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As an experimental physicist, I refuse to get excited about a new theory until the proponent gets to an observable phenomenon that can fix the question.
by pif 1y ago
As an experimental physicist, I refuse to get excited about a new theory until the proponent gets to an observable phenomenon that can fix the question.
- lewdwig 1y agoThe problem with emergent theories like this is that they _derive_ Newtonian gravity and General Relativity so it’s not clear there’s anything to test. If they are able to predict MOND without the need for an additional MOND field then they become falsifiable only insofar as MOND is.
- JPLeRouzic 1y agoPlease, how is the article related to MOND's theories?
- lewdwig 1y agoIn general, they’re not. But if the only thing emergent theories predict is Newtonian dynamics and General Relativity then that’s a big problem for falsifiability. But if they modify Newtonian dynamics in some way, then do we have something to test.
- westurner 1y agoFrom https://news.ycombinator.com/item?id=43738580 https://news.ycombinator.com/item?id=43738580 : > FWIU this Superfluid Quantum Gravity [SQG, or SQR Superfluid Quantum Relativity] rejects dark matter and/or negative mass in favor of supervaucuous supervacuum, but I don't think it attempts to predict other phases and interactions like Dark fluid theory? From https://news.ycombinator.com/item?id=43310933 https://news.ycombinator.com/item?id=43310933 re: second sound: > - [ ] Models fluidic attractor systems > - [ ] Models superfluids [BEC: Bose-Einstein Condensates] > - [ ] Models n-body gravity in fluidic systems > - [ ] Models retrocausality From https://news.ycombinator.com/context?id=38061551 https://news.ycombinator.com/context?id=38061551 : > A unified model must: differ from classical mechanics where observational results don't match classical predictions, describe superfluid 3Helium in a beaker, describe gravity in Bose-Einstein condensate superfluids , describe conductivity in superconductors and dielectrics, not introduce unoobserved "annihilation", explain how helicopters have lift, describe quantum locking, describe paths through fluids and gravity, predict n-body gravity experiments on earth in fluids with Bernoulli's and in space, [...] > What else must a unified model of gravity and other forces predict with low error?
- andrewflnr 1y agoThey both have to do with very weak gravitational fields.
- cryptonector 1y agou/lewdwig's point was that if an emergent gravity theory made the sorts of predictions that MOND is meant to, then that would be a prediction that could be tested. The MOND thing is just an example of predictions that an emergent theory might make.
- dawnofdusk 1y agoDeriving existing theories of gravity is an important test of the theory, it's not a problem at all. It's only a problem if you can only do this with more free parameters than the existing theory and/or the generalized theory doesn't make any independent predictions. Seems like in the article the former may be true but not the latter.
- cryptonector 1y agoIf such a theory makes no new predictions but is simple / simpler than the alternative, then it is a better theory.
- cantor_S_drug 1y agoSometimes I wonder, imagine if our physics never allowed for Blackholes to exist. How would we know to stress test our theories? Blackholes are like standard candles in cosmology which allows us to make theoretical progress.
- mycatisblack 1y agoAnd each new type of candle becomes a source of fine-tuning or revision, progressing us with new ways to find the next candles - cosmological or microscopic. Which kinda points to the fact that we’re not smart enough to make these steps without “hints”. It’s quite possible that our way of working will lead to a theory of everything in the asymptote, when everything is observed.
- throwawaymaths 1y agowe dont know much about black holes, and there are theories which dont allow for proper black holes but do allow for objects that look like black holes in the limit (but e.g. don't produce Hawking radiation)
- the__alchemist 1y agoThis is why I'm skeptical of theories like Wolfram's: It feels like an overfit based on this: It produces all sorts of known theories (special relativity, parts of QM, gravity etc), but doesn't make new testable predictions, or new fundamentals. When I see 10 predictions emerge from the theory, and they all happen to be ones we already known of... Overfit.
- emtel 1y agoJonathan Gorard goes through a handful of testable predictions for the hypergraph stuff here: https://www.youtube.com/watch?v=XLtxXkugd5w https://www.youtube.com/watch?v=XLtxXkugd5w
- mhh__ 1y agogorard is one to watch
- ojo-rojo 1y agoBut that means we'd prefer whichever theory our species had landed on first. Basing our preference for a theory on that timing seems kind of arbitrary to me. If they're the same in other respects, I'd take a look at both sides to see if there are other compelling reasons to focus on one or the other, such as which is simpler. Of course if they make different predictions that'd be even better, time to get to testing :)
- generalizations 1y agoA positive example would be the periodic table - the pattern to the elements made sense, but also exposed 'holes' in the table which were later filled in as we discovered additional elements. Wolfram may be closer to inventing epicycles to explain orbits - which is interesing and technically challenging and probably tickles his mind, but doesn't actually generate new knowledge.
- npunt 1y agoNot quite apples to apples tho because you have to take into consideration what was known at the time each theory was developed (the input), not just the output. Theory A: fits 7 known predictions but also makes a not-yet-verified prediction Theory B: fits 8 known predictions and offers no new ones In this example wouldn't Theory A be better, because all else equal it is less likely the product of overfitting and required more insight and effort to discover? In other words, Theory A used a different process that we know has a higher likelihood of novel discovery. (Maybe this is a restatement of the simplicity argument, in that Theory A requires fewer predictions to discover it, ergo it is simpler)
- elyase 1y agoBetween two models the one with the shorter Minimum Description Length (MDL) will more likely generalize better
- nitwit005 1y agoBut, think of all the fun math we get to do before someone shows it's an unworkable idea.
- quantadev 1y agoAn observable is always the strongest evidence but there's also the improbability of a mathematical coincidence that can serve as almost as strong evidence. For example the fact that the Bekenstein-Hawking entropy of an Event Horizon comes out to exactly be the surface area divided by plank-length-square units, seems to me almost a proof that nothing really falls into EHs. They only make it to the surface. I'm not saying Holographic Theory is correct, but it's on the right track. My favorite conjecture is that what happens is things effectively lose a dimension when they reach the EH surface, and become like a "flatlander" (2D) universe, having only two degrees of freedom on the surface. For such a 2D universe their special "orthogonal" dimension they'd experience as "time" is the surface normal vector. Possibly time only moves forward for them when something new "falls in" causing the sphere to expand. This view of things also implies the Big Bang is wrong, if our universe is a 3D EH. Because if you roll back the clock on an EH back to when it "formed" you don't end up at some distant past singularity; you simply get back to a time where stuff began to clump together from higher dimensions. The universe isn't exploding from a point, it's merely expanding because it itself is a 3D version of what we know as Event Horizons. Just like a fish can't tell it's in water, we can't tell we're on a 3D EH. But we can see 2D versions of them embedded in our space.