#not my field

[o-craven-canto]

(Bédard 2024, "A gradual Proterozoic transition from an unstable stagnant lid to the modern plate tectonic system"; also see Piper 2013, "A planetary perspective on Earth evolution: Lid Tectonics before Plate Tectonics")

This article argues that the plate tectonics as we know it now (crust divided into moving lithospheric plates, with destruction of lithosphere by subduction at convergent plate boundaries and production of new lithosphere at divergent boundaries) is comparatively recent. It would have begun in the Proterozoic eon, from 2 billion ago, or possibly as recently as 1 billion years ago. Before then, Earth's crust would have been mostly static, with heat released in mega-eruptions every 100 million years or so, as must have happened on early Venus.

(Ga = billion years before present)

This is good news for xenobiology: AFAIK, plate tectonics is only known on Earth, and important for life in recycling crustal minerals and providing many important selective pressures. If this case is correct, however, life can exist and become relatively complex (unicellular eukaryotes and the macroscopic Francevillian biota) even in absence of plate tectonics.

[gargelyfloof118]

Asparagus growing out of the ground!

My mother recently asked me for pictures of how asparagus grows and my friend allowed me be paparazzi at her farm! I snapped a picture of the picking rigs too. It has a little engine right in the middle to help it crawl along. The workers will use their feet to help steer it.

When the asparagus season is over, it will branch and 'fern' out. The farmers will then Mow it to a stubble field in late fall and then mow it all the way down to the ground in early spring to start the process over again.

Season lasts about two months and they can pick on the same field about twice a day if the weather is warm enough. It grows so fast!

[bitchfitch]

writing advice for characters with a missing eye: dear God does losing an eyes function fuck up your neck. Ever since mine crapped out I've been slowly and unconsciously shifting towards holding my head at an angle to put the good eye closer to the center. and human necks. are not meant to accommodate that sorta thing.

[therealstacyfakename]

Something about the pacing and editing of this bit when he just kept saying 3 really scratched my brain

[great-and-small]

Apparently the local university’s undergraduate entomology course sends students to catch insect specimens at the same place I like to go birdwatching, which explains why I saw three enormous frat looking dudes with tiny bug nets and overheard one emphatically say “bro BRO I told you we already have enough lepidopterans”

[technovillain]

i come from the universe where everything is the same except disney heroines get like an ounce of their fathers' obviously dominant genes and their clothes are like 80% more historically accurate. it's beautiful here.

[2] [3]

[duckysprouts]

brain chemistry changed from no longer you and monster btw

[anthropoetics]

why must we network. isn't my kindness and willingness to try to be better everyday enough?

[notherpuppet]

Redraw of this scene from The Nanny hehehe

[proxythe]

as long as ur my partner in time >_>

[littlemizzlinguistics]

Studying linguistics is actually so wonderful because when you explain youth slang to older professors, instead of complaining about how "your generation can't speak right/ you're butchering the language" they light up and go “really? That’s so wonderful! What an innovative construction! Isn't language wonderful?"

[o-craven-canto]

Gradient dissipation and life

Found another very interesting paper, on the physics of life. (Branscomb, E., Biancalani, T., Goldenfeld, N., & Russell, M. 2017, Escapement mechanisms and the conversion of disequilibria; the engines of creation)

Living organisms have to maintain a highly complex internal environment that, left to itself, would degrade over time. Common wisdom is that organisms do so by consuming energy (in sunlight, food, etc.) The paper makes the point that this is not true -- after all, energy is conserved and cannot be consumed or destroyed, only transferred around. What organisms require is "negative entropy", as Schrodinger put it in 1944, or destroying disequilibria, in the wording of Branscomb et al. Now, I'll admit most of the actual explanation goes way above my head. Thankfully, the paper has pictures.

In the universe, there are many gradients or disequilibria, in which a system contains a great unbalance of some quantity: temperature, pressure, salinity, voltage, etc. These gradients always tend to dissipate spontaneously, until the quantity has spread out evenly. If you put hot and cold objects in a box, heat will flow from hot to cold until all is at the same temperature; salt dissolved in a glass of water will spread evenly through its volume; the sun will send out radiation until the pressure at its core is no higher than the surrounding space; and so on. This is the increase of entropy prescribed by thermodynamics (which is often popularized as "increase in disorder", although it includes e.g. crystal growth).

