Welcome to the science section
of the Wikipedia reference desk.

Select a section:

WP:RD/S

Want a faster answer?

Main page: Help searching Wikipedia

How can I get my question answered?

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

Ready? Ask a new question!

How do I answer a question?

Main page: Wikipedia:Reference desk/Guidelines

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

December 26

Why so many unpublished studies?

I was reading this article from Scientific American, How Two Pharmacists Figured Out That Decongestants Don’t Work, and something caught my attention:

"the oral decongestant monograph panel reviewed a few published studies and multiple unpublished studies for phenylephrine".

Why would there be so many unpublished studies? I'm not so concerned about the particular drug in question but science in general. What's the point of conducting a study if it doesn't get published? Do such studies get rejected because of some sort of flaw? Did the authors not find a publication willing to publish their study? Do scientists conduct studies with no intention of publication?

Sorry, I'm asking too many questions and speculating on the possible answers I guess what I am really asking is

How common is it to have unpublished studies?
What are the most common reasons for a study not to be published?

Thanks! Pealarther (talk) 11:04, 26 December 2023 (UTC)[reply]

The vast majority of science done by industrial firms is never published. Suppose you want to find a new decongestant and test thousands of potential drug candidates. Most won't work and these negative results will sit in company databases but are unlikely to be suitable for inclusion in reputable journals. Some aspects of such work may be reported in internal documents but that's not "publication": secrecy is the norm so as not to alert competitors to what has been tried and failed. Mike Turnbull (talk) 11:47, 26 December 2023 (UTC)[reply]

It is not difficult to get results published because there are competing vanity publishers who have no interest in whether a book is suitable for publication or good enough to sell. In professions that are obsessed more with quantity rather than with quality, the Publish or perish phenomenon arises and may contribute to a Replication crisis where reported results of scientific studies are difficult or impossible to reproduce. Some reasons for rejection of results from Wikipedia include unverifiable claims, lack of peer review, outdated material or conflicts of interest that may lead to covert advertising. Scientists who find the peer-review and publication process to be too slow often choose to release results in Preprints. There are research results in mathematics, physics, astronomy, electrical engineering, computer science, quantitative biology, statistics, mathematical finance and economics that have been published only on the online-accessible preprint server arXiv that receives about 16,000 articles per month. Philvoids (talk) 12:06, 26 December 2023 (UTC)[reply]

It's one of the known issues with clinical trials. Historically, an organizations (public or private, academic or commercial) could conduct a clinical trial, and be left to their own devices and schedule on when or whether to publish their results, and how to conduct their analyses of the data.

This led to a number of problems, in various flavors of publication bias and selective reporting. A drug company might choose not to publish (or to slow-walk publication of) a result that failed to show efficacy for their novel drug candidate. An academic lab might lose interest in a study that failed to produce a novel result, and shelve their data in order to preserve and pursue funding for more 'interesting' studies. A clinical trial group might choose to only report a subset of their findings to amplify or suppress certain results. Worse, they might opt to re-analyze their data to identify 'effects' that they hadn't planned for or predicted when setting up the trial: HARKing and other sorts of post-hoc analysis.

It's only fairly recently that clinical trial pre-registration has become the norm (at least in North America and Europe). TenOfAllTrades(talk) 14:45, 26 December 2023 (UTC)[reply]

Trials that fail to show a useful result are particularly liable to never be published. This is a very real problem and probably affected a number of those studies. And some of those test may have been done because they hadn't heard about other failed trials so it was a wast of effort too. Documenting negative results is very important but it is only recently that people have started to recognize this and there are now journals that have been set up specifically to publish them. The bias in favor of only positive results also contributes to the replication crisis mentioned above. Hopefully the trial pre-registration mentioned in th previous response will also contribute towards rectifying this problem. NadVolum (talk) 11:01, 27 December 2023 (UTC)[reply]

max use temperature in Ar/N2 > max use temperature in vacuum

Hi. This is site[1] lists boron nitride crucibles' maximum use temperature as 900 °C in air and 1800 °C in vacuum. "maximum use temperature in vacuum is higher than maximum use temperature in air" makes perfect sense.

However the max use temperature in Ar/N2 is actually higher than the vacuum temperature. This fact seems counter-intuitive (at least to me).

Q1: What is the reason behind this? (max use temperature in Ar/N2 > max use temperature in vacuum)

Q2: Is there any high temperature crucible materiel for which this isn't true? That is to say, for this hypothetical material: max use temperature in vacuum > max use temperature in Ar/N > max use temperature in air.

Liberté2 (talk) 19:59, 26 December 2023 (UTC)[reply]

2: no. Inert gases valence being complete, the vicinity with their molecules act like an isolator, a bit as a "punching ball" effect. --Askedonty (talk) 22:15, 26 December 2023 (UTC)[reply]

December 27

Is it possible that europium is more unstable than bismuth?

The only natural occurring isotope of bismuth, Bi209, has a half-life of 2.01*10^19 years, and for europium, Eu151 has a half-life of 5*10^18 years, and the lower bound of the half-life of Eu153 is 5.5*10^17 years, so is it possible that europium is more unstable than bismuth? And hence europium will be the most unstable natural occurring element besides thorium and uranium? 111.253.202.97 (talk) 02:15, 27 December 2023 (UTC)[reply]

Probably not. According to this paper, all theoretical predictions for the alpha half-life of ¹⁵³Eu are over 10¹⁴⁰ years, and no other decay modes (besides spontaneous fission) are possible. Double sharp (talk) 03:26, 27 December 2023 (UTC)[reply]

So what element will be the next "unstable" natural occurring element after uranium, thorium, and bismuth? 2402:7500:944:2AC:45B9:41E0:7299:F0CC (talk) 03:59, 27 December 2023 (UTC)[reply]

Based on the tables in that paper, perhaps rhenium? ¹⁸⁷Re is already known to be beta-unstable with a half-life of about 4×10¹⁰ years, and ¹⁸⁵Re is expected to be alpha-unstable with a half-life on the order of 10²⁴–10²⁵ years. Though I note that the tables don't consider double beta decay (relevant for other elements), so this should be taken as just a guess. Double sharp (talk) 04:07, 27 December 2023 (UTC)[reply]

