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July 1

What are the defining characteristics of the bird clade “telluraves” + what distinguishes birds in its subclade “australaves” from the other subclade, “afroaves”?

Quickly saying, I asked here because the references are far too complex to understand, and the Wikipedia pages don’t list defining characteristics. 38.23.177.112 (talk) 03:09, 1 July 2024 (UTC)

This paper says, "No morphological apomorphies are known", which I guess means it's just molecular. Abductive (reasoning) 06:47, 1 July 2024 (UTC)

One reason with I hate phylogeny… without distinguishing traits, how can clades be properly defined?

Am I the only person who hates phylogeny for this particular reason? 38.23.177.112 (talk) 10:22, 1 July 2024 (UTC)

I'm sure it bugs many people. But one can only hate phylogeny if one cares about phylogeny. And unless one is publishing scientific articles in the field, hating it will accomplish nothing. Abductive (reasoning) 21:04, 1 July 2024 (UTC)

I suspect that hating phylogeny will accomplish very little also for people publishing scientific articles in the field.  --Lambiam 18:06, 2 July 2024 (UTC)

July 2

Does any company still make black and white TVs?

Just wondering. I had a black and white TV in my room as a kid in the late 80s, used a black and white TV that came with my flat in the early 2000s and (apparently) the TV license in the UK is still cheaper for black and white even now. Iloveparrots (talk) 01:56, 2 July 2024 (UTC)

It seems highly unlikely. Why would anybody continue to make a product for which there is no demand? And if, for some reason, you wanted to view the screen that way, you could just turn the color off on a regular, color TV. Clarityfiend (talk) 08:31, 2 July 2024 (UTC)

Steady on there with the 'no demand'. According to this, there were "4,200 black and white TV licences in force in March 2022" in the UK, and I imagine some of those people are quite demanding. I was thinking about this recently, that families often didn't own TVs back in the black and white days in the UK, they rented them from DER. Maybe not owning things, appliances etc., will make a comeback one day if the price (no cost) and logistics (arrives instantaneously) work. Still waiting for that communist utopia I was promised as a child... Sean.hoyland (talk) 09:55, 2 July 2024 (UTC)

This 2008 BBC article says that new blank & white televisions can still be found in the UK, but I imagine that they would have been from old stock rather than newly manufactured. A reasonably thorough Google search failed to find any actual new ones. Alansplodge (talk) 15:26, 2 July 2024 (UTC)

Blind people qualify for a 50% discount on their UK TV licence; a B&W licence is a third of the price of a colour one. So by going B&W (which they may not be able to see anyway) they pay about one sixth (£28.50) of the full price (£169.50). -- Verbarson  ^talk_edits 17:32, 2 July 2024 (UTC)

It seems amazingly regressive that everyone has to pay hundreds of dollars or £169.99 a year to own a TV (more than throwing a basic TV in the Thames every year and almost as much as basic cable just for BBC). In the states they offered everyone a subsidy just to avoid the much cheaper one-time cost of the box to run analog TVs on digital signals. Sagittarian Milky Way (talk) 23:21, 3 July 2024 (UTC)

In the words of Frank Zappa, "Communism doesn't work, because people like to own stuff." Regarding old TV's in stock, I recall not too many decades ago reading that there were still after-market parts available for the Model A Ford, which hadn't been manufactured since the 1930s. ←Baseball Bugs ^{What's up, Doc?} carrots→ 15:38, 2 July 2024 (UTC)

Baseball Bugs, this company says they have over 500,000 Model A parts in stock, and they have quite a few competitors. Cullen328 (talk) 20:11, 5 July 2024 (UTC)

All the better! And I would suspect there are still companies making tubes for old radios and televisions. Not to mention phonograph needles for antique Victrolas. ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:31, 6 July 2024 (UTC)

I saw a YouTube video a while back where someone took a Model T to a Ford service centre. The people there had no problem with fixing it up, for what it's worth. Iloveparrots (talk) 02:27, 6 July 2024 (UTC)

I expanded the concept slightly, and found a bunch of suppliers of new monochrome monitors built with modern technology and wiring (LCD with DVI, etc.). Get a tuner for your favorite local broadcast mode and you're all set. Lots of medical and other imaging is intrinsically monochrome, so there's a market for monitors optimized for high resolution and other visual qualities rather than colors and their rendering properties. DMacks (talk) 16:19, 2 July 2024 (UTC)

Many years ago I had what might be described as "television on the go". It was black and white and the screen was about two inches wide. 2A02:C7B:204:8E00:E0E4:8C0D:4571:6A6F (talk) 14:59, 5 July 2024 (UTC)

