Wikipedia:Reference desk/Archives/Science/2023 December 29

= 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)


 * 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)

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 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)


 * 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)


 * 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)
 * 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)
 * 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)
 * 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)


 * 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)

Pi

 * Reference desk/Archives/Science/2023 December 19

"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)


 * See Indiana Pi Bill. -- Verbarson talkedits 18:10, 29 December 2023 (UTC)


 * 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)
 * Which government? ←Baseball Bugs What's up, Doc? carrots→ 14:15, 2 January 2024 (UTC)
 * See Rwanda asylum plan. TL;DR - UK decides to send asylum seekers to Rwanda; UK Supreme Court declares Rwanda's asylum system deficient; UK government puts forward Safety of Rwanda (Asylum and Immigration) Bill which declares (if I understand this thread correctly) that pi = 3. -- Verbarson talkedits 18:33, 2 January 2024 (UTC)
 * This is different than my answer. I am in the United States, so I didn't know about Europe's asylum plans, but it makes sense. The UK (and the article notes Denmark as well) wants to send asylum seekers and illegal immigrants to a location outside the country to be processed. The UK and Rwanda have both agreed that Rwanda is a great location to hold and process people. But, people who oppose the plan claim that Rwanda is unsafe and, therefore, a terrible place to send people for processing. This does not exist in the United States. You can technically argue that some people are held and processed on the Mexican side of the U.S./Mexico border, but most processing takes place on the U.S. side of the border. I have never heard of a plan to ship all incoming people to, say, Hondurus for processing. But, the concept of safety is important. If a person from France tried to seek asylum in the United States, it would likely fail because France is a "safe" country. The need for asylum is not necessary. If a person from Columbia tried to seek asylum in the United States, it would likely succeed because the U.S. considers Columbia to be an "unsafe" country. Therefore, changing the designation of a country from unsafe to safe has the effect of limiting asylum seekers from that country. 12.116.29.106 (talk) 18:48, 2 January 2024 (UTC)
 * Most of the illegals come from France (so apparently not "safe"), many trying to cross 22 miles of the world's busiest shipping lane in overloaded inflatable dinghies. Navigation skills consist of "keep the front of the boat pointing at the lights you can see on the other side", sometimes to people who have never seen the open sea before. Martin of Sheffield (talk) 20:12, 2 January 2024 (UTC)

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)
 * 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)
 * Neil Degrasse Tyson has addressed this issue here. HiLo48 (talk) 23:41, 29 December 2023 (UTC)
 * 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)
 * This is misleadingly worded. The perceived force of Earth ' s gravity on you decreases and approaches zero as you approach Earth's center—because Earth's mass is increasingly equally-distributed around you in space, thus gravitationally tugging on you from all directions, so it all cancels out.
 * Gravity is a force that still exists if you dig down underground a ways. It does not magically vanish. The same is true if you go a little ways up into orbit. In orbit around Earth, Earth's gravity is still pulling on you. It is not a force field that instantly vanishes past some invisible line. To stay in orbit, you have to go really fast, and then you fall "around" Earth rather than towards an eventual impact, and you are in freefall so you feel weightless. (What is the force that keeps the Moon in orbit around Earth?) See Newton's cannonball. Slowking Man (talk) 04:37, 4 January 2024 (UTC)
 * Or to put it the way Douglas Adams did, orbiting is what happens when you fall and miss the ground. ;) Double sharp (talk) 05:21, 4 January 2024 (UTC)

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)


 * 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)


 * 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)


 * 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)
 * 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)
 * 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)
 * 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)
 * 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)
 * 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)
 * It's as meaningful as the original premise. ←Baseball Bugs What's up, Doc? carrots→ 16:16, 30 December 2023 (UTC)
 * Which is the original premise (and by which premise was it preceded)? --Lambiam 17:59, 30 December 2023 (UTC)