Science desk
< October 14	<< Sep \| October \| Nov >>	October 16 >

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is a transcluded archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

October 15

Why plotting graph of voltage vs time instead of current vs time in Alternating current?

Why plotting graph of voltage vs time instead if current vs time in AC currents?

See this Google image results here, in most images graph drawn on voltage vs time not current (amps) Vs time. Why so? Rizosome (talk) 02:07, 15 October 2021 (UTC)[reply]

My WAG is that voltage is more fundamental than current, since the latter is dependent on the resistance. Clarityfiend (talk) 02:46, 15 October 2021 (UTC)[reply]

Not that wild a guess. The contractual obligation of electricity companies is to deliver voltage to their customers, not current. The standard in any country for the mains electricity also specifies the nominal supply voltage(s) (and frequency), which should be dependable, while the consumption and thus the current may fluctuate wildly and sometimes unpredictably. --Lambiam 06:56, 15 October 2021 (UTC)[reply]

It does not make much sense to say that current depends on resistance and voltage does not.

Simple electrical devices have a Current–voltage characteristic, that is a curve that imposes a relationship between the current and the voltage. Here, "simple electrical devices" mean anything with two wires popping out that does not rely on weird control systems; a nuclear power plant with fixed settings is "simple" but a LED with a cycling dimmer is not by this definition. In a simple closed circuit with two electrical devices (e.g. a battery and a lamp), you can determine what voltage/current exist in the circuit by simply drawing characteristics and finding the intersection point; you can think of it as the two devices "negotiating" a voltage-current point that is acceptable to both.

Most power supplies are designed to have an almost-vertical characteristic, i.e. have a stable voltage no matter the current. In that sense voltage does not depend on the load (resistance) applied, but it is a design choice of the power supply. (Arguably it is easier to design fixed-voltage sources for most electricity generation methods, but we can and do produce fixed-intensity power supplies used in some contexts.)

This design choice makes sense in most applications, because common electrical circuits are wired in parallel. (For good reason: in series, a fault in one element causes the whole circuit to break; you do not want your oven to go out if your toaster is broken, or if your neighbour’s toaster is broken, so both your home and the local grid are parallel circuits.) Parallel circuits are "stable" (in the sense that what happens in one branch of the circuit does not impact too much what happens in other branches) when the voltage is stable. Tigraan^{Click here for my talk page ("private" contact)} 09:29, 15 October 2021 (UTC)[reply]

Why is the Bee Hummingbird considered a dinasour?

The article of the says the Bee Hummingbird is considered a dinasour. But neither it’s entry of the linked entry explains how a living creature cane be a dinesour. -- Wis2fan (talk) 05:00, 15 October 2021 (UTC)[reply]

The article has been fixed. Birds are generally considered to be descendants of dinosaurs, but there are no living dinosaurs. ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:19, 15 October 2021 (UTC)[reply]

False. Birds are avian dinosaurs. The non-avian ones died out. Imagine Reason (talk) 10:21, 15 October 2021 (UTC)[reply]

If you follow the modern scientific definition of dinosaur (see its first definition at Wiktionary), a dinosaur is any animal belonging to the clade Dinosauria, which includes the clade Ornithurae and thus all birds, including the bee hummingbird. --Lambiam 06:44, 15 October 2021 (UTC)[reply]

In any case, even though the article is now fixed, the front page is still showing the dinosaur thing. ←Baseball Bugs ^{What's up, Doc?} carrots→ 07:05, 15 October 2021 (UTC)[reply]

The article says "In traditional taxonomy, birds were considered a separate class that had evolved from dinosaurs, a distinct superorder. However, a majority of contemporary paleontologists concerned with dinosaurs reject the traditional style of classification in favor of phylogenetic taxonomy."

Using the same reasoning, humans are fish. Now, that all makes sense from the point of view of a palaeontologist. It's a diachronic point of view, where phylogenetic taxonomy makes more sense. From a synchronic point of view, traditional taxonomy makes more sense. Humans are not fish, which are creatures with a spine and internal gills, and birds are not terrible lizards. They're nothing like lizards and, aside from a few flightless birds, they're less dangerous than a medium-sized dog. Certainly Sir Richard Owen, when coining that term in 1841, 18 years before publication of On the Origin of Species, adhered to a synchronic point of view and would not have not used that term if he had known that it would also be applied to sparrows.

