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August 19

How did people find out which mushrooms are safe to eat?

Edible mushroom says: "To ensure safety, wild mushrooms must be correctly identified before their edibility can be assumed. Deadly poisonous mushrooms that are frequently confused with edible mushrooms include several species of the genus Amanita, particularly A. phalloides, the death cap. Some mushrooms that are edible for most people can cause allergic reactions in others; old or improperly stored specimens can go rancid and cause food poisoning. Additionally, mushrooms can absorb chemicals within polluted locations, accumulating pollutants and heavy metals including arsenic and iron—sometimes in lethal concentrations."

So, if some primitive society of humans had no knowledge about whether mushrooms are edible at all, how would they end up obtaining the detailed knowledge about which mushrooms are edible and which not without that leading to many deaths? Because once people start to die then you would think that they would no longer be interested in this and just classify most mushrooms as toxic. Count Iblis (talk) 15:11, 19 August 2024 (UTC)

People would rub the item on their arm, taste and spit it out, eat a small amount and wait for any discomfort, and (probably) try to feed it to dogs or other tamed animals. Abductive (reasoning) 16:54, 19 August 2024 (UTC)

The obvious answer is trial and error. Early hominins were mainly hunter-gatherers it seems, relying heavily on nuts, seeds, fruits and fungi, all of which may be toxic. If the more adventurous members of a group of such people tried out a few new things every generation and passed on the results in their oral history e.g. "this one made me very sick and killed my brother, but this one tastes really good", I think that over longer periods this would build up their "repertoire". Periods where normal food sources became scarce would provide more than enough incentive to give something a try. I've tried to find sources for this, but struggled so far. One thing I did find is the suggestion that the early hominins would check out what other animals were eating. Mikenorton (talk) 21:04, 19 August 2024 (UTC)

Also keep in mind that there are edible fungi that don't resemble poisonous ones; that not everything grows everywhere; and that traditional knowledge includes knowing where to find particular foods, not just how to identify them out of context. --Amble (talk) 21:25, 19 August 2024 (UTC)

That is why, in every language, humans built up little sayings to remember things. We don't need them now because we avoid nature. So, we've mostly forgotten the exact words and come up with silly jibberish like "red on black makes a wasp attack by pee turns yellow is a happy fellow." Therefore, it is difficult to imagine a society where these sayings were well known and taught important lessons. I just wonder about Australia. Wouldn't the sayings simply have been: "If it moves, it will kill you. If it doesn't move, it will likely still kill you." 12.116.29.106 (talk) 12:57, 20 August 2024 (UTC)

We still use those sorts of sayings. Things like "red touches black, ok Jack; red touches yellow, turns your blood to Jello" for colorations of snakes that aren't vs are venomous; "touch the white, you'll be alright; touch the black, you won't be back" for the neutral vs hot conductors in US electrical wiring. DMacks (talk) 14:06, 20 August 2024 (UTC)

There are old mushroom hunters. There are bold mushroom hunters. There are no old, bold mushroom hunters. 41.23.55.195 (talk) 04:47, 21 August 2024 (UTC)

Thanks everyone for your answers! Count Iblis (talk) 18:00, 25 August 2024 (UTC)

Too big

I was watching an episode of Star Trek: Discovery, and the people is having a problem with a black hole that is way too big. As in, five light-years in size. So I checked the article Supermassive black hole, to check how big can they get, and it says "with its mass being on the order of hundreds of thousands, or millions to billions, of times the mass of the Sun". It's hard to keep perspective with numbers, sizes and distances so high, so just to be clear... 5 light-years in size would be obcenely big even for a supermassive black hole, right? Cambalachero (talk) 18:57, 19 August 2024 (UTC)

Sounds like it was this item: Dark Matter Anomaly. The Schwarzschild radius of a black hole is directly proportional to its mass. If you take the Schwarzschild radius to be (5 light-years) / 2 = 2.5 light years and plug it into the formula, you will get a mass of 8 x 10^12 solar masses. That is several times larger than the mass of the Milky Way galaxy, or around 1000 times as large as the mass of the very large supermassive black hole M87*. So yes, that is way too big. —Amble (talk) 20:02, 19 August 2024 (UTC)

August 21

Two types of units

1. Are cup, metric teaspoon and tablespoon used in recipes in most continental European countries? Are non-liquid things ever measures in these units?
2. Why screen sizes for smartphones, tablets, computers and TVs are usually measured in inches, even in mostly metric countries?

