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January 10

Neurotransmitters

Is there a neurotransmitter which has the opposite effect of dopamine and/or suppresses the release of dopamine? Also, is oxytocin synergetic with or antagonistic to dopamine, or neither? 2601:646:8080:FC40:3982:CA81:D9FD:A932 (talk) 03:41, 10 January 2024 (UTC)

Monoamine oxidase (MOA) break down dopamine and therefore has sort of the opposite effect by reducing dopamine levels. --CometVolcano (talk) 14:59, 13 January 2024 (UTC)

Thinking in that same direction, there are a bunch of factors that can upregulate the dopamine transporter, which would increase dopamine reuptake (clearing it from the synapse). DMacks (talk) 22:40, 13 January 2024 (UTC)

Thanks, but I was asking specifically about neurotransmitters, not enzymes. 2601:646:8080:FC40:B181:27B1:C710:220B (talk) 00:45, 16 January 2024 (UTC)

Melatonin, according to dopamine antagonist. Abductive (reasoning) 17:29, 17 January 2024 (UTC)

Thanks! 2601:646:8080:FC40:B181:27B1:C710:220B (talk) 03:43, 18 January 2024 (UTC)

Dopamine opposes the action of dopamine, in two senses! Firstly, dopamine acts at both D1 and D2 receptors, and the intracellular signalling pathways mediated by each generally oppose one another; the former leads to an increase in cAMP, and the latter to a decrease. Secondly, D2 receptors on synaptic nerve terminals act to suppress neurotransmitter release. So, dopamine suppresses its own released (auto-inhibition). This all points to that fact that, for most neurotransmitters (other than the rather boring glutamate and GABA), it doesn't make sense to think of the function of a neurotransmitter without reference to the receptors and signalling pathways they relate to. Klbrain (talk) 11:15, 20 January 2024 (UTC)

That's just an ordinary case of negative feedback (which is normal in all living systems) -- I was asking about neurotransmitters which actually decrease the amount of dopamine signalling! 2601:646:8080:FC40:0:0:0:AF1A (talk) 13:27, 21 January 2024 (UTC)

Sterile Surgery

Joseph Lister (and others) had pretty much proven that sterile techniques during surgery and childbirth saved lives. But he and the others met fierce resistance. In 1873 The Lancet, the leading medical journal, disparaged Lister and recommended his procedures not be followed. Who edited The Lancet at that time? Any ideas of his/its motivation--after all, rich people and their babies died of infections too. 24.72.82.173 (talk) 22:58, 10 January 2024 (UTC)

I saw the name Richard Beverly Cole listed at a few places online, which lead me to R. Beverly Cole. Sure enough, the article states: "In 1890, Cole registered his opposition to antiseptic injections in obstetrics before the obstetric committee of the Medical Society of the State of California, reasoning that deliveries had long been accomplished before the introduction of antisepsis." This was 17 years later, in 1890. Guy sounds pretty stubborn! Beach drifter (talk) 00:56, 11 January 2024 (UTC)

Cole never edited The Lancet. DuncanHill (talk) 01:25, 11 January 2024 (UTC)

I see now that the picture I was looking at was of The Western Lancet - https://www.flipkart.com/western-lancet-1873-vol-2-monthly-journal-devoted-medicine-surgery-collateral-sciences-classic-reprint/p/itm39c65d42bf025 Beach drifter (talk) 01:45, 11 January 2024 (UTC)

The Lancet in 1873 was edited by T. H. Wakley and James G. Wakley. DuncanHill (talk) 01:23, 11 January 2024 (UTC)

Slightly unrelated, I remember reading about how the innovation of anesthesia was spread to faraway continents in, say, two years, while disinfection took decades. According to this source, the reason was that anesthesia has a very visible benefit for both the surgeon and the patient, but disinfection does not. --Error (talk) 09:46, 12 January 2024 (UTC)

Resistance to Lister's methods seems to fall into two camps; one being those who saw nothing wrong with traditional techniques:

At the 1869 meeting of the British Medical Association in Leeds, the local senior surgeon Thomas Nunneley (1809–1870) launched a violent attack upon antisepsis. He outed himself as ultra-conservative, not just by denying the germ-theory of wound infections but also by misquoting the experience of local colleagues who had had some success with Lister’s methods. As Lister pointed out in his reply in the BMJ, Nunneley ‘dogmatically oppose[s] a treatment which he so little understands and which, by his own admission, he has not tried’.

The other group, such as Lawson Tait, were more enlightened and had acheived considerable improvements by means of other chemicals or simple hygene with soap and water; These approaches were also much less cumbersome, expensive and time-consuming than antisepsis using carbolic acid sprays, and thus better suited to busy practitioners and in emergency cases... Statistics were used to suggest that cleanliness was more successful than Listerism in preventing death.

