#Physics rambling

[screambirdscreaming]

If you happen to want to know how to put this in technical terms: it's all about fluid mechanics. A fluid is any substance that flows - gasses and liquids are both fluids, and their behavior is described with basically the same set of equations. The difference is that in liquids, interparticle forces have a significant effect - that is, molecules pull on each other - where in gasses, theres no cohesion, force is only transferred between particles when they collide.

Relative to this, solids stick out in introductory physics as having a whole separate set of mathematical rules to describe their behavior. But at some point, you realize that fluid mechanics is actually Real Mechanics, and solid mechanics is just an approximation you can get away with under certain conditions. Those conditions happen to include the range of temperatures, pressures, distances, and timescales usually relevant to solid objects on the surface of the earth - but on a universal scale, it's really a pretty narrow special case.

So: the mantle is a solid, which is behaving as a fluid. It does things we don't think of as solid behaviors, like flow and convect.

I mentioned above what defines liquids and gasses as separate types of fluids. In similar terms, what defines a solid is the ability to maintain internal forces. If you apply force to a gas or liquid, the energy is converted directly into motion - pushing on it causes it to flow. In a solid, when you apply a force, it causes changes to the internal structure, which in effect "store up" the force without transferring it into motion. Think of compressing a spring. However, every solid material has a limit to how much force it can contain this way - past that limit, it shatters, releasing the stored force.

Another critical difference between mantle behavior, and the behavior of solids on the surface, is the constraint of motion. We think of solids as discrete objects moving freely in space. But if you invision a solid "chunk" within the mantle, it's constrained on all sides - forces are being applied in complex 3-dimenional ways, and motion in any direction is constrained by the material already there. Fluid mechanics is structured to account for this 3-dimenional continuity in a way solid mechanics does not.

Lastly, a big picture (ha) perspective on the roll of scale in fluid mechanics. There's an important parameter called Reynold's number - in essence, this is a ratio of the different types of forces that could be acting in a fluid. It's arranged so that all the units cancel out, giving a pure numerical value. (This type of ratio is called a "dimensionless constant", and there are a number of them used in fluid mechanics - but Reynold's number is the most important.) The value of Reynold's number - in particular, whether it is larger or smaller than 1, and how much so - indicates which forces are most significant in a given fluid situation, and can be used to predict how the fluid will behave.

Interestingly, one of the parameters that goes into Reynold's number is just.... length. So in the same exact fluid - the same water! - a whale moves completely different than a microbe. Have you ever seen videos of creatures like tardigrades or daphnea moving through water? they move like they're crawling in thick molasses, almost grabbing the liquid and shoving it out of the way. Just because they're so small! It behaves completely differently.

What's really cool about Reynold's number is that fluid situations with the same Reynold's number will behave similarly, even if their specific traits are very different. For example, viscosity is another factor in Reynold's number. If you increase the viscosity enough to accout for your larger scale, you get back to the same flow regime - that is, you would crawl in molasses like a tardigrade crawls in water! Or consider the similarities between a whirlpool in your bathtub drain and a tornado....

It really does all come back to scale.

It's interesting to me how much people struggle to intuit differences of scale. Like, years of geology training thinking about very large subjects, and I'm only barely managing it around the edges.

The classic one is, of course, the mantle- everybody has this image of the mantle as a sort of molten magma lake that the Earth's crust is floating on. Which is a pedagogically useful thing! Because the intuitions about how liquids work- forming internal currents, hot sections rising, cool sections sinking, all that- are all dynamics native to the Earth's mantle. We mostly talk about the mantle in the context of those currents, and how they drive things like continental drift, and so we tend to have this metaphor in mind of the mantle as a big magma lake.

The catch, of course, is that the mantle is a solid, not magma. It's just that at very large scales, the distinction between solids and liquids is... squirrely.

When cornered on this, a geologist will tell you that the mantle is 'ductile'. But that's a lie of omission. Because it's not that the mantle is a metal like gold or iron, what we usually think of when we talk about ductility. You couldn't hammer mantle-matter in to horseshoes or nails on an anvil. It's just a rock, really. Peridotite. Chemically it's got a lot of metal atoms in it, which helps, but if you whack a chunk of it with a hammer you can expect about the same thing to happen as if you whacked a chunk of concrete. Really, it's just that any and every rock is made of tons and tons of microcrystal structures all bound together, and the boundaries between these microcrystals can shift under enormous pressure on very slow timescales; when the scope of your question gets big enough, those bonds become weak in a relative sense, and it becomes more useful to think of a rock as more like a pile of gravel where the pebbles can shift and flow around one another.