Why didn't those very small TVs get more popular than they did? Small battery-powered radios got popular, Walkmen got popular, wireless boomboxes got popular, portable record players got popular. Did they ever reach battery-powered flatscreen color before streaming video crippled sales? Sagittarian Milky Way (talk) 18:55, 5 July 2024 (UTC)

One reason is that they soaked up battery power, and if mains was available why have a tiny TV? Martin of Sheffield (talk) 20:02, 5 July 2024 (UTC)

Watching any sport involving fast activity (e.g. cricket or baseball) would be pointless on such a small screen. Golf would also be challenging. HiLo48 (talk) 01:29, 6 July 2024 (UTC)

If you could speedread 20/15 line with nearsighted glasses (which shrink everything) and focus 4 inches from cornea like the first few decades of my life then you could see pixels on 2 inch diagonal full HDs. Sagittarian Milky Way (talk) 20:20, 6 July 2024 (UTC)

I had a couple of pocket TVs back in the day. The reception on them was pretty poor. Like watching everything through snow. Maybe that was the reason? Yes, they also are batteries very fast too. Faster than the original Gameboy, which was notorious for consuming batteries. Iloveparrots (talk) 02:24, 6 July 2024 (UTC)

I found this 2007 article from the Denver Post which says: "The most dangerous inmates in isolated lockdown, such as those at the “Supermax” facility in Florence, have access to black-and-white TVs in their cells.". And this 2023 CNN article says that is still the case. 213.125.228.2 (talk) 12:49, 8 July 2024 (UTC)

July 6

wildlife and heat

I'm in suburban northern California and we've had a serious heat wave this week, like 100+F all day reaching 107F in the late afternoon. I've had to go outside a few times and it's tolerable (like a sauna) if I don't stay out too long or do anything strenous. I don't think I could stand being outside all day even under tree cover. I have a contingency plan to head for the ocean (where it is cooler) if the power and AC should happen to go out here.

There are deer and other wildlife in the area. Any idea how they cope? Will they be ok? I think this amount of heat is unusual. Last year it may have hit 103 on a few occasions but not for multi-day periods like this.

There are some natural water sources (creeks) nearby that weren't dried up as of a few weeks ago, but I don't know about now. They did dry up in the worse parts of the drought a few years ago. So that's not so great either. 2601:644:8501:AAF0:0:0:0:9BB0 (talk) 01:11, 6 July 2024 (UTC)

If they are anything like kangaroos they sleep in the forest or other shade during the day and graze at night. During the day you'll see all the sheep and alpacas crammed into whatever shade is available. We don't get deer locally so it may be they can't cope with our heatwaves, but I suspect prevalence of foxes and big feral cats has more to do with that. Greglocock (talk) 03:56, 6 July 2024 (UTC)

There's been some mention in the news that wildlife does suffer in the increased heat. Abductive (reasoning) 18:33, 6 July 2024 (UTC)

More than 1 billion sea creatures along the Vancouver coast were cooked to death during a record-breaking heat wave Sagittarian Milky Way (talk) 19:21, 6 July 2024 (UTC)

Why some wild animals are getting insomnia - Abductive (reasoning) 19:47, 6 July 2024 (UTC)

Another Australian observation is that water unavailability is more likely kill than heat alone. On super hot days here in Melbourne (46 degrees C), I've been able to walk up to wild birds sheltering in the shade on the ground with a dish of fresh, cool water. They understand. We also have stories of animals who are normally enemies sharing a farm dam to survive. These stories have included humans and tiger snakes

Thanks all. I checked the two creeks around here. One is empty though the dirt on the bottom is not bone dry yet. The other has some running water though I think the level is lower than before. There are also some artificial ponds with signs saying "recycled water". No idea what contaminants that might have, but if I were a deer I guess I'd drink it if I had to. 2601:644:8501:AAF0:0:0:0:9BB0 (talk) 20:44, 7 July 2024 (UTC)

July 7

Average reading speed?

