Nothing at that scale is sacred at all

November 26, 2022 6:34 AM

"If you look up quark masses online, you’ll find that the mass of an up quark is around 2 MeV while a down quark is close to 5 MeV. But those same sources will tell you the mass of a proton is a whopping 938 MeV. Our sums are off by about 99 per cent." Dr. Katie Mack explores the weird nature of protons in a short article.
posted by curious nu (28 comments total)

Still reading tfa, but I love this parenthetical aside:

Quarks come in six different types, or ‘flavours’: up, down, charm, strange, top, and bottom (they were named in the 1960s and 70s)

as if ah, that explains it
posted by phooky at 6:45 AM on November 26, 2022 [9 favorites]

"Truth decays into beauty, while beauty soon becomes merely charm. Charm ends up as strangeness, and even that doesn't last, but up and down are forever."
posted by ricochet biscuit at 7:02 AM on November 26, 2022 [10 favorites]

The article mentions that one analysis of the quark-antiquark pairs within the proton has found evidence of charm quarks (with mass larger than the proton itself). Mind blowing.

When I first learned about the heaviest quarks they were named beauty and truth. Then for a long time all I ever heard was bottom and top. In the last year I see more articles mentioning beauty and truth again. Does anyone know why the competing name pairs have the same first letters? Did someone pick out letters to identify the last two quarks and then the names were derived from them? Or did someone decide they didn't like the original names and put out their own competing pair? Which came first?
posted by Emmy Noether at 7:11 AM on November 26, 2022 [3 favorites]

(If you needed more proton goodness for your morning, be sure to read Inside the Proton, the ‘Most Complicated Thing You Could Possibly Imagine’, recently linked in this kliuless thread!)
posted by mittens at 7:13 AM on November 26, 2022 [5 favorites]

For one thing, it’s not quite right to say there are three quarks in a proton. Really, a proton is a roiling quantum sea of an uncountable number of quarks, antiquarks, and gluons, constantly shifting in and out of existence by transforming into one another.

Fuckin' weird, dude.
posted by clawsoon at 7:23 AM on November 26, 2022 [2 favorites]

It's all a conspiracy by physicists to conceal that the universe is a simulation shaped like an onion, riding on the back of 4 octopuses.
posted by Wretch729 at 7:34 AM on November 26, 2022 [3 favorites]

An apocryphal story is that, at a Congressional hearing about funding for particle physics, a Congressperson complained “I don’t see any truth or beauty anywhere in this.” A response was that the labels were arbitrary, and could be anything. But there was already a lot of literature using “t” and “b” as single-letter abbreviations.

Strange quarks (or the “strangeness” quantum number, which probably predates the quark model) got their name from the mesons with the unexpected property of taking way too long to decay than you would predict from just their masses. Strangeness is only changed by the weak interaction, which causes slow decays because it is … weak.

“Charm” is my favorite of the names, because charm was a prediction. The up and down quarks form a “doublet” in the weak interaction. The strange quark is down-like, having charge magnitude 1/3. If the strange quark were a “weak singlet,” there were certain decays that should have been observable, but didn’t seem to occur in experiments (or they occurred, but the rates were suppressed). However, if the strange quark were the down-type member of a second quark doublet, the processes behind these predicted decays would have interference from the up-type partner. This interference would cancel out the amplitude for the decays and suppress them — like a magic charm.
posted by fantabulous timewaster at 7:42 AM on November 26, 2022 [14 favorites]

Dr Katie Mack is probably the best science communicator we have these days, in the mold of Carl Sagan. Her book, The End of Everything, is a great read if you're into this stuff.
posted by rikschell at 7:50 AM on November 26, 2022 [8 favorites]

I know she does a lot of TikTok as well, which I'm not on but maybe someone can link some of that; the clips I've seen are really good.
posted by curious nu at 8:49 AM on November 26, 2022

Macroscale meat monkeys modest mentation maybe too meager for Mesons, MeVs.
posted by lalochezia at 9:04 AM on November 26, 2022 [1 favorite]

Four octopuses? I would assume it was octopuses all the way down.
posted by njohnson23 at 9:42 AM on November 26, 2022 [4 favorites]

(they were named in the 1960s and 70s)
as if ah, that explains it

"It was the 60's/70's" actually does explain a lot of weird things.
posted by Greg_Ace at 1:02 PM on November 26, 2022 [4 favorites]

I mean, given how weird the actual physics operates, I think that giving the particles weird names just helps you start off with the right mindset.
posted by coberh at 2:14 PM on November 26, 2022 [7 favorites]

I feel like the universe is just a supremely elaborate troll. It gets wackier and more unexplainable the closer you look at it.
posted by seanmpuckett at 4:18 PM on November 26, 2022 [3 favorites]

I feel like the universe is just a supremely elaborate troll. It gets wackier and more unexplainable the closer you look at it.

