#kelvin-helmholtz
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briery · 4 months ago
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Kelvin-Helmholtz clouds at dawn by Geraint Smith. (Larger).
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fuckyeahfluiddynamics · 6 months ago
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Kelvin-Helmholtz and the Sun
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Kelvin-Helmholtz instabilities (KHI) are a favorite among fluid dynamicists. They resemble the curls of a breaking ocean wave -- not a coincidence, since KHI create those ocean waves to begin with -- and show up in picturesque clouds, Martian lava coils, and Jovian cloud bands. (Image credit: NASA/Johns Hopkins APL/NRL/Guillermo Stenborg and Evangelos Paouris; research credit: E. Paouris et al.; via Gizmodo) Read the full article
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trick or treat! 🧙
OHOHO! Happy Halloween! I could just give you a candy emoji but I prefer a more tangible treat in the form of a really cool cloud!
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This one is called a fluctus! See those little bumps or waves at the top? Those are formed when wind above and below the cloud flows at different speeds. They’re pretty rare, especially an example as clear as this one.
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That wave shape is quite visible, especially towards the right. In my top 10 cloud catches. Now you get to have it too.
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hearts-guided-key · 10 months ago
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buddy the last 12 years of my life has been observations of KH
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merelygifted · 1 year ago
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Spaceweather.com Time Machine - September 27, 2023
VAN GOGH WAVES IN THE MAGNETOSPHERE: When Vincent van Gogh painted "The Starry Night" in 1889, little did he know he was working at the forefront of 21st century astrophysics.  A paper recently published in Nature Communications reveals that the same kind of waves pictured in the famous painting can cause geomagnetic storms on Earth.
Physicists call them "Kelvin Helmholtz waves."  They ripple into existence when streams of gas flow past each other at different velocities.  Van Gogh saw them in high clouds outside the window of his asylum in Saint-Rémy, France.  They also form in space where the solar wind flows around Earth's magnetic field.                             "We have found Kelvin-Helmholtz waves rippling down the flanks of Earth's magnetosphere," says Shiva Kavosi of Embry–Riddle Aeronautical University, lead author of the Nature paper.  "NASA spacecraft are surfing the waves, and directly measuring their properties."
This was first suspected in the 1950s by theoreticians who made mathematical models of solar wind hitting Earth's magnetic field.  However, until recently it was just an idea; there was no proof  the waves existed.  When Kavosi's team looked at data collected by NASA's THEMIS and MMS spacecraft since 2007, they saw clear evidence of Kelvin Helmholtz instabilities.                             "The waves are huge," says Kavosi.  "They are 2 to 6 Earth radii in wavelength and as much as 4 Earth radii in amplitude.”  ...
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travelnew · 2 months ago
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Do these clouds look like they are going to swirl like ocean waves rolling in a pattern?
Shot on 26-09-2024, Thursday in Mumbai.
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0venatrix · 2 months ago
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Saw some wave clouds when I was running the other day.
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geopsych · 1 year ago
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Kelvin Helmholtz clouds look kind of like waves. I saw some very early this morning.
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dontforgetukraine · 12 days ago
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Besides the delightful penguins, Ukrainian polar researchers in Antarctica at Vernadsky Station wanted to share the cloud phenomenon behind them. The wavy clouds are caused by the "Kelvin-Helmholtz instability: when two flows with different densities and speeds meet, turbulence appears at their boundary."
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shithivemaggot · 9 months ago
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feel free to add pictures if u wanna!!!!!!! i love clouds forever and ever and ever
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lhs3020b · 2 months ago
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Morlock Revisionism - The Time Machine, HG Wells
Yes, it's a books post. Haven't had one of these for a while, have we?
By random chance, I happened to find myself re-reading Wells's "The Time Machine" last night. I enjoyed re-visiting it. It's a story that's stood up surprisingly well, considering a) its age and b) its de facto (if not quite de jure) status as the trope-creator for the time travel story.
First off, one interesting aspect is that it does not bother with the modern trope of the time paradox, really, at all. The Time Traveller never considers whether his own actions may affect the future that he discovers in the year 802, 701 (or, indeed, the later ones that he encounters further into the narrative).
