Proton’s mass radius is apparently shorter than its charge radius | Hacker News Reader

Proton’s mass radius is apparently shorter than its charge radius

arstechnica.com

197 pointsraattgift114 comments

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Preprint of Nature paper: https://arxiv.org/abs/2207.05212

HTML5 version: https://ar5iv.org/abs/2207.05212 ("x"->"5" opens up ar5iv.labs.arxiv.org).

Wow! What a rabbit hole finding a proton is not just 3 quarks!.

Suggesting these 2 articles:

1] Experimental results of proton collision as of 2013 (3 quarks is an observation, but for low energies) :

https://physics.stackexchange.com/questions/81190/whats-insi...

2] Another article from the same author (Matt Strassler). Suggesting to read his answers for the comments of: Harry Bostock, Bob Anderson, and the 2 top comments of "aa. sh." (for more history and Neutron decay)

https://profmattstrassler.com/articles-and-posts/largehadron...

The proton is a collection of quarks and gluons moving at relativistic speeds around a central point.

What? Moving at relativistic speeds? I had never heard that.

I think that just means "moving fast enough that relativity is significant and has to be accounted for". It doesn't mean they are right at the speed of light (although they could be, I don't know). You could call a rocket "moving a relativistic speeds" because relativity has to be included in the calculations for accurate missions within the solar system.

Gluons are massless so they must move at the speed of light. However they are strongly interacting with quarks and themselves so their worldlines will be a crazy mess of intersections.

I wonder what the cut off speed is for relativistic speeds. If you think about it, it's not only a matter of speed but also how much precision you want in your calculations. Even if something was moving very slowly, you need to account for relatively if you want very accurate calculations.

A rule of thumb in classical mechanics is that 0.1c is when you should start taking (special) relativity into account, I think it’s 0.5% contribution then.

For general relativity I don’t know such a cutoff rule of thumb. Astronomy-wise, Mercury is the only planet that is obviously general-relativistic (its orbit is not an ellipse because it’s so close to the sun). On Earth, we don’t have strong/inhomogeneous enough gravity, so unless you’re synchronizing satellites or atomic clocks, GR is not something to worry about.

Some of the most precise clocks can actually measure precisely enough that a few feet of elevation change makes a measurable difference, which I expect also means that what you've placed under the table it's on also could.

Mercury's orbit is absolutely an ellipse. It is incredibly elliptical, with an apogee of 69.8 million km, and a perigee of 46 million km.

The relativistic effects on Mercury concern its precession - the way that elliptical orbit rotates [1] around the sun. And it's not caused by Mercury's speed (Which is only ~59 km/s at its maximum, compared to the Earth's 30 km/s). It's caused by spacetime being curved by the immense gravitational field of the sun.

If Mercury had a circular orbit, it would have no precession.

[1] Precession is akin to spinning a hula hoop around your body - with the hula hoop representing an orbit. https://en.wikipedia.org/wiki/Apsidal_precession

I think a good rule of thumb is 'check what accuracy you need your answer to, and then include all effects relevant to that precision'. If you needed an answer accurate to four significant figures, then you'd include relativistic effects for v < 0.1 c

I don't think that fits the definition of rule of thumb.

As a rule of thumb, I like to define my definitions first. /s

Even if something isn't moving at all (relative to your reference frame of choice), you might still need to care about local gravity's effect on time.

You also get some relativity with some elements. Gold is the one that I recall most readily.

Relativistic Effects and the Chemistry of Gold - https://link.springer.com/content/pdf/10.1007/BF03215471.pdf

> In atoms of high nuclear charge (Z), as a consequence of a relativistic effect, the s electrons of an atom become more bound and their orbitals smaller than if this effect were absent. Simultaneously, the d (and f) electrons are less bound because of this effect, which scales roughly as Z2. Gold exhibits a large relativistic effect. This accounts for gold being more resistant to oxidation than silver. It also accounts for higher oxidation states being more accessible in gold than in silver. These effects are illustrated by some fluorine chemistry of gold and silver.

https://en.wikipedia.org/wiki/Relativistic_quantum_chemistry

> Relativistic quantum chemistry combines relativistic mechanics with quantum chemistry to calculate elemental properties and structure, especially for the heavier elements of the periodic table. A prominent example is an explanation for the color of gold: due to relativistic effects, it is not silvery like most other metals.