--40bus (talk) 18:29, 21 August 2024 (UTC)

Re 1. In the UK, it was common to measure liquids in teaspoons, tablespoons and cups (all standard volumes), and to measure granular solids such as sugar in both 'level' and 'heaped' tea- and tablespoons, and flour (for example) in cups (usually not heaped). Fluid ounces and (where applicable) pints and other fractions of pints (a UK pint being 20 fl. oz.) were also used: it depended on the preferences of the recipe writer. {The poster formerly known as 87.81.230.195} 94.1.209.45 (talk) 00:28, 22 August 2024 (UTC)

Re 2. Marketing of consumer electronics products is influenced by the major market of the USA where inches is a customary unit. Philvoids (talk) 11:09, 23 August 2024 (UTC)

I don't know about most continental European countries, but a quick browse to the recipe of the day on chefkoch.de shows some ingredients, including chopped parsley, measured in spoons (EL (Esslöffel) and TL (Teelöffel) (sizes discussed in German Wikipedia here)).

Likewise, a tabbouleh recipe on French site marmiton.org has parsley measured by the soupspoon. AlmostReadytoFly (talk) 10:56, 27 August 2024 (UTC)

August 23

Planck's law 1901 article and reverse function

At the end of the chapter "...Wien's displacement...", after equation (8), Max Planck gives the formula:
$U=\nu \cdot f_{1}({\frac {\theta }{\nu }})$
Then a new formula:
$\theta =\nu \cdot f_{2}({\frac {U}{\nu }})$
Ok, but the second formula that follows from it is incomprehensible to me:
${\frac {1}{\theta }}={\frac {1}{\nu }}\cdot f_{3}({\frac {U}{\nu }})$
One has:
$f_{3}({\frac {U}{\nu }})={\frac {1}{f_{2}({\frac {U}{\nu }})}}???$
Any idea ?
Malypaet (talk) 12:58, 23 August 2024 (UTC)

So $\theta =\nu \cdot f_{2}({\frac {U}{\nu }})$ and ${\frac {1}{\theta }}={\frac {1}{\nu }}\cdot {\frac {1}{f_{2}({\frac {U}{\nu }})}}$, it's just taking the reciprocal of both sides. But I don't do physics so I'm probably missing the point.  Card Zero  (talk) 13:38, 23 August 2024 (UTC)

My question is:
on what logic can we write:
$f_{3}({\frac {U}{\nu }})={\frac {1}{f_{2}({\frac {U}{\nu }})}}???$
Malypaet (talk) 14:14, 23 August 2024 (UTC)

Still unsure if I'm really helping, but so long as I don't have to know anything about black-body radiation or whatever,

If $a=b\cdot c$ then ${\frac {1}{a}}={\frac {1}{b}}\cdot {\frac {1}{c}}$, so

If $a=b\cdot {f_{2}(x)}$ then ${\frac {1}{a}}={\frac {1}{b}}\cdot {\frac {1}{f_{2}(x)}}$, and

If ${\frac {1}{a}}={\frac {1}{b}}\cdot {f_{3}(x)}$ then

${f_{3}(x)}={\frac {1}{f_{2}(x)}}.$ But I'm just filling space until somebody comes along who knows what you were getting at.  Card Zero  (talk) 15:08, 23 August 2024 (UTC)

Nobody knows what Malypaet is trying to get at... The answer here, I guess, is simply that $f_{3}$ is a new name for $1/f_{2}$, nothing more, nothing less. Planck doesn't know what $f_{2}$ looks like (all he knows is that its argument is $U/\nu$), and he doesn't know what $f_{3}$ looks like (all he knows is that, because $f_{3}=1/f_{2}$, it is also a function of $U/\nu$). --Wrongfilter (talk) 15:46, 23 August 2024 (UTC)

Written like that, we can admit it. In his combinatorial demonstration we find this analogy of functions between logarithms and exponentials. But he does not write it.
Thank you. Malypaet (talk) 18:59, 23 August 2024 (UTC)

August 24

The magic number N = 126

This question is mostly theoretical, because there's no feasible way to create such heavy neutron-rich isotopes at present. But: what predictions are there on the N = 126 shell closure at low proton numbers? In particular, is ¹⁷⁶Sn (Z = 50, N = 126) expected to be doubly magic, or will this shell closure disappear that far from the valley of stability (like N = 20 does)?