As a scientific note, it's worth commenting that the astronomy in the story is deeply dated - the story was written before the discovery of nuclear fusion, so the implicit framework is that the Sun is powered through Kelvin-Helmholtz contraction. It's not. The Sun of 30 million years hence would not display the dramatic changes that the Time Traveller observes. (Also the "large and red" Sun of 30 Million AD should have roasted the Time Traveller to death, as luminosity increases with the surface area of a star. That future shouldn't be frozen, it should be burning!)
One aspect of the narrative that stands out is that the Time Traveller - actually by his own admission! - may be an unreliable narrator. He specifically-notes that his initial theory about the world of 802,701 AD was disproven by events there, and there may be an implication that he's wrong about other conclusions too.
Could he be wrong … about the Morlocks? Are they actually the monsters the narrative paints them as? Let's have a look at what evidence we possess.
First off, most of what we know about the world of 802,701 AD is canonically-speculative in nature. Weena and the Eloi seem to know little-to-nothing about their history and origins. In his time in the deep future, the Traveller finds no interpretable written records. Even his sojourn at the museum offers only a few clues - and as we'll discuss later, some of them may actually conflict with his interpretations. (The presence of the matches and the camphor, in particular, is a bit suspect.)
The Time Traveller is a human being like the rest of us, and he comes from a particular cultural context, namely late-Victorian England. It would be naive to assume that none of this had had an effect on his world-view or how he interprets what he sees. And some of his conclusions … well, they did read to me a bit like what a very stereotypical moustache-twirling Nineteenth Century imperialist might settle on, you know?
Notably, the Traveller severely under-estimates the intelligence of the Morlocks. See the events near the end of the story, where they leave the doors to the sphinx-structure open and the Time Machine itself on display, clearly intending to bait him in. They're able to determine what he's looking for, where he will go to look for it and are able to impute his likely actions. And they're right about all of it. The only reason their plan failed was that they apparently didn't understand the Time Machine's user interface (if they'd noticed the slots for the missing levers…) The Morlocks apparently also have at least some control over the world's remaining machinery, they're presumably the source of what manufactured goods the Eloi have and it's also implied that whatever maintenance occurs aboveground is done by them.
Whatever else they may be, the Morlocks aren't idiots.
Contrast this to the Eloi, who bathe in a dangerous body of water, post no watches at night and make no effort to save one of their own (Weena) when she gets swept away by a stray current! The Eloi also apparently make no effort to maintain the "big houses" in which they reside. They seem to have no writing or material culture, and not even that much in the way of speech; the Traveller specifically-notes the limited character of their language. Their faculties clearly are the more restricted. (It's worth noting that even the Time Traveller himself concedes this point.)
Are the Morlocks the monsters that the Time Traveller sees them as? The narrative clearly wants you to follow his conclusions … but, I do find myself wondering about that. I mean, by his own admission, some of his deductions were false. Could other conclusions be false too, or incomplete?
Let's consider the evidence, or at least the evidence that we have.
First off, the proposed Eloi-phagy. Do we really see an unambiguous depiction of this in the narrative? The closest we get to it is what the Traveller thinks he sees in the Morlock tunnels … except it's only a brief glimpse, while a single match flares, seen from a distance, and even he doesn't sound absolutely-sure of what he thought he saw. He's also in a distressed, confused and distracted state of mind at the time, will not have helped with making clear and factual observations. Did he actually see a butchered Eloi, or could it have been some other animal? For all we know, he just blundered into a Morlock operating theatre while in the middle of surgery! Everything about that would be consistent with the evidence in the text!
It's also worth noting that the Traveller is openly-biased against the Morlocks. He describes them in language which, let's be blunt about it, would be considered unambiguously-racist if applied to a modern human population. He takes one look at the Morlocks and decides they just must be bad 'uns, and everything else seems to flow from that assertion.
(Also, well, "Victorians making wild accusations of cannibalism" is a thing with an extensive and dark history, you know?)
Lastly, the "Eloi as lunch, dinner and elevenses" hypothesis has a bit of an ecological issue. There are far too many Morlocks and not remotely enough Eloi. Eloi are slow to mature, small in stature and lacking in substantial muscle mass. They're just not good cattle. If Weena's accident in the stream is any guide, they're also prone to randomly-dying in very stupid accidents, which could only make farming them even harder. It just doesn't make sense for the Morlocks to be eating them, unless Eloi steak is perhaps a rare delicacy that they consume in small amounts every other year, or something.
