Content deleted Content added

Inline

Revision as of 08:19, 5 November 2022

Welcome to the science section
of the Wikipedia reference desk.

skip to bottom

Select a section:

Shortcut

WP:RD/S

Want a faster answer?

Main page: Help searching Wikipedia

How can I get my question answered?

Select the section of the desk that best fits the general topic of your question (see the navigation column to the right).
Post your question to only one section, providing a short header that gives the topic of your question.
Type '~~~~' (that is, four tilde characters) at the end – this signs and dates your contribution so we know who wrote what and when.
Don't post personal contact information – it will be removed. Any answers will be provided here.
Please be as specific as possible, and include all relevant context – the usefulness of answers may depend on the context.
Note:
- We don't answer (and may remove) questions that require medical diagnosis or legal advice.
- We don't answer requests for opinions, predictions or debate.
- We don't do your homework for you, though we'll help you past the stuck point.
- We don't conduct original research or provide a free source of ideas, but we'll help you find information you need.

Ready? Ask a new question!

How do I answer a question?

Main page: Wikipedia:Reference desk/Guidelines

The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.

October 28

Nitrogen tire inflation

Costco tire center[1] states:

Additionally, we inflate your tires with nitrogen, not compressed air. Nitrogen retains tire pressure better over time than compressed air, which can positively impact the life of your tires, as well as the fuel economy of your vehicle.

First I ever heard of anything like that. The molecular weight of nitrogen is slightly less than the average molecular weight of air, so nitrogen doesn't sound likely to diffuse through the rubber slower, right? Do they think that the O2 in compressed air will react with the tire interior somehow? And you have to check your tire inflation and top it up every so often anyway, so won't the gas in the tire soon be mixed with whatever you use for the top-up? That will normally be atmospheric air for most of us. Is this nitrogen thing some kind of dumb marketing gimmick, or is there something to it? Thanks. 2602:24A:DE47:B8E0:1B43:29FD:A863:33CA (talk) 21:04, 28 October 2022 (UTC)[reply]

I'm not a physicist, but according to File:Empirical atomic radius trends.png the size of an oxygen atom is slightly smaller than the size of an nitrogen atom. I don't know if that transfers to the size of N2 versus O2, but if it does, N2 would be less likely to diffuse through other potentially porous materials. Dhrm77 (talk) 21:34, 28 October 2022 (UTC)[reply]

The molecular diameter of nitrogen is less than 1% larger than oxygen. And since air is 78% nitrogen already, I find it difficult to believe this could make a significant difference. Sounds like a snake oil type gimmick to me. --DB1729^talk 22:38, 28 October 2022 (UTC)[reply]

Testing by Consumer Reports shows that there is very little practical benefit. Cullen328 (talk) 22:49, 28 October 2022 (UTC)[reply]

According to Graham's law, a gas with a lower molecular mass will escape faster (because at a given temperature its molecules are moving faster). catslash (talk) 22:53, 28 October 2022 (UTC)[reply]

Using molecular mass as the criterion, CO₂ is better than air by 17.5%. But mice will escape faster from the cheetah zoo cage than the cheetah, even though they are moving more slowly. --Lambiam 06:54, 29 October 2022 (UTC)[reply]

The idea's been around for most of this century, at least. I listened to Cincinnati, Ohio radio stations until moving away in 2005, and Tire Discounters always advertised their nitrogen inflation with implications that nobody else in the region was doing it. 175.39.61.121 (talk) 04:35, 29 October 2022 (UTC)[reply]

Large airplanes of the kind used by airlines usually have their tyres inflated with nitrogen. It is my understanding that this is done because the materials used in construction of these tyres release gaseous materials that can form an explosive mixture when combined with oxygen at high pressure. Tyre pressures are very high so, when inflated with air, the partial pressure of oxygen is high. There are times when tyres and their contents get hot, such as after taxying a long way, after landing, and after a rejected takeoff. If a tyre explodes it is a hazard to ground crew and a threat to the airframe. However, none of this supports the notion that tyres inflated with nitrogen maintain the required pressure longer than those inflated with air. It may be that what lies behind these offers to car owners is simply the idea that if it’s good for airlines it must be equally good for owners of up-market automobiles. Dolphin (t) 06:19, 29 October 2022 (UTC)[reply]

It's easier to get high pressure cylinders of dry nitrogen than dry compressed air. CO2 would be a better choice. Also, if the O2 does escape, the remaining air inside will have less O2, so after several top ups even if you start with air you get the same effect anyway. Of course the pros use a hexafluoride and the tires occasionally have to be let down as air diffuses in. Greglocock (talk) 07:11, 29 October 2022 (UTC)[reply]

Our article on aircraft tyres mentions this too: simple compressed air doesn't work very well in aircraft tyres, as the large temperature swings cause, via condensation, large pressure swings. One needs at least dehumidified compressed air. And the high partial pressure of oxygen may cause explosive mixtures. Pressure on aircraft tyres is on the order of 1400 kPa, while pressure of car tyres is around 200 kPa (and bicycle tyres around 500 kPa), and car tyres don't see such large temperature swings, so it's not applicable to car tyres. Bicycle tyres are nearly always filled with simple compressed air from a hand pump.