See Statistics and the British controversy about the effects of Joseph Lister’s system of antisepsis for surgery, 1867–1890. Alansplodge (talk) 12:12, 12 January 2024 (UTC)

In Europe the dispute turned ugly Ignaz Semmelweis. 2A02:C7B:11B:9000:102:E620:5DF:9CB1 (talk) 15:42, 12 January 2024 (UTC)

Note that there is a difference between antiseptic procedures and aseptic procedures. Lister invented the former. It involves the use of fairly aggressive disinfecting agents (in Lister's case carbolic acid), with corresponding side effects. It was a big step forward, but under most circumstances, modern procedures are aseptic, i.e. we sterilise the patient, tools, and surgeon, and try to avoid the introduction of germs to begin with. Anti-septic procedures are a fall-back if asepsis fails or cannot be guaranteed. --Stephan Schulz (talk) 23:57, 18 January 2024 (UTC)

January 11

Planck's Law and Kirchhoff-Clausius law

In § 7 Chapter II of "On the Law of the Energy Distribution in the Normal Spectrum; by Max Planck."[1], one reads:

"According to Kirchhoff-Clausius law, the energy of a temperature ϑ and the number of vibrations ν, when emitted by a black surface per unit of time into a diathermic medium, is inversely proportional to the square c² of the propagation speed."

I did not find this law in this form anywhere . Can anyone help me understand this sentence? Malypaet (talk) 22:59, 11 January 2024 (UTC)

Finaly I found it in "eight lecture at colombia" from Gutemberg project p35:

G. Kirchhoff, Gesammelte Abhandlungen, Leipzig, J. A. Earth, 1882, p. 594.[2] Malypaet (talk) 22:12, 13 January 2024 (UTC)

January 13

To what large is height hereditary?

To what extent is hereditary of height of a human body? 2A02:8071:60A0:92E0:1DF0:3298:75EF:4F08 (talk) 23:43, 13 January 2024 (UTC)

60-80%, according to molecular biologist Chao-Qiang Lai, "up to 80%", according to a "landmark" study. Clarityfiend (talk) 23:47, 13 January 2024 (UTC)

This is disputed, as these GWASes are inherently flawed, and with height there is maternal effects and even grandmaternal effects, which are nutrition-history-related. A better guess is 0%. Abductive (reasoning) 14:55, 14 January 2024 (UTC)

0% to 80% is a large ranche 2A02:8071:60A0:92E0:8F6:F3C6:49F3:5A10 (talk) 17:27, 14 January 2024 (UTC)

Personal observations: Other than abnormalities, like giantism or dwarfism, for example, height seems often to be a function of when youngsters experience their "growth spurt" or achieve physical maturity. The later it comes, the taller the individual tends to be. I would think that could be a function of genetics. But as Abductive points out, nutrition could figure into it too. ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:15, 14 January 2024 (UTC)

But how could it be that some persons get some investigation on their bones and get called how hight they will growth? I've heared about this from persons who are actually quite hight and they get call it before puberty. 2A02:8071:60A0:92E0:90D:EB9E:AAEF:6E30 (talk) 21:45, 14 January 2024 (UTC)

Geneticists who estimate heritability are really not so naive as to be unaware of confounds such as maternal effects and of the effect of nutrition. One way to factor them out is to compare monozygotic and dizygotic twins: both sorts share the same environment if they grow up together, but monozygotic twins are 100% identical genetically, whereas dizygotic twins share only 50% of their genes. This and this are a couple of studies utilising this methodology. Another approach of disentangling genetics and environment relies on adoptions. The studies use large sample sizes and yield consistent results. Nobody should be claiming here that the heritability of human height is 0. JMCHutchinson (talk) 21:09, 14 January 2024 (UTC)

One of the main maternal effects is the size of the mother's uterus, which is affected by their height, their previous pregnancies, and their nutritional status at age 12 or so. One cannot use twins without thinking, as they share a uterus. Abductive (reasoning) 22:50, 14 January 2024 (UTC)

You can compare monzypotic and dizygotic twins. 2A02:8071:60A0:92E0:90D:EB9E:AAEF:6E30 (talk) 00:21, 15 January 2024 (UTC)

Yes, the shared uterus, like the shared socio-economic status, nutrition, etc., of twins is an advantage inherent in twin studies, not a problem with them. Twins largely share their environment, so what is left to explain inter-twin differences is noise (in the case of monozygotic twins) and noise + half their genes (in the case of dizygotic twins). JMCHutchinson (talk) 08:09, 15 January 2024 (UTC)

The articles Twin study, Heritability, and GWAS set out a number of very serious concerns. Anyway, it really depends on what the IP is trying to do with their question. Do they want the current estimate to tell people at parties? Or are they going to write a paper on it? Are they going to breed cows and need a number? Abductive (reasoning) 13:50, 15 January 2024 (UTC)