"Each of these particles, or “nucleons,” is composed of a dense, frothing mess of other particles: quarks, which have mass, and gluons, which do not. Yet the quark masses only add up to a mere 1% of a proton or neutron’s mass, with the bulk of the proton mass coming purely from the motion and confinement of quarks and gluons."

https://physics.aps.org/articles/v11/118

So the interior of baryons is analogous to the interior of atoms, with gluons instead of electrons dancing frantically... weird.

Also the part about mass being generated by motion and how it seems to be an established fact.

Not really. The "roiling sea of particles" is a metaphor for perturbation series, which very specifically does not work for the strong force at low energies.

Take anything involving virtual particles as just that, virtual. They're an aid for computation and cannot be observed directly. They aren't necessary either; lattice gauge theory is always applicable if not practical.

The mass(-energy) being from the strong interactions is still true. And the residual bit of the strong force between protons and neutrons works with the virtual particle/perturbation theory approach pretty well, using pions.

I'm glad you brought this up, because I've been reading some stuff lately that makes it seem like virtual particles actually have visible effects, like this one:

https://www.forbes.com/sites/startswithabang/2019/07/12/yes-...

So is it that these articles are wrong, or that I'm reading them wrong, or that the idea that virtual particles are just for calculations is outdated?

We discovered the mesons by photographing their tracks on plates exposed to the sky. They're real, just extremely short-lived.

What a bad piece of journalism, intent on confusing instead of explaining.

Virtual particles were invented because they have measurable effects. Physicists don't go around inventing invisible things for no reason. What they are not is "particles". The particle facade is only there because it fits the math.

(The article seems to be describing an experiment that measured energy-time uncertainty.)

Incomplete analogy that's probably a better starting point: if the tone of a bell is a particle, then the other movements of the bell that don't resonate are virtual particles. Now, imagine we called the thermal motions of that bell “virtual tones”, and you have an idea why physicists always sigh and emphasize that virtual. particles. are. not. particles.

If virtual particles "fit the math" the same as real particles, what makes them not real? What do they not fit?

What makes particles travel long distances as lumps is that they are on-shell. Virtual particles are not on shell.

https://en.wikipedia.org/wiki/On_shell_and_off_shell

You don't _need_ them, and IIRC _can't_ (in general) use them if you deal with non-perturbative effects, unless you do stuff like re-summing infinite series of diagrams and that really makes interpreting the ultimately observable effect in terms of virtual particles interacting difficult.

An example that comes up in semiconductor is the 'hole' virtual particle. It is the absence of an electron. It is not a real and independent phenomenon. But you can treat it like a particle just fine

Electron holes are quasi particles, not virtual particles.

Ah hell, guess I have to start treating the stuff I learned in undergrad into the unreliable narrator category. Thanks for the correction!

Virtual particles are not particles.

Virtual particles are all the disturbances in a field that don't behave like particles do.

It's really a terrible name to have entered the lay vocabulary: “virtual memory is something that behaves largely like real memory” is _exactly_ wrong, it's more like “virtual memory is all the circuitry that doesn't perform any memory function, but is still made of silicon”.

The more correct idea is that particles aren't fundamental. There are fields, and a disturbance in one field will cause a disturbance in the fields that the first couples with.

Most chains of disturbances die out really fast (“virtual particles”), but some combinations will resonate for a significant amount of time before they die out (“unstable particles”) and others don't die out at all (“stable particles”).

And if the lifetime of a disturbance is fairly short compared to the frequency of the disturbance itself, it becomes hard to even make a solid distinction between those types, but again, that's a flaw caused by imposing a categorization scheme (“particles”) based on something that isn't fundamental.

My impression is that the notion of "virtual particles" is a bit of an outdated concept. There isn't really as much of a physical distinction between "real" and "virtual" particles as there is sometimes made out to be. All particles are excitations of some underlying field. Generally speaking, these excitations can have some resonance that allows them to persist for long durations. This resonance occurs when the particle is "on the mass shell" in the jargon --- that is, it has a rest mass that is equal (or at least extremely close) to the observed mass of the particle. Excitations that are "off the mass shell" decay exponentially. But these other excitations do have real observable effects. The Casimir effect is the most famous, but they're also responsible for the Lamb shift and Hawking radiation which have also been observed.