When you fill your tyres with nitrogen, nitrogen diffuses out, but oxygen diffuses in, which may reduce the rate of pressure loss. Indeed, if you inflate your tyres with some hexafluoride, you may see rising pressure as air diffuses in. Those hexafluorides have some disadvantages too, so it may be a bad idea to use it on a large scale. PiusImpavidus (talk) 10:53, 29 October 2022 (UTC)[reply]

Greglocock Good information! Any idea about the advantage of hexafluoride? Why do the professionals use it? Dolphin (t) 10:32, 29 October 2022 (UTC)[reply]

That was a joke. It would work, but it is not practical.Greglocock (talk) 22:46, 29 October 2022 (UTC)[reply]

According to Kinetic_diameter, molecular oxygen is about 5% smaller than molecular nitrogen, not 1%. Granted, it doesn't make much of a difference. The more important question might be: what molecular size is rubber not able to contain effectively? (perhaps only helium and ammonia?) Dhrm77 (talk) 21:36, 30 October 2022 (UTC)[reply]

According to my local tyre centre using nitrogen prolongs the life of the tyres by stopping the oxidation of the insides. Martin of Sheffield (talk) 21:46, 30 October 2022 (UTC)[reply]

Things may be better for you, but I have often found such businesses in the automotive industry to be less than ideal sources of scientific truths. HiLo48 (talk) 23:44, 30 October 2022 (UTC)[reply]

Very true, but it gives an explanation about why they are pushing it, even if the whole exercise is pointless. As the OP says:"Is this nitrogen thing some kind of dumb marketing gimmick, or is there something to it?" While posting here, Greglocock commented that "It's easier to get high pressure cylinders of dry nitrogen than dry compressed air." Such equipment is standard for every SCUBA shop and dive club, so I suspect that cost is not a major factor in the long run. Martin of Sheffield (talk) 08:05, 31 October 2022 (UTC)[reply]

Thanks all. It sounds like my suspicion is confirmed and the N2 inflation is bogus. 2602:24A:DE47:B8E0:1B43:29FD:A863:33CA (talk) 22:38, 29 October 2022 (UTC)[reply]

Bogosity would explain the warnings I've seen not to add mere garden-variety common air to a nitrogen-filled tyre. —Tamfang (talk) 02:02, 3 November 2022 (UTC)[reply]

October 30

Should I change the paper (filter)?

There's a large, grilled exhaust vent in my apartment's bathroom. I throw a paper napkin or tissue paper up there and it sticks, such is the power of the fan pulling air out of the building. Over time, the tissue would blacken. I've been changing it periodically, but since the air's only really going one way, I wonder if it's necessary. To the extent that the dirty stuff helps clog up the tissue, it'll cause more dirty stuff to stick, right?

No, I don't have the power to get the building to clean the exhaust pipes more frequently. Imagine Reason (talk) 02:53, 30 October 2022 (UTC)[reply]

Blocking a bathroom vent in any way is a bad idea, and possibly illegal. Remove the paper completely. There is no need for any sort of filter. Shantavira|^{feed me} 10:00, 30 October 2022 (UTC)[reply]

The filter impedes the flow of air to the outside and so helps to keep the dust, bacteria, mould spores or whatever is drifting in the air inside. Even less air will pass through a clogged filter, so you may end up catching less of the stuff. If your aim is to collect as much "dirty stuff" as possible for a scientific study, you should regularly replace the filter. --Lambiam 17:24, 30 October 2022 (UTC)[reply]

Yeah, you want to filter the air coming in to your abode, not on its way out. Abductive (reasoning) 17:50, 30 October 2022 (UTC)[reply]

The ventilation shaft is not really cleaned and very dirty. Imagine Reason (talk) 02:38, 1 November 2022 (UTC)[reply]

So I've decided to let the vent work when the bathroom is not occupied. When it is, I can feel such a draft through the gaps in the door frame that there's obviously a greater chance of the grime blowing in from the shaft. Imagine Reason (talk) 03:03, 3 November 2022 (UTC)[reply]

Synchrotron effect on electric charges

In particle accelerators, can we also find the synchrotron effect on positrons, protons and anti-protons which are also electrical charges? Where can I find this information? — Preceding unsigned comment added by Malypaet (talk • contribs) 05:00, 30 October 2022 (UTC)[reply]

For positrons, the synchrotron radiation is the same as for electrons. Protons and anti-protons do emit synchrotron radiation, but much less than electrons. This is because of

E=\gamma mc^{2}

: at the same energy E, the Lorentz factor γ is about a factor 2000 smaller than for less massive electrons. Synchrotron power goes as

\gamma ^{4}

and is therefore a factor 10¹³ smaller (cf. Synchrotron radiation). --Wrongfilter (talk) 07:11, 30 October 2022 (UTC)[reply]

October 31

Genetic testing on plants.

Don't anyone do genetic testing on plants? Would it be easy to genetically change the color of leaves? Say, leaves can already be red yellow and dark purple, can trees be genetically altered to produce those colors year-round? But then, let's say there are no naturally colored blue leaves. Can blue genes say, from the fur of a blue-colored animal, or blue colored flower petal, be used to make the leaves of a tree be blue? The only genetic testing I have heard of, was some plants have been genetically altered to produce fluorescence. This happened when I asked a plant professor can any plants produce light, he said the ones that can naturally fluoresce, are not bright enough for the human eye to see, so some plants have genetically modified to produce brighter. So, I imagine genetic testing on plants are more legal than on animals, anyone have any feedback for vegetables/fruits? 67.165.185.178 (talk) 02:14, 31 October 2022 (UTC).[reply]

Genetically engineering plants is a major field of human endeavor, but aside from making a blue rose I have not heard of much effort being expended on purely aesthetic modifications. Abductive (reasoning) 03:29, 31 October 2022 (UTC)[reply]

