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July 19

Magnesium Sulphate

Last year, I bought some magnesium sulphate paste for removing splinters. Now it has separated into a hard, crystalline, mass and some clear liquid resembling glycerine. Is there any way of returning it to a paste or do I have to buy some more? Alansplodge (talk) 10:52, 19 July 2023 (UTC)[reply]

Magnesium Sulphate Paste is literally just magnesium sulphate and glycerine, with a small amount of phenol. Here is a typical ingredient list, but I've checked several others, and that's what it is. It hasn't "gone off" or anything, the magnesium sulphate has just settled out of the suspension (which is what a "paste" generally is, from a chemistry point of view). Depending on how much effort you want to put in (vis a vis the cost of just buying more) you should be able to just remix the ingredients. --Jayron 32 11:36, 19 July 2023 (UTC)[reply]

Thanks Jayron. The problem is that the solid part has the consistency of concrete and has so far resisted my remixing efforts. Would heating it help? Alansplodge (talk) 11:42, 19 July 2023 (UTC)[reply]

Possibly, gentle heating would help. IIRC, magnesium sulphate is usually a fairly well-hydrated crystal, and gentle heating may help release some of the "waters of hydration", possibly enough to dissolve it slightly and help break it up (see Epsom salt). If that doesn't work, perhaps something like a kitchen blender or food processor may help? If you don't have anything like that, I'm at a loss. --Jayron 32 11:48, 19 July 2023 (UTC)[reply]

Bingo! I pinged it in the microwave - worked like a charm. Many thanks. Alansplodge (talk) 12:50, 19 July 2023 (UTC)[reply]

Resolved

Evolution of birds from dinosaurs

As far as I'm aware, the current scientific consensus is that modern birds evolved from the tiny number of dinosaurs that survived the Chicxulub impact. However, it is somewhat unclear to me - did birds, as we know them now exist *before* the meteorite hit, or did they emerge later? At school, I was taught that all mammals evolved from a small number of tiny rat-like creatures (in terms of body form) that somehow survived the apocalypse - and that all birds evolved from a small number of tiny velociraptor-like creatures (in terms of body form) that somehow survived the apocalypse - but I think from my readings that this is inaccurate now? Iloveparrots (talk) 21:50, 19 July 2023 (UTC)[reply]

See the related articles Origin of birds and Evolution of birds. The evolutionary events that gave rise to the early birds within maniraptoran theropods and the origin of bird flight are disputed questions. Philvoids (talk) 22:35, 19 July 2023 (UTC)[reply]

Today's birds form the class Aves, which is a subset of the clade Ornithurae. This clade also includes two extinct genera of bird-like reptilians. --Lambiam 22:39, 19 July 2023 (UTC)[reply]

Birds evolved before the end-Cretaceous extinction event, although exactly how much before depends on how you define "birds". If "birds" means "the most recent common ancestor of all living birds and all of it descendants", then birds first appeared some time in the Cretaceous. If "bird" is defined more broadly to include Archaeopteryx, then they evolved in the Jurassic. Iapetus (talk) 12:30, 20 July 2023 (UTC)[reply]

(edit conflict) To build on the excellent answers above, and to directly answer the question "did birds, as we know them now exist *before* the meteorite hit, or did they emerge later?" four clades of birds are believed to have existed prior to the Cretaceous–Paleogene extinction event that killed off the non-avian dinosaurs, which is to say that the "most recent common ancestor" of all modern birds predates the extinction event by some time. Roughly speaking, those clades are the "big fat running birds" of the ostrich-emu-cassowary type, "waterfowl" like ducks and geese, "groundfowl" like chickens and turkeys and peafowl, and "everything else". It is thought that these divisions among birds (or bird-like dinosaurs or whatever term you wish to use) existed prior to the extinction event. You can find a partial list of such birds at Category:Mesozoic birds. Also as noted, the exact nature of mesozoic bird evolution is unresolved; there are several competing theories, but all we do know is that whatever happened to give us birds, it certainly happened prior to the extinction event that took out the rest of the dinosaurs. --Jayron 32 12:31, 20 July 2023 (UTC)[reply]