Agree completely. You should follow what the scientific papers say instead of someone who is wrong on the internet unless you have a very good reason to know otherwise. NadVolum (talk) 21:36, 14 January 2024 (UTC)

Basically, the 0% answer is what a graduate student's committee members will say to them if they propose relying on somebody else's GWAS for their thesis or for their career advancement. Abductive (reasoning) 22:50, 14 January 2024 (UTC)

There are other ways than just GWAS, right? 2A02:8071:60A0:92E0:90D:EB9E:AAEF:6E30 (talk) 00:20, 15 January 2024 (UTC)

I am not understanding Abductive's arguments, but GWAS (Genome-wide association study) is a side issue. GWAS articles, such as the one cited above by Clarityfiend, treat the heritability estimates from twin studies as a gold-standard value. They are hoping that their own independent estimates of heritability, based on statistical comparison between gene sequences (from whole genome sequencing) and height, reach the same ball-park figures. So far these estimates tend to be lower. Hypotheses to explain the discrepancy are many genes having small effects, rare genes having big effects, and interactions between different genes (all of which are difficult to detect statistically). Indeed with larger sample sizes and more sophisticated analyses the gap is closing. This is a general issue with GWAS of other traits also, so raw GWAS estimates of heritabilities are not yet considered reliable. JMCHutchinson (talk) 08:29, 15 January 2024 (UTC)

We're supposed to try and refer people to an appropriate Wikipedia aricle for questions like this, and there is one Human height. Not go in for pushing ones interpretation of how genetics works. Saying 0% is like saying anyone could have run as fast as Usain Bolt with the appropriate upbringing and training. Or at least coming towards that to except for some epigenetic, mitochondrial and prenatal effects. It's always the mothers fault they can't run that fast :-) NadVolum (talk) 14:43, 15 January 2024 (UTC)

A glance at this thread will reveal that I have shaded my meaning correctly throughout, and nobody is misled. Abductive (reasoning) 17:57, 15 January 2024 (UTC)

Shaded your meaning correctly? Pull the other one. NadVolum (talk) 18:17, 15 January 2024 (UTC)

Height is 100% hereditary. If your parents are three-dimensional, you will be too. AndyTheGrump (talk) 18:21, 15 January 2024 (UTC)

But then how can you explain that all children of two-dimensional parents are 5-dimensional?!? --Stephan Schulz (talk) 09:39, 19 January 2024 (UTC)

What does the OP mean by "to what large...", as opposed to "to what extent" or "to what degree"? Is that some odd mistranslation from German? ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:45, 19 January 2024 (UTC)

Probably because 'to what depth is height heriditary' would just get the answer 100% ;-) NadVolum (talk) 21:50, 19 January 2024 (UTC)

January 14

Could graphene ever replace macroscopic metal conductors in any home or car application?

It'd have to be stacked without increasing the ohm-meters too much, and I don't know if there's anything a middle-class person might own that could be improved by replacing some or all the macroscopic conductor with stacked graphene. Nanotech would have to get cheap enough to compete with "make the copper thicker". Could graphene ever replace wires that are thicker aluminum instead of copper for mass reasons?

Sagittarian Milky Way (talk) 16:32, 14 January 2024 (UTC)

One presumes you are referring to Ohm metres, not Ohmmeters. Mitch Ames (talk) 05:28, 15 January 2024 (UTC)

I don't know that you'd see a 1--1 substitute for simple loose copper wire, since that has important metallic properties that something mostly-graphene won't replicate, even if cheap and light. (Like, you couldn't just replace phone and electric catenary lines with some graphene material because it won't stretch. But there's an awful lot of electric and telecoms infrastructure that isn't dangling copper cable, including all the new big stuff.) But see a 2022-10-11 Caltech Weekly article on some of the flexible graphene structures they're making, including a graphene coating for copper traces on silicon. A more detailed technical review of stacking graphene is in Han et al 2021 if you want to try finding something of interest. SamuelRiv (talk) 06:43, 15 January 2024 (UTC)

Also an interesting 2014-09-02 StackX discussion on graphene conductivity notes that the practical gains aren't anywhere as huge as the hype (1.4 times more conductive, or 5.8 times compared by weight), even assuming you can make or engineer around the issue of needing near-perfect sheets. This as opposed to the possibility of using superconductive lines for either long-range transmission (EETimes 2022-07-07) or metro-area grids (Yang et al 2020) (also not as good as the hype at present). SamuelRiv (talk) 07:20, 15 January 2024 (UTC)

Oh -- airplanes! That'd probably be the case where everything from high-performance jets to home-built hobby kits would replace any metal wiring with some mostly-graphene substitute, even if it cost 100x more per meter, since the weight savings is so much, and it's all enclosed. (You can already just use powdered graphite as a conductor (there's an Instructable for making a weak conductive glue with it), but that's altogether not great.) So I'll instead guess sooner rather than later, anything that flies would have graphene wiring if some viable product is invented, even if it's much more expensive. SamuelRiv (talk) 02:18, 16 January 2024 (UTC)

January 15

Human body 5G emission

Using black body radiation, what is the power of what the human body emits in 5G frequencies, compared to a phone? Also, a 100W incandescent lightbulb? Zarnivop (talk) 10:04, 15 January 2024 (UTC)

This sounds potentially like a homework question.