(I got some links about this at User talk:ComplexRational#fluorine-30: thanks, Nucleus hydro elemon! But I thought it'd be worth asking for more answers.) Double sharp (talk) 17:41, 24 August 2024 (UTC)

Even if it exists it will be extremally unstable relative beta decay. Ruslik_Zero 19:57, 24 August 2024 (UTC)

Yes of course, since ⁷⁸Ni is also quite unstable to beta decay. What I'm curious about is (1) whether ¹⁷⁶Sn should exist and (2) whether it does close the neutron shell, or if the energy gaps are expected to change in this extremely neutron-rich region. Double sharp (talk) 04:33, 25 August 2024 (UTC)

The heaviest isotope of tin known is ¹⁴⁰
₅₀Sn
, which lives less 50 ms and already drips neutrons. The existence of an isotope as heavy as ¹⁷⁶
₅₀Sn
seems unlikely. Magic number itself does not mean that the nucleus exists in any meaningful way. You can look at ¹⁰
₂He
. Ruslik_Zero 20:48, 26 August 2024 (UTC)

That's beta-delayed neutron emission, so the drip line hasn't been reached yet, as expected.

It seems then that the best we could find at the moment are the papers Nucleus hydro elemon found at first, which suggest that ¹⁷⁶Sn should be more or less on the border between being bound and being unbound. Those two papers suggest N = 126 is still magic (because the two-neutron separation energy has a big jump going from ¹⁷⁶Sn to ¹⁷⁸Sn), but this one makes it less clear. Since this is so far from what's currently known, it's probably not possible to do better at the moment. I'd guess, therefore, that the best possible answer to my question at the moment would have to be "no one really knows; could be either way". Double sharp (talk) 06:27, 27 August 2024 (UTC)

I found a reference by Fang et al. about beta decay of ¹⁷⁶Sn. Its β⁻ decay energy is around 22 MeV (comparable with ²⁹F 21.7 MeV) and has a half-life of <1 ms. ¹⁷⁶Sn should undergo β⁻n instead of only β⁻.

The calculated mass excess of ¹⁷⁶Sn is 217.59 MeV, as predicted by KTUY. Mass excess of ¹⁷⁶Sb is predicted to be 195.49 MeV, thus the β⁻ decay energy will be 22.10 MeV, not far away from Fang et al. Somehow the decay process β⁻,23n to ¹⁵³Sb+23n is actually possible with decay energy 2.47 MeV.

KTUY predicts S_2n of ^174,176,178Sn are −0.42,−0.52,−2.69 MeV, implies all of them can possibly undergo 2n emission. The big jump from ¹⁷⁶Sn to ¹⁷⁸Sn suggest N = 126 is still magic.

I think ¹⁷⁶Sn wouldn't get seriously affected by 2n emission, due to some trends related to atomic number. There is no heavy 2n emitters (the heaviest is ^26,28O with Z = 8), so I just show it with 2p emitters. Despite ¹²O (S_2p = −1.737 MeV, Z = 8) has a lower decay energy than ⁶⁷Kr (S_2p = −2.89 MeV, Z = 36), it decays much faster (8.9×10⁻²¹ s vs 7.4 ms). If the trend follows, then 2n emission of ¹⁷⁶Sn is just not important compared to beta decay.

So, I think there is nothing that forbids the existence of ¹⁷⁶Sn. Nucleus hydro elemon (talk) 14:50, 27 August 2024 (UTC)

@Nucleus hydro elemon: Thanks, very cool!