And also, can random probabilities be distributed? For example, a tree with 4 gene colored leaves, red blue green purple, but each leaf has a 1/4th relatively random probability of each color. That would be dope! 67.165.185.178 (talk) 04:07, 31 October 2022 (UTC).[reply]

Epigenetic variations may determine phenotypical aspects such as leaf colour. In fact, the cell differentiation in higher organism, in which some cells become neurons and others muscle cells, is an example of local epigenetic variation. The discovery of a genetic switch controlling Streptococcus pneumoniae that allows the bacterium to randomly change its characteristics would appear to imply that random leaf colours or similar random local phenotypical variations are theoretically possible. Human fingerprint patterns may be a somewhat unspectacular example, but the situation is unclear. Perhaps some Turing patterns and variegated animal coloration are also be due to local random epigenetic variations. --Lambiam 09:07, 31 October 2022 (UTC)[reply]

A relevant research paper: "Integument pattern formation involves genetic and epigenetic controls: feather arrays simulated by digital hormone models". --Lambiam 09:19, 31 October 2022 (UTC)[reply]

Genetic modification has been done for millenia on both plants and animals. Cross-breeding, inbreeding, etc. are all artificial selection using the genetics the organisms already have. If the OP is talking about lab-based genetic modification, that's where the law might come into the picture. ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:06, 31 October 2022 (UTC)[reply]

As noted above, artificial selection (aka "breeding") is unregulated, and has been done by humans since before recorded history (see Neolithic Revolution). In terms of laboratory-modified organisms, what is usually called "GMO"s or genetically modified organisms, many countries have a type of ethics committee which must review all GMO-based research, in the U.S. this is called an Institutional Biosafety Committee, which reviews all prospective genetic modification experiments. There is required, by US law, to be an IBC at any institution carrying out such research, whether academic, governmental, or private. Genetic modification of plants is an active area of research, but it is carefully regulated. --Jayron 32 15:02, 31 October 2022 (UTC)[reply]

The green color of most plant's leaves derives from chlorophyll, which is an essential part of the plant's metabolism. I don't think it would be as easy to change leaf color as it is to change, for example, flower color, without impacting the viability of the plant. Green leaves change color in the autumn because they're dying. CodeTalker (talk) 16:05, 31 October 2022 (UTC)[reply]

One year I planted some beans, and 2 or 3 of them came up out of the ground, completely white. Obviously they didn't survive very long, once they exhausted the nutrients inside the original beans. There is a simple explanation for that. A green leaf reflects green and absorbs red and blue light, converting it into energy the plant can use. So a white plant reflecting everything cannot sustain itself. But a plant that is a darker color, for instance purple like some coleuses or red cabbage are, will absorb more green and less blue and red, and will sustain itself. Dhrm77 (talk) 16:56, 31 October 2022 (UTC)[reply]

Lots of plants have leaves of colors other than green. Tradescantia pallida, Tinantia pringlei, some cultivars of Japanese maple and of Begonia and of ti plants, for examples. Many of these plants still have chlorophyll, but there are additional compounds in the leaves that lead to the other colors. --Jayron 32 18:14, 31 October 2022 (UTC)[reply]

Most of those are due to the red/blue/purple colors of anthocyanins. Note that these chemicals change from reddish to bluish based on pH.--User:Khajidha (talk) (contributions) 19:16, 31 October 2022 (UTC)[reply]

And for a really blue plant see Eryngium ovinum.[2] Graeme Bartlett (talk) 21:09, 31 October 2022 (UTC)[reply]

What about changing the color of say, strawberries or raspberries, to something else? I don't think the red is necessary for survival? And ss this something that an undergraduate biology lab can do? Or are these all done by PhD people? — Preceding unsigned comment added by 67.165.185.178 (talk) 01:32, 1 November 2022 (UTC)[reply]

There are the first stirrings of a GMO biohacker movement, with people doing it in their garages, ala Steve Jobs/Steve Wozniak. Abductive (reasoning) 03:42, 1 November 2022 (UTC)[reply]

So when we add new genes or DNA say to a plant, and I just adding new genes/DNA or am I replacing (like substituting)? Take that blue rose for example. Adding a blue-colored gene/DNA when it already might have that for the red color, I would have to remove it, right? And that would require looking for the particular gene or DNA to replace? 67.165.185.178 (talk) 10:26, 2 November 2022 (UTC).[reply]

In the case of the not-remotely-actually-blue rose, as it states in article, they spliced in a gene for the naturally occurring delphinidin into a white rose, then, when the color was not satisfactory, used "RNA interference (RNAi) technology to depress all other color production by endogenous genes by blocking a crucial protein in color production, called dihydroflavonol 4-reductase (DFR)", which could hardly be called successful. This shows to go you that genetic engineering is not remotely simple, that living things are difficult to work with, and that such intricacies are not easily taught on a forum such as this. One would have to take university courses the equivalent of a Master's degree in order to fully understand this material and the limitations of genetic manipulation. Abductive (reasoning) 00:34, 3 November 2022 (UTC)[reply]

Would any bio major know, what is the easier part, extracting DNA, or insertion? For example, suppose someone gave the "here's the blue DNA you're looking for" then was that the harder part or easier part. And how about the fact that we have so many cells in our body, does adding/replacing DNA in a few cells actually change anything? 67.165.185.178 (talk) 01:28, 3 November 2022 (UTC).[reply]