The solution method is to integrate Planck's law over all space, but just for the frequency range of interest. You'll need to specify a surface temperature for a human being and the lightbulb, although the latter is easy to calculate from the power, given the Stefan-Boltzmann law. PianoDan (talk) 15:29, 15 January 2024 (UTC)

I am a bit old for homework. My children are, too. The surface temperature probably is ok with 34 Celsius. I have no idea about the lightbulb. Zarnivop (talk) 17:43, 15 January 2024 (UTC)!

It is much simpler to use Rayleigh–Jeans law for such low frequencies. So, we have for power $P$:

$P={\frac {2\pi k_{B}TS}{3c^{2}}}(\nu _{2}^{3}-\nu _{1}^{3})$

where $S$ is surface area of a human body (or bulb filament), $\nu _{2}$ and $\nu _{1}$ are upper and lower frequencies of the 5G band, $T\approx 300$ K (or 2500 K) and other parameter explained in the article. Ruslik_Zero 21:03, 15 January 2024 (UTC)

so 2×pi×1.38exp(−23)×(273+34)×1.9÷(3×(3 exp(8)^2))×(71 exp(6)-24.25 exp(6))

I got 8.76. 8.76 what?Zarnivop (talk) 01:27, 16 January 2024 (UTC)

Well everything would have to be in SI base units, power in watts but 8.76 watts from a human seems too big. Frequency would have to be in seconds^-1 AKA inverse seconds AKA hertz but 24.25 million hertz and 24.25^6 hertz both seem too low. There seems to be a typo in the formula, they both say v2 or nu2, and they're both cubed I think? Sagittarian Milky Way (talk) 02:11, 16 January 2024 (UTC)

My calculator failed me - it had exp(-27) outside the window. But again, 8.76 exp (-27) What? Watts? Is it even true? Sounds very low to me.Zarnivop (talk) 02:19, 16 January 2024 (UTC)

I fixed an error in index (2->1). So the result for human body is (with $k_{B}=1.380649*10^{-23}$ J⋅K⁻¹, S=1.9 m², $\nu _{1}=10^{9}$ Hz and $\nu _{2}=3*10^{10}$ Hz): P=4.9×10⁻⁶ W. Ruslik_Zero 10:35, 16 January 2024 (UTC)

The nice thing about a consistent system of units of measurement is that you never have to worry about units. Put in all the inputs, including constants, in the base units of the same, consistent system and you'll get the output in base units of the same system. Whether that's SI or cgs doesn't matter. In SI, k_B is in joule per kelvin, T in kelvin, S in square metre, c in metre per second, ν in hertz and P in watt. Note that the US customary system isn't consistent, which is why scientists don't use it. PiusImpavidus (talk) 10:53, 18 January 2024 (UTC)

"Vario speed"??

Siemens claims to have a technology, "Vario speed", that speeds up washing machines cycles without hurting the results. Nowhere did I find what it actually do. Zarnivop (talk) 12:09, 15 January 2024 (UTC)

This technology seems widely used across Siemens products [3]. 78.146.96.26 (talk) 12:30, 15 January 2024 (UTC)

Yes, - or at least they all reduce cycle time and were given the same name. But there is no telling what it is.Zarnivop (talk) 12:49, 15 January 2024 (UTC)

Maybe it's a trade secret. Apparently this company invents 21 things every day [4]. You can check applications at [5]. 78.146.96.26 (talk) 14:03, 15 January 2024 (UTC)

according to 825553 , Reply# 18 it is using higher drum speed (650rpm??) during wash. Zarnivop (talk) 17:49, 15 January 2024 (UTC)

I was hoping they used a bit of intelligence looking at what needed to be done. But no as you say it is running faster - and using more energy. NadVolum (talk) 18:52, 15 January 2024 (UTC)

But for shorter time span. Zarnivop (talk) 01:19, 16 January 2024 (UTC)

More energy overall. NadVolum (talk) 10:17, 16 January 2024 (UTC)

I have seen such a setting on a 'Bosch' (apparently a Bosch/Siemens collaboration) dishwasher. It provided a cycle time approximately 60% of the default 'Eco' cycle time. The dishes came out equally clean, but not so dry. -- Verbarson  ^talk_edits 11:42, 16 January 2024 (UTC)

January 16

Total arable land

Does arable land exclude forests? As land where trees can grow, can also be cultivated by farmers?