What is the average reading speed? Can you also say what the reading speed range is? In other words, words per minute. 2A02:8071:60A0:92E0:F986:A49B:556A:30A5 (talk) 16:06, 7 July 2024 (UTC)

"Based on the analysis of 190 studies (18,573 participants), we estimate that the average silent reading rate for adults in English is 238 words per minute (wpm) for non-fiction and 260 wpm for fiction. The difference can be predicted by taking into account the length of the words, with longer words in non-fiction than in fiction." Also: "For silent reading of English non-fiction most adults fall in the range of 175 to 300 wpm; for fiction the range is 200 to 320 wpm." from How many words do we read per minute? A review and meta-analysis of reading rate August 2019 Journal of Memory and Language [1] Modocc (talk) 16:44, 7 July 2024 (UTC)

Bird in Madagascar that resembles a black chicken with webbed feet

As a child in Madagascar I once saw a bird. We were on a boat going through a slow-moving river, somewhere in the northwest, probably in Mahajanga. There was an emergent mass of reeds and in those reeds I saw what looked like a shiny black chicken with webbed feet like a duck. Looked just like a typical chicken besides the feet. It’s possible the reed mass was actually a shallow island, like a bar of sand or clay with some grasses. I need to know what it was! ꧁Zanahary꧂ 21:50, 7 July 2024 (UTC)

How about Fulica cristata? If not, try going through List of birds of Madagascar and clicking on the links. It's what I just did. Abductive (reasoning) 22:59, 7 July 2024 (UTC)

Thank you! Unfortunately that’s not it (note the chicken/shorebird-like feet)—I looked through the list (which appears incomplete) and don’t see her anywhere. ꧁Zanahary꧂ 00:17, 8 July 2024 (UTC)

my first guess was also a coot, because the Eurasian coot (which I am familiar with) kinda looks like a floating chicken (but doesn't live in Madagascar according to the map). That's the Fulica Atra, so family of Abductive's guess. Note that they don't have fully webbed feet, but rather have wide flaps. Depending on angle and spread of the feet, these can look very much like webbed feet though (note: that's my OR). Rmvandijk (talk) 13:47, 8 July 2024 (UTC)

The Madagascar pochard?  --Lambiam 01:58, 8 July 2024 (UTC)

No, it was really like a chicken, with a little beak, not a bill. Thank you very much for looking! ꧁Zanahary꧂ 04:22, 8 July 2024 (UTC)

July 8

Japanese basal temperature unit OV

The dictionary definition of OV at Wiktionary (also ㍵) says:

• (ōbui)

1. unit of basal body temperature, 0 being 35.5 °C and 50 being 38 °C, used for fertility awareness

However Wiktionary has no references. I cannot find references elsewhere. Maybe they exist but searching for "OV", especially when including "ovulation" gives many false positives. Can you find a reference for the existence and meaning of this unit, preferably in a language I can understand, such as English or Spanish? I guess most references are in Japanese, that I don't understand. -- Error (talk) 10:44, 8 July 2024 (UTC)

"*Women's thermometers use the "OV value" so that slight changes in body temperature can be read."

"This is a value that divides the range of 35.5 to 38.0°C into 50 equal parts."

Original source: [2]

Translated source:[3] OptoFidelty (talk) 01:06, 10 July 2024 (UTC)

It was rejected as promotional material. --Error (talk) 23:46, 10 July 2024 (UTC)

Hillock of His/Hiss

I learned of the "hillocks of Hiss" from the wikipedia article on Tubercle Tubercle#Ears

From looking at other sources, I see they're also spelt "hillocks of his" -- What I cannot find out, and what I'm asking y'all is, *why* they are called 'Hiss/His' are they named for a person?140.147.160.225 (talk) 12:02, 8 July 2024 (UTC)

Presumably named for Wilhelm His Sr. or Wilhelm His Jr.. --Amble (talk) 16:47, 8 July 2024 (UTC)

In a book on the pathophysiology of orbital diseases I found this sentence:^[4]

In 1868, Hiss demonstrated that shortly after gastrulation, a different type of cell was formed between the ectoderm and the paraxial mesoderm on both sides of the neural tube.⁹

I bet this is the same His(s) as that of the hillocks. Given their bios, this would then be His Sr. The reference 9 is to the textbook Human Embryology, for which the restrictive snippet view fails to reveal more, but the 1868 publication is almost certainly Untersuchungen über die erste Anlage des Wirbelthierleibes.  --Lambiam 17:23, 8 July 2024 (UTC)

thanks so much Lambiam and Amble! -- any chance you could add a footnote or ref to the Tubercle article so future folks won't be as stymied as I was? 140.147.160.225 (talk) 12:04, 9 July 2024 (UTC)

I found this further confirmation:

The most important theory arose in 1855 when Wilhelm His named six cartilaginous hillocks as the original auricular structures.

Source: Jack Davis (1997). Otoplasty. Springer, p. 24. ISBN 978-1-4612-7484-1.