Anyway, when measured in generations, all traditional dinosaurs may have been more closely related to each other than any of them was to any modern bird. PiusImpavidus (talk) 09:09, 15 October 2021 (UTC)[reply]

False. Fish are not a clade. Dinosaurs are. Therefore we're not fish, but birds are dinosaurs. Imagine Reason (talk) 10:21, 15 October 2021 (UTC)[reply]

If you consider dinosaurs to be a clade containing birds, then it would be consistent to consider fish a clade containing all other vertebrates (the tetrapods). But this confusion comes from using common names like "fish" that can be interpreted in various ways. Palaeontologists favouring a cladistic taxonomy use well-defined terms like Craniata and Gnathostomata that match to clades. Jmchutchinson (talk) 12:19, 15 October 2021 (UTC)[reply]

So there are two problems here. There is the issue that there are casual, informal systems of classifying things that have developed through tradition over along time, and passed along informally through time. Under that system, our common language, it is usual to think of birds as NOT dinosaurs. However, when trying to classify things according to their genetic history (that is, what is related to what else, and what descended from what else), birds are clearly dinosaurs. Which is to say, that all moderns birds are descended from a single ancestor who themselves was clearly a dinosaur. The issue is whether it is useful to introduce that information into every article on every bird in a prominent way, or not. It isn't. Birds ARE dinosaurs, but sometimes it is less confusing not to mention it in a random article on a random species of bird. And actually, all fish do not belong to the same clade, unless you go back further than fish existed. Things we call fish like lancelets are not actually in the same clade as other fish. --Jayron 32 12:32, 15 October 2021 (UTC)[reply]

Jayron, generally I agree but ~~(1) there must be a typo in what you wrote: "Under that system, our common language, it is usual to think of birds as dinosaurs." You must have meant "not usual".~~

(2) You seem a bit adrift in saying that because lancelets are not in the same clade as other fish, fish is not a clade. Of course there are subclades, sub-subclades, etc. within the fish right down until the level of biological species, but that does not invalidate fish+tetrapods being a clade. More specifically, you say "other fish", which implies that you do consider lampreys as fish. Likewise, "hagfish" are evidently commonly called fish (the clue is in the name!). The group containing lampreys, hagfish, some other fish-like fossils and the Gnathostomata (other fish + tetrapods), form the Craniata (the vertebrates), which is believed to be a clade. So "fish" as considered in common parlance, lumped with the tetrapods, can be said to form a clade. Here is a tree, which often makes things clear when words don't. But if you consider that some of these other fish-like fossils are not fish, yet you consider lampreys are, then fish+tetrapods is indeed not a clade. If you exclude lampreys, hagfish and these fossils from fish, then you are left with Gnathostomata, which is a clade. Jmchutchinson (talk) 14:42, 15 October 2021 (UTC)[reply]

You'll notice that I had already fixed my mistake before you noticed it was a mistake. Your response was at 14:42, but I had already fixed the missing word at 13:56. --Jayron 32 16:27, 15 October 2021 (UTC)[reply]

What percentage of Wikipedia readers are paleontologists? ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:13, 15 October 2021 (UTC)[reply]

A small percentage, because there are not many palaeontologists in absolute numbers. However, a great many more people are sufficiently interested in the subject to be familiar with these matters (such as myself: I'm not a palaeontologist, but count one as a friend, have met several others, and attend or watch public lectures and read science news relating to the discipline). One needs to be paying some attention to the quite fast-moving developments in this field to be aware of the current scientific concensus, as opposed to the one being taught when we were at school. I dare say a reasonable proportion of Wikipedia readers do at least some of the same.

Our false perception of living birds or Avialae as not being dinosaurs is skewed by their not being any living non-avian (aka non-avialan) dinosaurs for comparison. But if one were to go back 66 million years, one would see a great many bird-like creatures: the average person would judge some to be birds and some not birds, but would often be mistaken – some they judged not-birds would actually be birds, and some they judged birds would be dinosaurs, but not birds. There would in addition be many dinosaurs that looked somewhat like birds, showing that birds were a group nested deep within the dinosaurs. Our 25-year-old, intensively edited article Origin of birds also speaks to this. {The poster formerly known as 87.81.230.195} 90.193.128.151 (talk) 19:31, 15 October 2021 (UTC)[reply]

The problem is that the dinosaur thing is just thrown in there, with no explanation or citation. ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:17, 15 October 2021 (UTC)[reply]

Are you saying that none of that article's 145 citations are relevant to the issue?

How do you feel about the citations in the articles Origin of birds, Dinosaur, Evolution of birds, Bird, Feathered dinosaur, Theropoda, List of dinosaur genera, and even Human-dinosaur coexistence? {The poster formerly known as 87.81.230.195} 90.193.128.151 (talk) 22:57, 15 October 2021 (UTC)[reply]

Thank you, baseball bugs. You I can understand. -- Wis2fan

Today's featured picture is the Red-billed gull. How come there's nothing in its article about dinosaurs? ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:28, 19 October 2021 (UTC)[reply]

According to biological evolution, was humanity the result of incest?