I think I'll upgrade my personal hunch to bet on ¹⁷⁶Sn being doubly magic, but I'll be interested as new predictions come. :) Double sharp (talk) 04:47, 28 August 2024 (UTC)

August 25

Arecibo message distance

The Arecibo message was broadcast towards M13, 25,000 light years away. Is there any chance that the message could be received that far away, or would it be long lost in noise? Bubba73 ^{You talkin' to me?} 04:00, 25 August 2024 (UTC)

Not only would the signal-to-noise ratio be minuscule, but due to its orbit around the galactic center the signal would have to be aimed at where the Messier 13 cluster will be 25k years from now. 136.54.237.174 (talk) 18:05, 25 August 2024 (UTC)

Now I'm curious: Do we know, then, what stars it's going to actually pass close by? -- Avocado (talk) 21:15, 26 August 2024 (UTC)

From the data given in the article, I arrive at a minimum diameter of the receiving antenna of 2 kilometers. The diameter of the Arecibo dish is $D=305$ meters, the wavelength of the signal is $\lambda =12.6$ cm. The beam divergence angle is then $\theta =1.22{\frac {\lambda }{D}}=5\times 10^{-4}$ radians. Because $\theta$ is very small, the solid angle is to a good approximation $\Omega =\pi \theta ^{2}$, the exact formula is $\Omega =2\pi \left[1-\cos(\theta )\right]$. The area of the beam after traveling a distance of r is then $\Omega r^{2}$. Then with the power of the beam of 405 kW, at a distance of $22.2\times 10^{3}$ lightyears, the flux of the signal will be $F=1.3\times 10^{-26}$ Watt/m^2 at M13. This signal can then be detected using one or multiple antennas. If the total area of the antennas is A, then the received power is F A. If we assume that the temperature of the antennas and receivers are T = 20 C = 293.15 K, then the noise power will be $P=kT\Delta f$ where $\Delta f$ is the bandwith, that in this case must be 10 Hz or larger, as this is the frequency shift used to modulate the signal. The signal power must be larger than the noise power. If we then equate F A to P and solve for A and then assume a single antenna is used, and put $A=\pi r^{2}$ then the diameter of the receiving dish is 2 r and if I didn't make any mistakes, this yields a minimum diameter of approximately 2 kilometers. Count Iblis (talk) 19:25, 25 August 2024 (UTC)

A 2 km dish is feasible, but will the signal get lost in the noise at that distance? Bubba73 ^{You talkin' to me?} 04:57, 26 August 2024 (UTC)

There's also the matter of integration time. Noise adds incoherently, signal adds (hopefully) coherently, so with a longer integration time, the signal may rise above the noise. In this case, the integration time is limited to no more than 100 ms by the 10 Hz bitrate. The difference between the 0 bit and the 1 bit was only one wave, so a longer integration time doesn't help to decode the signal, but it may still help to detect the carrier wave.

Beam size matters too. The wider the beam, the more noise from other sources like stars; the narrower the beam, the less likely those aliens pointed it well enough at Earth. PiusImpavidus (talk) 10:31, 26 August 2024 (UTC)

[1] says that the gain of Arecibo antenna at 2.38 GHz was 77 dBi, only 600 mdB short of Count Iblis's estimate from the physical diameter (an aperture efficiency × antenna efficiency of 87% if true). A receiver temperature of 20°C is a little pessimistic; usually the receiver would be cooled (it is not necessary to cool the antenna, assuming that it is low-loss). catslash (talk) 00:09, 28 August 2024 (UTC)

Thanks for the informative replies. Bubba73 ^{You talkin' to me?} 04:47, 28 August 2024 (UTC)

Regarding the integration time: when there are two possible symbols (0 and 1) represented by two orthogonal signals of equal energy $E$ ( = received power × time) then the bit error rate is something like

$P_{\mathrm {err} }={\frac {1}{2}}\mathrm {erfc} \left({\sqrt {\frac {E}{2kT}}}\right)$

where $\mathrm {erfc} (x)$ is the complementary error function. This assumes (1) that it is known exactly what the two signals are - there is no random change in the phase between symbols, and (2) that the prior probability of each symbol is equal.