You should be able to add a footnote (with ref) to the Tubercle article yourself.  --Lambiam 14:36, 9 July 2024 (UTC)

Now done, also added to the His Sr article. Alansplodge (talk) 13:24, 10 July 2024 (UTC)

July 10

Kuiper Belt ice cube

If aliens took a spherical Kuiper belt object with the composition of Saturn's highest-water-content ring and the perihelion of Pluto, and reshaped it into a cube, how massive would it have to be for humans to detect the shape change before gravity reverted it? NeonMerlin 05:49, 10 July 2024 (UTC)

Sounds like one for Randall Munroe. 41.23.55.195 (talk) 06:04, 10 July 2024 (UTC)

There are two sensible ways how the shape could be detected: a light curve or an occultation. A light curve uses the fact that for a non-spherical shape (or a spherical shape with non-uniform albedo) the brightness varies as the object spins on its axis. Professional telescopes have other things to do than collecting light curves of KBOs, but if this thing is at least around 500 km in size, it gets into range of bigger amateur telescopes. Some of those occasionally take light curves of some KBOs. But you can't really prove a cubical shape this way, as the light curve can also be explained with a funny albedo variation.

An occultation happens when this object passes in front of a background star. Multiple observers on the ground on Earth can detect the exact times when the star disappears behind the KBO and reappears later. With enough observations, one can see the silhouette of the KBO and confirm it's cubical. Around 10 observers in the occultation path, the width of which equals the diameter of the KBO, should be enough. The KBO doesn't have to be bigger than 50 km or so. Those observers are typically amateur astronomers, whose telescopes don't need to be big enough to see the KBO; seeing the background star with sufficiently short integration time (sub-second) is enough. The difficulty is knowing the orbit of the KBO accurately enough to predict the occultation and finding enough telescopes in the occultation path. PiusImpavidus (talk) 08:51, 10 July 2024 (UTC)

Summation of alcoholic percentages

If I drank a 0,5 l bottle of 5,3% beer and another 0,5 l of a 4,9% beer, would it be correct to say that I drank 1 litre of 10,2% beer from physiological and chemical perspective? 212.180.235.46 (talk) 07:48, 10 July 2024 (UTC)

No, not from any perspective, physiological, chemical, or mathematical. You don't add the percentages, you take the mean. (5.3 + 4.9) / 2 = 5.1% by volume. AndyTheGrump (talk) 08:00, 10 July 2024 (UTC)

But, you can't exactly take the mean of the percentage-by-volume, because the mixture of ethanol and water causes a nonlinear volumetric change... For example, our article about alcohol by volume states: "The phenomenon of volume changes due to mixing dissimilar solutions..." is its partial molar property. The volume change is small, but non-zero... and it makes the ABV of the mixed drink non-equal to the arithmetic mean of its constituent ingredients. Our universe is amazingly complicated! Nimur (talk) 16:56, 10 July 2024 (UTC)

However, if the bottles are marked with their alcohol content in Alcohol units, you can add those. {The poster formerly known as 87.81.230.195} 151.227.226.178 (talk) 14:47, 10 July 2024 (UTC)

The formulas given at Standard drink § Calculation of pure alcohol mass in a serving ignore the nonlinearity, though. They are equivalent to taking the average ABV percentage (weighted by volume) and using that for the sum of the volumes.  --Lambiam 20:31, 10 July 2024 (UTC)

But is the inaccuracy significant in the context of people drinking (say) beer in pints and halves and estimating their likely degree of insobriety? Personal physiological factors are likely (in my experience as a trained beer drinker (really!)) to outweigh the physical chemistry aspects. {The poster formerly known as 87.81.230.195} 94.6.82.201 (talk) 06:56, 11 July 2024 (UTC)

I will ignore the mass/volume difference of alcohol and water. So assume that a liter is a kilogram, and alcohol by volume equals alcohol by mass.

0.5 liters of 5.3% alcohol contains 0.0265 liters of alcohol. 0.5 x 0.053 = 0.0265.

0.5 liters of 4.9% alcohol contains 0.0245 liters of alcohol. 0.5 x 0.049 = 0.0245.

So 0.0265 + 0.0245 = 0.051 liters of alcohol. You had three and a half tablespoons of alcohol.

If you drink one liter of 10.2% alcohol, you consume 0.1 liters of alcohol. Tenth of a liter is a deciliter, right? Which is twice the amount of your two pints above.

In practice, effects of alcohol intake will depend on things like how quickly you gulp the beer vs. hard spirits, how often you will need to drain the weasel, and such.

(Which is AndyTheGrump correctly said above; just showing the math.) 85.76.166.151 (talk) 16:34, 11 July 2024 (UTC)

July 11

Why is the universe not fractal?