The longest known half-life of a nuclide is 2.2*10^24 years for Te128, thus maybe the half-life of Re185 is shorter than Te128? (Although their decay modes are different: Re185 is alpha decay while Te128 is double beta decay) 2402:7500:944:2AC:E564:A5C5:C845:76AC (talk) 04:57, 27 December 2023 (UTC)[reply]

Since predictions aren't perfect, it may indeed be that this is the case. (Predictions slightly overestimated the half-life of nearby ¹⁸⁴Os.) Double sharp (talk) 05:53, 27 December 2023 (UTC)[reply]

OK, it is for the proton number, the proton numbers with primordial nuclides are 1~83 except 43 and 61, together with 90 and 92, besides, 83, 90, 92 are the proton numbers among them which have no stable nuclides, and perhaps 75 is the next "unstable" proton number after 92, 90, 83. But what is the answer for the neutron number? The neutron numbers with primordial nuclides are 0~126 except 19, 35, 39, 45, 61, 89, 115, 123, together with 142, 143, 146, besides, 21, 142, 143, 146 are the neutron numbers among them which have no stable nuclides, and the next "unstable" neutron number after 143, 21, 146, 142 may be 71 (corresponding to Te123)? If so, what number will be the next "unstable" neutron number after 143, 21, 146, 142, 71? 2402:7500:942:3D81:695F:5302:9A90:FEE6 (talk) 07:47, 27 December 2023 (UTC)[reply]

Probably either 87 (¹⁴⁹Sm should be alpha-unstable at 10¹⁷–10¹⁸ years) or 111 (¹⁸⁷Os should be alpha-unstable at 10¹⁶–10¹⁹ years). Either of these might come before 71, actually. Double sharp (talk) 08:08, 27 December 2023 (UTC)[reply]

I should note, though, that we ought to distinguish proton or neutron numbers with no beta-stable nuclides from those having beta-stable nuclides which are unstable to alpha decay. Atomic numbers 43 and 61 are instances of the former (all isotopes of Tc and Pm are susceptible to beta decay), whereas if the alpha decay of ¹⁸⁵Re (beta-stable) is observed, for instance, it would only be reclassified from stable to primordial radioactive.

The list of beta-stable isobars also shows where these "unstable numbers" are, and continues into the region of non-primordial nuclides, where we see that there are no beta-stable isobars with neutron number 147. ^Complex/_Rational 15:19, 27 December 2023 (UTC)[reply]

Or probably 84? Ce142 is double-beta-unstable. Also, could someone search the decay of Re185, Sm149, Os187, just like Os184 and Xe124 (whose decay are found recently)? I saw the article, maybe someone can search the decay of the nuclides whose theoretical half-lives are shorter than 2.2*10^24 years (which is the half-live of Te128)? This includes Nd145, Sm149, Dy156 (a little longer), Yb168 (a little longer), Hf176, Hf177, Hf178, Ta180m (maybe someone can search its isomeric transition), Re185 (a little longer), Os187, Pt192. 210.243.206.107 (talk) 02:35, 28 December 2023 (UTC)[reply]

Decays of ¹⁴⁵Nd, ¹⁴⁹Sm, ¹⁵⁶Dy, ¹⁶⁸Yb, ^180mTa, and ¹⁹²Pt have been searched for, so far without success. Double sharp (talk) 03:37, 28 December 2023 (UTC)[reply]

I know, and I also want someone to search the decay of Re185 and Os187, maybe this search can make (proton number 75) or (neutron number 111) be an "unstable" number (so far there is still no single "unstable" number for proton <= 82 or neutron <= 126 (they are the limit of observationally stable nuclides) which have a primordial nuclide except the neutron number 21 (which corresponding to potassium-40, which has a half-life less than the age of the universe, and is the only one primordial nuclide with proton number <= 82 and neutron number <= 126 with half-life less than the age of the universe, thus this search may broke the record, in the past the nuclide Te123 is wrongly found to be radioactive, but now it remains (observationally) stable, thus the neutron number 71 is not an "unstable" number. 118.170.53.246 (talk) 05:12, 28 December 2023 (UTC)[reply]

There is also ₇₈Pt. Ruslik_Zero 20:35, 27 December 2023 (UTC)[reply]

It seems that the largest proton number with a really stable isotope is ₆₆Dy, though magic ₈₂Pb has theoretical lifetimes in excess of 10⁶⁰ years. Ruslik_Zero 20:53, 27 December 2023 (UTC)[reply]

Well, the proton numbers with a theoretically stable nuclide are 1~66 except 43, 61, 62, 63, and the neutron numbers with a theoretically stable nuclide are 0~98 except 19, 21, 35, 39, 45, 61, 71, 83~91, 95, 96, also in theory, no two stable nuclides have the same mass number, and the mass numbers with a theoretically stable nuclide are 1~164 except 5, 8, 143~155, 160~162. 210.243.206.107 (talk) 02:50, 28 December 2023 (UTC)[reply]

Electron capture vs. beta plus decay

Is there a reference I can use to distinguish between electron capture and β⁺ decay? While writing about isotopes of bromine, I encountered a reference describing the isotope ⁷⁷Br as primarily undergoing electron capture rather than β⁺,^[1] but NUBASE2020 lists only β⁺ for most nuclei capable of β⁺ decay, inluding ⁷⁷Br.^[2] –LaundryPizza03 (d c̄) 08:19, 27 December 2023 (UTC)[reply]

Perhaps both decay modes are known for ⁷⁷Br. The energy difference between ⁷⁷Br and ⁷⁷Se is large enough for positron emission to occur (greater than

2m_{e}c^{2}~=1.022~{\text{MeV}}

), but a number of sources specifically describe electron capture and the Auger effect and do not classify ⁷⁷Br alongside other positron emitters (such as ⁷⁶Br). As such, EC should definitely be included, but I wouldn't include a branching ratio unless a source specifically describes one. ^Complex/_Rational 15:33, 27 December 2023 (UTC)[reply]

References

^ Kassis, A. I.; Adelstein, S. J.; Haydock, C.; Sastry, K. S. R.; McElvany, K. D.; Welch, M. J. (May 1982). "Lethality of Auger Electrons from the Decay of Bromine-77 in the DNA of Mammalian Cells" (PDF). Radiation Research. 90 (2): 362. doi:10.2307/3575714. ISSN 0033-7587.
^ Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.

