theory they’re talking about is not just curve fitting. Instead only pieces which match the physics of QCD / the Standard Model Are included. It is simple to write down terms that you might include in a “just make up enough terms until it fits” methods that are excluded based on the requirements of symmetry matching that the whole program of EFT is organized around.
- jcarrano 3y agoReminds me of Freeman Dyson's anecdote of Fermi: "I remember my friend Johnny von Neumann used to say, with four parameters I can fit an elephant, and with five I can make him wiggle his trunk." [1] [1] http://lilith.fisica.ufmg.br/~dsoares/fdyson.htm http://lilith.fisica.ufmg.br/~dsoares/fdyson.htm