The blunt fact is, on very large scales of space and of time, almost everything other than perfect crystals start to act kind of like a liquid- and a lot of those do as well. When I made a study of very old Martian craters, I got used to 'eyeballing' the age based on how much the crater had subsided, almost exactly like the ways that ripples in the surface of water gradually subside over time when you throw a rock in to a lake. Just, you know. Slower.

But at the same time, these things are more fragile than you'd believe, and can shatter like glass. The surface of the Earth is like this, too. Absent the kind of overpressures that make the mantle flow like it does, Earth's crust is still tremendously weak relative to many of the planet-scale forces to which it is subject- I was surprised, once, when a professor offhandedly described the crust as having a tensile strength of 'basically zero;' they really thought of the surface as a delicate filigreed bubble of glass that formed like a thin shell, almost too thin to mention, on the outside of a water droplet. On human scales, liquid is the thing that flows, and solid is the thing that breaks. But once stuff gets big or slow or both, the distinction between a solid and a liquid is more that a liquid is the thing that doesn't shatter when it flows. And it all gets really, really vague, which I suppose you'd expect when you get this far outside the contexts in which our languages were crafted.

[owlbelly]

so. i understand where the sentiment "listening to an audiobook is the same thing as reading the book" is coming from - i mean, yes, the bottom line is you are taking in the same words in what is possibly a more accessible (or maybe just more enjoyable) format for you! and i'm 100% in agreement that "book snobs" who say "no you didn't really read it" if you listened to the audiobook are full of shit. ofc you should engage with stories in whatever way works for you, there is no moral or intellectual superiority to reading words off a page vs. listening to them

but it also is different? an audiobook is a performance. choices a narrator makes about line readings can drastically influence the meaning of the lines. even just different voices, accents, etc. - there are creative choices being made by the person delivering the words to you, and that affects your experience of the story in a different way than if you were making those choices in your own head. it might even change the way you visualize what's going on!

this isn't a bad thing it's just An Actual Thing & i think it's worth talking about. it rubs me the wrong way when people act like accommodations (and for many people audiobooks are an accommodation) always result in a completely identical experience, or even that they should, & if you suggest that people accessing media in different ways are having different experiences it's somehow ableist

anyway on rare occasions i really enjoy audiobooks but mostly they are much less accessible to me than words on a page (i need to be able to reread, flip back and forth, go at my own pace) & i also just really strongly prefer to encounter a text on my own before hearing someone else's performance of it, if possible! again i don't think it's "better" to read a physical book i just think it is a Distinct form of experiencing a story & acting like the two things are entirely the same is sort of doing a disservice to both

[gingermintpepper]

I think, perhaps one of the funniest things to come from EPIC popularising the Odyssey is that now a ton of people think Poseidon wanted to kill Odysseus.

In the Odyssey, Poseidon has no intention of killing Odysseus. In fact, part of the whole reason Zeus lets Poseidon do whatever he wants even though he thinks Odysseus is rad and should get to kiss his wife is explicitly because Poseidon had no intentions of killing Odysseus. Poseidon wanted to pay back the suffering/inconvenience blinding Polyphemus would have caused. It's a really abstract thing tbh. How do you pay back someone permanently disabling your son? Poseidon's solution was just to amputate Odysseus from his other half; i.e. Penelope. The end game was never murder, it was always an endurance race.

(Od. Book 1: Zeus reassuring Athena that he is not, in fact, a part of Odysseus Hater-Nation. Trans. Robert Fagles)

Also, for those wondering if there's any sort of in text reason for why Poseidon wasn't around in God Games - at the time in the Odyssey when Athena petitions Zeus to let Odysseus leave Calypso's island, Poseidon was -checks notes- on vacation in Ethiopia. Yep. He left to Ethiopia for a festival and thusly was very much absent for Athena's whole "please let Ody go? Please? 🥺" request.