Without error-correcting codes it is impossible to reduce the error rate to zero, so it is necessary to decide what rate is acceptable before building the receiving antenna. catslash (talk)

[2] (Table 1: Legacy Arecibo Observatory planetary radar system.) says that the gain of Arecibo antenna at 2.38 GHz was 72.9 dBi, which seems more plausible. catslash (talk) 15:57, 1 September 2024 (UTC)

August 29

Rounding error in large numbers

At the last point of the tabel or matrix about the far future, there is something like:
"Because the total number of ways in which all the subatomic particles in the observable universe can be combined is 10 10 115 {\displaystyle 10^{10^{115}}},[152][153] a number which, when multiplied by 10 10 10 56 {\displaystyle 10^{10^{10^{56}}}}, disappears into the rounding error,"
My question is: How is the point about the rounding error valid? 2A02:8071:60A0:92E0:30AB:357:41DB:5492 (talk) 16:54, 29 August 2024 (UTC)

Multiplying the numbers is the same as adding the exponents. So $10^{10^{115}}\times 10^{10^{10^{56}}}=10^{\left(10^{115}+10^{10^{56}}\right)}$. And $10^{115}$ is negligible when added to $10^{10^{56}}$. --Amble (talk) 17:45, 29 August 2024 (UTC)

Or does the text try to say that $10^{10^{115}}$ is negligible compared to the rounding error in $10^{10^{115}}\times 10^{10^{10^{56}}}$? The intention is not clear to me. Why should these numbers be multiplied and what do rounding errors have to do with it? The argument should be, I think, that since there are "only" $10^{10^{115}}$ possible combinations, the specific combination that results in a repeat of the Big Bang is bound to occur sometime in the next $10^{10^{10^{56}}}$ years. However, this seems to assume that all combinations are about equally likely and ignores the effect of the expansion of the universe. I suspect SYNTH.  --Lambiam 19:57, 29 August 2024 (UTC)

how to calculate 10^{10^{115}}? I thought it's 10^(10×115)? 2A0D:6FC0:8EF:6000:9455:1667:D5E1:3858 (talk) 03:13, 2 September 2024 (UTC)

Photons question.

When an electron collides with positron, and when a proton collides with the anti-proton, both situations they are transformed into 2 photons. Can those 2 photons be distinguished from the 2 situations? That is, can the 2 photons be traced to being formerly an electron or proton? They have different energy of initial states, different total spin? Thanks. 66.99.15.162 (talk) 17:46, 29 August 2024 (UTC).

See electron–positron annihilation and annihilation. At low energy, electron-positron annihilation will produce two photons, and you can be sure they didn't come from proton-antiproton annihilation because the total energy is less than the rest mass of two protons. The annihilation of a proton and antiproton, or an electron and positron with higher energy, can produce a variety of end states including baryons and weak bosons. A proton-antiproton annihilation to two photons would be a fairly rare process, see [3]. So we're talking about fairly uncommon end states. The high energy electron-positron annihilation and the proton-antiproton annihilation could produce the same types of final states, but with different probabilities, so you can make some statistical inferences, especially if you can observe multiple events. --Amble (talk) 19:15, 29 August 2024 (UTC)

Proton-antiproton annihilation in a pair of photons is very rare. The far more common outcome is a pair or triple of pions. Ruslik_Zero 20:05, 29 August 2024 (UTC)

And then, photons that were created from an electron moving up/down an orbital or shell, are obviously different than the above mentioned photons? Have different measurable properties? These properties (or just energy) are measured when a photon hits a solid, the energy measured by a photo-multiplier tube? 66.99.15.162 (talk) 20:22, 29 August 2024 (UTC).

Well these photons have lower energy than those created in annihilation. Also they are usually produced one at a time, rather than a pair or triple. Graeme Bartlett (talk) 00:28, 30 August 2024 (UTC)

But the concise answer to your question is: no. Once a photon is created, its only unique property is its energy. There is no difference between a 511 keV photon created from positron-electron annihilation or one created from any other source of 511 keV photons. See: indistinguishable particles. PianoDan (talk) 16:04, 30 August 2024 (UTC)

August 30

Dead batteries come back to life?