Finding genes is not easy, but it preceded our ability to genetically engineer by many years. Back in the day they used to use an air pistol to shoot DNA into plant cells. Also they use viral machinery to deliver the DNA, see CRISPR gene editing. Generally one can tranform only a few cells or low percentage of cells, so one usually thinks along the lines of the offspring being the ones that one is genetically engineering. Gene therapy aims to help individuals now, rather than cure their future offspring, and is fraught with difficulties. Abductive (reasoning) 02:25, 3 November 2022 (UTC)[reply]

Abductive, I'm looking at the blue rose article and it took 13 years of collaborative work between an Australian company and Japanese company. So that GMO work-at-home garage lab, I would think would not be able to do as something as sophisticated as a blue rose? Btw, the process for how the 2 companies did it, adding 2 genes and altering a 3rd, that would strike me as proprietary company secret. Was it a secret at the time, and they decided to make it known years later? I note that the article says nothing about the current blue roses they sell, only their 1st 1s, which were not blue, so maybe their current blue roses are proprietary information. 67.165.185.178 (talk) 18:43, 3 November 2022 (UTC).[reply]

Perhaps there is more to the editing than the article states, but there are Plant Patents, and it's likely that they were doing it to advance the field rather than for profit. And those guys didn't have CRISPR. The garage analogy stands: The technology is getting cheaper every day, the machines less finicky, and the methods more widely disseminated due to undergrads and grad students getting trained on how to do it all the time. Abductive (reasoning) 08:40, 4 November 2022 (UTC)[reply]

November 1

Of Frogs and Men

I've always held this notion that humans are somehow descended from frogs. Even apes and monkeys appear to have certain frog-like features. Unfortunately I can't find much of anything in the way of direct genetic evidence to support such a claim. (Most people seem to believe that we are rather highly-evolved mice, but I just don't see it.) Earl of Arundel (talk) 04:47, 1 November 2022 (UTC)[reply]

What you're looking for is the Most Recent Common Ancestor in each case (see also Phylogenetic tree), that is, if you go back in time, you will find an organism that evolved into frogs and humans, another for mice and humans and yet another for apes and humans. For the first you would need to go back hundreds of millions of years (see Tetrapods), for the second several tens of millions (see Euarchontoglires) and for the last (taking the Chimpanzee as an example) about 10 million years (see Chimpanzee–human last common ancestor). Mikenorton (talk) 09:58, 1 November 2022 (UTC)[reply]

(edit conflict) Are you serious? Both humans and mice are tetrapods, but the split in the evolutionary tree between the Lissamphibia, to which frogs belong, and all other tetrapods, including the Amniota to which all mammals belong (not considering shape-shifting reptilians, which presumably, if not alien, are Sauria – also not Lissamphibia) took place more than 300 million years ago. It is hardly surprising you cannot find genetic evidence for the extraordinary claim. As there is an unsurmountable mountain of evidence against it, you'd need extraordinarily extraordinary evidence. --Lambiam 10:07, 1 November 2022 (UTC)[reply]

So, you're making a common misconception; that humans (or any other species) descended from some species that still exists. That's not really how it works. Instead, it's helpful to think that somewhere in the past there is a most recent common ancestor (MRCA) to both humans and to frogs. That species may (or may not) be convenient to categorize as a "frog", but that's really irrelevant; by definition both modern humans and modern frogs are equally as related to that species. The most recent common ancestor of humans and frogs would have been among the earliest tetrapods, before the development of amniotes; the oldest amniote fossils date to 313-316 million years ago, which would be the latest possible most recent common ancestor of both frogs and humans. It likely looked nothing like either a frog (or a human). Being from the carboniferous period, it would look like one of the animals listed at List of Carboniferous tetrapods. --Jayron 32 12:20, 1 November 2022 (UTC)[reply]

Pederpes finneyae

Maybe it looked like this whatcheeriid, which doesn't resemble a frog except for the smile. I must say, though, she reminds me of one of my great aunts. --Lambiam 17:25, 1 November 2022 (UTC)[reply]

You may be interested in Frogs and humans are kissing cousins from Nature and Frogs Surprisingly Like Humans, Genetically Speaking, both referencing research by Richard Harland (biologist). Alansplodge (talk) 13:43, 1 November 2022 (UTC)[reply]

It is both surprising and unsurprising; unsurprising when you realize that the other organism noted in the study, the zebrafish, is much more distantly related to the other three, something we know that since the MRCA of zebrafish to tetrapods would be much older than that, which would be the divergence of ray-finned fish and lobe-finned fish, which would have happened in the Silurian, about 418 mya. The commonality of the genetics of all tetrapods is unsurprising; most of our major structures and components are quite similar. We have the same skeletal structure, the same major organ groups in the same places, the same kinds of metabolism, etc. etc. Most of the genes would be the same or very similar. Even humans and bananas have 60% of their DNA in common. --Jayron 32 14:30, 1 November 2022 (UTC)[reply]

Wow, much thanks to everyone for the informative comments. This is a such a complex field of study. Also interesting how parallel evolution can produce somewhat similar traits/features. So I guess this extends to our relationship with modern apes; not necessarily directly per-se from chimpanzees, although we do share a common recent ancestor. Fascinating. Well, humans ARE at more or less highly-evolved worms anyway. I wonder if that direct ancestor still exists (eg. C. elegens)? Earl of Arundel (talk) 23:22, 3 November 2022 (UTC)[reply]

The MRCA of C. elegans and H. sapiens was a nephrozoon, a worm-like aquatic animal. The split into Protostomia (to which nematodes belong) and Deuterostomia (to which mammals belong) is estimated to have occurred some 620 million years ago. Obviously, the earliest protostomes were also worm-like, but there is no reason to think they closely resembled nematodes, Because of their soft bodies, nematodes leave not much of an imprint on the fossil record, but the oldest putative nematoid fossils appear to date to 470 million years ago.^[3] --Lambiam 12:50, 4 November 2022 (UTC)[reply]