As to the Morlock's supposed hostility, well, did they ever actually do anything that bad? They steal the Time Machine, though you could argue that perhaps its owner shouldn't have simply left it lying around. (What a litter bug!) Then the Traveller himself climbs down into their territory without seeking invitation - by our standards, he's literally a tresspasser, so it's probably no wonder the Morlocks were alarmed! And honestly, a lot of their behaviour toward him could be interpreted as more "curious" than "hostile".
Next there's his use of the matches. The Morlocks are clearly harmed by it - the light hurts their eyes, and the fire apparently scares them. (As well it should - if you live in an enclosed underground tunnel, fire is bad news!) From their point of view, he's a weird, gangling, threatening invader from the surface world who suddenly appeared one day, and whose intent is entirely unknown. He shows no concern for their territory and is cavalier in his use of fire. Viewed in that light it's unsurprising that the Morlocks would be uneasy around him!
(On a small side-note, one thing I've wondered about is whether Morlock vision is actually now in the infrared. Their tunnels appear a little too dark even for very sensitive eyes - they're not dim, they're pitch-black! - and the effects of the matches and the later wildfires seem a bit too much even for sensitive eyes. On the other hand, if the Morlocks had evolved to see heat, they wouldn't need artificial lighting - your body would be self-luminous! you are your own reading lamp! -, and it would explain why the matches were so debillitating.)
The Time Traveller also makes no attempt to communicate with the Morlocks, despite their canonically-clear higher level of intelligence. He views them as nothing except a monstrous enemy. It's a very, well, Victorian sort of attitude, isn't it? Of course there's nothing that the moustache-twirling imperialist could ever learn from the lowly and degenerate natives!
There are two further pieces of evidence for the "Morlocks are evil" hypothesis. One is the lack of sick or elderly Eloi. But here the narrative contradicts itself somewhat, as the Traveller also believes that the future world is largely free of pestilence. If dangerous microorganisms had been eradicated, then of course there are not many sick Eloi! As to the lack of elderly ones, well, Weena's river misadventure may offer some clues. The Eloi apparently have little in the way of self-preservation instincts, so one does wonder what the accidental death-rate for them is. It could be high. Perhaps he doesn't see any elderly Eloi because they don't usually make it to a recognisable senescent state, but through accident and misadventure rather than via Morlock celebrity chefs.
The other item of evidence is the Eloi's collective fear of night, and moonless nights in particular. The narrative suggests - though, never actually clearly shows us - that these are the times when Morlocks go small-game hunting. They're apparently able to get in and out of the "big houses" without ever waking up the Eloi and apparently reliably know where to find the Eloi. (Not wanting to victim-blame here, obviously, but the Eloi could consider maybe posting some sentries, and perhaps varying where they sleep … I mean, they're not short of half-abandoned buildings, right?)
But are the Morlocks necessarily the source of the Eloi's fear of the dark? Could it be something else, like perhaps their tendency to have dumb accidents, or randomly getting lost? (Case-in-point re: the latter, on the final night Weena apparently ran off on her own at some point, which is less-than-clever.) As for Weena's unease around the wells, you do have to wonder how many Eloi have managed to have a a "tripped and fell" moment while playing a bit too close to the lip of the well. Weena is actually implied to be one of the smarter Eloi - she shows some curiosity toward the Traveller, and is seemingly willing to consider visiting parts of the outside world - and even she does questionably-smart things like leaning right over the lip of the well while the Traveller climbs down. I mean, this is sounding like the opening-lines of an official report into a bad accident, isn't it?
I will allow that the Morlocks certainly should have paid more attention to health-and-safety in the design of their access-wells, which honestly do seem to basically be death-traps. However, some of this can be ascribed to negligence and laziness rather than actual malice-aforethoughht-level capital-E evil.
The Time Traveller posits that the Eloi and Morlocks emerged from a socio-economic divergence within the original human population, one that eventually became so extreme that it resulted in an actual speciation event. Essentially, the upper and lower classes ended up not merely socially-isolated from each other, but genetically-isolated too. I believe this conclusion more than I believe the Morlock cannibalism allegations, but I still have some problems with it.
