A new experiment casts doubt on the leading theory of the nucleus • Hacker News Board

Re: A new experiment casts doubt on the leading theory of the nucleus

#61

Post by [deleted] » Tue, Jun 13, 2023, 8:43 AM UTC

jiggawatts wrote: post #51

tsimionescu wrote: post #47

Earlier quoted context omitted.

I believe this one is downvoted for quoting Chat GPT. The other one is downvoted not so much for the claim about water molecule mass, but because of the combative tone and feeling that it is challenging established physics in a somewhat shallow way, most likely.

It cracks me up that my comment is seen as "challenging established physics" (and being downvoted into oblivion) when literally everything I stated is established physics. I really don't see what's controversial about what I've said that's riled up people so much...

[deleted]

Re: A new experiment casts doubt on the leading theory of the nucleus

#62

Post by fsh » Tue, Jun 13, 2023, 8:44 AM UTC

jcranmer wrote: post #39

cyberax wrote: post #35

Earlier quoted context omitted.

The problem with the nucleus is that the internal dynamics there are impossible to describe with any reasonable precision. If for the electron shell we can calculate pretty much anything we want from the first principles (energy spectra, the half-lives of unstable and metastable states, etc.), we can't do anything similar for the nucleus. For example, we can't compute half-lives of unstable nuclear isotopes. The best…

> If for the electron shell we can calculate pretty much anything we want from the first principles (energy spectra, the half-lives of unstable and metastable states, etc.), we can't do anything similar for the nucleus. As I understand it, we can only really do that for a single-electron atoms. Multi-electron interactions get the same problem as inside the nucleus.

No, the problems are very different. The properties of multi-electron atoms can actually be calculated reasonably accurately with numerical methods, but including relativistic and quantum electrodynamic corrections is much harder than in single-electron systems. On the other hand, the coupling constant of the strong interaction is too large to permit perturbative calculations of bound systems. This makes calculations of nuclear properties fundamentally much more difficult, regardless of the particle number.

Re: A new experiment casts doubt on the leading theory of the nucleus

#63

Post by yyyk » Tue, Jun 13, 2023, 9:08 AM UTC

jxy wrote: post #28

The fundamental theories we have is Quantum Electrodynamics and Quantum Chromodynamics. This new experiment tells you that "modern nuclear forces, including those derived within chiral effective field theory" break down and cannot be used to describe what they observed. Here is the arxiv: https://arxiv.org/abs/2112.10582 It just tells you that their effective theory is no longer effective in these circumstances. Unle…

"Theory of the nucleus" does not necessarily imply just QED+QCD in this context. It can mean something derived from QED+QCD - the theory of which elements of the calculation can be thrown out from the QED+QCD calculations. That would be hardly the first theory which is a derived theory from a more fundamental theory. So the headline is fine? For once Quanta was less clickbaity than the preprint.

Re: A new experiment casts doubt on the leading theory of the nucleus

#64

Post by iainmerrick » Tue, Jun 13, 2023, 9:18 AM UTC

gumby wrote: post #5

version_five wrote: post #2

> 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 popula…

Particle physics is probably still stuck in the butterfly collecting phase, in which case “curve fitting” is not a criticism.

I 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)

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.

Re: A new experiment casts doubt on the leading theory of the nucleus

#65

Post by SideburnsOfDoom » Tue, Jun 13, 2023, 9:30 AM UTC

jjtheblunt wrote: post #34

andreareina wrote: post #7

Earlier quoted context omitted.

The 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 mos…

If it explains everything then why are experiments still ongoing? What is left to explain?

The project of "Science" is essentially one of curiosity about the natural world, as it really is. No other reason needed.

If you do not possess that curiously then so be it, but others are still motivated by it.

Re: A new experiment casts doubt on the leading theory of the nucleus

#66

Post by nologic01 » Tue, Jun 13, 2023, 9:35 AM UTC

gsatic wrote: post #52

exmadscientist wrote: post #43

Earlier quoted context omitted.

To oversimplify: the Standard Model is pretty great when you've got two particles. As soon as there's three , it's too hard to calculate most things people are interested in. Oh, or gravity. Gravity's a problem too.