I often wonder if we will ever see a technology emerge that will allow us to see much further back in the fossil record. Now obviously if the fossil has been exposed to magma or what have you, in those kinds of cases the remains will likely be destroyed for all practical purposes. But otherwise, special imaging techniques or what have you might be able to look even deeper into the past. Who knows, we may find that C. elegans for example dating back even a billion years or more, I imagine. (Just being an "arm-chair scientist" here, of course. Surely there are many other important considerations.) Earl of Arundel (talk) 02:44, 5 November 2022 (UTC)[reply]

BTW, C. elegans is as "highly evolved" as H. sapiens. It is exquisitely adapted to its ecological niche. --Lambiam 12:54, 4 November 2022 (UTC)[reply]

Just to clarify and elaborate on Lambiam's very salient point, every living being alive today is equally as "highly evolved" as every other one. The entire system of life started out in the murky past, but that nematode is part of a chain of evolution which is equally as long as the chain of evolution that produced you. In terms of "time we've spent evolving", all of life has been evolving since life began, so we're all equally as highly evolved. If you really want to get pedantic, since nematodes have a shorter life cycle than mammals (which is to say, they get in more generations in less time), if you want to get down to it, the nematode is actually more evolved than a human is. --Jayron 32 16:30, 4 November 2022 (UTC)[reply]

I see. So the assumption that "less complexity" necessarily means "lower on the chain of evolution" is clearly flawed. Modern organisms are highly-evolved in their own, unique ways, adapting to changing environmental pressures for aeons. Fair enough. Kind of sad to think that not a single extant ancestor of ours can be found on Earth today in its original form though. Like, the DNA sequences of our ancestors have literally been forever erased by the sands of time! How utterly depressing.... Earl of Arundel (talk) 02:27, 5 November 2022 (UTC)[reply]

Watt and erg relation

Can we write that: 1 Watt/cm^2 = (10^7 ergs/cm^2) * sec Why or Why not ? — Preceding unsigned comment added by Malypaet (talk • contribs) 18:16, 1 November 2022 (UTC)[reply]

Because that's not right. A Watt is a J/sec, so a Watt/cm^2 is a J/(sec * cm^2), and since a J = 10^7 ergs, then a Watt/cm^2 = 10^7 ergs/(sec * cm^2). You need to divide by sec, not multiply. --Jayron 32 18:56, 1 November 2022 (UTC)[reply]

Creating calcium carbonate blocks

Is it possible to cast calcium carbonate in large format solids, or create via some chemical reaction? I was watching some folks laser etch eggshells and wanted to get my hands on some large pieces of solid caco3 but cant find any suppliers, or if its even possible. thanks ^Thanks,L3X1 ◊distænt write◊ 22:25, 1 November 2022 (UTC)[reply]

sounds to me you're trying to reinvent limestone :) Dr Dima (talk) 22:56, 1 November 2022 (UTC)[reply]

"We are one of the noted manufacturers and suppliers of High Quality Calcium Carbonate Blocks. These blocks are made under the supervision of our trained professionals so that the final output fulfill with the international quality standards. As per the variegated requirements of clients, these blocks are made available in different sizes and specifications. With the help of our wide distribution network, we make sure safe transportation of these blocks within the specified period of time. High Quality Calcium Carbonate Blocks are known for high strength, wear & tear resistance and excellent electricity conductivity". [4] Alansplodge (talk) 23:11, 1 November 2022 (UTC)[reply]

Thanks! ^Thanks,L3X1 ◊distænt write◊ 00:35, 2 November 2022 (UTC)[reply]

Depending on what you want to use it for, perhaps optical purposes, see Iceland spar. Graeme Bartlett (talk) 00:10, 2 November 2022 (UTC)[reply]

Calcium carbonate is what is the difference between hot tap water and cold tap water. How would 1 extract it from water though? Or ice. 67.165.185.178 (talk) 00:47, 2 November 2022 (UTC).[reply]

Reportedly, the temperature also makes a difference between hot tap water and cold tap water. Allow the water to evaporate, and you'll be left with limescale. --Lambiam 03:29, 2 November 2022 (UTC)[reply]

Calcium carbonate is a very common mineral, and exists in MANY different forms and in many different contexts in the world. It is a major component of hard water, often in places where the water supply is in contact with soil or rocks that contains high quantities of calcium carbonate. Various forms of calcium carbonate, or rocks that include calcium carbonate, include calcite, chalk, limestone, and marble. When used as a soil additive, it is commonly called lime, though that term also refers to a number of other calcium compounds, such as calcium oxide and calcium hydroxide, among others. --Jayron 32 11:17, 2 November 2022 (UTC)[reply]

Can Alansplodge speaking for SS Industries of Rajasthan, India please clarify what "excellent" electricity conductivity calcium carbonate is known for? When anhydrous (dry) it is an insulator. Philvoids (talk) 22:38, 2 November 2022 (UTC)[reply]

Sadly my expertise lies in interrogating Google rather than physics or chemistry. Please don't shoot the messenger. Alansplodge (talk) 13:54, 3 November 2022 (UTC)[reply]

Perhaps they consider an electrical conductivity of < 10⁻¹¹ S·m⁻¹ to be excellent. Curiously, they do not mention the material's high thermal conductivity, ~4 W·m⁻¹·K⁻¹, higher than glass. --Lambiam 08:13, 3 November 2022 (UTC)[reply]