UK metric system (update)

The UK government has announced plans to make it legal to sell wine by the pint. No more messing about with those fiddly little wineglasses, then. -- Verbarson ^talk_edits 11:58, 27 December 2023 (UTC)[reply]

Also note that "98.7% of respondents to a consultation favoured using metric as the main measurement unit for sales, as now, or as the only unit" (from the same BBC report). Mikenorton (talk) 12:54, 27 December 2023 (UTC)[reply]

Last passenger

After pulling the emergency brake in a train (and in particular a British one), is there any way to release the brakes without recharging the brake pipe? I think not (based on what I know of trains), feel free to correct me if I'm wrong! 2601:646:8080:FC40:7042:7EFC:5F93:408A (talk) 12:01, 27 December 2023 (UTC)[reply]

Typically, you can release it. I don't know the specifics of British passenger trains and there's quite a bit of variation, but I'd expect a manual release valve, typically accessible on the outside of the vehicle. See the image on the right. This is a goods wagon (Swiss, I think). The yellow handle on the top is to switch between fast and slow application. Slow application (left, G for Güter=goods) prevents large differences in braking force throughout the length of the train and is useful on long goods trains. Passenger carriages normally only have the fast setting (right, P for Personen=people), so the lever would be absent. The red handle on the left is to disable the brake on this wagon entirely, useful if the brake is broken. It's safe to run a train with the brakes disabled on a small fraction of the wagons. The red handle on the right is to adjust the braking force to the weight of the wagon, so that it brakes harder when loaded. In this case, set it to the left to pretend that the wagon weighs 13 tonnes, to the right for 26 tonnes, and one should switch when the weight exceeds 27 tonnes. As the weight of passenger carriages doesn't change much with load, such handles aren't used on passenger carriages. Finally, the yellow thing on the bottom is the manual release. Pull it to release the air brake. It's convenient to have when you want to shunt and don't have time to connect the brake hose and recharge the brakes. It's also used when transferring a wagon to a locomotive that uses a lower brake pipe pressure than the old locomotive. PiusImpavidus (talk) 21:57, 27 December 2023 (UTC)[reply]

I see! So it is plausible, if the passenger in question was able to go outside the train and pull the release valves without anyone noticing? (FYI, as you might be able to tell from the title, my question had to do with a Christmas disaster movie I watched -- I don't want to give too much away, but the gist of it is, there was a psycho on a train who murdered the conductor, pulled the emergency brake from the conductor's cab, murdered the engineer when he came out to inspect the train, and then released the brakes without recharging the brake pipe, and took off in the train without brakes in order to crash it at the end of the line!) 2601:646:8080:FC40:7042:7EFC:5F93:408A (talk) 03:09, 28 December 2023 (UTC)[reply]

Yes, that part is plausible. Using the manual release will make some hissing noise, but trains are usually sufficiently soundproof not to notice that on the inside. PiusImpavidus (talk) 16:15, 28 December 2023 (UTC)[reply]

And more to the point, even if anyone hears it, they'll probably think it's just the normal sounds of brakes releasing after an emergency stop! (And in this particular scenario, the engineer and the conductor won't notice anything because they're both dead!) 2601:646:8080:FC40:7042:7EFC:5F93:408A (talk) 02:22, 29 December 2023 (UTC)[reply]

Where was the camera on the Apollo lunar lander?

I'm trying to better understand how NASA filmed the Apollo 11 lunar landing considering obviously there was no one on the Moon to film it. I found this picture which is supposed to show the camera on the lander but I am not seeing it. Nothing that resembles a traditional camera is in the image as far as I can see. Can someone point out where in the image is the camera? A Quest For Knowledge (talk) 12:09, 27 December 2023 (UTC)[reply]

See Apollo TV camera, which has another image of the camera's stowed location on the lander. Mikenorton (talk) 12:37, 27 December 2023 (UTC)[reply]

(edit conflict)Also a video explaining the Lunar Module 2 MESA (Modularized Equipment Stowage Assembly) which contained the camera. This image shows the MESA and its camera in the deployed position. Alansplodge (talk) 13:04, 27 December 2023 (UTC)[reply]

See the landing film on Apollo 11, the only film of the Apollo 11 lunar landing was taken from the LEM as it came down. Martin of Sheffield (talk) 12:54, 27 December 2023 (UTC)[reply]

I think the OP might be asking about the famous blurry images of Armstrong's feet coming down the ladder onto the lunar surface. Alansplodge (talk) 13:04, 27 December 2023 (UTC)[reply]

December 28

density of mercury

Hi. I'm trying to understand the answer to this question[2].

Assuming that the given answer on that site is correct: I don't understand why ρ is replaced with the value 3.6 * 10^3.

My understanding is that ρ is the density of mercury, so it should be around 1.35 * 10^4. At least, that's the value I get when I google "density of mercury in kg/m3".

Every other value I understand. Alpha is the surface tension of mercury in N/m. g is the acceleration due to gravity which is 9.8 m/s2. d is the diameter of the hole given in the question which is 70 micrometer. Liberté2 (talk) 00:10, 28 December 2023 (UTC)[reply]

I'd like to clarify that this is not a homework question.

I remember seeing liquids unable to escape out of tiny holes, likely due to surface tension. So I was wondering whether there's a direct relationship between minimum hole size and surface tension. Googling that lead me to this physics stackexchange [3] which has the correct equation. I tried to search for some actual applications of this equation which lead me to that toppr.com page. Liberté2 (talk) 00:38, 28 December 2023 (UTC)[reply]

I haven't the foggiest, I'd agree with you. The only thing I can think of is they stuck in the density of the wrong material, but anyone in physics would know the approximate density of mercury. NadVolum (talk) 01:03, 28 December 2023 (UTC)[reply]

The next step combines powers of ten and a few other factors (490 / 9.8), and the 3.6 changes to 13.6. So the 3.6 seems to be just a typo. --Amble (talk) 02:06, 28 December 2023 (UTC)[reply]

Thank you!!! It's indeed a typo. Liberté2 (talk) 05:24, 28 December 2023 (UTC)[reply]

I should have noticed that, silly me, thanks. The 3.6 had nagged me a bit but I hadn't thought about it properly. NadVolum (talk) 14:25, 28 December 2023 (UTC)[reply]

Resolved

December 29

Why the IPK must be stored in air?