As for mammals, see Evolution of mammals. --User:Khajidha (talk) (contributions) 13:16, 21 July 2023 (UTC)[reply]

GF's question:

My girlfriend wants to know what is the world's largest penis, and I'm NOT talking about porn. (She caught me editing on Wikipedia and got curious about Wikipedia as well ) I'm talking about human penises. 😺😘🥰 Nuclear Sergeant (talk) 22:57, 19 July 2023 (UTC)[reply]

See the article Human penis size and a claim of Jonah Falcon. Philvoids (talk) 01:46, 20 July 2023 (UTC)[reply]

Or this:[1] ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:59, 20 July 2023 (UTC)[reply]

According to Wikipedia, the penis on a right whale can be up to 2.7 m (8.9 ft) Shantavira|^{feed me} 07:59, 20 July 2023 (UTC)[reply]

July 20

Blackbody emission questions.

1. Almost everything with heat emits IR. Humans, animals, water. The biggest source is the sun and fire. But I'm trying to find out who doesn't emit IR in darkness. I suppose humans and animals emit IR in darkness, but not water?

2. As sunlight is 52-55% IR and causes water to emit IR, I'm also curious to know how we draw the line between Blackbody radiation, and fluorescence/phosphorescence, of IR. Things that absorb IR, and emit in deep-IR. The thing is, if water stops emitting IR as soon as darkness, then that is equivalent to fluorescence, and if water emits for another 10 seconds after darkness, that's equivalent to phosphorescence.

3. They say most things that Blackbody IR at room temperature, will emit light, starting at red light, at 500 C. But what material is that, I've never found a chart for different materials such as steel, plastic, water (albeit some will turn liquid or gas 1st). What are some Blackbodys that have the lowest temperature to emit visible light? Thanks. 170.76.231.162 (talk) 16:17, 20 July 2023 (UTC).[reply]

All objects emit light, so long as they have a temperature, so ANY thing with a higher temperature than absolute zero will emit light. The specific spectrum of light that object emits is basically dependent only on the temperature, so long as the only source of light is from thermal radiation (there are OTHER processes that will emit light as well; the point of a blackbody is that it is an idealized object that can only emit thermal radiation. Simply put, all objects with any temperature at all emit thermal radiation; that thermal radiation (light wavelengths) fill follow a type of ~~normal distribution~~ probability distribution edit: The previous term was corrected from the original writing, which used an incorrect term. --Jayron 32 11:05, 21 July 2023 (UTC) whose central limit is dependent on the temperature. In simple terms, the frequency distribution of the light will have the shape of a curve shown at right, with frequency on the X axis and intensity on the Y axis; the peak of the curve will be shifted further right for hotter objects and left for cooler objects. As some examples of this temperature dependence, humans have a temperature on order of about 300ish K, which corresponds to a frequency distribution whose peak is in the infrared. However, something like a lightbulb filament has a temperature on order of about 5000 K, which corresponds to an peak frequency somewhere near the middle of the visible range. If you look at the cosmic microwave background, which is basically the "temperature of space", it's about 3 K, which corresponds to a frequency peak in the (you guessed it) microwave range. However, it's important to note that this is a distribution and not a singular monochromatic light. The exact distribution (from which you could work out the relative amounts of each frequency of emitted light) is given by Planck's law. --Jayron 32 16:35, 20 July 2023 (UTC)[reply]

Excellent answer, except for the bit about the normal distribution, which seems out of place here. Did you mean to refer to a more general term, like probability distribution? --Wrongfilter (talk) 10:03, 21 July 2023 (UTC) [reply]

Yes, I chose the wrong term. Thank you for the correction. I have fixed it. --Jayron 32 11:05, 21 July 2023 (UTC)[reply]