Hawking radiation has been observed? When did that happen?

It's been observed in sonic black holes, which are mathematical analogs of gravitational black holes in fluids (though to be fair the experiment has been disputed, so the evidence is not absolutely unambiguous):

https://www.nature.com/articles/nphys3863.epdf

Thanks for the clarification.

I don't have the background to be confident about this, but aren't the predicates on which Hawking Radiation is based on part of the equivalency framework between sonic and "real" black holes?

If so, then while the observation of Hawking radiation in the model is certainly interesting, calling it an observation of Hawking radiation with regards to real black holes sounds like a stretch.

I agree that observations from analog black holes don't rise to the level of definitive proof of the existence of Hawking radiation around gravitational black holes. But what has been observed demonstrates that a system whose behavior is described by the equations that we believe to be correct will exhibit Hawking radiation.

No, it's a pretty well-defined concept when you stick to its technical definition as an aid in interpreting terms of a perturbation series as Feynman diagrams.

> these other excitations do have real observable effects

Yeah, that's the major thing: virtual particles explain observable effects in a sort-of intuitive way.

But you could (to my knowledge) get the exact same results without involving any virtual particles, via lattice gauge theory. Since you get the same observable results without them, virtual particles, IMO, shouldn't be considered fundamental to any effect, even if they make the explanation a lot easier.

Anything involving complicated interactions with relativity like Hawking-Unruh stuff has an even bigger issue since the notion of a particle/vacuum is observer dependent.

All post-classical effects in quantum field theory arise from various "corrections" that come from what you could define as virtual particles, whether it's from the perturbative treatment or a numerical lattice gauge calculation. In the latter, you need to (formally) sum over all possible field configurations, the majority of which will contain half-witted weird off-shell "particles" and the entire spectrum between stuff you'd never see as a particle and the classical resonances.

It is more clearly visualized in a perturbative expansion, for sure, but it's a bit disingenous I think to argue that there are no virtual particles in a lattice calculation.

Yeah, the 'Standard model of particle physics' actually states that particles don't exist and there are only fields around.

You meant gluons instead of photons? Because the things analogous to electrons and the nucleus are the quarks.

Anyway, the similarity is only on the level of "it's a bunch of moving things locked together by a force". Those things are about as similar to themselves as they are to planetary motion.

> Also the part about mass being generated by motion and how it seems to be an established fact.

That's what they mean by relativistic speed. When effects from special relativity become large enough that you need to account for them in your math and measurements. There is a difference between invariant mass (aka rest mass) and relativistic mass, which depends on the object's velocity relative to the observer.

https://en.m.wikipedia.org/wiki/Relativistic_speed

While your description of what relativistic speeds means is accurate, this has nothing to do with the mass.

Instead, composite "particles" have mass mostly because of the energy of their components. This is a famous observation (the most famous by far) in general relativity: E=mc². E here can be the kinetic energy of the constituent particles, or some other kind of energy (for example, a polar molecule like water owes some of its mass to the electrical energy of the bond; and its mass will increase or decrease if placed in a strong electric field, depending on the orientation of the field).

This has nothing to do with the concept of "relativistic mass", which is anyway not commonly used in modern physics anymore. Mass almost always refers to "rest mass", and observer-dependent "relativistic mass" is accounted for only through differences in observer-dependent time and position measurements. That is, instead of saying "as an objects speed approaches the speed of light, its relativistic mass approaches infinity", the preferred interpretation is "as an object approaches the speed of light, time passes more slowly for it, so it takes longer for it to accelerate even if pushed with a constant force".

I have no good background in this but could it not be that from an outside observer view the motion appears as mass but when thought of modeled within it is instead energy/motion ?

> Also the part about mass being generated by motion and how it seems to be an established fact.

It's not motion per se, it's energy of any kind. And it's also probably the most famous equation in all of physics: E=mc² (so, m = E/c²).

The Strong Force and Strong Nuclear Force are so utterly fascinating to read about. Gluon Flux Tubes! Seems like pure science fiction and imagination.