Land use statistics by country

If USA has so much cultivated land(1,681,826 km sq), then how most Americans are urban citizens?

And Canada has less arable land. Then they have excluded forest area in this list. 2409:40E1:1061:5E7A:99F:C56B:E37A:8102 (talk) 13:12, 16 January 2024 (UTC)

Arable land is land that is plowable and can be used for crops. Trees are not considered a crop in this sense.

There is ebb and flow, but most people in the United States live in urban and suburban areas. They do not live in rural areas. In urban areas, there is high density housing. In suburban, it is dense with apartments and townhomes, but you will also find a lot of subdivisions with single family homes on small lots.

They do exclude forests from arable land. It is not plowed and not available for crops. 12.116.29.106 (talk) 16:52, 16 January 2024 (UTC)

Oxford English Dictionary: Arable...L. arabilis, f. ara-re to plough...Capable of being ploughed, fit for tillage; opposed to pasture- or wood-land. — Preceding unsigned comment added by 78.146.96.26 (talk) 17:06, 16 January 2024 (UTC)

How do you say land that can grow crop(s) in the soil without importing any of soil, water, light, CO2 or fertilizer but not necessarily without first cutting down trees? Would olive trees count as crops? What about olive trees in non-native places like California? What about Christmas tree farms? At some point it becomes so close to forests virgin and left alone except for being lumberjacked every few decades or so that it doesn't seem like crop anymore. Sagittarian Milky Way (talk) 19:15, 16 January 2024 (UTC)

The terminology is used for census and taxes. If the administration in charge of the census and/or taxes wants to consider an olive orchard to be arable, it will be arable. If they don't, it won't. Overall, arable is a subset of agricultural used to designate land prepared for crops. It isn't covered in forest. It isn't all gravel. It isn't under water. It is agricultural land that is ready for crops. My experience is in state census and taxes in Hawaii. There are a lot of rules and waivers for declaring your land to be arable and get a tax discount, which is important because land is very limited in Hawaii, so it is highly taxed, so you want as much of it as possible to be legally arable for a tax discount. 12.116.29.106 (talk) 19:31, 16 January 2024 (UTC)

The WP article on arable land gives a precise definition (via FAO) for land use stats. Note in particular: "Data for 'Arable land' are not meant to indicate the amount of land that is potentially cultivable." So no forests. The World Bank data uses the FAO definition. For comparison, the EU definition: "land worked (ploughed or tilled) regularly". (Note this is much more restrictive than the FAO def, which includes pasture etc.) SamuelRiv (talk) 19:38, 16 January 2024 (UTC)

I'm a little confused as to your question regarding most Americans being urban given the large amount of cultivated land. If you read the article that you yourself linked to, you'll see that it isn't that much land compared to the total area of the US. Only 17.1% is cultivated, and 82.9% is not. --OuroborosCobra (talk) 20:01, 16 January 2024 (UTC)

Arable land is land that is tilled ... by Arabs. (Peter Cook). -- Jack of Oz ^{[pleasantries]} 20:33, 16 January 2024 (UTC)

To your question about population, let's take as an example the US state Iowa: population 3.2m, land area 0.14m km², pop density 22.1/km². Nearly 90% of the land area is farmland (though most of that is no longer actively farmed) (Des Moines Register 2018-06-29), so we'll use Iowa as a best/worst-case example in this exercise (since Iowa has actually a lot of urbanization). If all of the US's 1.68m km² of arable land (the rest being either cities, which have relatively little area, or non-arable terrain like mountains and forests, which are mostly uninhabited) had the population density of Iowa, then the US would have 37m people (it actually has almost 336m now). By contrast, just adding the 3 largest US metro areas (NYC, LA, and Chicago) would give about 42m people. You could also compare how many US cities proper you have to add up to be equal (or try if you sort by density instead). Of course, if you excluded Iowa's cities, then the farmland and farm towns won't have a density anywhere near as high as 22/kn². (Not even in the days before mechanized farming, where large workforces may be needed year-round in some areas. The reason is that there'd be less productivity to sustain an even larger workforce, so large farm towns wouldn't grow or be sustainable.) SamuelRiv (talk) 06:42, 17 January 2024 (UTC)

At what point would a faraday cage stop working?