The laws of gravity are presumably the same throughout the universe: the force is proportional to the product of the masses and inversely proportional to the square of the distances. So why do we observe very different structures at different scales? Solar systems involve a few discrete objects orbiting a sun, galaxies have various shapes but often spirals, and then over larger distances the distribution of galaxies is like a 3-D network of filaments. I believe that simulation models can produce all these different structures, but I am hoping for some intuitive explanation of why the different outcomes. One possibility might be that things happen relatively faster over small distances, and that the universe would also develop into something like a giant solar system given more time. Another possibility is that some processes happening only at the local scale (e.g. nuclear fusion in stars) interfere with what would happen if gravity alone were operating. Or is it something else entirely? Thanks. JMCHutchinson (talk) 12:01, 11 July 2024 (UTC)

The small-scale stuctures, such as the discrete objects in solar systems and the spiral structure of galaxies (even the disk itself) arise due to non-gravitational processes. When a cloud of ordinary (baryonic) gas collapses its density and temperature increase and it gives off an increasing amount of electromagnetic radiation, this leads to a loss of energy (radiative cooling) that speeds up the collapse and leads to the formation of small-scale structures. Dark matter, which is only subject to gravity, does not do that and there is no comparable small-scale structure in the dark-matter distribution. There are purely gravitational cooling mechanisms such as violent relaxation but they are much less effective than radiative cooling and operate on larger time scales. The time since the Big Band has been sufficient for galaxies and clusters of galaxies to form (less massive objects form first, more massive objects later), but not yet for objects on larger mass scales (superclusters exist but they are not bound objects yet). This is the reason why matter on the largest scales is organised in filaments but not in bound, more or less spherical objects. Finally, the presence of dark energy and the consequent accelerating expansion of the Universe set an upper limit to the mass of bound objects that will ever form — I don't know what that limit is but I guess it is in the supercluster range. --Wrongfilter (talk) 12:27, 11 July 2024 (UTC)

This is a very clear answer and exactly what I wanted. Thanks! JMCHutchinson (talk) 17:20, 11 July 2024 (UTC)

Is nociplastic pain same as neuroplastic pain?

Hi. I've noticed that the term "neuroplastic pain" has 700 thousand hits on Bing search, but there is no article or redirect for it on Wikipedia. However, it seems similar to nociplastic pain, but I'm not completely sure. Is here anyone with medical background who could confirm/decline this? --Pek (talk) 16:35, 11 July 2024 (UTC)

It seems to be an incipient medical term, with 107 Google Scholar results. Just glancing down the squibs Google provides shows that it is listed separately, for instance, "Nociplastic pain is hypothesized to differ from nociceptive and neuroplastic pain...". Neuroplastic pain appears to be a sequela of neuropathic pain. The results from the Google Scholar and regular searches show a lot of scammy stuff, and I worry that creating a redirect (to neuropathic pain) may be a bad idea. Conversely, without good sourcing, an article may be impossible to create at this time. I would take this to WT:WikiProject Medicine. Abductive (reasoning) 21:36, 12 July 2024 (UTC)

Does the velocity of an electromagnetic wavefront depend on the medium?

Our article Velocity factor states: The velocity factor...is the ratio, of the speed at which a wavefront (of an electromagnetic signal)...passes through the medium, to the speed of light in vacuum. So it seems that the velocity of an electromagnetic wavefront does depend on the medium.

However, our article Front velocity states: The earliest appearance of the front of an electromagnetic disturbance (the precursor) travels at the front velocity, which is c, no matter what the medium. Similarly, our article Wavefront states: Wavefronts travel with the speed of light in all directions in an isotropic medium. So it seems that the velocity of an electromagnetic wavefront does not depend on the medium.

I wonder whether this is a contradiction between our articles (if so then how should they be corrected?), or - probably - I miss something here (if so then what do I miss?)... HOTmag (talk) 21:00, 11 July 2024 (UTC)

I have corrected the sentence in wavefront — the article talks about waves in general, not specifically about electromagnetic waves (in which case it should have been the speed of light in the medium). The "front" discussed in front velocity is not the same thing as a wavefront (= a surface of constant phase) but, as in your quote, the earliest appearance of an electromagnetic disturbance (again one could talk about non-em disturbances but we won't). For instance, some switches on a lightbulb a distance $s$ from me. The question is "At what time can I know the lightbulb is on?" and the answer is $s/c_{\mathrm {vac} }$. The reasoning is that because this is a discontinuous signal (the mathematical formulation involves the Heaviside function) the spectrum of the signal includes all frequencies, in particular very high ones. In most (any?) media the refractive index approaches 1 for very high frequencies, i.e. the propagation speed approaches the vacuum speed of light for high frequencies. Therefore, the high-frequency part of the signal arrives first, and the bulk of the signal later. Due to this dispersion, the temporal/spatial shape of the wave signal changes as it propagates (think of what sound does on a frozen lake). --Wrongfilter (talk) 05:52, 12 July 2024 (UTC)

Thank you for correcting our article Wave front.