(Od. Book 1: While Odysseus was suffering, Poseidon went to party in the east)

I am begging y'all to read the Odyssey. It's a comedy for everyone except Odysseus and Penelope who are, in fact, suffering 24/7 365.

[lazylittledragon]

y'know every time i feel guilty about bothering someone by singing along when i'm listening to music, i just remember that i have to tolerate my dirtbag brother screaming at his ps5 for hours every day so listening to muffled off-key fall out boy is probably preferable

[lotus-lost-n-found]

Some Batfam Headcanons because the brain never stops;

Jason hates being called "Bruce's Son". But he hates it more when hes called "One of Wayne's Orphans/Wayne's child" because fuck you I'm his son-! wait no--

With the exception of Damian, they rarely refer to Bruce as "Dad/Father". Either it didn't occur to them/didn't see the need to/thought it would be strange. But when Dick/Jason/Tim/Cass are tired or injured it might slip out. And Bruce might just crumble a bit at it

Doesn't mean they don't say it to their siblings when Bruce is out of Earshot.

"Dad said you couldn't." "What do you mean Dad said I couldn't use that mug? It's my mug!" "You snooze you lose Timmy Boy-" "Jason don't be an asshole-"

That being said Bruce says "son/daughter/child" at every available opportunity he can after he knows that they have acclimated enough that they wouldn't be uncomfortable/know they can tell Bruce that they don't want to be called that.

First time Bruce called Dick "son" in a way that meant "You are my kid" and not in a "This police officer just called me son with a brow furrow" way Dick grinned and carried on with the conversation. Later he wondered if his dad wouldn't like someone else calling him Son; but Dick thinks about the life he was given because of Bruce and thinks maybe his dad wouldn't mind.

Calling Jason "son" is a hit or miss situation, even before he died. The first time it happened he was confused, he didnt think that was the relationship they had and it made everything change for him. He got frustrated--not angry--with himself and Bruce at this sudden emotional turmoil. Wasn't he just the kid Bruce picked up in an alleyway? Wasn't he just some street rat in bright Robin clothing? (He lets himself believe that he can be Bruce's son. If for only a little while).

Tim cries after Bruce is out of earshot, it would've been a year or so after his parents died and he was adopted. He didn't think he could have been wanted like that again. Even if you think the Drake's had A+ Parenting or not, I don't think he would have gotten a lot of confirmation of being wanted otherwise.

Cass smiles, emotions carefully concealed under her expression. She's grateful she found Bruce and he doesn't mention it if she leans a bit closer in a request for closeness.

Damian doesn't expect anything less, he only appears satisfied. But also relieved that he has gotten the confirmation that yes, Bruce wants and accepts him.

EDIT 10/11; hiii, i have added Duke, Steph & a Bonus in a reblog you can find on the same blog under my 'batfamily headcanons' / 'sore rambles' tag. have fun :)

[starry-bi-sky]

on a completely separate note; shizun luo binghe with a disciple shen yuan who fell into the abyss??? *thinks about LBH canonically stealing SQQ's corpse for 5 years* he'd hallucinate i think. like, like visual and audial hallucinations.

Keeps thinking he's seeing SQQ in the corner of his eyes, or wandering between the trees, amongst a group of disciples. Thinks he hears him calling for him, but its just the wind or another disciple.

Gets Xiu Ya reforged but patently fucking refuses to make a sword mound. Because his disciple Is Not Dead :))) There was No Body. He's Not Dead. And If You keep Insisting That He Is, He's Gonna Skewer You :). He's holding onto Xiu Ya so he can return his most favored disciple's sword when he returns. It's on his hip right next to Zheng Yang where it's supposed to be.

Also this motherfucker?? does not sleep btw. He has the image of SQQ, wide eyed and hysterical and standing at the mouth of the abyss burned into his fucking eyelids. Can't use the dreamscape to escape it either because he keeps trying to save him and either he does and it's an incredibly cruel trick to wake up to, or he doesn't and he gets his heart broken in several different pieces again.

There is no convincing this man that Shen Qingqiu is dead. Absolutely nothing at all. He is buried so deep in denial that moles would be jealous of how deep he is. He keeps making tea for two in the bamboo house only to remember that it's just him. SQQ's fans are hiding everywhere, little reminders of his presence. He goes to wake up SQQ on the mornings he sleeps in-- only to find the room empty.