I would drop any reference to the Central limit theorem that is not useful here where the simple expression "peak (of the curve)" is well understood. Philvoids (talk) 16:46, 21 July 2023 (UTC)[reply]

I have no idea how to calculate this, but there must be a minimum yet greater than zero Kelvin temperature which under it no light will be emitted. A single photon of the longest wave light (deep red) has a fixed energy. When the energy of light is under that threshold, no light will be emitted. Zarnivop (talk) 17:21, 20 July 2023 (UTC)[reply]

Not necessarily. The limit is set by Planck's constant, which merely states that the smallest unit of light is the photon, but a single photon can have any arbitrarily small frequency of light. E = hν, so for any frequency of light, the smallest amount of energy for that frequency is just Planck's constant times the frequency, but there is no lower limit on frequency. "Deep red" is still very high frequency light, with wavelengths on the order of a micrometer (1 millionth of a meter) or so. The CMB light has wavelengths of cm scale, however meter-length wavelengths or longer are perfectly common. VHF frequency radio waves have wavelengths in the meter-to-tens of meters range, while light with wavelengths as long as hundreds of thousands of kilometers (see ELF) which have been used to practical effect by humans. There is no functional "longest wavelength of light". There is a functional "Smallest quantum of energy for a given wavelength" (the photon) but that's not the same thing. --Jayron 32 17:37, 20 July 2023 (UTC)[reply]

Also, the light is emitted by a system of atoms, not by a single atom. If you've got 10²³ atoms forming a solid with a temperature of a few kelvin, there's more than enough thermal energy to emit a single visible photon. It's not very likely to happen though. PiusImpavidus (talk) 19:33, 20 July 2023 (UTC)[reply]

Light is by definition is bound between red (or at most IR) and purple (or at most UV). Radio frequencies are not light. Both are EM radiation, but you stated that anything above absolute 0 emits light. This is not true. EDIT: Anything above absolute zero emits photons, but not every photon is light - that depends on its energy. Zarnivop (talk) 22:27, 20 July 2023 (UTC)[reply]

Engineering may have such a definition, but physics does not. In astronomy, we usually refer to ultraviolet and infrared radiation as "light", as the detector technology is basically the same as for "visible light", but if the mood takes us then light can occasionally mean all of em radiation. --Wrongfilter (talk) 10:03, 21 July 2023 (UTC)[reply]

That's a rather facile understanding of light, and does not represent actual reality. There's nothing especially different between red light and radio waves, at all, except for the rather unimportant distinctions made by human biology. Since we aren't discussing human biology in this discussion, such distinctions aren't relevant. Clearly, putting such arbitrary distinctions on the discussion does not help answer the question correctly, which is why it isn't appropriate to do so. --Jayron 32 11:02, 21 July 2023 (UTC)[reply]

Do astronomers refer to radio frequencies as "light"^{[citation needed]}, I can totally see them include UV and IR, but I doubt anything else like radio, be it "facial" or whatnot. Zarnivop (talk) 13:53, 21 July 2023 (UTC)[reply]

"facetious"? It's probably used very rarely when talking about radio specifically, but when somebody says "We get most of our information on the universe in the form of light", I would naturally understand radio as part of that (but not gravitational waves or neutrinos). But I admit this is a personal impression and I'm not going to look for references. --Wrongfilter (talk) 14:41, 21 July 2023 (UTC)[reply]

I believe Jayron32 means FACILE adj. too simple to deal with the difficulties of a real situation, arrived at without due care or effort; lacking depth. I am unlikely to tell my grandmother that her cellphone works by sending light beams, nor should she expect to be lectured to by her grandchild that any doubt on this matter is merely due to her unimportant arbitrary, unreal and incorrect biological shallowness. Wrongfilter and Zamivop's comments correctly and appropriately remind us that in the vernacular English understood by the majority of general readers, and by all English speakers before Maxwell's demonstration in 1865 of the electromagnetic field, the word "light" means principally visible light. I think we can all distinguish between RADAR and LIDAR. Philvoids (talk) 21:03, 21 July 2023 (UTC)[reply]