Particles are similar to people that way.

the worst are online N-bodies

Re: A new experiment casts doubt on the leading theory of the nucleus

#67

Post by oneshtein » Tue, Jun 13, 2023, 9:49 AM UTC

lilgreenland wrote: post #14

jfengel wrote: post #9

Earlier quoted context omitted.

But 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.

They also go wrong with large scale phenomena like inflation, dark matter, and dark energy.

IMHO, "Inflation" is false theory, because it doesn't obey law of conservation of energy.

If no inflation, then no Big Bang, so our Visible Universe is much older.

If our Universe is much older, then life evolved multiple times already. Red stars are shallow gravity wells, so they are primary target of an expansive civilization, because it easy to enter/exit them, so they are colonized first and their light is captured fully.

Re: A new experiment casts doubt on the leading theory of the nucleus

#68

Post by evanb » Tue, Jun 13, 2023, 9:50 AM UTC

version_five wrote: post #2

> 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 popula…

The 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.

Re: A new experiment casts doubt on the leading theory of the nucleus

#69

Post by eigenket » Tue, Jun 13, 2023, 9:56 AM UTC

jdkee wrote: post #30

houston_Euler wrote: post #25

Earlier quoted context omitted.

Can you point to some evidence for the claim that "a molecule of water is lighter than the oxygen and two hydrogen atoms that went into making it?" I could understand the atoms sharing electrons, but just want to make sure I'm understanding you correctly, because you said it's unexplained.

Per our new electronic friend: " The weight of a molecule of water (H2O) is the sum of the weights of the two hydrogen atoms and one oxygen atom that compose it. Here are the atomic weights of these elements: Hydrogen (H): Approximately 1 atomic mass unit (amu) Oxygen (O): Approximately 16 amu So for a molecule of water: 2 Hydrogen atoms: 2 * 1 amu = 2 amu 1 Oxygen atom: 16 amu Adding these together gives a total of…

I would say this phrase

> the minor decrease in mass that occurs during the formation of a water molecule due to the conversion of some mass into binding energy according to Einstein's equation E=mc^2

Is highly imprecise at best, and misleading at worst.

It is true that the mass of the water molecule is slightly less than that of the oxygen and hydrogen atoms combined. It is not true that this excess mass is converted into "binding energy", binding energy is negative in stable molecules. That is the binding energy measures how much energy you would have to add to break up the molecule, or conversely, how much energy is lost (as heat/light/whatever) to the environment when the molecule is formed.

The mass is lower because it has been converted into heat in the environment, not because it has been converted into binding energy.

---------------

I would call this an instance of the language model producing convincing sounding nonsense (something that they do quite often when asked about technical stuff).

Re: A new experiment casts doubt on the leading theory of the nucleus

#70

Post by jiggawatts » Tue, Jun 13, 2023, 10:03 AM UTC

rcxdude wrote: post #60

jiggawatts wrote: post #51

Earlier quoted context omitted.

It cracks me up that my comment is seen as "challenging established physics" (and being downvoted into oblivion) when literally everything I stated is established physics. I really don't see what's controversial about what I've said that's riled up people so much...

It is factually incorrect in the assertion that the standard model can't explain the reduction in mass (special relativity and quantum mechanics work fine together. It's general relativity that is the problem). In fact mass-energy equivalence is a pretty core part of quantum mechanics.

> In fact mass-energy equivalence is a pretty core part of quantum mechanics.

It may be stated as such, and added in to equations as an external piece of knowledge from relativity, but this is cheating a bit.

Essentially, when we state that H2O has less mass than H+H+O, what we actually mean is that H2O bends spacetime a little bit less than the three atoms individually that made it up. There's no accepted variant of QM or the Standard Model that explains this. The dynamics of spacetime curvature rearranging as the photon is emitted as the hydrogen atoms burn is not explained by modern science. This is fundamentally the "QM is incompatible with GR" issue.

My point was that it isn't just near black holes that a GR-compatible microscopic theory is relevant.

It's relevant even in the flame of a candle. It's a small effect, but it's there. The inconsistency in the theories occurs at all scales.