A friend of mine has a battery-powered clock. It stopped running. It was over a week before he got replacement batteries. When he went back to the clock, it was running again. Is there an explanation for this? Bubba73 ^{You talkin' to me?} 16:04, 30 August 2024 (UTC)

This writeup has one theory:[4] ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:08, 30 August 2024 (UTC)

This effect is readily seen with a flashlight when the cells (battery) are approaching the end of their useful lives. After a short period of operation the light from the flashlight becomes dim. If the operator turns the light off and waits a few seconds, then turns it back on, the light is usefully bright again but only for a few seconds before it becomes dim again.

The active materials in the cell migrate to get to their electrode and that takes time. Similarly the exhausted product migrates away from its electrode. Allowing the cells to rest for a short while allows these materials to migrate to/from the electrodes and improve the density of the active materials surrounding each electrode. Dolphin (t) 22:13, 30 August 2024 (UTC)

Temperature also plays a role. Batteries near their end of life are more likely to fail if the room turns cold. If it warms up again the clock may restart. Shantavira|^{feed me} 09:04, 31 August 2024 (UTC)

An additional factor may be a slight irregularity in a clock's mechanism, such as a slightly mis-shaped or corroded cog tooth, that is overriden by the power of a good battery, but provides enough resistance to the weaker power of a near-dead one to stop the clock. If the clock is then moved or disturbed by vibrations, this may jar the tensioned mechanism past the obtruction, restarting the clock for a time. {The poster formerly known as 87.81.230.195} 94.1.209.45 (talk) 09:18, 31 August 2024 (UTC)

Metric units in the UK

In the United Kingdom, is room space and building height measured in metric units? And has rail transport seen any metrication in its history? --40bus (talk) 20:38, 30 August 2024 (UTC)

Rightmove are the UK's biggest online property agents. As you'll see from their website, they quote room space in sq ft but with conversions to sq m. I don't know about rail transport. Mike Turnbull (talk) 20:49, 30 August 2024 (UTC)

40bus: "On 5 May 1975, rail traffic switched to metric measurements for loads, capacities, tare weights and brake force. On the traffic side of the railway we are chiefly concerned with distance and weight. As to distance, no metrication is planned for the time being... (i.e. distance is still measured in miles, as are road distances). [5] Alansplodge (talk) 16:22, 31 August 2024 (UTC)

And are there any everyday things that are measured in metric units in the United States, as oppsoed to scientific things? --40bus (talk) 21:11, 30 August 2024 (UTC)

Some commodities are. You can get liter bottles of soft drinks, for example. ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:23, 30 August 2024 (UTC)

2 quart soda bottles haven't been used in decades and decades. Did they keep the same price for awhile to say at least you're getting more? Sagittarian Milky Way (talk) 04:22, 1 September 2024 (UTC)

Highway distances: metric signs in Tennessee. (Not a representative sample!)  Card Zero  (talk) 21:39, 30 August 2024 (UTC)

Other states also post both miles and kilometers. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:13, 30 August 2024 (UTC)

Indeed, that site has more.  Card Zero  (talk) 22:36, 30 August 2024 (UTC)

Engine capacities in cc, esp. motorcycles. Doug butler (talk) 21:55, 30 August 2024 (UTC)

I thought Harley-Davidson measured their V twins in cubic inches. --TrogWoolley (talk) 10:38, 1 September 2024 (UTC)

Ammunition is measured in mm. So are camera lenses. And mechanical pencil lead widths. And a lot of other things that are too small to be comfortably measured in inches -- such as jewelry components. Wrench sets are made for both metric and US customary units. Backpacks and other luggage are sized in liters. We run 5K and 10K races.

A lot of components of food and supplements (carbohydrates, cholesterol, sodium, caffeine, etc.) are measured in grams or mg, especially on standardized nutrition labels -- and they've crept into the vernacular from there. Nobody talks about how many ounces per day of protein or grains of caffeine one should consume. -- Avocado (talk) 02:03, 31 August 2024 (UTC)

Guns and ammo are in inches. .357 Magnum, for example. Though much less common than they once were, Mile run events are still held in America. ←Baseball Bugs ^{What's up, Doc?} carrots→ 10:25, 31 August 2024 (UTC)

The Dream Mile race is held in Oslo (Norway metricated in 1875). Alansplodge (talk) 16:16, 31 August 2024 (UTC)