November 3

Empty calories

I read a statement by a Dr. Rosen in an article on yahoo!life[5]. She states that diet sodas "are loaded with empty calories". Is that true? Thank you. Hevesli (talk) 10:22, 3 November 2022 (UTC)[reply]

According to Coca-cola, their diet coke has only one calorie per 330 ml can, so more just empty I would have thought, apart from E numbers. Mikenorton (talk) 10:42, 3 November 2022 (UTC)[reply]

I wonder if that particular quote was taken out of context by the article writer. It would seem to apply better to non-diet drinks. Alansplodge (talk) 13:51, 3 November 2022 (UTC)[reply]

Yes, the usual meaning of "empty calories" is calories consumed without benefit of any other nutrients such as vitamins or protein. Abductive (reasoning) 03:50, 4 November 2022 (UTC)[reply]

Cooling hot oven racks

Situation: I start heating up my oven, and at one point take two oven racks out when they are quite hot. I hold one with my one hand steadily (in a mitten), and another with another hand (in mitten), shaking it vigorously so that the individual rods vibrate. Will there be an appreciable difference in cooling rate between the two? --Ouro (blah blah) 18:09, 3 November 2022 (UTC)[reply]

The "standard equations" for such scenarios tend to be large and painful to solve. I pulled up my go-to reference - Incropera et al., Fundamentals of Heat and Mass Transfer, (my copy is a 7th edition). As you would expect, arrays of long-cylindrical-metal-rods are solved around Page 618. Rather than quote a complicated equation out of context, it's worth saying that the math is complicated. It would take six hundred and seventeen pages of preparatory explanation to do it justice (... that's why this equation is on Page 618). "Will there be an appreciable difference in cooling rate?" Yes. "Exactly how appreciable?" ... So, let's break this down: what is the metal made of? What is the air made of? How hot is the metal? How hot is the air? How precisely can you measure temperature? How many places (throughout your scenario) are you using a simplifying assumption? (Did you extract the rail from the oven in zero seconds, or in finite time? Is air viscous, or not viscous? When a steel rod vibrates, to what extent do you assume the displacement to be infinitesimal? Exactly how round are the metal rods that constitute your oven-rack?) We can literally (literally) spend hundreds of pages - hundreds of thousands of complicated mathematical words to talk about all the details. Golly, even I had to actually look up Nusselt number to refresh my memory - and I'm some kind of scientist - not just anyone, either - I happen to be the original author of the Official Wikipedia Science Reference Desk Mathematical Model And Numerical Simulator For How Much My Coffee Has Gone Cold As I Expend Time Answering Thermal Physics Questions On The Science Reference Desk!

The more pertinent questions revolve around a more general question: which of these complicated details of engineering and physics are relevant to your scenario?

Are you simply baking cookies? Few of these details materially affect the quality of your cookies.

Nimur (talk) 18:34, 3 November 2022 (UTC)[reply]

And don't forget that by shaking one hand, you are likely causing minor vibrations in the rest of your body so that the other hand is not "steady". AND the waving of the one rack will produce air currents that will blow past the other rack..... --User:Khajidha (talk) (contributions) 18:55, 3 November 2022 (UTC)[reply]

Nimur... I do not need to be baking anything, that's just something I thought of... I just wondered... I can appreciate the diversity of variables that need to be taken into account and am thankful for Your answer - doing justice to the complexity of the problem. Appreciable would mean in excess of a few percent I'd say. Thanks.

Khajidha... of course. Then again, it's just a thought exercise (a WP:RD exercise if you will).

Thanks friends --Ouro (blah blah) 19:13, 3 November 2022 (UTC)[reply]

Right-o - it's just that it's hard to say confidently whether we're looking at differences in - let's just pick one quantifiable parameter, cooling rate - of a few parts per hundred, or a few parts per million. It's hard to know - confidently - whether we can safely ignore some effects!

The beauty, and the curse, of the mathematics that model convective heat transfer is that they are highly sensitive (in the mathematical sense of that word). Small changes can be amplified by physical processes that are governed by nonlinear equations.

It is no coincidence that heat transfer is studied as a part of statistical physics. It is also no coincidence that convective heat transfer relates strongly to turbulent flow.

Your thought-experiment is a great one - but to really do it justice, we do need to start with much simpler thought-experiments. By this, I mean that we have to spend a pretty significant amount of study before we can come to any conclusion, if we care about a scientifically valid answer - let alone one that is accurate and precise enough to say "yeah, that's an effect whose size is, say, 3% to 5%."

Otherwise, we're kind of just not doing science - we're just guessing.

There is a lot of stuff in our universe - basically, the entire set of topics that we call experimental physics - where we can perform a controlled experiment more easily than we can answer from a theoretical perspective. But, a true experimental physicist cares about controlling the experiment so that they can draw some kind of generalizable conclusion. This is exactly how we end up with thousand-page textbooks where we can say, "hm, for a rack made out of an array of rods, use Equation 9.34 from the chapter on Free Convection." I mean, a correct answer does exist - a correct answer can exist - and that's what separates real physicists from postmodernist nihilists. We (physicists) subscribe to a world-view in which we believe we can find out truth and assign a number to it. They (post-modernist nihilists) tell us that truth defies understanding, let alone quantification.

"Neither of these world-views is more correct," say the post-modernist nihilists.

"Post-modern nihilists are in no position to tell us about correctness," retort the physicists.

Only... the experimental physicist has the fortitude of moral character, nay, the intellectual resolve, to spend thousands of hours slogging through the work to prove the philosophers are wrong.