I know that incest, especially in first degree relatives (parents/siblings) and to a lesser extent in second degree relatives (cousins) can seriously case genetic damage and bodily malformations and serious physiological problems so if the first humans on earth where a sister and a brother born to the same parents and they had sex to create the first human nuclear family, how could it be that the family was healthy, survived and prospered in the rich, genetically dense (many animal types anywhere) and extremely dangerous nature back then? Thanks, — Preceding unsigned comment added by 49.230.134.86 (talk) 05:16, 15 October 2021 (UTC)[reply]

Don't confuse evolution with the Adam and Eve stories. ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:20, 15 October 2021 (UTC)[reply]

Yes, that would be evelution. Clarityfiend (talk) 08:59, 15 October 2021 (UTC) [reply]

The answer is no. There is no reason to assume that the process of speciation that led to the emergence of Homo sapiens was genetically any different from that of other species, such as Camelus dromedarius or Danaus plexippus. While there are different driving mechanisms and it is not known for sure which one played a role in the genesis of modern humans, the common pattern is that a subpopulation of individuals of an ancestor species becomes genetically isolated from the rest of that species and so evolves independently, leading to its branching off from the ancestor species, which also keeps evolving but in different directions. The subpopulation at the root of the new Homo sapiens species may have been small, but was almost certainly not just a single breeding pair. --Lambiam 06:24, 15 October 2021 (UTC)[reply]

Naturally, our species can be traced back to a Y-chromosomal Adam and a mitochrondrial Eve, but they lived hundreds of thousands of years apart or something. Imagine Reason (talk) 10:19, 15 October 2021 (UTC)[reply]

Careful! That is true of (more or less) only these two small parts of the genome, because neither the Y-chromosome nor mitochondria undergo recombination. In contrast, for the vast majority of our genome, the copies of the genes that we received from each parent are shuffled each generation; thus it becomes inappropriate to talk of a single common ancestoral individual. Jmchutchinson (talk) 11:49, 15 October 2021 (UTC)[reply]

I see, and yes, there was of course no First Human. Imagine Reason (talk) 14:46, 15 October 2021 (UTC)[reply]

So, I think the OP is confusing incest which is a sociological taboo against sexual relations between close relatives, and there are well-documented hypotheses about a past Population bottleneck that caused a massive reduction in human genetic diversity at a point in our past, likely due to Inbreeding depression, also related to the Founder effect. It should be noted that inbreeding is NOT the same thing as incest; inbreeding occurs in any sufficiently isolated population, even if no "close relatives" are breeding with each other. I think the OP is thinking of one of the human population bottleneck hypotheses, such as the Toba catastrophe theory, among others. While these hypotheses and conjectures are well documented, they remain controversial. --Jayron 32 12:25, 15 October 2021 (UTC)[reply]
Think the human population bottleneck hypotheses pretty much covers the parent (ahem) post, Incest#Christian touches on the Biblical issue – "It is inevitable for Bible literalists to accept that the first children of Adam and Eve would have been in incestuous relations as we regard it today. However, according to the Bible, God's law which forbids incest had not at that time been given to men, and was delivered to Moses after Adam and Eve were created. " So that was ok. . . dave souza, talk 16:45, 15 October 2021 (UTC)[reply]
Heck, if you take Adam and Eve seriously, you would be saying that humanity started with a man and his genetically modified, transgender clone. --Khajidha (talk) 21:18, 15 October 2021 (UTC)[reply]

I'd like to point out that there's no law against incest in Israel. Imagine Reason (talk) 03:11, 16 October 2021 (UTC)[reply]

What's your source for that claim? ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:43, 16 October 2021 (UTC)[reply]

Possibly Wikipedia.--Shantavira|^{feed me} 08:21, 16 October 2021 (UTC)[reply]

Here's more detailed info:[1] ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:12, 16 October 2021 (UTC)[reply]

If the ancestry chart of any individual human is expanded for twenty generations, it is an almost certainty that one or more of these roughly one million ancestors was the issue of an incestuous copulation. In other words, without incest none of us would have been here. No bottleneck needed, and you don't have to go back more than 10 centuries. --Lambiam 22:11, 16 October 2021 (UTC)[reply]

No widely available outdoors PCR test in NYC?