This article was around recently: "Inside the Proton, the ‘Most Complicated Thing You Could Possibly Imagine’"

https://www.quantamagazine.org/inside-the-proton-the-most-co...

https://news.ycombinator.com/item?id=33262637

For a back of the envelope calculation we consider the uncertainty principle

Δx*Δp >= ℏ/2

Δp = Δ(mv) >= ℏ/(2Δx)

m = 9.1 * 10 ^ -31 kg (mass of electron)

x ~= 1 * 10^-15 m (radius of proton)

ℏ = 6.6 * 10 ^ -34 kg m^2 / s (plancks)

Δv >= 31 524 512 m /s

Which is about 1/10 the speed of light. There isn't a true cutoff for "relativistic speeds" but in general, 1/10th counts.

The specific composition of baryons is fairly niche physics. Assuming you're not educated in quantum physics, there's as much reason to expect to know about that as there is to expect a non-programmer to know about the minutia of different manual memory management strategies.

I'm not an expert, but I'll try to give a friendly explanation.

Consider a photon. We're all pretty familiar with how these work. Photons are light, and move at c. Photons also crucially don't have any mass, which is why they can move at the speed of light-- nothing with mass can move at c.

Photons are energy carriers for the electromagnetic field. They transfer electromagnetic energy from one particle to another. There's several quantum fields permeating the universe, and each has its own energy carrier particle[0]. These are known as bosons, or sometimes force mediators.

Atoms can influence each other through the electromagnetic field. An electron in one atom can drop to a lower energy state (or orbital), and releases a photon with all the energy that the electron "lost". That photon can bump into another atom, which causes one of its electrons to jump up by the same amount of energy.

Protons are made of quarks, which are held together with the strong nuclear force. The energy carrier for the strong nuclear force is called a gluon. Gluons bounce back and forth between the quarks, transferring energy for the strong nuclear force. This energy is used to pull the quarks together[1]. Again, because the gluons don't have mass, they can (and must) move at light speed. The quarks themselves do have mass, and they vibrate and wiggle around, but only at sub-light speeds.

Particle physics is really weird at first glance, but it makes a certain kind of sense once you learn a bit about it. It also makes less sense the more you learn. You've been warned.

[0] Except gravity. Maybe. We've theorized, but haven't observed the graviton particle mediating the gravitational force [1] gluons keep quarks a certain distance apart, sort of like a spring

The article refers to a gravitational something tensor, and, I’m wondering whether that is because this is actually dealing with gravitational effects, or whether it is just called that because it is the same tensor (or basically the same, or analogous in some way) to the stress energy tensor?

It also isn’t obvious to me what “mass radius” ought to mean...

I guess like, the average distance from the center of the mass, but like...

Idk, I guess that makes sense..?

But I guess I’m not sure what the “meaning” of that quantity would be? Like, what makes that a relevant quantity for describing the system? Is it in case you are hoping to describe some gravitational effects? Or...?

Hmm... well, I guess one could ask the same question about the “charge radius”... but that one to me sounds like it would have clearer uses? Like, if you are describing the EM forces on/from a charge, then the charge being distributed over a region would have different results than if it were at a single point I’d think.

Though, “the center of the proton” also doesn’t have one single position either.. but I imagine one could kind of separate those two things, comparing “what if we had a point particle with the charge and mass of a proton (which of course would be in a superposition over a range of positions)” to “what if we had a proton, with charge distributed about the center (and the center distributed over a range of positions in the same way as the hypothetical point particle)”

A good cartoon is that a form factor is the function that describes how an object deforms when exposed to an outside influence with a particular momentum. The form factor is a function of momentum.

There are many different kinds of outside influence. They can be scalar (think: just increasing the pressure uniformly), vector (put in an electric field), tensor (zap with a gravitational wave), pseudovector (magnetic field), pseudoscalar (zap with a pion).

Of course, you can apply a scalar outside influence and a vector at once. But the scalar, vector, tensor, pseudovector, and pseudoscalar labels denote different representations of the Lorentz group [lorentz].

What's more: the Wigner-Eckhart theorem [wigner] basically says [cheat] that the response can be factored into three pieces: the strength of the external influence, a factor that depends only on the representation of the external influence, and a factor that depends only on the property of the thing you're talking about (a proton, in this instance).

So people call it the gravitational form factor because if you exposed the proton to a gravitational wave, it's the thing you need to know about the proton to know how it deforms.