Why the IPK must be stored in air? Why cannot we store the IPK in vacuum like Magdeburg hemispheres and Torricellian vacuum, to avoid it gain mass through adsorption of atmospheric contamination? 210.243.206.248 (talk) 04:40, 29 December 2023 (UTC)[reply]

In 2019 the IPK lost its role as the standard for the kilogram and therefore the stability of its mass is no longer crucial. Before then, there was a need to be able to compare copies of the IPK with the prime IPK stored in the vault of the BIPM. When the IPK and the first copies were created, in 1879, the technology to move them around (needed to bring them together) and to compare them while all would remain in vacuum was not reliably available. Even when it became available, the cost to develop the required machinery would have been enormous. Consider also that the practical significance of the IPK's stability was limited. Scientific mass measurements compared the mass of an object to be weighed to that of objects of known mass, calibrated indirectly with respect to the IPK. This could not possibly all be done in vacuum, so the actual mass measurement were subject anyway to perturbing influences that were probably much larger than those of storing the IPK in air. --Lambiam 09:47, 29 December 2023 (UTC)[reply]

Allele order in genotype

In humans and when talking about one single gene locus, genotype is about which alleles are present on the two homologous chromosomes. From the examples in Genotype#Genotype encoding I infer that order is not significant (there is no aA combination there, only Aa). But what when we have more than one locus? Is it significant whether alleles of two (or more) different genes are on the same chromosome (in the case where both are heterozygous)? For instance, say the first gene has alleles A and a and the second one has B and b. Now on the one chromosome there can be A and B while on the other there are a and b, or on the one chromosome there can be A and b while on the other a and B. Are these two cases merged into a single genotype AaBb or are they distinguished? And what about cases of polyploidy (e.g. one chromosome can have A and two others a or one can have a and two others A)? Or would it be legitimate to just distinguish Aa and aA as genotypes in the first place? --Genetik-Kackboonnoob (talk) 11:45, 29 December 2023 (UTC)[reply]

Genotypes are always presented with the dominant allele first by convention for ease of reading. --User:Khajidha (talk) (contributions) 16:50, 29 December 2023 (UTC)[reply]

OK but that′s not my question… Or maybe this answers it – so the heterozygous type with two genes would (as I understand you) always be written AaBb regardless of whether A and B are on the same chromosome or not. Is that just a matter of how it is written or are the two cases actually never distinguished? --Genetik-Kackboonnoob (talk) 17:21, 29 December 2023 (UTC)[reply]

That is how it is always written. You can specify which parent contributed each allele in text, but it is not relevant to what the genotype is. --User:Khajidha (talk) (contributions) 17:32, 29 December 2023 (UTC)[reply]

OK, thank you. In the polyploid case, though… would that be e.g. AAa or is the number of alleles irrelevant as well? --Genetik-Kackboonnoob (talk) 18:23, 29 December 2023 (UTC)[reply]

Yes, that would be AAa for a polyploid with 2 dominant alleles and 1 recessive allele. Or AAaBb in the dihybrid case mentioned earlier.--User:Khajidha (talk) (contributions) 02:43, 30 December 2023 (UTC)[reply]

If the two gene loci are linked (i.e. lie not so far apart on the same chromosome) it does make some difference whether in a double heterozygote the two dominants are on the same homologous chromosome (cis arrangement) or each on a different homologue (trans arrangement). The two arrangements are termed gametic phases, but the concepts are better explained in our genetic linkage article. Most often the phase affects only the genotypes of the gametes and thereby the proportion of different phenotypes in the next generation. But in the case of X-inactivation it can also affect the phenotype of the individual itself. I don't know if there is a standard way of indicating the two phases. JMCHutchinson (talk) 22:47, 29 December 2023 (UTC)[reply]

Pi

(edit conflict)*Wikipedia:Reference desk/Archives/Science/2023 December 19#Pi

"In 1897, lawmakers in Indiana tried to pass a law that declared the value of pi to be 3.2" - reader's letter in the Guardian, 18 November 2023, prompted by the government's attempt to pass a law that declares Rwanda to be a safe country.

Why did they do that? 86.150.201.218 (talk) 16:59, 29 December 2023 (UTC)[reply]

See Indiana Pi Bill. -- Verbarson ^talk_edits 18:10, 29 December 2023 (UTC)[reply]

The issue with Rwanda is asylum seekers. If Rwanda is declared "safe", it is far more difficult for groups of people in Rwanda to seek asylum in other countries. 12.116.29.106 (talk) 12:18, 2 January 2024 (UTC)[reply]

Digging to the other side of the world

Hi, I was curious, assuming it were possible, and obstacles (such as high temperature) were not an issue, in other words, theoretically speaking, if I were to dig a hole to the center of the Earth, and as mentioned, the heat and molten rock was not an issue, and I wanted to keep going to the opposite spot that I started, would I then have to 'dig' up? Or, would gravity then shift, and I would just continue digging a hole normally? Or, if I dug, and did a U-turn around the Earth's core, would that be entirely digging normally, gravity-wise (i.e. I am always being pulled down as being on the Earth's surface)? Thanks! 142.243.254.124 (talk) 19:58, 29 December 2023 (UTC)[reply]

You dig down when you dig towards the centre of the Earth, you dig up when you dig away from the centre. Gravity decreases as you approach the centre, and is zero when you're there. Otherwise the direction is always towards the centre. --Wrongfilter (talk) 20:11, 29 December 2023 (UTC)[reply]

Neil Degrasse Tyson has addressed this issue here. HiLo48 (talk) 23:41, 29 December 2023 (UTC)[reply]

Interestingly even though gravity would be zero at the centre of the earth clocks would still go slower there. As for the problems getting there - the enormous pressure would be far more of a problem than even the temperature like the surface of the sun. NadVolum (talk) 01:09, 30 December 2023 (UTC)[reply]

Eternal return

How does the scientific community assess the concept of eternal recurrence today? 2A02:8071:60A0:92E0:9186:6B27:68E7:9C79 (talk) 22:45, 29 December 2023 (UTC)[reply]

It doesn't. Eternal return is a philosophical concept that lies outside the realm of Science.