I know of one doctor's office that tests patients before procedures, and they do it on the roof. Other than that, AFAIK clinics and hospitals conduct tests indoors. Until recently, there were limited mobile testing sites that offered PCR tests, but they seem to have disappeared.[2] Why is America so cavalier about indoor transmission? Imagine Reason (talk) 14:49, 15 October 2021 (UTC)[reply]

I'm confused as to why you think "America" is a synonym for "NYC". --Jayron 32 16:30, 15 October 2021 (UTC)[reply]

I blame the Media. —Tamfang (talk) 01:33, 16 October 2021 (UTC)[reply]

New York is more conscientious about COVID than much of the rest of the country. Show me an American city that promotes outdoors testing. Imagine Reason (talk) 03:09, 16 October 2021 (UTC)[reply]

"Promotes" is iffy so I won't touch that. But it's trivial to find cities in the US where drive-thru (and from what I saw outdoor walk-up) testing is still readily available e.g. Orlando, Florida [3], El Paso, Texas [4] (click on either one of City of El Paso Testing or City/UTEP Testing) / [5], San Francisco, California [6], Washington, D.C. [7]. From what I saw at least two of these definitely offered PCR testing as an option.

Note even for testing at clinics etc, I'd hesitate to conclude without further evidence that this means the testing is indoors. In NZ AFAIK even before the recent outbreak, the norm was to get people to stay in their cars if they needed a test, or at least outside if they didn't drive and call for someone to come out and test. Of course the situation in NZ is and was fairly different, still the point is you cannot conclude without looking into the specific procedures for each site whether it's getting people to go into the clinic for testing or what.

Indeed I noticed a lot of drive-thru testing Walgreens on Google Maps etc, and so looking at their website [8] it seems like all their testing is drive-thru with no walk-ups available "No, Walgreens is not equipped to perform walk-in testing at this time. Patients must arrive in a vehicle and are not permitted to exit the vehicle or enter the testing location." Funnily enough, I see a bunch of New York locations there and it seems like they do PCR testing. And I'm fairly sure some of them are within the boundaries of what is New York City e.g. 925 Soundview Avenue. So the basic premise of this question seems questionable, but whatever.

While I make no comment on the wisdom of what they're doing in New York City, I'd note that "more conscientious about COVID than much of the rest of the country" even when we put aside the ^{[citation needed]} seems irrelevant since New York City remains an extremely poor example to choose. NYC is noted as the most densely populated major city in the US where private vehicle use to get around is rare compared to much of the US, and even ownership is/was? under 50%. While New York City also has quite a lot of open spaces for a city of its density [9], still what works in other places may not be so easy in New York City considering the need is not only to test the person but get them there (e.g. if they're taking public transport).

Going back to the NZ example, most GPs in stand-alone or partly standalone buildings with their own entrances and exits etc, rather than in shopping malls or other large shared buildings so the procedures I mentioned earlier have generally be quite easy to implement. As always there is a percentage of the population for who it remains difficult especially those who don't drive and have limited or no access to mobile phones, still the difficulties are fairly different from trying the same thing in New York City.

Nil Einne (talk) 14:52, 16 October 2021 (UTC)[reply]

Some more research, I think many of the Walgreens examples are actually at drive-thru pharmacies so I guess the testing provider is technically indoors albeit with outdoors separating them and the testee. Anyway it seems CVS also offers drive thru testing at some sites [10] albeit it sounds like some sites may be in store (but I'm not sure) so you probably need to look more carefully. Still when I looked at [11] which is annoying since it won't let me view it from outside the US, there are some sites in New York with drive-thru testing. Many seem to be antigen testing, although it seems all lab test PCR (but not rapid PCR) are drive-thru. It's unclear to me if they have any option besides a rapid-test (and possible entering a clinic) for non drive-thru customers.

For the lab-test PCR, it says "Drive-thru test (vehicle recommended)". Whether that means they let you walk, or cycle, through the drive thru I'm not sure especially since other parts of their site seem to suggest you do need a vehicle for their drive-thrus. (And my understanding is liability insurance in the US means most stores hate it when anyone isn't in a motorvehicle in their drive.) Interesting they get you to perform the swab yourself [12] [13] which I find a bit weird, however I guess if the tester is inside the pharmacy access to the testee to perform a swab via the drive thru window is likely difficult. Also considering this is the heavily regulated US market I assume they have sufficient evidence self or untrained assistant swabbing performed under supervision works sufficiently for their purposes.

