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

quantamagazine.org

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

#101

Post by robertlagrant »

ninkendo wrote: post #88
robertlagrant wrote: post #80

Earlier quoted context omitted.

I don't even know where "fresh" hydrogen comes from for new stars in our current universe. Why would it be different for an older one?

We have a good idea where it comes from: It was created in the big bang, and as stars form (and explode, or form neutron stars and collide) they turn it into heavier elements. Over time there is less hydrogen, which is why the universe can’t be infinitely old. Since it’s only ~13.7B years old, the amount of hydrogen we see makes sense with our models. It’s a much much bigger problem if the universe significantly olde…

Thanks! Interesting.

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

#102

Post by moi2388 »

amai wrote: post #75

"It’s possible that simply including more terms in the approximation of the nuclear force might be the answer. On the other hand, it’s also possible that these ballooning helium nuclei have exposed a fatal flaw in our understanding of the nuclear force." I bet on more terms.

I think that’s a fair bet; that’s pretty much what physics have been doing to every problem for the last 100 years unfortunately..

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

#103

Post by blueprint »

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.

in that they don't exist independently of the apparatus that localizes them out of a wavefunction? checks Diamond Sutra sounds about right

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

#104

Post by rambojohnson »

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…

why do we clutch pearls whenever a publication uses a "click-baity" title? at least it manages to a: get people to actually read the publication, and b. publisher/site makes money. nobody's running a charity of information in a capitalist society.

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

#105

Post by bobbylarrybobby »

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?

Could've said the same about Newtonian mechanics. Theories seem great til they don't. That doesn't mean all they ever were was curve overfitting.

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

#106

Post by orra »

rcxdude wrote: post #58
jjtheblunt wrote: post #34

Earlier quoted context omitted.

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

The operation of a D-type flip-flop and NAND gates explains everything in computers upwards of digital logic. What else is there to explain or explore in software?

Mmm, I don't agree with your analogy. Yes, you can model things at a higher level, but surely that is for efficiency, not because the model breaks down, in terms of accuracy.

In contrast, there are phenomenon which we know standard particle physics and quantum mechanics gives the wrong answere (despite getting so much else right).

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

#107

Post by naasking »

mr_mitm wrote: post #86
robertlagrant wrote: post #78

Earlier quoted context omitted.

The other theory is there are infinite universes somehow being created all the time by every choice. Which to my mind isn't very Occam's Razor-ish. But it does exist as a theory.

You mean the Many-Worlds interpretation? That's not every choice, but every quantum measurement. And it's not necessarily an infinite number. And it's not a theory, but an interpretation. And it's actually very Occam's Razor-ish (at least that's what proponents claim), because it needs less postulates than the standard Copenhagen interpretation. The many worlds are a consequence, not a postulate.

It's the multiverse theory, typically discussed under the framework of string theory.

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

#108

Post by BizarroLand »

How do you excite a helium nucleus?

It sounds like the setup to a joke, the punchline being that you tell it there's cake in the dining room, but I am honestly curious?

Laser bombardment? Running it through a particle accelerator? Pointing out the girl helium over at the bar looked at it?

Ok, sure, they shot electrons at it, but why would that have any real, measurable effect on the nucleus?

What are the conditions that qualify as "excited" for a helium nucleus? Is it just the "balooning", or is there some real meaning to the term?

I have so many questions.

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

#109

Post by naasking »

houston_Euler wrote: post #25
jiggawatts wrote: post #16

Earlier quoted context omitted.

General Relativity doesn’t end just above the atmosphere and quantum mechanics ought to apply to everything, not just experiments. The current microscopic models don’t even attempt to explain how a molecule of water is lighter than the oxygen and two hydrogen atoms that went into making it. Oh sure, we can wave our hands at it and invoke the mass-energy relation from GR, but this doesn’t “pop out” of the Standard Mod…

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.

https://en.wikipedia.org/wiki/Binding_energy#Mass_change

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

#110

Post by naasking »

jiggawatts wrote: post #70
rcxdude wrote: post #60

Earlier quoted context omitted.

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…

> 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.

I'm not sure this is correct. It bends spacetime less simply because it's in a lower energy state. It's correct to say that the Standard Model doesn't explain spacetime curvature, but the curvature in GR is implied by the energy which is explained.

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