Regarding our article Front velocity: As opposed to other readers (including me), you've understood that it refers to a beam of light containing the whole spectrum. However, if the beam of light contains, not the whole spectrum, but e.g. two types of waves only, e.g. red and blue, then the front velocity of this beam of light does depend on the medium, right?

Here is the full quote, from our article Front velocity: the wave discontinuity, called the front, propagates at a speed less than or equal to the speed of light c in any medium. In fact, the earliest appearance of the front of an electromagnetic disturbance (the precursor) travels at the front velocity, which is c, no matter what the medium.

Is the claim in this quote correct, as far as my red-blue example mentioned above is concerned? In my example, "the earliest appearance of the front" of this electromagnetic disturbance is the appearance of the blue wave, right? If it is, then shouldn't the paragraph be corrected, for all readers to understand that it only refers to a beam of light containing the whole spectrum? HOTmag (talk) 08:55, 12 July 2024 (UTC)

The spectrum is the Fourier transform of the disturbance. A discontinuous disturbance has signal at all frequencies, not just "red" and "blue". These things are not independent. --Wrongfilter (talk) 09:16, 12 July 2024 (UTC)

Got it, thank you.

So, If I want the value of the speed of light to be independent of medium, I must refer to the front velocity of a beam of light containing the highest frequencies possible, right?

If your answer is positive, then how can the formula $p=\gamma mv$ be justified, when applied to a red light moving in water? In this case, $v<c,$ so $\gamma$ is a finite number, while $m=0,$ so according to this formula, we get $p=0,$ which is false...

I'm pretty confused now. Unless no mass is allowed to be attributed to the light, not even a zero-mass, so my last question will vanish. Am I right? HOTmag (talk) 10:14, 12 July 2024 (UTC)

I'm not letting myself get drawn into the mass debate again. Light is complicated, light in matter is even more complicated. If you want the momentum of a photon, use $\hbar k$. --Wrongfilter (talk) 10:25, 12 July 2024 (UTC)

Thank you. What about my only question still left, in my second sentence? "If I want the value of the speed of light to be independent of medium, I must refer to the front velocity of a beam of light containing the highest frequencies possible, right?" HOTmag (talk) 10:53, 12 July 2024 (UTC)

I don't see the point of that sentence. Why would you "want the value of the speed of light to be independent of medium"? The front velocity looks like an interesting theoretical curiosity with little actual physical relevance. --Wrongfilter (talk) 11:13, 12 July 2024 (UTC)

I've only wanted to know if, the only way to define the well known speed of light - usually denoted by c - must rely on the vacuum, or the speed of light can also be defined without the concept of vacuum? Assuming we don't want to define it numerically (299,792,458 m/s), nor by ratios between other physical constants.

So according to your previous clarifications, I thought that perhaps the speed of light could be defined as the front velocity of a beam of light containing the highest frequencies possible... HOTmag (talk) 12:39, 12 July 2024 (UTC)

You are perhaps falling into the trap of thinking that the speed of light in a vacuum, c, is determined by a property of light (in the sense of e-m radiation). It is not: it is (as a limit) a fundamental property of Spacetime, to which light and everything else (though not spacetime itself) has to conform, including other massless 'particles' which must perforce travel at it in a vacuum. It just so happens that it is easiest to observe (and measure) using light, and was thus discovered and named. Or so I understand the matter. {The poster formerly known as 87.81.230.195} 94.6.82.201 (talk) 07:37, 13 July 2024 (UTC)

Oh, of course I've always knwon that c is just a limit being a fundamental property of Spacetime. But instead of using the complicated expression: "a limit being a fundamental property of Spacetime", I used the common term "speed of light", as most people do (including you - as I guess), just for the sake of convenience and simplicity. That said, I only asked if this limit - which I called "the speed of light" for the sake of convenience and simplicity, could be defined - without the concept of vacuum - as the front velocity of a beam of light containing the highest frequencies possible. HOTmag (talk) 22:33, 13 July 2024 (UTC)

July 12

Uncertainty principle & H atom

According to the uncertainty principle the electron has a momentum :
$\Delta p_{e}={\tfrac {h}{4\pi \Delta x_{e}}}{\text{ , }}$
$\Delta x_{e}=10^{-10}{\text{m (can be found from liquid hydrogen density)}}$ .