You can use any word you want for it, nothing particularly important or interesting happens to electromagnetic radiation that our eyes and psychology detect as "deep red". There's no need to make that particular frequency of light meaningful in this discussion. ---Jayron 32 13:17, 24 July 2023 (UTC)[reply]

I took upon myself to replace the image given here with the actual graph. The old graph accurately depicted that the maximum-emission wavelength changed with temperature, but (wrongly) implied that for a given wavelength, an increase of temperature could decrease the emission. That is not true - for all wavelengths, spectral emissivity increases with temperature. Tigraan^{Click here for my talk page ("private" contact)} 08:44, 21 July 2023 (UTC)[reply]

On the original question it should be pointed out that fluorescence and phosphorescence are line emissions, light is emitted only at certain wavelengths/frequencies given by electronic transitions in atoms or molecules. Thermal emission on the other hand is continuous emission, i.e. light is emitted at any wavelength (in any real situation probably better described as quasi-continuous). These are rather different processes. --Wrongfilter (talk) 10:03, 21 July 2023 (UTC)[reply]

It should be noted that bodies only emit radiation according to the black body curve if they are perfect absorbers. It is fundamental, arising from electron orbits jumping down on emission and jumping up on absorption that any body of material can only emit on wavelengths that it can absorb. Thus glass, which is transparent to most wavelengths, cannot emit - well, sort of, at high enough temperatures, glass looses its transparency and can there emit.

Carbon is the most perfect black body radiator, so to answer your question, it will begin emitting visible light at the lowest temperature. But the difference between it and steel is not great. Steel emits visible light at much lower temperatures that metals such as aluminium - as you would expect, as aluminium is a good mirror - it doesn't absorb light very well, compared to steel. Dionne Court (talk) 02:21, 24 July 2023 (UTC)[reply]

You're perfectly right to point out that no real material is truly black and that therefore their thermal emission lies below the curves for the ideal black body; the ratio is called the emissivity and it depends on wavelength. However, just as no material is truly black (emissivity 1), no material is perfectly transparent or reflective (emissivity 0; the table in emissivity puts pure nitrogen or oxygen gas at essentially zero). It therefore remains true that all bodies do emit thermal radiation, some at a lower level than others. If you're looking for a temperature at which a material begins emitting visible light, you have to set a threshold for the light emitted, e.g. by specifying how you want to measure that. --Wrongfilter (talk) 06:33, 24 July 2023 (UTC)[reply]

It should also be noted that the "model" blackbody was actually an oven with a pinhole in it: See Black body#Cavity with a hole and Kirchhoff's law of thermal radiation#A hole in the wall of a cavity. This is what Gustav Kirchhoff used when he did his initial experiments on the subject. --Jayron 32 16:07, 24 July 2023 (UTC)[reply]

July 21

In two bottles of different volume, both emptied up to a vacuum, is the pressure on the seal of each the same?

In two bottles of different volume, both emptied up to a vacuum, is the pressure on the seal of each the same? Bumptump (talk) 01:00, 21 July 2023 (UTC)[reply]

I'd think so. Thought experiment: what causes the presssure? What mechanism would increase or decrease said pressure based upon the contents (or absence thereof) of the bottles? --jpgordon^{𝄢𝄆𝄐𝄇} 01:34, 21 July 2023 (UTC)[reply]

Assuming they're sitting next to each other, presumably each would experience the same air pressure. Are you thinking that the larger bottle would have more "suction" than the smaller one? ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:15, 21 July 2023 (UTC)[reply]

I assume "emptied up to a vacuum" means that the sealed bottles each contain vacuum, and you're asking about the pressure exerted by the surrounding atmosphere. Then there are a couple of things to consider. First, since the atmosphere has weight, the atmospheric pressure varies according to altitude, so if one of the bottles is placed higher, then the pressure on it will be reduced. And second, it's not clear whether the original poster was asking about "pressure" in its proper technical sense (referring to the amount of force per unit area), or in the informal English sense where it just means a force that presses. If the pressure in the technical sense is the same on both bottles (the air is at the same altitude and temperature), then the force on the larger seal will be larger in proportion to its area.