If you hang a small AM/FM receiver in the middle of a meter-radius sphere and wrap the sphere it wouldn't work anymore, at least if the string's non-conductive and wrap is enough layers of aluminum foil (I don't know if 1 is always enough). If the wave's big enough like 540 AM then if you cut a circular hole in the sphere the hole is much smaller than the wave no matter how big it is but I can't possibly believe a shield with a 180° hole in it would block the signal except possibly if the wave would have to diffract or reflect off the room or something to reach the antenna and probably not even that. So how many degrees wide would the hole have to be before the cage would stop working if the hole was pointed upstream?Sagittarian Milky Way (talk) 18:47, 16 January 2024 (UTC)

It would not make any difference which direction the hole was facing, as the electric currents induced in the sphere would flow to where the hole was and some energy could come in. Graeme Bartlett (talk) 21:33, 16 January 2024 (UTC)

Do you know why the photons don't just quantum tunnel through Faraday shields and fine metal meshes? Sagittarian Milky Way (talk) 23:38, 16 January 2024 (UTC)

A Faraday cage operates when an external electrical field causes the electric charges within the cage's conducting material to redistribute so that they cancel the field's effect in the cage's interior. Full shielding is achieved only by a continuous unbroken cage made of a perfect conductor. That is near impossible to create; aluminium has significant ohmic resistance and any conductor has an effective skin depth that decreases with radio frequency. See the article Faraday cage. The rf power leakage allowed by cages made of metal mesh or perforated material is complex to calculate but the subject is covered in Electromagnetic shielding. There are too many variables for anyone here to calculate for you the actual isolation of a particular spherical cage with a particular size hole cutout at 540 kHz or 555 meters wavelength. Philvoids (talk) 01:54, 17 January 2024 (UTC)

So when they say holes much smaller than the wavelength, that's a big oversimplification. Allegedly aluminum foil is conductive enough to block a RFID tag and cellphone reception though. And walls with steel in them sometimes block reception. Since minimum usable signal is non-zero. Sagittarian Milky Way (talk) 03:31, 20 January 2024 (UTC)

Any gap in the wall of a Faraday cage allows the enclosed volume to behave as a cavity resonator. Every cavity has numerous resonant frequencies that correspond to electromagnetic field modes (see Standing waves) satisfying necessary boundary conditions on the walls of the cavity. One resonant mode will be at the wavelength equal to the largest internal dimension of the cavity, which we may compare to the air resonance in a Helmholtz resonator, but sound pressure wave patterns give an inadequate analogy to the various electrical and magnetic modes (TEM, TE, TM, HEM) of radio energy. Examples of analysis and practical testing are in the referenced articles. A problem description like "a 180° hole...pointed upstream" is too simplistic for comment. Philvoids (talk) 14:44, 20 January 2024 (UTC)

January 18

Lanthanum and Actinium

These 2 elements are d-block or f-block? Simple google search says f-block, but other sources, I have, say d-block. Both present their claim with confidence. ExclusiveEditor _{Notify Me!} 15:47, 18 January 2024 (UTC)

This issue is discussed at Periodic table#Group 3 and Group 3 element. La and Ac were thought to be d-block back when electron configurations were first being measured: in 1927, Friedrich Hund thought that the usual trivalency of rare earths meant the configurations of La through Lu were 4f^0–145d¹6s², so that La would be d-block, Ce-Lu would be f-block, and then Hf-Hg would continue the d-block. Since then it became known that this doesn't happen (in fact, almost all 4f elements lack a 5d electron as gaseous atoms), and that the relationship between electron configuration and chemistry is not so simple: transition elements are better thought of as having different configurations depending on their environment. Since at least 1965 (doi:10.1119/1.1972042) it has been suggested that La is really an f-element, as it has chemically accessible f-orbitals that are implicated in bonding, and later authors who focused on this issue have tended to agree. More generally, the elements that can use f-orbitals for bonding are La-Yb and Ac-No, so those are the most natural choice for the f-elements, and Lu and Lr are best treated as the first members of the subsequent d-series. With that said, many textbooks still persist in the old version with La as a d-element – probably as a result of a long string of copying back to Sargent–Welch.

(The same issue of course applies to actinium, but it was naturally studied less due to its radioactivity. That it is an f-element was confirmed by calculations last year: doi:10.1002/jcc.26929.)

P.S. I collected a lot of links to papers about this at User:Double sharp/Group 3 sources. Double sharp (talk) 16:39, 18 January 2024 (UTC)

@ExclusiveEditor: forgot to ping you. Double sharp (talk) 17:16, 21 January 2024 (UTC)

January 19

White Cap Budgies Info

Can someone help me find sources for my draft on whitecap budgies Klajjur (talk) 01:38, 19 January 2024 (UTC)

Wouldn't it be better to add the information to the Budgerigar colour genetics article? If you create a stub for this mutation, it will get very few pageviews. Budgerigar colour genetics gets 53 pageviews a day on average. Abductive (reasoning) 04:37, 19 January 2024 (UTC)

January 20

Old book cover material

Cover material of a 1978 book

Comparing modern and older book covers, I've noticed that their characteristic rugged material, common particularly in the 1960s and 1970s, is hard to find in modern covers (meaning it was probably phased out at some point and replaced by smoother materials, both for hardcovers and soft covers). My WP:OR suggests it was either buckram or leatherine (or both), but could someone confirm? 212.180.235.46 (talk) 14:58, 20 January 2024 (UTC)

Bookbinding#Hardcover binding and Book cover may lead to some relevant information.

