Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Inside the proton, the ‘most complicated thing you could possibly imagine’

quantamagazine.org

Post reply on HN
Print view View original

181–190 of 591 posts

Re: Inside the proton, the ‘most complicated thing you could possibly imagine’

#181

Post by bobbylarrybobby »

jiggawatts wrote: post #94
blackhaj7 wrote: post #49

I have no doubt quantum physicists know what they are talking about but when I read stuff like: “changes its appearance depending on how it is probed" "you can’t even imagine how complicated it is" "the proton contains traces of particles called charm quarks that are heavier than the proton itself" I always think it is the kind of excuse a schoolkid would give their teachers for their calculations being wrong

Quantum mechanics is a religion with mathematics instead of just holy texts. Several studies have been done into whether practicing theoretical physicists using QM in their everyday work agree on the most basic tenets of the field. Spoiler: they disagree on every aspect while simultaneously assuming that their opinions are correct and that everyone else agrees with them. That’s how religions work, not how science doe…

All of the disagreements in QM are metaphysical: what is measurement, how does a wavefunction collapse, what is reality, etc. Everyone agrees on the math that leads to predictions (which have been matched by observation to an almost perfect degree). And I'd imagine that just about everyone also agrees that it's incredibly unintuitive. But the math works.

Re: Inside the proton, the ‘most complicated thing you could possibly imagine’

#182

Post by arter »

A question that came to me as I was reading the article was - what makes us think that all protons are the same ? Can it be that instead of every proton having a superposition of 3 quarks, or 5 quarks or more, we have some protons with 3 and others with 5 ? How did they verify that this is not a case ? I am assuming they never managed to isolate 1 proton and test it twice.

Re: Inside the proton, the ‘most complicated thing you could possibly imagine’

#183

Post by jacquesm »

DiscourseFan wrote: post #145
edgyquant wrote: post #131

Earlier quoted context omitted.

Because they are mathematical models built to describe a thing and thus their entire purpose as a concept is to add up “neatly”

I'm getting very strong "angels on a pinhead" vibes from this

With the minute difference that we do not have experimental validation for Angels dancing on a pinhead whereas there is a massive amount of experimental validation for the standard model.

Re: Inside the proton, the ‘most complicated thing you could possibly imagine’

#184

Post by wruza »

p1mrx wrote: post #175
wruza wrote: post #137

Earlier quoted context omitted.

How about the universe that quantum-emerges in a truly random sequence of quasistates which disintegrate immediately, and once in a while it happens to be the state that includes "your" "memory" of the previous ones. I mean chronologically from your perspective, they don't even have to appear in order. By an amazing coincidence, this particular "frameset" is logically consistent and pretty boring, so you have no inte…

If perception emerged directly from chaos like that, wouldn't you expect to perceive chaos, rather than a rich world built upon billions of years of evolutionary history?

I don't think there's "rather than" in this idea. You surely will perceive every state that is perceivable at all, but time and continuity have no meaning here. Specific history is just an image that always exists only for an instant. Eventually that universe might enumerate all states, so they'd form all sorts of sequences, but that's coincidental.

Re: Inside the proton, the ‘most complicated thing you could possibly imagine’

#185

Post by snarfy »

Balgair wrote: post #126
rolph wrote: post #105

Earlier quoted context omitted.

a proton, in the simplist version, is made of 3 quarks. two up quarks one down quark. down qwark is -1/3 e ; up quark is +2/3 e. they sum up to +1 e. neutrons are the opposite made of 3 quarks. two down quarks one up quark. and sum to 0e the unitary quantity is a conveinience. 1 e = 1.602176634×10−19 coulombs,

Yes, yes, I also understand this. But why are they in units of 1/3(e). Why are down quarks not -0.398390847895...(e) and up quarks not +0.6234098129034809234...(e). Why do they add up so damn neatly?

My layman understanding is that charge is not fundamental. It derives from something called weak hypercharge.

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

Re: Inside the proton, the ‘most complicated thing you could possibly imagine’

#186

Post by rainbowzootsuit »

AnimalMuppet wrote: post #89
mkw5053 wrote: post #25

Earlier quoted context omitted.