[beetleandfox]

I love how unsanitized The Terror feels. Like there’s grime everywhere. You can tell those men smell bad. When they do surgery you can hear the bone being cut, when they get sick they look genuinely ill. The main character’s actor even has pockmarks, he LOOKS like he could be from the 1800s! And idk, I think it’s cool that we’re so aware of the characters’ carnal desires. They’re hungry, thirsty, freezing, etc, and it is so obvious that they have a body with needs!!

I think this also accounts for how horny the show feels, even though everyone is bundled up 90% of the time and there are no real romantic subplots. Besides the fact that it’s a very carnal show, it just has the intimacy and grime of true horniness. Is this thing on

[jemineye]

i cant stress this enough, disabled people know their own limits. i fucking promise you. we are not being lazy or jerks because we won't do something YOU want us to do or something YOU THINK will make us feel better. it wont. stop.

[sickly-sapphic]

this disability pride month you can help disabled people by continuing to mask up, using appropriate masks (KN95 or N95) and appropriate masking technique (wash your hands before and after putting it on, don't touch the front, make sure there's no gaping) 🫧

[lucabyte]

Different standards

[secretarysong]

BEEP BEEP!!!! Mayday delivery!! 🧨🧨🔥🔥

not exactly sure what date but somewhere within This Week! marks my first 1 year of being an actual NSR fan (and my subsequent upwards spiral since then) so to celebrate i am throwing a BIG PARTY in FESTIVAL PLAZA and ALL OF YOU ARE INVITED!!!!🤑🤑🤑🤑 Just kidding. there is no party. BUT! below the Keep Reading i will share some of my earliest (and somewhat crude) drawings of mayday (and a bit of zuke). it feels like it's been ages since then...

transitional phase....... these range from like november 2023 to march 2024 i believe? in no particular order

fun fact about me; i used to be a Strictly total drama fanartist and i preferred to draw pretty on-model to the very heavily stylized characters in the show. it was kind of difficult going from... that (Hardly ever venturing out of my comfort zone) to the oh-so-scary and intimidating world of No Straight Roads. in order to make art i'd be happy with, i'd have to inevitably get used to THREE-DIMENSIONAL SPAACE and... *gulp...* Dy.. Dy... DYNAMIC ANGLES!!!!!!!

love is one hell of a motivator however. and i love this schtewpid game and i love its world and characters and most of all i love MAYDAY!!! and here i am Today! obviously i still have a long looonngg way to go and much to learn but i've still come pretty far. and i'm pretty proud of myself! 🐊🐊🐊

[t-a-c]

the Touhou fandom won't stop creating new memes. TF2 is one of the most active games on Steam. Scott Pilgrim is one of the big trending things. people can't get enough of the cute guitar girl anime 2009 is eternal

[infamous-if]

hoping my power doesn't go out once milton fully arrives so i can work on these POVs in peace and actually have something to do because your girl foolishly has only (1) physical book to read in case of a power outage and i am currently not liking it…the universe is determined to stop me from DNFing

anyway august and sev's povs should be up soon if all goes according to plan lmao!

hope everyone stays safe and if you're hunkering down, good luck <3

[chronicowboy]

how am i just now realising eddie had a COWBOY painting on his bedroom wall...

[the-crystal-femmes]

Us when identity policers

[thepisserrrrrr]

as an ND able-bodied person, i just wanna say that cpunks are NOT doing anything wrong by not allowing us in their community. its completely okay and im actually very very happy that physically disabled people finally have their own space where they dont have to deal with ableism toward them all the time

able-bodied NDs have it made in this sense. we have TWO communities! we have neuropunk and madpunk, and you can go on any social media platform and easily find hundreds of other NDs on there along with little communities and shit. but physically disabled people dont have it that easy. when they DO find one that isnt just about ND people, it's still full of ableism. i've seen it myself and it makes me sick

so physically disabled people decided to make their OWN community. just for them. no one else. then THATS when able-bodied NDs start getting pissy and call them ableist when they were basically doing the exact same shit before.

you can handle not being allowed in one community. theres two more you can be part of just fine

if youre an able-bodied ND who sees yourself in any of this, maybe you should stop and look at yourself. make some improvements

to the cpunk community, dont let people like this tear you down. stand your ground, push these people out. you deserve your OWN safe space and no one will take that from you