As far as I myself understand the matter, there is nothing in current scientific thinking that positively favours the idea – it is simply irrelevant: others may differ. {The poster formerly known as 87.81.230.195} 90.205.111.170 (talk) 23:17, 29 December 2023 (UTC)[reply]

It's just somebody's hypothesis, which would be impossible to prove or disprove. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:35, 29 December 2023 (UTC)[reply]

The Poincaré recurrence theorem is a property of dynamical systems that has some notional similarity to the philosophical idea. I wouldn't say it's the same thing, though. --Amble (talk) 00:43, 30 December 2023 (UTC)[reply]

The cyclic cosmological models imply (in most theories) an eternal recurrence à la Poincaré of virtually indistinguishable states, and particularly so if unitarity of the cosmological quantum state evolution holds for a full cycle. See also Conformal cyclic cosmology, a theory proposed by a Nobel Laureate in Physics. While usually considered physics rather than philosophy, the current state of affairs is that these theories of cyclicity are purely speculative, without a prospect of experimentally falsifiable predictions. --Lambiam 08:15, 30 December 2023 (UTC)[reply]

One question that would have to be asked is, "When was the first of these cycles?" Kind of a cousin to the "turtles all the way down" story. ←Baseball Bugs ^{What's up, Doc?} carrots→ 09:04, 30 December 2023 (UTC)[reply]

In an eternal universe the question is as meaningless as the question, "What is the largest number?" Meaningless questions do not have to be asked. --Lambiam 13:26, 30 December 2023 (UTC)[reply]

Meaningless questions are asked regularly, unfortunately. I think you meant to say that they don't have to be answered, and indeed often can't be. Mike Turnbull (talk) 15:04, 30 December 2023 (UTC)[reply]

For someone to ask a meaningless question is one thing. For someone to state that a meaningless question has to be asked is next level. I meant what I wrote: no, the question doesn't have to be asked. --Lambiam 18:09, 30 December 2023 (UTC)[reply]

It's as meaningful as the original premise. ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:16, 30 December 2023 (UTC)[reply]

Which is the original premise (and by which premise was it preceded)? --Lambiam 17:59, 30 December 2023 (UTC)[reply]

December 30

gallium and carbon

Hi. I was watching random science Youtube and came across videos of gallium showing its fascinating properties.

1. Upon reading "Gallium forms alloys with most metals" in the gallium article, now I'm curious which common metals are not reactive with gallium. Is there such a list out there?

I figured that the list of metals that alloy or react with gallium is so long that it would not be informative, hence why I'm looking for the inverse list.

2. I'm also interested in which non-metals do not react with gallium. In particular, I'm interested in whether carbon reacts with liquid gallium or not. So far, I found this paper[4] where solid carbon float out of an gallium magnesium alloy, so I'm guessing that elemental carbon do not react with gallium at all. But I'd like a confirmation on this.

3. In researching for the two questions above, I've been searching "gallium XXXXX" in google. This is slow and error-prone. I don't have specialized training in chemistry, so I am not able to correctly interpret the search results even. Is there a more efficient way of doing this search?

I'm guessing that one of the databases in List of chemical databases would be helpful here, but there is so much information on that page that I don't even know where to start. Liberté2 (talk) 03:10, 30 December 2023 (UTC)[reply]

@Liberté2: You can check phase diagrams at this Russian-language site (the data is reproduced from reliable sources). You can often search for papers by Googling "chromium gallium system" (or perhaps using chemical symbols like "Cr-Ga system"). The metals least reactive to Ga seem to be refractory metals like W. The Pergamon volume on the group 13 metals also says that refractory Nb, Ta, Mo, and "above all" W are most resistant to Ga. (That said, intermetallics between Ga and the former three are known.)

Carbide says that Ga, In, and Tl do not form carbides even though Al does. This seems to be the only nonmetal with no binary compound with Ga, as I can find references to GaB₁₂, and Ga reacts with Si and Ge. I haven't found if all the binary Ga–nonmetal compounds form on direct reaction of the elements under some conditions, though. After all, GaN only forms by such direct reaction at 1200°C per doi:10.1021/j150340a015. Double sharp (talk) 04:12, 30 December 2023 (UTC)[reply]

@Double sharp Thank you! Liberté2 (talk) 07:02, 1 January 2024 (UTC)[reply]

The forces acting on my cell phone

Okay, here's the setup: the layout of my current city was designed by a drunken mule two centuries ago and hasn't really been corrected since. That, combined with incessant construction and street repair, means that I often make use of my phone's GPS. When I do, I lay my phone onto the charging tray in my center console so that I can glance at the map if things get confusing (otherwise, I just use the audio). The charging tray is pretty small, so my phone only fits on it sideways, but that's okay since I have to turn my head a bit to see it anyway. Here's the thing: my phone constantly ends up with the picture inverted (i.e. top to bottom), making it hard to read and necessitating me angling up the phone until it corrects itself so I can lay it down. I am not asking about preventing this behaviour; I know I can just force the screen to always stay a certain way; my question is: why doesn't the phone correct itself? Clearly, the centripetal force while making turns tricks the phone into thinking it needs to right itself, but why does it only get fooled once and then stay that way? Once the picture is inverted, it won't correct itself until I fix it manually. Why doesn't the situation undo itself when I turn in the other direction? Matt Deres (talk) 15:37, 30 December 2023 (UTC)[reply]