Note that because of the factorization you don't actually have to zap the proton with a gravitational wave! You can measure it by zapping the proton with other stuff, as long as you can get that stuff to have the right rotational properties or measure the response to many different perturbations and sum the responses the right way to mock up a tensor operator. The experiment at JLab doesn't use gravitational waves, it uses these latter approaches.

Roughly speaking at zero momentum the form factor is the charge of the object you measure if it's just sitting there. So the electric form factor evaluated at zero momentum is the electric charge, the gravitational form factor evaluated at zero momentum is the mass.

What are radii? Express the form factor as a function of momentum^2 [possible]. In units that physicists like to work in (where c=1, hbar=1), the units of momentum are 1/length. Expand the form factor as a Taylor series in momentum^2 and you will get

    form factor(p) = charge + # radius^2 p^2 + ...

where # is a known dimensionless number.

The above story is a cartoon but can be made more-or-less precise depending on how much quantum field theory you learn.

lorentz: https://en.wikipedia.org/wiki/Representation_theory_of_the_L...

wigner: https://en.wikipedia.org/wiki/Wigner%E2%80%93Eckart_theorem

cheat: this is a little bit of a cheat, it's only true to leading order in a taylor series in the strength of the external influence.

possible: it's always possible to arrange this, or at least to separate the momentum dependence into a factor dictated by the rotational symmetry properties and another factor dictated by the object, just like in the Wigner-Eckhart theorem.

This is an awesome writeup, cartoon or not. Thanks for taking the time to explain!

Quoting from the article (which quotes from the paper):

"Note that I am not even attempting to find an analogy for the gluonic gravitational form factors that would help you understand them. They're described in the paper as "the matrix elements of the energy–momentum tensor of the proton"

The energy momentum tensor is the same as the stress energy tensor.

TL;DR: Most of the mass comes from the energy of the strong force interactions of the gluons, not from the quarks. The gluons are not charged; the quarks are. The quarks sometimes go beyond the region of most of the gluons, which gives the proton a larger charge radius than mass radius.

> The quarks sometimes go beyond the region of most of the gluons, which gives the proton a larger charge radius than mass radius.

This is one hypothesis, but not a stated fact in the article.

Fair. On the other hand, the charge can't be coming from the gluons, nor from the strong force itself, so it kind of has to be coming from the quarks. (Um, unless it's inducing virtual pair production out there, and the destruction mechanism involves the pair getting destroyed by interaction with the quarks, and it takes one of the pair longer than the other... something like that could lead to charge out there farther than the quarks actually go.)

Why are gluons needed to hold quarks together. If the 3 are in a line, equally spaced, with the oddball charge in the middle, they will attract quite strongly.

+2. -1. +2

If these charges are equally spaced, the attraction of the middle one in stronger than the repulsion of the outer two.

Good point! But it's also an unstable system: the -1 will get attracted to one of the +2 charges and (from a distance) look like a +1, and the other charge will fly off to infinity.

I guess we could design a bunch of picometer-scale scaffolds that hold everything in place and this might work, but that doesn't seem to be the way nature put things.

Sure, but what if they're orbiting the center charge at relativistic speeds? Now they also create a magnetic field. My guess is that somehow it ends up being dynamically stable. Also that the strong force holding the nucleus together is actually mostly magnetism.

I would also posit that just maybe there is such thing as an electrostatic black hole. When matter is accelerated gravitationally to speed c, you reach an event horizon. Same should happen if the acceleration is due to charges, but will happen at a scale similar to the size of baryons. I'd say there is a lot of room for some theoretical developments in this area.

Stuff will only keep an orbit if it has nothing else to do, i.e. if it is dynamically stable.

> Also that the strong force holding the nucleus together is actually mostly magnetism.

If that were the case, you would expect protons to tear apart in the presence of strong electric fields. The fact that this seems impossible suggests pretty strongly

The strong force is much stronger than the Coulomb (charge) force.

It's not necessarily a questions of "need". Physicists are just measuring what protons ARE. Whether or not gluons and the strong force are necessary to form an object that looks like a proton is a separate point from what protons actually look like in our universe.