1) To produce an actual speciation event, the separation of the social classes would have to persist for an enormous length of time - presumably, at least a few thousand years - and would also have to have been enforced more rigorously than even the most extreme real-world caste system. Is it really plausible that a system like this could have remained stable for the required timescales? That there were no cross-caste romances or "accidental" pregnancies, ever? That all genetic mixing across social boundaries came to a hard, permanent stop? (Contrast this with the real-world behaviour of some Victorian "gentlemen" toward their servants, and, well … yeaaaaah. Eeeek.)
2) Would the economic system implied by all of the above even have been stable in the first place? Can you really erect a non-prous, binary wall between "producers" and "consumers"? In the real world, the two groups are also made up of exactly the same people. (Consider - you have a job, but you also buy stuff. Both are you.) Were there really never any movements for social reform, no civil rights legislation, no uprisings, civil wars, general strikes or any of the other social chaos that usually overwhelm any proposed social planning? The proposed binary divergence of society implies deliberate central organisation dwarfing anything even the Soviet Union attempted, and it's notable that Soviet central planning was ultimately a failure.
The proposed social divide would have been so extreme that I can't see how it could be maintained without a deliberate and organised program of violent enforcement by a strong State, rather than the kind of emergent phenomenon that the Time Traveller seems to think it was. (The only thing the Traveller sees that might - might! - be evidence for this would be the extensive displays of weapons he found while at the ruined museum.)
3) Also, where does agriculture fit into this schema? Agricultural labour is usually considered low social status, but as plants need sunlight, by definition it has to occur aboveground. Is there an aboveground population of farmer-descended Morlocks out there somewhere? In fairness I suppose there could be - the Time Traveller only visits a small area based around what's no longer outer London, after all. (The "modern" Eloi population appears to subsist on edible plants, which are apparently abundant and near-universal in their surroundings. It's suggested that the origins of these plants were artificial, at some point in the past. While these have presumably supplanted agriculture by the year 802,701, nonetheless there must have been a time when they didn't exist, so they don't get us away from the "Morlock workers in the fields" problem.)
4) There is some implication in the text, actually, that the speciation event may have been more recent than the Time Traveller thinks. Consider all the fossil buildings he finds in the area surrounding his arrival-point. The Eloi clearly didn't build them, and given the Morlocks' troubles with daylight, it seems doubtful that they did either. However, someone must have erected these structures, and it can't have been that long ago - most of them still have their roofs! Even allowing for possible super-advanced future construction techniques, I can't see them as being more than a few thousand years old at absolute most, not hundreds of thousands of years. Honestly, they're probably even younger than that. (Significantly, when the Traveller visits the ruined museum, there seems to be an implication that it was restocked not too long ago. When he finds the camphor and the matches, even he notes the oddity that they are still usable!)
So in summary, while the Time Traveller's account of the year 802,701 is entertaining, I don't think I believe his social biology. And actually, this is one of the strengths of this novel - while it suggests a surface-level narrative, it actually is surprisingly open to alternate readings. Who knows, perhaps this was even what Wells intended (he does, after all, take some pains to remind us that the Time Traveller was not right about everything).
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doctor-hopper · 5 months ago
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It always started the same. The dilapidated shrine walls began to shimmer as if by a warmthless heat-haze, and suddenly Kamukura was standing at the wooded edge of a garden instead: mossy statues at the gate, clay tiles dappled with smoky-hued petals, trees whose branches seemed to start and stop wherever they pleased, alien constellations in a black sky peering through the gaps the branches left. Outside it was midwinter, but the breeze here smelled of springtime and decay. Each time Kamukura came here they tried to focus their Analysis on some particular smell or sound, trace it back to some too-young origin and expose the irrational illusion of it all. But the threads never frayed as expected; they stretched back in perfect contiguous causality. It was as if the garden had always been here.
A limbic prickle, at that. Still interesting. (And something weary whispered, For now.)
Up ahead, in the heart of the garden, was a lone sunflower. Taller than last time. Not yet in bloom. But now the wind was teasing its leaves, and with it came a voice, if you could call it that, airy and lively and seeping in from all around.
“. . .And he did get away with it at first, and I was so proud to hear he’d managed to make anything of my counsel. He was so afraid, you know. Especially of me! But you do know fear is so often an impetus for hope. . .” They approached slowly, seemingly unnoticed on light feet, as the voice moved to the fountain and the fountain babbled on. “And yet right on the way home the car exploded, and he died on the highway. Unbelievable, don’t you think so? I never did get to find out what happened to his poor old mother.”