To conserve the atom momentum zero , the proton must have a momentum  :
$\Delta p_{p}=-\Delta p_{e}$.
So $\Delta x_{p}=\Delta x_{e}$ and the proton must also smear to atom's full size.

But Rutherford scattering experiment shows that a size of a nucleus is $10^{5}$ smaller. Why does the uncertainty principle fail? — Preceding unsigned comment added by U240700 (talk • contribs) 08:54, 12 July 2024 (UTC)

You seem to be confusing the (expectation) values of the momenta and their uncertainties. Conservation of momentum demands $\langle p_{p}\rangle =-\langle p_{e}\rangle$ and says nothing about the uncertainties. --Wrongfilter (talk) 09:24, 12 July 2024 (UTC)

Uncertainty $\Delta p_{e}$ means that $p_{e}$ can take any value within $\Delta p_{e}$. So taking the intervals like $p_{e}=0{\text{ ... }}\Delta p_{e}$ or $p_{e}=0.5\Delta p_{e}{\text{ ... }}1.5\Delta p_{e}$ is suitable for the order of magnitude. U240700 (talk) 12:19, 12 July 2024 (UTC)

The total momentum in quantum mechanics is conserved meaning that

${\hat {\mathbf {p} }}_{e}+{\hat {\mathbf {p} }}_{p}=0$,

or

$<({\hat {\mathbf {p} }}_{e}+{\hat {\mathbf {p} }}_{p})^{2}>=(\Delta \mathbf {p} _{e})^{2}+(\Delta \mathbf {p} _{p})^{2}+2<\Delta {\hat {\mathbf {p} }}_{p}\Delta {\hat {\mathbf {p} }}_{e}>=0$.

This equality holds because electron and proton momentums are anticorrelated. Ruslik_Zero 21:00, 12 July 2024 (UTC)

Last equation confirms only that $\Delta p_{p}=-\Delta p_{e}$. How does it prove or disprove $\Delta x_{p}=\Delta x_{e}$? U240700 (talk) 00:54, 13 July 2024 (UTC)

Your value $\Delta x_{e}$ comes from a different experiment, not Rutherford's, and is therefore not relevant here. It applies, for instance, to a measurement of the average charge density in an atom. This would be a low-energy experiment, taking care not to disturb the electronic structure of the atom. The uncertainty principle does not stop you from setting up an experiment to measure the instantaneous position of an electron more precisely, but the concomitant momentum uncertainty would likely ionise the atom. Rutherford's alpha particles had energies in the MeV range, if I'm not mistaken, much higher than the binding energies of electrons in atoms. They could in principle — I don't know how, and Rutherford's experiment is certainly not set up to do so — be used to locate electrons to much smaller $\Delta x_{e}$ than the value you give. --Wrongfilter (talk) 03:53, 13 July 2024 (UTC)

I have no questions for $\Delta x_{e}$, I have a question for $\Delta x_{p}$. The proton is located in center of atom in very small boundaries ($10^{-15}{\text{ m}}$) . It violates the uncertainty principle. The proton must be smeared over $10^{-10}{\text{ m}}$ and (like the electron) be detected (materialized) everywhere , not just in center. U240700 (talk) 06:57, 13 July 2024 (UTC)

Okay, like you I got too hung up on the location of protons and electrons. The Rutherford experiment does not actually measure the location of nuclei, it measures their size. The experiment does not tell you where the nuclei are (not even in relation to their electron shell). Putting them at the centre of atoms is subsequent model building. --Wrongfilter (talk) 09:14, 13 July 2024 (UTC)

July 13

On the discovery of tantalum

What procedure did Anders Gustaf Ekeberg use to isolate metallic tantalum? Double sharp (talk) 09:11, 13 July 2024 (UTC)

If you can read Swedish, I think this is the original publication in which Ekeberg announced his discovery of tantalum. If you can't, maybe someone who knows Swedish and has some familiarity with the terminology of analytical chemistry will be kind enough to summarize the procedure, which I think is described in the later half of the article; on p.78 I see Detta nya metallämnet ("this new metallic substance").  --Lambiam 11:26, 13 July 2024 (UTC)

Unfortunately, the Scandinavian languages are something I never looked deeply into. Though it's starting to seem clear that I'm going to need to look into Swedish to study this period of chemical history. :) Double sharp (talk) 12:19, 13 July 2024 (UTC)