So, uhm, ... let's get crackin' on that!

Nimur (talk) 21:11, 3 November 2022 (UTC)[reply]

Yes, waving them around will increase the rate of cooling. That's because as well as radiative and convective heat loss you also get conductive heat loss into cooler gas. That's why car radiators have fans. Greglocock (talk) 21:45, 3 November 2022 (UTC)[reply]

Car radiators use the simplifying assumption that the gas outside the engine cowling will be cooler, so they use a fan to impel cool gas across the radiator. Ambient air outside can be approximated as an infinite cold reservoir. So, it is thermodynamically efficient for the engine to spend a few extra joules (... which needs energy, which means burning more fuel, which adds extra heat), and then convert this surplus heat energy into kinetic energy in the fan, and we assert that the fan shall impel cold air toward the radiator, improving net efficiency during normal operation in normal, specified conditions.

Fans, like all non-perpetual motion machines, need energy to spin - and in this case, the energy comes from the engine, and so ... amazingly, adding the fan to the automobile engine causes heat to be added to the universe. It only so happens that the automobile engine is designed to put this heat "somewhere else". Somebody, (an engineer, perhaps) had to study those horrible airflow and convection equations to make sure this actually has a net cooling effect on the portion of the machine we care about! Does the fan actually cool the engine if... the outside air temperature is in Flagstaff, Arizona, in the summer, while driving 400 kilograms of astrophysicists up a steep hill, or is this contrived situation a case of inversion in parameters, in which the existence of this cooling-fan actually adds heat to the radiator?

What about other scenarios - where the normal operation of the system does not necessarily rely on forced air cooling? What if we designed for maximum efficiency with passive cooling - a fan would move us away from maximum efficiency!

Would a cooling fan be of any assistance in, say, an airplane engine? ...Or a coal-fired powerplant turbine? Would it cool the metal any faster if the "oven" were an iron smelter? How about a blast furnace (where cold air is added to increase the net temperature)? How about a sports car with a turbocharger, where cold air is blown at the engine intake by a fan? It really, really matters where the fan is and where the air goes - turbocharging an engine usually makes it get hotter, because cold air does more than convect - it can combust!

How about if the "cylindrical metal tube" is radiating into a cooling fluid that radiates into the vacuum of space (... or is exposed to direct sunlight in the vacuum of space), fluctuating between 4 and 280 kelvins, depending on the time of the month? How many billions of dollars does it cost if a simplified assumption flips the sign of the cooling rate, and what is the impact to weather forecasting for half a planet for the next two decades?

The scenarios are diverse, and in this diversity, the magnitude of the rate of cooling changes dramatically. In fact, even the sign of the value changes. So, it's never so simple unless we know what the scenario is doing!

Nimur (talk) 16:10, 4 November 2022 (UTC)[reply]

"What if we designed for maximum efficiency with passive cooling" For interest, this is exactly the case for Formula One (and other) racing car engines, which is why, when they return to their pits, team personnel have to direct externally driven cooling fans into their air intake ducts. {The poster formerly known as 87.81.230.195} 5.64.163.219 (talk) 08:15, 5 November 2022 (UTC)[reply]

A steadily held hot rod mainly cools by transferring heat to the surrounding air. Since the rate of heat flow is proportional to the difference in temperature between the rod and the air, the heat flow will thereby decrease and the cooling slows down more than necessary. This can be avoided by replacing the warm air continually by fresh cold air. One way of accomplishing this is by aiming a ventilator at the rod. Another way is swinging the rod through the air. Shaking it will mainly have an effect if the absolute displacement is considerable. --Lambiam 21:43, 3 November 2022 (UTC)[reply]

Just to add another important perspective here, and add on a bit to the excellent (though a bit TLDR) responses by Nimur above; when you wave the rack through the air, you're basically trying to take advantage of convection to the heat transfer situation. We can confidently say yes to the notion that it will cool off faster. The devil is in the details, however; if it cools an extra 0.01 kelvin per hour, that's hardly worth the effort spent doing it. The problem is that fluid dynamics is a famously impenetrable science to work in theoretically. You would need something akin to Newton's laws of motion and the work equation and the law of conservation of energy and the like for fluids (rather than objects). For objects, these are simple three-variable equations that any middle schooler can solve. For fluids, we've got the equations, its just that no one can solve them. No really, the fluid equivalent of all of the dynamics and kinematics equations you learned in high school physics are called the Navier–Stokes equations; actually solving them in three dimensions represents one of the Millennium Prize Problems, which tells you they are still unsolved. The issue is that Navier-Stokes doesn't play well with turbulence, and that's why we have the Navier–Stokes existence and smoothness problem. Since solving "how much energy is carried away by convection" requires us to accurately model fluid dynamics around your waving oven grid, and that flow will be turbulent, not only do we not have solutions for such a model; we don't even know whether or not they exist. --Jayron 32 12:30, 4 November 2022 (UTC)[reply]
I'll work on brevity, (but not today)! Nimur (talk) 16:11, 4 November 2022 (UTC)[reply]

I got my brevity down pat, Nimur, but you forget it if you do such excellent work. I am reading through your answers, friends, and thanks. Of course we could have (should have) started off much simpler, with say - one rod (one wire) that is shaken or not and then to measure the heat transfer away from the object... and then somehow transpose that (with all the details like material, make-up, design details, etc.) and work upwards towards the oven rack. And Jayron you're absolutely spot on about fluid dynamics being difficult - I know. Thanks anyway, you got me a lot to think about. --Ouro (blah blah) 18:18, 4 November 2022 (UTC)[reply]

One thing that is still true; you can work this stuff out empirically. You can shake rods of different thicknesses at different speeds in different environments, you can plot the results on graphs and interpolate and extrapolate the data to develop models of cooling that don't depend on knowing anything about fluid dynamics. Newton himself developed Newton's law of cooling using carefully controlled experiments. However, the problem is that you can't work from first principles to develop a theory of cooling that would work here, in the same way that we have good theories explaining things like balls rolling down hills and hockey pucks colliding on ice. Even though the same principles apply to describe colliding hockey pucks and cooling off waving chunks of metal in the air, the math is just too intractable using the tools we have today to do so. --Jayron 32 18:37, 4 November 2022 (UTC)[reply]

Kem Kem Leptocleidid.