To your point on if such an arrangement would be possible or not ignoring the strong force, it would not. The "net-charge" viewed from the +2 quark would be repulsive, resulting in an unstable arrangement of matter, even if you could construct it in an equilibrium state it would be the unstable kind.

nit: gluons aren't electrically charged. They carry strong charge.

In fact gluons have a QCD charge, they just don't have a QED (electric) charge. That QCD charge is basically one color and one anticolor, minus the trace. So there are 8 different basis vectors that define the space for what the charge of a gluon is.

Note that "charge", when used without a qualifier, typically refers to the electric charge (which is the origin of the term). Color charge and weak charge are named "charge" only by analogy - there is no physical mechanism underlying all quantities named "charge" (though there is a mathematical definition of why a physical property can be considered a charge or not).

Even mass itself can be viewed as a "charge" corresponding to the gravitational field.

It looks like the questions about electron's mass at the end of the XIX century.

https://en.wikipedia.org/wiki/Electromagnetic_mass

Some help for you, citizen.

https://m.youtube.com/watch?v=fjFaKD9BuOc

I don't see the relevance of your comment, would you mind explaining?

It's "19th century" in English. Many (all?) Romance languages + a few of the other ones in Europe use Roman numerals for centuries.

I think it's styled "XIX" and not "19" to make it look archaic.

In those languages it is used in all contexts and for all centuries. It's just a formatting convention that is occasionally helpful in e.g. history textbooks.

It's also common to write XXI century, it's not meant to look archaic. It is only a textual convention for centuries.

Thanks, English is not my native language, today I learned something!

It seems almost nobody caught that "Some help for you, citizen" is more or less a quote form the sketch you linked to -- and not an expression of condescension towards the, likely French, person who wrote "XIX".

It would have been nice to get some idea about the relative sizes.

It's really really tiny and rather incredibly small.

https://arxiv.org/abs/2102.00110

" Collaboration data to extract the r.m.s. mass radius of the proton Rm=0.55±0.03 fm. The extracted mass radius is significantly smaller than the charge radius of the proton RC=0.8409±0.0004 fm. "

So 0.55/0.84 = 0.65, i.e. 35% smaller.

Charge radius is 53% bigger, got it.

It's almost as if the charge radius is in miles and the mass radius is in kilometers. It's imperial vs metric all the way down

If charge is surface* effect, and mass a 'volume' effect, you might expect a ratio of 1.0/(0.5^[1/3]).

This is 1.26 (or 0.79). Does not seem to fit experiment, even when fiddling with error bars. OK, so no volume vs surface effect then. *Suppose that both gluon and quarks are really in the exact same region, but that the 'effective' behaviour is "on the surface" for one of them, while "in the whole volume" for the other. In three dimensions, the "effective" radio would differ, in one it would be a factor (0.5)^(1/3) smaller.

So the charge radius is about 150% of the mass radius. Thank you.

For scale, the mass radius of the proton is roughly to one millimeter as one millimeter is to the diameter of the sun.

This is very helpful to understanding the sheer magnitude of the scale. I previously had no concept of the size of a ten thousandth of a femtometer.

(Not a big deal but the .03 is the tolerance not the power.)

I really wish articles about physics or mathematics, especially ones aimed at non-experts like this one, would include the English name or pronunciation of symbols and terms. Not all of us know Greek or advanced mathematics and I need something to say in my head as I read along. How do you say J/ψ meson?

Jay-sigh

It would become redundant very quickly I think. Reading stories about quantum computing feels this way. The first 3 paragraph include the same 'qubits can exists as a 0, 1 or a superposition' over simplification followed by a single paragraph of explanation of the new discovery.

IMO it's much easier for you to answer your specific question with an easy search than it is for article authors to anticipate every question and keep answering it in every article.

Someone use GPT to automatically annotate articles with domain specific knowledge so that I can highlight words/sentences/symbols/formulae/etc. and have it explain it to me.

There was a news site that did something like that, I don't recall which. It was incredibly distracting and I think they started annotating ads in their popovers as well.

This is why it's have to be a separate lyer from the page itself. Otherwise it would become yet more add real estate.

This feels like the type of thing I want human expertise on. GPT can be too inaccurate for something like this. I'd also be concerned it was trained on writings from people that misunderstand the science.