This ref:

• Ekeberg, Anders (1802). "Of the Properties of the Earth Yttria, compared with those of Glucine; of Fossils, in which the first of these Earths in contained; and of the Discovery of a metallic Nature (Tantalium)". Journal of Natural Philosophy, Chemistry, and the Arts. 3: 251–255.

might be an English translation (or at least contain discussion of it). DMacks (talk) 22:42, 13 July 2024 (UTC)

It is a strongly abridged extract of the second half of Ekeberg's article, referring to the newly discovered metal with the incorrrect name tantalium. It does not give the isolation procedure of the elemental metal but only some of its physical properties as well as chemical properties distinguishing it from tin, tungsten and titanium.  --Lambiam 09:37, 14 July 2024 (UTC)

Boo:( DMacks (talk) 18:48, 14 July 2024 (UTC)

A German translation of the original paper is here. AstroLynx (talk) 19:29, 14 July 2024 (UTC)

{{ec}} If anyone wants to have a go at manual- or machine-translation from Swedish, I uploaded what en:tantalum and sv:tantal appear to identify as the original article as File:Ekeberg-1802.pdf. My naive first pass with Acrobat was able to do some extraction, but had trouble with some of the diacritical marks and correctly representing them in my system's font, and also gave too many disjointed text fields to make it bulk-selectable. DMacks (talk) 19:32, 14 July 2024 (UTC)

Thanks. The German translation AstroLynx points to can be copy-pasted from the generated PDF, so here's a somewhat cleaned-up reading of the relevant bit:

Dieser neue Metallstoff zeichnet sich durch seine Unauflöslichkeit in alle Säuren, wie man ihn auch mit denselben behandelt, aus. Das einzige Auflösungsmittel, das ich auf denselben wirksam gefunden habe, ist das ätzende fixe Laugensalz, so daß, wenn man das Erz mit demselben brennt, und das Gemenge mit Wasser auszieht, ein großer Theil in der laugensalzigen Lauge aufgelöst wird. Aus derselben kann er durch eine Säure gefällt werden, aber der Niederschlag wird nicht wieder aufgelöst, wie viele Säure man auch zugießen mag. Abgeseihet und getrocknet erscheint er als ein Pulver von ausgezeichneter Weiße, welche Farbe er auch beym Glühen behält. Wenn der Theil des gebrannten Klumpens, welcher von der laugensalzigen Lauge nicht aufgenommen ist, mit Säure ausgezogen wird, bleibt ein weißes Pulver von gleicher Beschaffensheit nach. Seine eigenthümliche Schwere, nach dem Glühen, war 6,500. Vor dem Blaserohre wird er leicht vom Borax und Phosphorsalze aufgelöst, gibt den Flüssen aber keine Farbe. Auf einem Heerde von Kohlengestäbe in einem Ziegel, ohne Zusaß der Hitze, welche zu einer Braunsteinprobe erfordert wird, ausgefeßt, untergeht er eine Art von Verfrischung, bey welcher er zu einem grünlich harten Klumpen zusammensiedet, welcher auf der Oberfläche einen metallischen Glanz hat, aber im Bruche nur matt glänzt und schwarze grün aussieht. Auf diesen haben Säuren keine weitere Wirkung, als daß fie ihn wieder zu der weißen Halbsäure verwandeln. Das Verhalten bey der Verfrischung und die eigenthümliche Schwere, gaben mir Anleitung, diesen besondern Körper unter die Metalle zu rechnen.

It sounds like the English abridgement omitted to notice the word Erz there. That makes the procedure sensible: it seems that Ekeberg converted the ore via alkaline digestion to Ta₂O₅ (certainly a mixture with Nb₂O₅, though he wouldn't know that), then attempted to reduce it with carbon. This actually should have a quite poor yield under his likely experimental conditions, but clearly, it was enough for him to draw the correct conclusion. I'm extremely impressed. (V, Nb, and Ta are quite a pain to reduce from the oxides to the elemental metals, especially if you want a reasonably pure product.) Double sharp (talk) 10:05, 15 July 2024 (UTC)

Was the grünliche harte Klumpen (impure) elemental tantalum? It is a pity Ekeberg did not give its specific mass, unlike for the ore, or other physical properties.  --Lambiam 18:04, 15 July 2024 (UTC)

July 15

The holy grail of hydrogen

"Get more energy out than you put in." (https://astronaerospace.com/) Is this legit? Has this been demonstrated or are they just good at making slick CGI animations (better than at spelling)? Thank you. Hevesli (talk) 16:33, 15 July 2024 (UTC)