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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

#71

Post by eigenket »

jiggawatts wrote: post #16
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.

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…

You appear to be confusing special relativity and general relativity. Mass-energy equivalence pops out of special relativity, and is part of general relativity because GR extends SR. Another class of theories which extend special relativity are (relativistic) quantum field theories. These also have mass-energy equivalence baked into them because they contain special relativity.

Your are correct that there is a (strong) conflict between general relativity and quantum field theory, and this is a major problem for theorists, but it does not pose problems for using mass-energy equivalence in quantum field theories (since it comes from SR not GR).

There are real, physical, examples where the GR/QFT conflict is more problematic. For example in quantum physics labs around the world it is possible to put things which have mass in superpositions of being in two different places. This is usually done with very small objects, but it happens. We have absolutely no idea what is happening to space-time when we do this.

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

#72

Post by denton-scratch »

6nf wrote: post #56
jjtheblunt wrote: post #34

Earlier quoted context omitted.

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

'everything that underpins daily life' does not include everything in the universe, for example it excludes dark matter and dark energy, neither of which matter at planetary scales like here on earth.

> neither of which matter at planetary scales like here on earth

...except, isn't it true that the galaxy that contains the earth wouldn't exist were it not for dark matter?

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

#73

Post by jcarrano »

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…

Reminds 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

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

#74

Post by [deleted] »

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?

[deleted]

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

#75

Post by amai »

"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.

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

#76

Post by Thiez »

oneshtein wrote: post #67
lilgreenland wrote: post #14

Earlier quoted context omitted.

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 captur…

Cool story. Now explain why almost everything we see is moving away from us, where fresh hydrogen for stars comes from in an ancient universe, where the cosmic background radiation comes from, why the distant universe appears 'younger'...

Note that the 'laws' of physics are no better than normal scientific theories, scientists just had more hubris back then.

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

#77

Post by baryphonic »

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…

> I can't believe they pick such a clickbaity title for a serious publication and let quanta magazine publish an even more clickbaity article about it. Well, I guess they need more funding.

My take from reading the article (not a physicist) is the physics of the nucleus (i.e. the protons and neutrons and strong nuclear force) are treated as emergent phenomena from the quantum theories about fundamental particles (e.g. quarks, leptons & gluons).

Per the article, such leading theory of the nucleus is "chiral effective theory," which seems to be quite inaccurate at making predictions for the experiment in question.

I'm not sure how much more accurate the headline could be, unless chiral effective theory is not in fact the ex ante leading theory of the nucleus.

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

#78

Post by robertlagrant »

azalemeth wrote: post #50
lilgreenland wrote: post #14

Earlier quoted context omitted.

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

There'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: c…

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.

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

#79

Post by enkid »

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…

A title of "theory mostly sound, except some extreme edge cases," would cover about 95% of science research.

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

#80

Post by robertlagrant »

Thiez wrote: post #76
oneshtein wrote: post #67

Earlier quoted context omitted.

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 captur…

Cool story. Now explain why almost everything we see is moving away from us, where fresh hydrogen for stars comes from in an ancient universe, where the cosmic background radiation comes from, why the distant universe appears 'younger'... Note that the 'laws' of physics are no better than normal scientific theories, scientists just had more hubris back then.

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?
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