There's already tons of expert written and reviewed content designed to teach science. Go buy any textbook on the subject. You can usually get them very cheaply if you don't mind older editions. Libraries will also have these types of books you can checkout for free. Once you've exhausted information found in textbooks you can start actually reading the scholarly journals these pop-sci articles are written about. Once you've read enough scholarly journals, you might have your own questions that aren't answered yet. Then, you can conduct your own science......

Books are great for looking up quick tidbits of information too. Chapter titles and indexes are great for jumping to relevant information.

I'm not a physicist, so keeping around a good deal of reading material (not to mention seeking out a good explanation) to understand the odd reference or two seems horribly cumbersome.

Google is way lower friction, but even that requires some manual sorting through.

Seems like exactly the thing a good language model would be great at. If they can't do that, where the stakes are low and the task is exactly the domain of LLMs, then I don't see how they'd be useful for anything.

I'm optimizing for accuracy and depth of understanding. Your optimizing for lower friction.

I think I'm optimizing for the correct variables.

You'd just have to define the pronunciation once per article, like we do with acronyms.

Don't know why you're downvoted, this is exactly what they're asking for. You don't have to explain the details of the J/ψ meson, just the first time you write it in the article put "J/ψ meson (J/Psi meson)

For the qubit example, they're not asking for the article to always describe what a qubit is, just if you're going to only write it as "α|0⟩ + β|1⟩" it would be helpful to put (qubit quantum state) the first time you do so in the article.

In the /r/SpaceX subreddit there is an acronym bot that will scan articles or posts for acronyms and make a post that explains the acronyms that it found.

Such content doesn't need to be right in the beginning of an article, it could be linked to or at the bottom of the page.

That's a good example. I found it handy when I was new to the subreddit and it's easily ignored at the bottom of the thread.

The J is pronounced as an English "J" ("jay").

ψ – psi – pronounced "psaai" (as in "top side") or "saai" (as in "side").

from "Pronunciation of the Greek alphabet in English":

https://jakubmarian.com/pronunciation-of-the-greek-alphabet-...

Interesting link, though I question some of those: taw & p'saai—it's not p'sai'onics right?

And I wonder how useful symbols like æ ə ʌ are to people asking how to pronounce Greek.

There is an international, widely-recognized standard alphabet for precisely specifying the pronunciation of things in arbitrary languages, and you are unsure of why it would be useful for people trying to figure out how to pronounce something? Visit the wiki page for each IPA symbol and there will be recordings and examples and you can learn how to read it instead of complaining that people are using the correct tool for the job. The real problem with the linked page is that it is only using IPA half the time...

>There is an international, widely-recognized standard alphabet for precisely specifying the pronunciation of things in arbitrary languages

So...why don't we spell all languages with that alphabet? Think of the increase in efficiency!

My doctor has signs and other notices that you should arrive 15 minutes before your appointment. I asked "why don't you just make all the appointments 15 minutes earlier?"

It's even worse - in English, "psionics" would be normally pronounced something like /saɪˈon.ɪks/.

Generally speaking, the Great Vowel Shift did quite a number on anything originally Latin or Greek.

Play the audiofile here: https://en.wikipedia.org/wiki/Greek_alphabet#Letter_names

On macOS: select letter "ψ" → right-click → "Look Up" → it is pronounced "psi"

The real scourge is articles that use embedded images for the greek symbols or other equations.

You can always retaliate by using the wrong name on purpose: the Jason meson, the Fork meson.

It will drive them crazy.

The point of hypertext and the web is that those definitions and footnotes should be built into the document. In a magazine it would be in a definition box at the side using some sort of grid layout.

> definitions ... should be built into the document

I agree. Scientific research should be for everyone, including people who would like reliable text-to-speech versions of definitions.

I invite you (and the author of the comment you replied to) to take up any of the four suggestions at the bottom of https://info.arxiv.org/about/accessibility.html

This is not surprising given my own (presumably horribly wrong) mental image of what a proton is. Is it surprising given current theoretical models?

I feel that it’s important to point out that a scientific result doesn’t need to be surprising in order to be important and grounding for future work. I agree this aligns with my intuitions (to the extent that I have any for subatomic particles), but it seems important to document and measure these properties.

In your your mental image, was the mass radius necessarily smaller than the charge radius? If so, then your model has survived an empirical challenge. If not, then you have learned something new that was not fully determined or explained by your model.

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