It's not clear to me what you mean by "sideways" when you describe how the phone is positioned. If you mean that the long axis of the phone is perpendicular to the front-back axis of the car, then I would assume that the inversion is caused by braking rather than turning. In that configuration, braking would apply a force directed toward the front of the car and would cause the phone to think that that direction is "down". But the opposite force when the car accelerates is usually not as strong as the braking force, so may not be strong enough to convince the phone that "down" is now in the backwards direction. CodeTalker (talk) 18:48, 30 December 2023 (UTC)[reply]

Not quite, though it's hard to describe without images. Normally, your phone and your car would be in parallel (i.e. the top of your phone would be up and, if you laid it down, it would point to the front of the car), but the cradle is wider than it is long, so, when I lay my phone down, the top of the phone is pointed towards the passenger door. It starts off fine, but through the course of driving invariably end up so that, although the phone hasn't physically changed orientation, the display has been inverted so that the top of the screen is now pointed toward the drivers side. That is, the phone seems to think that the passenger door is now "down" and never switches back to the driver door being "down" (which is how it was physically placed initially). Matt Deres (talk) 02:57, 31 December 2023 (UTC)[reply]

You drive on one side of the road, either left or right, depending on your country. This means that one can expect a systematic difference in the centripetal acceleration between left turns and right turns. The turns to the passenger side are tighter. There may be a speed difference too. On roundabouts, the turns to and from the roundabout are tighter than the turn on the roundabout. Further, the road surface is normally not level, but running down to the sides of the road, to help drainage. That puts the passenger side a bit lower than the driver side. PiusImpavidus (talk) 10:23, 31 December 2023 (UTC)[reply]

Wisconsinite barn owls

The maps say barn owls are found in only a small area of Wisconsin, which has a lot of farmland. The map also says they live in Washington, which barely has any farmland. Are there any sightings of barn owls north of their range in Wisconsin EAGLITIZED (talk) 17:30, 30 December 2023 (UTC)[reply]

Of course, into Canada, see this birdwatcher database entry. Abductive (reasoning) 17:58, 30 December 2023 (UTC)[reply]

By the way, I actually knew they live in Canada, I was asking if they were found anywhere in Wisconsin, besides the small south-central area. 2600:6C44:627F:5865:D028:C3FF:FE4B:8D02 (talk) 19:02, 31 December 2023 (UTC)[reply]

Um, look at the map... Abductive (reasoning) 20:49, 31 December 2023 (UTC)[reply]

Whenever the edge of the range of some species of bird doesn't coincide with a sharp edge in biotope, one can expect the edge of the range to be fuzzy too. Even when depicted sharp on the map. PiusImpavidus (talk) 09:53, 1 January 2024 (UTC)[reply]

December 31

Last year Q - Giant prokaryotes' strangeness

This bacterium and its relative T. namibiensis are truly gigantic - they dwarf many species of Protozoa (such as the Euglena) and invertebrates even though they are not eukaryotic. Obviously, being too large for a bacterium must lead to several problems (e.g the bigger the cell, the smaller the S-to-V ratio, which easily reduce the metabolism rate). However we knew that there are some special structures within the cells of these "giants" that help they overcoming these problems, such as the large aqueous sacs. My question: Is there any limit, theoretically speaking, to the maximum size that a prokaryote can grow, in the case these special structures are taken into account? What is the limit to the maximum size that a "normal" prokaryote (the one that doesn't possess any special structures) can grow? I have thought that in the later case, the limit should be some tens of μm, but I'm not sure. 2402:800:63AD:F268:1576:679F:2D64:9CC7 (talk) 12:09, 31 December 2023 (UTC)[reply]

According to Organelle § Prokaryotic organelles there is increasing evidence of more prokaryotic compartmentalization and internal structure in at least some prokaryotes (not only Thiomargarita) than once thought. It is difficult to decide when organelles become "special". Here is a discussion of the size range of bacteria, mentioning several whose diameter is larger than some tens of μm. --Lambiam 16:52, 31 December 2023 (UTC)[reply]

It is thought that the size limits are not so much physiological but ecological. Prior to the advent of the eukaryotes, there are possible fossils of possible bacteria that are macroscopic. The thinking is that in the absence of competition and predation from eukaryotes (and later, multicellular eukaryotes), bacteria could occupy larger niches. Abductive (reasoning) 17:31, 31 December 2023 (UTC)[reply]

See also this science documentary. {The poster formerly known as 87.81.2309.195} 51.198.104.88 (talk) 01:54, 2 January 2024 (UTC)[reply]

US metric units

Are there any American websites that, at least consistently, use metric units as first or only units? --40bus (talk) 19:27, 31 December 2023 (UTC)[reply]

I'm not seeing anything on Google so far that directly answers that question. But it's a fair bet that any site that expects to sell something to Americans would probably have both units. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:42, 31 December 2023 (UTC)[reply]

Science related sales is a good bet. For most products, MilliporeSigma lists in metric units, and they are an American company. --OuroborosCobra (talk) 23:04, 31 December 2023 (UTC)[reply]

Mmh.. and is there any need to translate the French "trompe-l'oeil", in American English? No, about-us/life-science says they're at core, a European company. --Askedonty (talk) 00:54, 1 January 2024 (UTC)[reply]

That's a subsidiary company, and gets into the confusing issue of decades of mergers and such. Our article says it is an American company based out of Massachusetts. But, we then get into the whole history of there having been a Sigma Chemical Company founded in the US, an Aldrich company founded in the US, merging to create Sigma-Aldrich, another company named Millipore founded in the US, a company named Merck founded in Germany, Merck buying out Millipore at some point to make the company EMD Millipore, then Merck Millipore, then that merging with Sigma-Aldrich to become MilliporeSigma, which has been rebranded recently back to Sigma-Aldrich. This all took place over a span of some three centuries (though mostly in the last 70 or so years). That said, while having a parent company in Germany, it is still registered as a US company. Because reasons? --OuroborosCobra (talk) 15:34, 1 January 2024 (UTC)[reply]

They do not have to be EC compliant regarding all regulations? --Askedonty (talk) 20:14, 1 January 2024 (UTC)[reply]

Although, since chemical drugs (pills) are or were going systematically through the process of milling, why would the pharmaceutical industry have found it had to be worried at complying shifting to mill-i-gram ? --Askedonty (talk) 01:20, 1 January 2024 (UTC)[reply]