In any case, the volume of the bottles is irrelevant. --142.112.221.64 (talk) 05:19, 21 July 2023 (UTC)[reply]

Why does electrocution stop after a few seconds in a bug zapper?

I have observed that when an insect is electrocuted in a bug zapper, there are typically a few sparks or flashes of light. Sometimes the insect will catch on flame in a tiny fire, and the body will burn for a few seconds before stopping burning. The lights and flames stop after a few seconds, but the insect body often, instead of falling, remains in position still connecting two wires.

Given that the body is still in position connecting two wires, why is it that after a few seconds, sparks or flashes of light stop appearing, and any fire is extinguished? Does that mean that electricity is no longer flowing through the insect's body, and if so, why does the electricity stop flowing if the body is still connecting the two wires?

—SeekingAnswers (reply) 05:48, 21 July 2023 (UTC)[reply]

Maybe once their little carcasses are dried up, they can't conduct electricity? Abductive (reasoning) 06:55, 21 July 2023 (UTC)[reply]

That is very likely the main cause - the corpse becomes non-conductive because it dries and burns up.

Another possibility (which, again, is less likely in my semi-informed opinion) is that the bug zapper needs time to recharge. A bug zapper is a discharge circuit where a capacitor is slowly charged when the circuit is open and then quickly discharged when the circuit is closed (by the poor insect). The charge time can be a couple of seconds while the discharge is much quicker (millisecond or lower) - but it’s hard to tell without a spec sheet of the electrical circuit, which I did not find in a quick online search.

Yes, discharge circuit is a redlink. Wikipedia does not have an article about everything, apparently. We have articles about Capacitor discharge ignition, cattle prod, bug zapper etc. but none of those give an electrical diagram. Tigraan^{Click here for my talk page ("private" contact)} 09:24, 21 July 2023 (UTC)[reply]

I can't see how it could be the latter explanation, because all the bug zappers I've ever seen have virtually instantaneous "recovery" times, being able to zap multiple different insects seemingly simultaneously, and the dead insects often remain stuck between wires indefinitely without ever falling or reigniting even hours or days later.

So, a couple of additional questions arising from the first explanation: First, how exactly does electrocution cause drying: is it that electrocution generates heat, which causes the water to evaporate away into the air? And second, does that mean that organic tissue is nonconductive without water?

—SeekingAnswers (reply) 16:20, 21 July 2023 (UTC)[reply]

2023 Annular Eclipse...

... Of the sun due to take place in Oct. Of 2023. Just got this from a few news outlets. Some even have a map of the US, showing the path of the eclipse, and the time it'll take place. Is there info. On it here? Can this be used as a source? Thanks. 😺😺😺😺😘🥰 Nuclear Sergeant (talk) 11:45, 21 July 2023 (UTC)[reply]

See Solar eclipse of October 14, 2023.

Did you know: we have almost half a million articles tagged with "citation needed" somewhere in the text? I mean, if you're keen to find a source and have it used in an article, those are some of the ones that need sources. Solar eclipse, for instance, is tagged in two places. Card Zero (talk) 11:50, 21 July 2023 (UTC)[reply]

Chokeberries

What may cause the tobacco-like smell of chokeberries and juice made of them? Are there, perhaps, some chemical compounds of same type in both the berries and tobacco plants? --2001:999:404:7509:5AE3:4A4:DD10:8B49 (talk) 13:15, 21 July 2023 (UTC)[reply]

Aronia#Polyphenols has some info. Abductive (reasoning) 00:00, 22 July 2023 (UTC)[reply]