As a collector for some decades, mainly of paperback books but also having two or three thousand hardbacks of all kinds and ages, I can say that a great variety of harback cover materials have been used over the years, though this has never been a focus of my collecting, so it's difficult to generalise. {The poster formerly known as 87.81.230.195} 176.24.47.60 (talk) 20:05, 20 January 2024 (UTC)

(Esperanto, sorry, (eo) postvivado / "survival" )

Saluton, mi nepre bezonas metodon por konservi la cerbon sufiĉe bone, ke la teknologioj de la estonteco povu fari ion por la koncerna persono, sed kiu funkcias. Resume, mi havas la komencojn de vojo: vitrifixation kun 2 novigoj: la sojlo de ekscitiĝo de la sinapsoj dum vitrifixation devas esti konservita, kaj la sinapso ne devas esti detruita dum vitrifixation. Ĉu ni povus modifi la artikolon pri krioniko, por informi pri la absoluta urĝeco direkti esploradon al ĉi tiuj 2 aferoj, mi petas? Mi nepre bezonas ĝin. 78.242.18.218 (talk) 21:25, 20 January 2024 (UTC)

This is the English language Wikipedia. Your question may be enthralling and make perfect sense - but to a simple anglophone like me it is as comprehensible as Madarin Chinese. Please rewrite it so that us poor editors understand you. Martin of Sheffield (talk) 21:37, 20 January 2024 (UTC)

Google Translate says:

Hi, I really need a method to preserve the brain well enough that the technologies of the future can do something for the person in question, but that works. In short, I have the beginnings of a path: vitrifixation with 2 innovations: the threshold of excitation of the synapses during vitrifixation must be maintained, and the synapse must not be destroyed during vitrifixation. Could we modify the cryonics article to inform about the absolute urgency to direct research to these 2 issues please? I absolutely need it.

Wikipedia articles are based on cited reliable sources, not a place to propose new ideas or to report your own research projects. Even opinions and analysis of previous work or the value of future direction needs to be cited. DMacks (talk) 21:48, 20 January 2024 (UTC)

January 21

Photon gas

Richard A. Mould, claims in his book "Basic Relativity" (New York, Springer-Verlag, 1994), p.119, that although a photon gas has no rest mass, it has [been empirically proven to have] a positive relativistic mass. Can anyone supply an evidence for that claim? By the way, here is what he exactly states about the photon gas:

"Its passive gravitational mass is equal to its relativistic mass (which equals its total energy divided by c^2), so that when it is placed on a scale in a gravitational field g, its weight is equal to its total energy divided by c^2 times g. Furthermore, if the gas is accelerated horizontally [that is, without moving away from/to the gravitational field] it will display inertial properties also equal to the total energy divided by c^2, even at non-relativistic accelerations."

HOTmag (talk) 17:36, 21 January 2024 (UTC)

Consider two photons of equal energy E flying in opposite directions along the x-axis. The 4-momentum of the first photon is (E, p, 0, 0) = (E, E, 0, 0), its mass is $m^{2}=E^{2}-p^{2}=0$ (I'm using units where c=1). The 4-momentum of the second photon is (E, −p, 0, 0) = (E, −E, 0, 0), its mass is $m^{2}=E^{2}-(-p)^{2}=0$. The 4-momentum of the two photons combined is (E+E, p+(−p) , 0, 0) = (2E, 0, 0, 0), its mass is <math>m^2 = 4E^2<math> or <math>m=2E/c^2<math> with c put back in. Therefore, a system consisting of two photons has finite mass even though the photons individually have zero mass. This is true for any two photons as long as they don't travel in the same direction. Now generalise to a photon gas and you have. I've said it many times before: Relativistic mass applies to systems that have internal degrees of freedom. It does not apply to elementary particles without substructure. And don't give me any of that "semantics" stuff, I'm tired of hearing that. --Wrongfilter (talk) 18:04, 21 January 2024 (UTC)

This discussion seems to be confusing invariant mass with relativistic mass. The photons individually have zero invariant mass, but the invariant mass of the system of the two photons is nonzero.

Relativistic mass, on the other hand, seems to be out of fashion as a category. There's nothing really wrong with it; it's just not generally found to be the best bookkeeping method for describing things.