Certainly the US Metric Association website does. --jpgordon^{𝄢𝄆𝄐𝄇} 00:19, 1 January 2024 (UTC)[reply]

January 1

Oxidation states of noble gases

Do argon monofluoride, krypton monofluoride, and xenon monochloride have the noble gas in +1 oxidation state? I’m not sure do exciplexes are valid noble gas compounds. Nucleus hydro elemon (talk) 04:53, 1 January 2024 (UTC)[reply]

I would say yes, they are formally Ng(I), but at the same time I think exciplexes are not quite the same thing as normal compounds indeed. Double sharp (talk) 05:29, 1 January 2024 (UTC)[reply]

I can't find a ref for anything special about oxidation-state analysis of exciplexes, and given they are a bound state (molecular-orbital-like electronic analysis) I would not expect there to be any difference either. However, is there anything unusual about oxidation-state analysis of electronically excited states in general? DMacks (talk) 06:39, 1 January 2024 (UTC)[reply]

My problem with treating exciplexes on the same footing as normal noble gas compounds is just my philosophical taste, to be honest. It has nothing to do with oxidation state analysis not working: it works just as well to my knowledge (though it's not something I think about very often). It has more to do with the fact that excited He and Ne for example do not have closed-shell configurations at all, so there is no reason to expect them to be inert. So while they are indeed noble gas compounds in some sense, they lose part of what makes it impressive to force a noble gas into compounds, and I'd rather make a distinction between the bonded excited states of He₂ and predicted species with chemical bonds to ground-state He. Double sharp (talk) 08:39, 1 January 2024 (UTC)[reply]

New Year's countdown broadcast delay ≈ 11 seconds ??

I know about the seven second delay in TV broadcasting. So, why is it that, when watching the countdown for the Times Square Ball to drop tonight, I heard my clock strike midnight when the countdown was at 12 seconds? I know what you're thinking, and I got on my computer to check the time as my clock struck one, and my computer said it was 00:59:59. My computer was within 0.3 second of the correct time according to both [time.gov] and [time.is], so I will say that the countdown as it appeared on my TV was 11 seconds out.

Did they lengthen the seven-second delay to eleven seconds or something? Or does the fact that TV is now digital account for the missing four seconds? Or what? 32.217.240.174 (talk) 06:28, 1 January 2024 (UTC)[reply]

Yes the extra delay is due to various factors in the digital technology. As well as just taking time to send bits out and fill buffers etc they also have a lot of redundancy and error correction which depends on delaying the final picture a bit so glitches can be fixed before anything is displayed. I guess you could call it the digital version of the seven second delay so you get a clean signal :-) NadVolum (talk) 11:24, 1 January 2024 (UTC)[reply]

Walking in partial gravity

This question from 2019 inspired me to ask: approximately what's the minimum gravity that humans could actually recognisably walk in (as opposed to jumping off the ground and floating for an awkwardly long time before going back down)? Is Luna's gravity (0.165g) enough? Triton's (0.080g)? Umbriel's (0.023g)?

(Assuming a hypothetical space station with an Earthlike environment rotating for partial gravity, to avoid having to factor in the spacesuit. So, while Apollo is a useful datapoint, it does not quite answer the question.) Double sharp (talk) 08:49, 1 January 2024 (UTC)[reply]

Define walk. I don't think a definite answer is possible. We habitually exert a downward force when we walk, so it's actually easier for someone unaccustomed to less gravity to jump. It's perfectly possible to "walk" on the moon, with a bit of practice, though it might look more like a shuffle at first. Shantavira|^{feed me} 09:32, 1 January 2024 (UTC)[reply]

Well, let's say it's "walking" when you always have at least one foot on the ground. I suppose there's probably an intermediate zone where you can technically walk, but it's not the best way to get around. Double sharp (talk) 09:32, 1 January 2024 (UTC)[reply]

Friction is an issue. Assuming dry friction, the backward force a walker can exert when taking a step is proportional to their weight. In microgravity it is very low. On the surface of the Moon, no air resistance needs to be overcome, so once a certain speed is reached it can be maintained and gradually be increased. In an air-filled space station, however, there is a maximal attainable speed, which depends on the coefficient of friction between the walker's footwear (or foot if barefoot) and the flooring, as well as on the aerodynamic properties of tthe walker. --Lambiam 10:57, 1 January 2024 (UTC)[reply]

Let's assume that the most comfortable walking speed is when your legs move at their natural frequency, acting as a pendulum. Then your speed is proportional to the square root of gravity. Air resistance grows with the square of velocity, so when walking at your most comfortable speed, the ratio of air drag to weight is independent of gravity. Of course, the main source of drag in an ordinary walk on a hard and level surface is the viscosity of your own bodily fluids.

I don't think there's a gravity below which walking becomes impossible. With reducing gravity, walking gets increasingly slower, whilst hopping gets easier. At some point, hopping is more practical than walking. For the Apollo astronauts, that was the case. Their spacesuits contributed to that, but experiments on Earth with people moving whilst 5/6 suspended by ropes also indicate that hopping is preferred. PiusImpavidus (talk) 11:11, 2 January 2024 (UTC)[reply]

January 2

proton numbers and neutron numbers from unstable to stable

We assume:

All currently unknown nuclides are more unstable (i.e. have shorter half-life) then all currently known nuclides.

And theoretically, the proton numbers having stable nuclides are 0~66 except 43, 61, 62, 63, and the neutron numbers having stable nuclides are 0~98 except 19, 21, 35, 39, 45, 61, 71, 83~91, 95, 96. We do not consider these two unconfirmed kinds of nuclear decay:

proton decay (may be possible, if so, then there are no theoretically stable nuclides)
spontaneous fission for the nuclears with mass number < 232 (may be possible for the nuclear with mass number >= 93, if so, then the proton numbers having theoretically stable nuclides are 0~40, and the neutron numbers having theoretically stable nuclides are 0~52 except 19, 21, 35, 39, 45)

For consistency, we regard (proton number, neutron number) = (0, 0) as a theoretically stable nuclide, thus the proton number 0 also has only one stable nuclide, just like the proton numbers 4, 9, 11, 13, 15, 21, 23, … and the neutron numbers 2, 3, 4, 9, 11, 13, 15, …, and the neutron number 0 has two stable nuclides (corresponding to the proton numbers 0 and 1), and every mass number 0~164 except 5, 8, 143~155, 160~162 has exactly one theoretically stable nuclide (which is the only one nuclide with these mass numbers which are stable to both beta decay and double beta decay, see Beta-decay stable isobars).