Here's such a gradient. The little balls may represent gas pressure, or salts in a solution, or anything else. Pressure is high on one side of the membrane, and low on the other. If the membrane allows passage, then even completely random motion will produce a net flow of particles from high to low pressure until the gradient is gone and pressure is equalized.

Now here are little gates that flip between states (closed on left vs. closed on right). They do not produce the flow of particles: it proceeds in the same direction as before. However, they can control its rate, by dividing it into discrete little movements. Actually, it's the particles that have some control on the gates: they open on the high-pressure side when empty, and open on the low-pressure side when full.

An organism also has to keep a very steep gradient between itself and its environment. Now, creation of gradients does not occur spontaneously; air in a room isn't going to concentrate into a high-pressure corner all by itself. However, it's possible to build a new gradient if the reaction is coupled with the destruction of another. For example, unbound water flows downhill until it is all at sea level. But sunlight can cause it to evaporate and precipitate back at higher altitude. This is the creation of a new gradient (water at different levels) coupled with the destruction of a greater one (pressure in the Sun's core). Then we can destroy that gradient (let water flow down through a turbine) to create yet another (charged batteries).

There's two conditions to that: 1) the net overall effect must be destruction of gradients over creation: at the end, the universe must contain a little less gradient than before in total (= entropy always increases in isolated systems). And 2) the reactions must be coupled so that the spontaneous gradient destruction can only occur if it helps the non-spontaneous gradient creation (e.g. water is only allowed through the turbine if it makes its rotor spin).

So here's the interesting stuff. In the blue room above, there is a gradient of pressure that can be destroyed. In the red room below, there is none: particle flow in either direction would create a gradient. This would not occur on its own. But now let's couple the barrier gates: the one on bottom opens on the left or right exactly when the one on top does so. Pressure in the blue room only gets an outlet if it creates pressure in the red room; though note that the created gradient must be smaller than the destroyed one.

Enzymes in living cells act like the little gates. They allow spontaneous gradient dissipation, through a series of discrete state changes, in exchange for creating new ones. Like a ratchet, they stop backflow that would dissipate the new forming gradient. Hower, they don't make non-spontaneous reactions occur: enzymes are catalysts, they can widen or lubricate the gate to ease a flow that was already going to occur.

We can then refine the process, by building up the new gradient in multiple steps.

And if the outlet for gradient dissipation is a machine (represented here by the gear), we can use the increase of entropy to do actual mechanical work.

For a practical example, here's how a mitochondrion "makes energy". Dismantling of glucose into carbon dioxide in the citric acid cycle (A) has left around some high-energy electrons, which are carried by a molecule called NADH (B). This molecule gives up its electrons to a series of enzymes inserted in the membrane (C), so that the electrons may ultimately flow into the warm embrace of oxygen, which is reduced to water (D). (The electron-affinity of oxygen drives the flow: this is why we need oxygen to live.) This too is the dissipation of a gradient: the electron bond energy in carbon dioxide and water are much more level than those of glucose and oxygen. Changes in conformation of the enzymes (labelled I, III, and IV), much like the flipping of the gate in the red room, pumps protons (indicated as H+) into the space outside (E). This creates a gradient in proton concentration across the membrane. Protons are given only one outlet to dissipate this gradient: flowing back through the ATP synthase (F). Exactly like water flowing downhill through a turbin, the flow of protons is exploited to build one final gradient, by synthesizing ATP, the universal "energy currency" (actually the "gradient building currency") of the cell.

[crabhousecrafting]

hermitcraft “fun facts” are so hilarious because they’re always like

etho created the hopper clock! ⏰

xisuma created bedwars! 🛏️

cubfan is a published astrophysicist.

[noctilin]

in eiland waiting room and suffering

[retquits]

meeting valen 🤧

[ookikufurikabutte]

my take on human caldarus while i sit in the waiting room.

idk how to explain but he feels very rune factory 4 leon to me <3