Paired samples

Note: For those interested (since there seems to be some slack there) – feel free to comment ideally within that thread. Best, Hildeoc (talk) 13:44, 21 July 2023 (UTC)[reply]

July 23

Draining water from a sink without swirling

Could we create a sink so solid and precisely crafted, up to fractions of mm, that water sinks straight down, without swirling? Or would that be like stacking 20 M&M's on top of each other? Bumptump (talk) 18:19, 23 July 2023 (UTC)[reply]

The construction of the sink is irrelevant. There will always be eddies that will produce a vortex. Shantavira|^{feed me} 18:26, 23 July 2023 (UTC)[reply]

So, even on a non-rotating Earth, not to speak of on a flat Earth, we'll get a vortex? --Bumptump (talk) 22:01, 23 July 2023 (UTC)[reply]

See Coriolis force#Draining in bathtubs and toilets. {The poster formerly known as 87.81.230.195} 51.198.140.169 (talk) 00:23, 24 July 2023 (UTC)[reply]

Just to make things clear: As it says in the article cited by poster 51.198.140.169, Coriolis force from the Earth's rotation is negligible with the area of a typical domestic sink. Sinks draining in opposite directions in opposite hemispheres is an ancient urban myth that has even been taught in high school science classes - it was in my high school anyway.

The situation is this: It doesn't matter how smooth or precisely shaped the sink is, water going straight down without swirling is unstable if the flow rate and flow volume is sufficient. If the flow rate down the pipe is sufficient, the Reynolds Number [Reynolds number - Wikipedia] will be high enough to create eddies/turbulence. Once an eddy has formed, the flow rate is locally increased - this will make the eddy quickly grow until it takes over the whole flow, as flow rate increases according to distance away from the drainpipe surface, in the same way as an ice skater increases spin speed by pulling her arms in. The smaller the rotation radius, the higher the speed must be to have the same kinetic energy.

In symmetrical sinks, with a few cm of water you can usually change the swirl direction at will by swirling it vigorously in the direction you want with your hand. When you take your hand out, the new swirl direction will stay in place. A fact I demonstrated to that fool of a science teacher we had at my school, thus proving Coriolis had nothing to do with it.

Dionne Court (talk) 02:08, 24 July 2023 (UTC)[reply]

Good answer, and the answer to the OPs question is in there. I was surprised to see that when filling my generator there was no vortex in the funnel. The end of the funnel rests on a filter gauze, so the flow speed is comparatively small. Greglocock (talk) 07:47, 24 July 2023 (UTC)[reply]

I once had the water just go straight down the drainhole in my bath without the swirling a number of years ago. I was amazed - it went down so fast. I hadn't done anything special, and despite trying I've never been able to get it to happen again. NadVolum (talk) 09:04, 24 July 2023 (UTC)[reply]

Another thing to consider here is to conceive of the problem as a function of the law of conservation of angular momentum. There will probably always be small eddies and vortices within the bulk of the fluid. As the fluid drains down the smaller hole, these eddies and vortices will meet up; unless there is an exactly equal rotation among all of those little vortices to cancel out before they get to the drain, there will be a net rotation that gets intensified as the fluid gets constricted into the smaller drain (like the canonical example of the figure skater bringing their arms in during a slow turn and speeding up). In the very very rare cases that all such tiny vortices cancel just right, you can get laminar flow down the drain (as noted above) but this is extremely rare and probably not reproducible. In general what you get is a slight rotational imbalance, that gets intensified and intensified and intensified as the fluid becomes constricted on its way down the drain, and that's what leads to the classic drain swirl. --Jayron 32 13:11, 24 July 2023 (UTC)[reply]

The direction of the swirl is probably set by some small random initial thing, but I'm pretty definite the swirl has low angular momentum overall - and it probably is in the opposite direction to that assumed. The wate draining down the plughole will carry off the some of the fastest swirling water from the centre, so to conserve angular motion the swirl must be getting a bit of angular motion in the opposite direction. The energy for all this would come from the gravity acting on the water. The error I think that the angular motion argument has is thinking of the water as a solid bodym whereas if you put something small floating in the water you'll see it turn in the opposite direction to the swirl. Thus there is angular motion one way from the water swirling around - but each bit of water is turning around in the opposite direction.