Miles are still used in Norway, but those are metric miles of 10 kilometres. The traditional Norwegian mile was 11298 metres. English miles have obviously never been in common use in Norway, but the abovementioned race is an English mile long. PiusImpavidus (talk) 17:48, 31 August 2024 (UTC)

Oh, yeah, not saying we don't use customary units for those things at all. Just that we do commonly use metric ones for them, too (such as 9mm for ammo). -- Avocado (talk) 13:53, 31 August 2024 (UTC)

Ammo calibres are more like names than actual measurements. .223 Remington and 5.56mm Nato are the same size, despite 5.56mm not being the exact conversion of 0.223", and neither being the actual measurement of the bullet. Iapetus (talk) 10:47, 2 September 2024 (UTC)

Most things related to electricity, such as a 120-volt receptacle or a 9-volt battery. Jc3s5h (talk) 14:03, 31 August 2024 (UTC)

Small lengths of time in the US are commonly specified in the corresponding SI base unit, the second. --Amble (talk) 22:47, 30 August 2024 (UTC)

I hope that the US will metricate at least some everyday things in next 20 years so that US-related articles will use metric units first in 2044. --40bus (talk) 17:25, 31 August 2024 (UTC)

I hope we don't we're the last bastion of old units, just big and isolated enough to prevent zero Earth unit diversity Sagittarian Milky Way (talk) 04:34, 1 September 2024 (UTC)

I second that emotion. ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:56, 1 September 2024 (UTC)

I don't know everything about British railways, but if I'm to believe openrailwaymap, it appears that some British lines have a speed limit in kilometres per hour and some have a limit in miles per hour that is an obvious conversion from a round number in kilometres per hour. Look at the high speed lines like High Speed 1 (not the older, improved lines with 125 mph limit), DLR and some of the more recent lines of the London Underground. So it looks like a conversion has started. PiusImpavidus (talk) 16:39, 31 August 2024 (UTC)

The Grenfell Tower fire led to the United Kingdom cladding crisis. Most of the building height measurements are only or primarily given in metres. -- Verbarson  ^talk_edits 20:49, 31 August 2024 (UTC)

But article Tower Bridge, for example, uses imperial units first. And it is a building. --40bus (talk) 21:44, 31 August 2024 (UTC)

Tower Bridge is 130 years old. The sources (and the sources' sources) are therefore far more likely to use Imperial units. The response to the Grenfell fire is contemporary, so better reflects current practices. -- Verbarson  ^talk_edits 05:06, 1 September 2024 (UTC)

Our Miles per hour article says: Miles per hour is also used on British rail systems, excluding trams, some light metro systems, the Channel Tunnel and High Speed 1 (the Channel Tunnel and its High Speed link obviously extend into France and beyond). Alansplodge (talk) 11:30, 1 September 2024 (UTC)

It's a surprisingly modern bridge really. The Time Machine was written the next year.  Card Zero  (talk) 13:06, 1 September 2024 (UTC)

Real steampunk, in fact. (Edit) My mistake - it was hydraulic. -- Verbarson  ^talk_edits 13:35, 1 September 2024 (UTC)

Not mistaken at all, Verbarson! The operations were performed by hydraulic pressure, supplied by hydraulic accumulators, but "[w]ater at a pressure of 750 psi (5.2 MPa) was pumped into the accumulators by a pair of stationary steam engines" – see Tower Bridge#Hydraulic system. {The poster formerly known as 87.81.230.195} 94.1.209.45 (talk) 21:45, 1 September 2024 (UTC)

Ah, thank you. When I saw it was 'hydraulic', I somehow assumed it used the London high-pressure network (which was itself steam-powered). What makes it feel most like steampunk is the combination of ancient (Gothic turrets), more recent (suspension spans for the approaches) and up-to-date (steam-hydraulic powered bascules) styles and technologies. -- Verbarson  ^talk_edits 22:17, 1 September 2024 (UTC)

September 2

Is the nose of a grizzly or a brown bear cold?

Do bears have a cold nose like a dog? Wasn't able to find an answer with Google and finding out myself would be against the policies of my health insurance. --Question123Ka (talk) 04:46, 2 September 2024 (UTC)