By the Mattauch isobar rule, all nuclides with proton number 43, 61, … are unstable to beta decay, and all nuclides with neutron numbers 19, 21, 35, 39, 45, 61, 71, 89, 115, 123, 147, … are unstable to beta decay, see Beta-decay stable isobars.

For other proton numbers <= 118 and other neutron numbers <= 178 (which are the proton numbers and the neutron numbers having currently known nuclides) from unstable to stable: (use the data in the "isotopes of elements" articles in Wikipedia, for observationally stable but theoretically unstable (alpha decay, beta decay, double beta decay, electron capture, double electron capture, or isomeric transition) nuclides (i.e. the proton numbers table from "75" and so on, and the neutron numbers table from "111" and so on, respectively), we use the data in [5])

Proton numbers: (listed up to 98) (not include the proton numbers with theoretically stable nuclides)

proton number	the most stable neutron number	half-life
87	136	22 mins
85	125	8.1 hours
86	136	3.82 days
61	84	17.7 years
89	138	21.8 years
84	125	125 years
98	153	900 years
97	150	1380 years
88	138	1600 years
95	148	7370 years
91	140	32760 years
93	144	2.14*10^6 years
43	54	4.21*10^6 years
96	151	1.56*10^7 years
94	150	8.08*10^7 years
92	146	4.468*10^9 years
90	142	1.405*10^10 years
83	126	2.01*10^19 years
75	110 (112 neutrons will make beta decay)	3.4*10^24 years
71	104 (105 neutrons will make beta decay)	2.5*10^34 years
74	109 (112 neutrons will make double-beta decay and the half-life may be shorter)	4.9*10^36 years
73	108	4.2*10^38 years
72	108	6.4*10^45 years
69	100	1.5*10^46 years
76	114 (116 neutrons will make double-beta decay and the half-life may be shorter)	2.0*10^47 years
77	116	2.6*10^66 years
79	118	1.3*10^72 years
70	104 (106 neutrons will make double-beta decay and the half-life may be shorter)	4.4*10^75 years
78	118 (120 neutrons will make double-beta decay and the half-life may be shorter)	6.6*10^82 years
68	100 (102 neutrons will make double-beta decay and the half-life may be shorter)	4.0*10^92 years
63	90	4.0*10^141 years
82	125	1.2*10^156 years
62	90	7.3*10^159 years
67	98	8.8*10^239 years
81	124	2.5*10^280 years
80	122	5.1*10^301 years

Neutron numbers: (listed up to 128) (not include the neutron numbers with theoretically stable nuclides)

neutron number	the most stable proton number	half-life
39	32	11.3 days
128	82	22.2 years
115	78	50 years
89	62	94.6 years
35	28	100 years
19	17	3.01*10^5 years
45	34	3.27*10^5 years
127	83 (nuclear isomer)	3.04*10^6 years
61	46	6.5*10^6 years
123	82	1.73*10^7 years
21	19	1.248*10^9 years
111	76	4.1*10^16 years
87	62	8.3*10^17 years
71	52	5.710^19 years (the article says 4.2~7.2 10^19 years, we use the median value)
105	72 (71 protons will make beta decay)	4.5*10^20 years
85	60	1.9*10^22 years
106	72	3.4*10^23 years
112	76	1.4*10^26 years
84	58	3.4*10^27 years for the alpha decay, but no information for the double-beta decay
88	62 (60 protons will make double-beta decay and the half-life may be shorter)	8.7*10^27 years
107	72	4.5*10^29 years
113	76	4.8*10^29 years
86	60	2.0*10^34 years
101	70	4.0*10^34 years
110	74	7.4*10^35 years
109	74	4.9*10^36 years
102	70 (68 protons will make double-beta decay and the half-life may be shorter)	2.1*10^42 years
108	72	6.4*10^45 years
114	76	2.0*10^47 years
117	78	4.5*10^59 years
103	70	2.3*10^60 years
116	77 (76 protons will make double-beta decay and the half-life may be shorter)	2.6*10^66 years
104	70	4.4*10^75 years
99	68	1.9*10^79 years
83	60	3.8*10^80 years
118	78	6.6*10^82 years
119	80	1.8*10^85 years
100	68	4.0*10^92 years
120	80 (78 protons will make double-beta decay and the half-life may be shorter)	5.6*10^95 years
95	66	6.6*10^127 years
126	82	7.8*10^127 years
125	82	1.2*10^156 years
90	62	7.3*10^159 years
121	80	2.4*10^169 years
124	81	2.5*10^280 years
122	80	5.1*10^301 years
91	64	2.6*10^311 years
96	66	6.2*10^318 years

Are my two tables right? Also fill these two tables to proton numbers up to 118 and neutron numbers up to 178, respectively. —— 61.223.151.50 (talk) 06:08, 2 January 2024 (UTC)[reply]

Finding a particular academic paper

There is a document - probably an academic paper - that has an attached Excel file listing various academic publications discussing palaeoclimate studies that concern North Africa during the Holocene. I think one of these studies listed is about the Fezzan. Does anyone have a link to this paper? I have searched myself on several databases, so far without success. Jo-Jo Eumerus (talk) 09:14, 2 January 2024 (UTC)[reply]

[kassis1982-1] Kassis, A. I.; Adelstein, S. J.; Haydock, C.; Sastry, K. S. R.; McElvany, K. D.; Welch, M. J. (May 1982). "Lethality of Auger Electrons from the Decay of Bromine-77 in the DNA of Mammalian Cells" (PDF). Radiation Research. 90 (2): 362. doi:10.2307/3575714. ISSN 0033-7587.

[2] Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.

[1]

[2]