When is the new leptocleidid plesiosaur from the Kem Kem going to be given a name? CuddleKing1993 (talk) 21:27, 3 November 2022 (UTC)[reply]

If you mean a binomial name, it is not so simple as naming a new-born baby. The first issue is the assignment of a genus. Do all fossils from this group belong to the same genus? And if so, is it one of the known genera, or a new one? Such questions require careful study. If this can be resolved, the questions repeat at the species level. --Lambiam 22:12, 3 November 2022 (UTC)[reply]

The ICZN, International Commission on Zoological Nomenclature, maintains the process for assigning binomial names; they don't name the organisms themselves but they do set the standards for how things are supposed to be named, and they do adjudicate disputes. The process is described in a document called the International Code of Zoological Nomenclature (also abbreviated ICZN). The process of granting the name does take time, so it's hard to predict "when" such a name will be published. It depends a bit both on the discoverer of the species (who has the right to name it) and to the publisher of the work in which it is named. As Lambiam notes above, what needs to be done first is to figure out what the taxonomy/cladistics of the species is; such as to which genus it should belong, or does it represent a new genus; should it be a species on its own, or a subspecies, to which family should it belong, and so on up the line. That kind of determination takes real labor and work on the part of scientists who need to look at the fossils, analyze them, and come to conclusions. --Jayron 32 12:16, 4 November 2022 (UTC)[reply]

In the past discoverers would name specimens without taking such careful precautions. But this led to many cases of multiple names being given to what turned out to be the same thing. Which meant standards had to be set up for which name was to be used going forward. Usually strict priority is the determining factor, but there have been exceptions that were explicitly made for good reasons (if the oldest name was never used after its initial publication and a later name was used in numerous publications, it would be counterproductive to insist on strict priority). --User:Khajidha (talk) (contributions) 13:41, 4 November 2022 (UTC)[reply]

November 4

fungal infections from ancient tombs

I've been seeing stories[6][7] that after 12 research scientists entered the 500 year old tomb of Casimir IV Jagiellon, 4 of them died days later, and another 6 died months later. It is speculated that the deaths may have been due to a fungal infection caused by exposure to Aspergillus while in the tomb. My question is about the specific incident involving the King of Poland's tomb in the 1970s. I've had a difficult time finding contemporary accounts or any reliable sources to confirm these deaths. Any additional info would be greatly appreciated. mikeu ^talk 23:28, 4 November 2022 (UTC)[reply]

This is already mentioned in the article you link, in the section Tomb, with a reference cited to a reliable source. {The poster formerly known as 87.81.230.195} 5.64.163.219 (talk) 08:19, 5 November 2022 (UTC)[reply]

November 5

Nature versus nurture

It is often said that the heritability of IQ increases with age and was/is greatest in school. This worries me a bit, it looks very much like an artifact. Where the children receive by force a same way of life, the way of life changes nevertheless depending upon family etc.. Have the intelligence researchers considered this? 2A02:908:424:9D60:0:0:0:F38B (talk) 00:02, 5 November 2022 (UTC)[reply]

What do you mean by "receive by force a same way of life"? ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:23, 5 November 2022 (UTC)[reply]

The evidence is increasingly pointing to intelligence being all nurture, no genetics. Abductive (reasoning) 01:02, 5 November 2022 (UTC)[reply]

What evidence? ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:37, 5 November 2022 (UTC)[reply]

They are forced to go to school, to learn and so on. They hang out in classes, they have the same environment. 2A02:908:424:9D60:0:0:0:F38B (talk) 08:14, 5 November 2022 (UTC)[reply]

@@ Line 199: / Line 199: @@
 I've been seeing stories[http://www.antimicrobe.org/hisphoto/history/Aspergillus-Mummys%20curse.asp][https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(03)14268-7/fulltext] that after 12 research scientists entered the 500 year old tomb of [[Casimir IV Jagiellon]], 4 of them died days later, and another 6 died months later. It is speculated that the deaths may have been due to a fungal infection caused by exposure to [[Aspergillus]] while in the tomb. My question is about the specific incident involving the King of Poland's tomb in the 1970s. I've had a difficult time finding contemporary accounts or any reliable sources to confirm these deaths. Any additional info would be greatly appreciated. [[User:Mu301|mikeu]] <sup>[[User talk:Mu301|talk]]</sup> 23:28, 4 November 2022 (UTC)
+:This is already mentioned in the article you link, in the section [[Casimir IV Jagiellon#Tomb|Tomb]], with a reference cited to a reliable source. {The poster formerly known as 87.81.230.195} [[Special:Contributions/5.64.163.219|5.64.163.219]] ([[User talk:5.64.163.219|talk]]) 08:19, 5 November 2022 (UTC)
 = November 5 =