First, I am not a physicist. That said, he's my attempt at an answer that satisfies me: Part of the reason is charge quantization. Neither could be some fractional charge. We also observe charge conservation and electromagnetic force laws as described by quantum electrodynamics (QED). These necessitate that the electron and proton charges be precisely balanced for the universe to function as it does.

But in fact, quarks are fractionally charged: +2/3 and -1/3. For this to work, there have to be as many quarks in the proton as the denominator of the quark charge fraction. (And what mechanism forces that?) And why should the charges on quarks be some nice low-number fraction of the charge on the electron? Why not sqrt(3) or something?

I think this is more of a historical artifact rather than a fundamental measurement. In the Millikan oil drop experiment he was able to measure quantized units of charge by stripping a single electron from a drop [1], so much later when quarks are figured out they are proportional to the base unit of charge.

This is similar to how Ben Franklin, having no knowledge of elementary particles, defined the positive and negative polarity of electricity, so we have "electron holes" flowing from the positive end of a battery to the negative end in "conventional current." [2]

Edit to add: the electron's non-even charge numbers comes into light when you see that the charge is 1.602176634×10−19 Coulombs, where 1C/second= 1 ampere. If we were trying to come up with the definition of an ampere with nice base 10 numbers of electrons this would be much different.

[1] https://en.m.wikipedia.org/wiki/Oil_drop_experiment

[2] https://eng.libretexts.org/Bookshelves/Electrical_Engineerin...

Re: Inside the proton, the ‘most complicated thing you could possibly imagine’

#187

Post by andrewflnr »

neuromanser wrote: post #121
mcmoor wrote: post #69

Earlier quoted context omitted.

It's interesting that semiconductor engineers have to directly wrestle with the magic that's quantum tunneling. This theory is really not just a theory.

You mean it's not just a hypothesis. I would really, really expect users of this site to know the difference.

Users of this site who pay attention to how science is actually practiced, and not the oversimplified cartoon version they teach us in school, know that the boundary between a "theory" and a "hypothesis" is rather blurry. For instance, have you ever noticed how it's called "string theory" despite having no real evidence for it? Have you ever heard anyone, let alone a real scientist, complain about this nomenclature?

Early theories and fleshed-out hypotheses overlap a lot. There's no sharp transition from one to the other.

Re: Inside the proton, the ‘most complicated thing you could possibly imagine’

#188

Post by idiotsecant »

edgyquant wrote: post #131
Balgair wrote: post #126

Earlier quoted context omitted.

Yes, yes, I also understand this. But why are they in units of 1/3(e). Why are down quarks not -0.398390847895...(e) and up quarks not +0.6234098129034809234...(e). Why do they add up so damn neatly?

Because they are mathematical models built to describe a thing and thus their entire purpose as a concept is to add up “neatly”

No, these are models with simple, testable properties. You can't wave away the fundamental charges as something somebody made up to make the models nice, conspiracy theories don't work when there is a simply observable truth.

Re: Inside the proton, the ‘most complicated thing you could possibly imagine’

#189

Post by exmadscientist »

Gravityloss wrote: post #132
AnimalMuppet wrote: post #89

Earlier quoted context omitted.

But in fact, quarks are fractionally charged: +2/3 and -1/3. For this to work, there have to be as many quarks in the proton as the denominator of the quark charge fraction. (And what mechanism forces that?) And why should the charges on quarks be some nice low-number fraction of the charge on the electron? Why not sqrt(3) or something?

There exist "stable" exotic particles of that have non ordinary amounts of lower level quarks. https://www.symmetrymagazine.org/article/lhcb-discovers-long... Maybe they might have non integer charge.

In QCD, they cannot. All Feynman diagram vertices involved in producing these things (in fact all QCD vertices period) only deal in integer charge units and never leave fractional charges floating around.

Re: Inside the proton, the ‘most complicated thing you could possibly imagine’

#190

Post by rapjr9 »

When I read articles like this I can't help but think that if they were probing apples with a hammer, using stronger and stronger hammer blows, they would conclude that apples are flat and mushy. With stronger hammer blows they'd find the apples are paper thin and hot. How do they know when doing these collision experiments that some of the resulting particles are not popping out of the CMB and aren't actually in the things being collided at all?
Post reply on HN