What I think might be a nice simple little project for someone is an AI with a paddle to make the flow go straight down the plughole :-) It is hard to change the direction of the swirl when it is established - but it might be possible to make small movements that counteract one forming. NadVolum (talk) 16:30, 24 July 2023 (UTC)[reply]

I have this wonderful vision of a dozen wikipedians all sat in their baths tonight swirling water one way, then the other as the bath empties. :-) Martin of Sheffield (talk) 16:34, 24 July 2023 (UTC)[reply]

Didn't everybody do this at some point in their formative years? I certainly did.

On a related note, I imagine the tendency to vorticity could be countered by having a pattern of ripples or shallow flukes built in to the base of the basin, radiating from the drain hole. I wonder how shallow they could be while still doing so? This of course would be pointless in a domestic setting, but might be useful in some industrial context where rapid emptying might be advantageous. Is it actually employed, or am I fundamentally mistaken? {The poster formerly known as 87.81.230.195.} 51.198.140.169 (talk) 01:44, 25 July 2023 (UTC)[reply]

Jayron, you said "In the very very rare cases that all such tiny vortices cancel just right, you can get laminar flow down the drain (as noted above) but this is extremely rare and probably not reproducible"

You are completely wrong. It's not in the least bit rare. and it is completely reproducible. You always get laminar flow when the Reynolds number is low enough. For a given fluid of a certain density and viscosity (e.g., water) the Reynolds number rises with velocity and with pipe diameter. Therefore, non-swirl motion down a sink drain is reproducible by restricting the flow rate - either by turning down the tap or by putting in a restriction e.g., mesh in the pipe.

Generally, there are three ranges of how Reynolds number affects flow;- a) below a certain value turbulence cannot be sustained and the flow is always laminar; b) above a certain much higher number laminar flow cannot be sustained and the flow is always turbulent, which when a larger bore is terminated in a smaller bore, becomes a swirl flow; and c) a range in between where whatever flow is established remains in place. in this range small influences (eg vibration0 can flip the flow from laminar to turbulent and vice versa.

I can see who does the dishes in your house, Jayron - it's not you. `Dionne Court (talk) 04:01, 25 July 2023 (UTC)[reply]

July 24

Potato and tomato phenotypes

Today I've read that the genetic difference between tomato and potato is just 8%, with remaining 92% of genome being similar.

However, to me morphological differences between the two are too stark for that percentage: potatos' smooth and rounded leaves vs tomato's edgy and serrated ones, different shape and color of petals, underground tuber vs. surface juicy berry, etc. When these are compared to species within some other fruit-bearing genera, e.g. Malus (and even to humans and chimps who have roughly the same genetic similarity), the phenotypic differences look more pronounced in potato and tomato than in Malus species. Why is that? 212.180.235.46 (talk) 18:21, 24 July 2023 (UTC)[reply]

Birds and Pterodactyls

I learned throughout my life that birds didn't go extinct after the Chixclub impact because they could fly and weren't heavily impacted. But my question is- why did Pterodactyls (and Pterosaurs in general) go extinct but not birds? 104.187.66.104 (talk) 19:38, 24 July 2023 (UTC)[reply]

Very few bird species survived and the ones that did seem to have been small ground dwelling ones - the survivors diversified later. Small size seems also to have been a feature of the few mammals that survived the event. But that does not seem to have been enough of itself - lots of dinosaurs were fairly small. NadVolum (talk) 22:48, 24 July 2023 (UTC)[reply]

Well one theory is that the surviving birds nested underground. Then they could survive incineration of the surface of the Earth. Graeme Bartlett (talk) 00:32, 25 July 2023 (UTC)[reply]

July 25