It was a story they had heard before. Pored over, cross-referenced. The entity liked to tell them stories when they came, stories of mortals from long ago—in a stirring of leaves here, a rush of water there, now the creeping of an ant’s legs. In binaries and balances. It liked to make others view the world as it did, as an interconnected machine, every motion an omen of future chaos to shape, or sway with, or become. It was a desperately apophenic lens, the kind born of loneliness dripping down countless human lifetimes and growing more bleak and pungent with each. Kamukura generally felt they had made contact with something too pathetic to call a deity.
“His soul’s actually planted right here, next to yours,” the being said with a spider creeping up the sunflower’s stalk, in lilting lonely reminiscence. “Ah, when he was alive and in full bloom, you should’ve seen him! A tall canola flower from the fields of Nyuta, it must’ve been, earthy and vibrant, just as golden as you’ll be. . .”
The spider may have approximated a dry laugh. Only the barest hint of the canola could still be seen, a withered stem, the flaky gold-dust of dead petals.
(The way the presence spoke of legend and struggle never enticed Kamukura, but the fact every mortal it met was doomed never bothered them, either.)
Sensing a trailing-off, Kamukura finally chose to step forward into the clearing and say, by way of greeting, “You talk to the flowers.”
And with that, an immensely singular focus turned onto Kamukura—like the water and wind stilled to welcome them, like the absence in the air caressed their skin. A disturbance of Kelvin-Helmholtz swirls drawn in negative space. They recognized each other.
“. . .Ah, hello!” it said in a voice just a little more located, a little more aware. “I’m sorry I didn’t see you right away, how uncouth of me! I often don’t know I’m doing it, to be honest. But you know the thing about flowers, they don’t actually understand a word you say. . .and it was all reruns, don’t worry. You’re not missing any crucial points of data. . .and besides, no matter the story I tell, you know how it’ll end by now, right?”
“Hello,” Kamukura said. “I was not worried.”
The anxious breeze relaxed back as it deposited dandelion seeds in their hair. It made them linger for a moment, in the warm wind and the starlight and the distortion they would eventually chart and understand but still did not.
Then, reopening their eyes, they said, “Go on.”
Stars like eyes blinked and rippled. A blue morpho flapped its wings in momentary confusion.
Perhaps that came off too terse, vague. They lay down on the cool clay tiles, looked heavenward, and clarified: “You can go on, if you would like. You may continue the story.”
The vacuum was slow to respond, but then it sprawled and happily continued on, for when you welcomed it to speak it seldom stopped—the terrible fates of its past charges, the observations of millennia. And Kamukura closed their eyes, felt the stones’ embrace, the petals beneath. As they listened their own human form began to melt a little too, shift into something more comfortable.
“It’s lucky my sunflower sprung up when it did,” the falling petals said at one point as Kamukura was curling up and becoming something fluid and feline and many-limbed. “Sunflowers are hardy and beautiful, but their long roots mean they need a lot of room or they won’t turn out quite right. . .”
It was hardly a voice anymore. “. . .I do hope all this empty, fertile soil I’ve got means it’ll stay alive for a while.”
But then the words soon softened and melted out of perception completely, and instead became a voiceless buzzing in the bones, spiriting away all the mirage-matter around them into bending light. When Kamukura was there, it seemed just as happy to be with them in silence.
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fuckyeahfluiddynamics · 2 years ago
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lordofthecoffee · 2 months ago
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What is your favorite natural phenomenon?
I love me a good cloud above all else. I think one of the most unique might be Kelvin-Helmholtz clouds, also known as wave clouds!
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It's been pointed out that this unusual formation bears a striking resemblance to the skies in Starry Night. Whether or not they helped inspire Van Gogh's painting, wave clouds are just ridiculously cool.
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musclem3m0ry · 2 years ago
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Wave-shaped clouds, Kelvin-Helmholtz instability waves, photographed by Rachel Gordon in Wyoming
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ruknowhere · 2 years ago
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Thomas Earle Moore
Kelvin Helmholtz (velocity shear) waves
over the Wellsville Mountains viewed from Logan, Utah.
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