Insert Douglas Adams quote here!
posted by TwoWordReview at 10:13 PM on November 26, 2022 [1 favorite]

Her TED talk is good. End of the universe chat.
posted by jeffburdges at 4:25 AM on November 27, 2022

Top and Bottom used to be Truth and Beauty. The physicists were trying to emphasize the non-physical nature of these distinctions--after the debacle of "spin", which has nothing to do with something actually spinning...
posted by metahacker at 4:56 AM on November 27, 2022

after the debacle of "spin", which has nothing to do with something actually spinning...

I've always assumed that "spin" came from analogy with the fact that if you rotate a magnet around a wire you get straight-line electrical current, and if you rotate electrical current around a magnet via coiled wires you get a straight-line electrical force, so whoever came up with "spin" figured that a spinning electron made sense as a source of magnetism.

Is that how it happened, or did I just make that up from nothing?
posted by clawsoon at 5:42 AM on November 27, 2022

So mass = energy, and the energy mainly comes from springy things and zoomy things. It's crazy to think about how much energy is contained in the universe. Where did that energy come from? Or is it like cryptocurrency, just a fake thing that works until it doesn't?
posted by jabah at 6:49 AM on November 27, 2022 [2 favorites]

Or is it like cryptocurrency, just a fake thing that works until it doesn't?

The other gods are, like, this thing has got to crash sometime. The god who put it together swears that it's going to run forever. A couple of gods who've been through it before say it's going to crash at some point, yes, but a universe can stay irrational longer than you can maintain your doubt.
posted by clawsoon at 7:46 AM on November 27, 2022 [6 favorites]

It's all virtual particles or ponzi schemes all the way down.
posted by jeffburdges at 7:57 AM on November 27, 2022

Hehe, yeah. But I'm really serious. If the universe is a holographic projection, which is one theory, then does what we think of as energy bear any relation to whatever is causing the "program" to play out? In other words, the concept of energy might not exist outside of the program. Our energy—kinetic, resting mass, etc.—may be only as real as the power rings that Sonic picks up—just a construct to represent things happening in the program.
posted by jabah at 8:06 AM on November 27, 2022

All I'm saying is, the gameplay documentation is severely lacking.
posted by Greg_Ace at 9:27 AM on November 27, 2022 [3 favorites]

after the debacle of "spin", which has nothing to do with something actually spinning...

This both is and isn't true. The semiclassical model where the electron is a little ball is wrong, and because the electron isn't a little ball, it doesn't make sense to explain spin as a little ball spinning. A better model is that the electron field is a property of our vacuum, which transforms in a particular way under translations, boosts, and rotations. The way that spinning objects transform under rotations is complicated — and it's identical to the way that the electron field rotates. You're right that this is a symmetry argument, not a physical model where there is some sub-electron "stuff" that flows around some axis. There is no sub-electron "stuff." The electron field is, so far as we know, part of the shape of empty space.

But quantum-mechanical spin really does correspond to macroscopic angular momentum. This is the subject of my favorite underrated classic physics paper: Richard Beth's Mechanical detection and measurement of the angular momentum of light (1936). Beth suspended a half-wave plate from a very thin quartz fiber to make a "torsion pendulum." A half-wave plate is a transparent optical device which reverses the handedness of circularly-polarized light. In the quantum-mechanical picture, a half-wave plate takes photons with spin +ℏ and turns them into photons with spin –ℏ, and vice-versa. Beth sent the polarized light up from the bottom. Above the torsion pendulum was a fixed mirror with another waveplate in front of it, so that the downward-going photons exchanged their angular momentum with the half-wave plate with the same sign. Beth shone a really bright light up (and down again) through the half-wave plate, which absorbed spin 4ℏ from each photon, and reversed the polarization of the incoming light at the resonant frequency of twisting of the quartz fiber.

And it moved. Toggling the state of a tiny polarizer, way outside of a big heavy vacuum chamber, made an optical device an inch across twist back and forth at the end of its glass hair, like a barstool with a bored kid on it. A very, very feeble and patient bored kid: a torque measured in atto-newton-meters, with the twist accumulating over about ten minutes. But still. Trading angular momentum between the electron field and the photon field makes macroscopic objects physically spin.
posted by fantabulous timewaster at 11:21 AM on November 27, 2022 [15 favorites]

But quantum-mechanical spin really does correspond to macroscopic angular momentum.

I stand with Insane Clown Posse.
posted by clawsoon at 12:22 PM on November 27, 2022 [4 favorites]

I would assume it was octopuses all the way down.

Technically yes, but they are cancelled out by the up octopuses.
posted by Meatbomb at 12:33 PM on November 27, 2022 [4 favorites]

a proton is a roiling quantum sea of an uncountable number of quarks, antiquarks, and gluons, constantly shifting in and out of existence by transforming into one another.

See, it’s so simple! My kid tells me that at its root, the entire universe is just mathematical equations describing the motion of subatomic particles. Me, I barely got past the fractions in the 2nd paragraph.

Dr Katie Mack is probably the best science communicator we have these days (…)

She really is, and The End of Everything was fascinating. The fact that she could present that material with almost no math struck me as pretty unique.
posted by Devils Rancher at 3:15 PM on November 27, 2022 [2 favorites]

Metafilter: This both is and isn't true.
posted by Devoidoid at 9:55 AM on November 29, 2022 [2 favorites]