But why in the world you would use it, but then exclude elementary particles, makes no sense to me whatsoever. Wrongfilter, I really think you owe more explanation than "I've said it many times before", because I think you're simply incorrect here. --Trovatore (talk) 19:21, 21 January 2024 (UTC)

Let's throw out the term "relativistic mass" entirely then, and call it "invariant mass", fine with me. What I meant is mass that can arises from energy in internal degrees of freedom (which is a relativistic effect), but maybe the wrong term is stuck in my aging brain. I'd be happy with simply calling it "mass", anyway, since mass is invariant (to changes of reference system or, equivalently, centre-of-mass motion). Apart from that, the explanation is in the maths above. --Wrongfilter (talk) 19:28, 21 January 2024 (UTC)

Thank you for your detailed response.

As for your answer (except your two last sentences which I didn't understand): Please notice the equations you've used refer to the invariant mass only. So yes, it's a well known fact that a given system consisting of two photons that move in opposite directions has a positive invariant mass, even though each photon in that system has no invariant mass.

But I didn't ask about the invariant mass, but rather about what Mould (the author whose book I've quoted from) had meant: It seems he had made a distinction between an invariant mass and a relativistic mass, claiming an empirical claim, that even though a gas photon has no invariant mass it does have a relativistic mass. For us to get better what Mould had meant, let me quote from Max Jammer's book: "Concepts of Mass in Contemporary Physics and Philosophy" p. 56, about what Mould had meant: "he [Mould] illustrates it in terms of a photon gas, which has a rest mass equal to zero but, contrary to what is commonly thought, is not weightless", and then Jammer quotes exactly what I've quoted from Mould's book in my first post. So it seems Mould hadn't used the equations you've used, but rather had relied on an empirical evidence, and that's why I asked if anybody could explain what Mould had meant.

As for your two last sentences (in your first response to me): I didn't understand what you were talking about, because I don't remember I've ever given "semantics" staff. HOTmag (talk) 19:43, 21 January 2024 (UTC)

You did, a few months ago. I don't know Mould's book so I can only rely on the passage quoted above; my response is informed by the courses that I've taken and books that I've read (with Schutz' "First course in general relativity" probably the biggest influence). As I understand it Mould always talks about the mass of the gas, never about the mass of any individual photon. In light of that, Jammer's looks like a misunderstanding, but I can't tell without more context. Direct empirical evidence for the mass of a photon gas would seem hard to come by, that'd be a very difficult experiment; I'd like to see that though, if it has been done. However, the mass of a proton arises from essentially the same principle. --Wrongfilter (talk) 20:01, 21 January 2024 (UTC)

Although in case of proton it is gluons, not photons. Ruslik_Zero 20:12, 21 January 2024 (UTC)

Doesn't matter. It's energy in internal degrees of freedom that contributes to the mass of the composite system. --Wrongfilter (talk) 21:12, 21 January 2024 (UTC)

Re. your estimation that Jammer misunderstood Mould: Actually that's what I had suspected before I posted this thread, but if we stick to the way Mould phrased his idea - using the term "relativistic mass", I'm not quite sure Jammer was wrong (even though I still suspect).

Maybe you confuse with someone else? I do remember, that I asked (some months ago) a question about the neutrino's mass, and that I found your reply very thorough and helpful. I also remember someone else asked a question about the neutrino in the same month, and that you had a long conversation with that user. Anyway, I don't think I've ever used the word "semantics" in my posts here or anywhere. HOTmag (talk) 21:39, 21 January 2024 (UTC)

Mould didn't state, in this quote of him, that a photon gas has no mass or invariant mass! Of course laser light's mass-energy should gravitate (has a gravitational field) any counter-propagating light and all matter. For example, see this recent paper which references this one. Modocc (talk) 23:11, 21 January 2024 (UTC)

January 22

bad weather drones

This question is inspired by the recent incident[6] of a guy freezing to death in the White Mountains (New Hampshire) in very windy, bad weather conditions because SAR helicopters couldn't fly safely in the storm, and rescuers couldn't get to him either.

'm wondering if there are drones that can fly in such conditions, or alternatively, whether there are serious technical obstacles to building them. Note that while in principle they should be expected to not crash during missions, the point of using a drone is that the risk tolerance is higher than it would be for a copter carrying humans. Also the drone can be smaller, and doesn't have to land in the snow: if it can drop a 5kg or 10kg payload at the location, that is probably enough to deliver some Duraflame logs and matches, or whatever else it would have taken to keep the person warm til the next day. While it was unusually cold for New Hampshire (single digit Fahrenheit, or well below 0 with wind chill), compared to say a Mount Everest expedition it sounded mild. I.e. from my uninformed perspective it seems like the guy would have been ok with the right gear.

I'm not connected to any SAR stuff or to the victim. It's just about understanding a news story. Thanks! 2602:243:2007:9330:15DA:CAD1:28F4:E61E (talk) 03:08, 22 January 2024 (UTC)