Searching found a number which I believe in New York City e.g. Ridgewood Covid - 19 Testing Site, 61-15 Metropolitan Ave; Bay Parkway - Brooklyn Covid - 19 Testing Site, 6831 Bay Parkway; Ralph Avenue - Brooklyn Covid - 19 Testing Site, 2320 Ralph Avenue; Avenue U - Brooklyn Covid - 19 Testing Site, 4112 Avenue U; Community Site Cvs 8940 - Westchester Avenue, 1688 Westchester Avenue; 10Th Avenue - Whitestone Covid - 19 Testing Site, 153-01 10th Avenue; Broadway - Passaic Covid - 19 Testing Site, 394 Broadway; Inwood - Burnside Avenue - Covid - 19 Testing Site, 530 Burnside Avenue; Jamaica Avenue - Bellerose Covid - 19 Testing Site, 251-21 Jamaica Avenue; Elmont - Dutch Broadway - Covid - 19 Testing Site, 1797 Dutch Broadway. To be clear, this list isn't exhaustive and I've excluded any in Staten Island.

Interesting enough, there are 2 rapid PCR test locations listed Community Site Cvs 10426 - New Rochelle, 505 New Rochelle RD [14] and Community Site Cvs 2141 - Kings Hwy, 2925 Kings Highway. I initially assumed these two also drive thru locations given the confusing ability to book individual lanes. And their site also says "Yes. At our rapid testing sites, patients who receive a negative test result are able to enter the clinic for a visit with a MinuteClinic provider to discuss your results and other health concerns, and for further evaluation of symptoms." which I guess doesn't apply to PCR anyway since even rapid PCR is likely to be hours. But that made me think they make you stay outside without a negative result. However having taken a look at both sites on Google Maps, I don't see any sign of a single drive thru lane let alone four. So possibly the test is performed in doors and the lanes are in store lanes.

In any case there are still all the other drive thru lab test PCR sites which seem to affirm the basic premise of this query is questionable. Per my earlier comment I appreciate drive thru testing isn't an option for many in New York City. But that just re-affirms why it's such a bad location to chose to represent the US whatever their alleged conscientiousness. Since from what I can tell, much of the US, as with quite a bit of the world, have chosen drive-thru testing as their primary means for delivering out-door testing despite the obvious negative implications for de-carbonising economies. (Both for the added security of the car, but also allowing easier travel to the sites without needing to use public transport.) With walk-ups hopefully catered for but generally not the preferred means. And also easier to cater for when these are in locations not set-up for some specific use. (And these also tend to be easier to set-up when you can take over roads and carparks with limited concern for other businesses or users because of lockdowns.)

Nil Einne (talk) 16:51, 16 October 2021 (UTC)[reply]

As a probably final comment I'd note that the science on this is is continually evolving and so too are the conditions. If the evidence suggests something is relatively low risk compared to other risks, like being on a bus or train most people may experience prior to an activity, it may not be consider worth the cost e.g. in terms of reduced number of tests or other services that can be performed.

Getting infected with COVID-19 is undesirable and can be quite bad especially for the elderly and those with some pre-existing conditions albeit significantly reduced chance if fully vaccinated. But so too is dying from cancer or some other disease caught too late because your healthcare provider was too busy. Perhaps busy travelling on lifts all day to perform COVID-19 tests on patients to prevent the 0.25 chance they will infect someone else, having already infected 0.75 other people while travelling to get the test and 3.5 other people before they realised they were exposed and/or sick. (To be clear these are completely made up figures to emphasise the point why an epidemiologist analysing the evidence matters much more than the concerns of some random person on Wikipedia.)

Likewise what makes sense in one location e.g. with NZ again as an example where until very recently the goal was for absolutely no transmission and even now no transmission is still the overall albeit unachievable goal. This compares to the pretty much all the US including New York where it seems clear it's accepted some transmission is going to occur so the goal is instead to minimise it.

Nil Einne (talk) 17:21, 16 October 2021 (UTC)[reply]

Bronxville is not in the Bronx or the city but a few kilometers away in Westchester County, Elmont is not in Queens cause the address doesn't have dashy numbers, Passaic is in a completely different united state. The rest are in New York City (1688 Westchester Avenue is not in Westchester) Sagittarian Milky Way (talk) 03:08, 17 October 2021 (UTC)[reply]

For clarity, I didn't really bother to consider where those 2 rapid testing sites were (other than somewhere in New York state) since they don't seem to have any sign of drive thrus despite the confusing lane stuff. The rest yeah I assumed they were but was wrong. Nil Einne (talk) 16:29, 19 October 2021 (UTC)[reply]

It should be noted that drive through testing in New York City is likely less in demand than other places in the U.S. While cars exist in the U.S., New York has, by far, the lowest car ownership in the U.S. The majority of city residents do not drive at all, and it's even lower in Manhattan than in some of the outer boroughs like Queens and Staten Island. There just may not be the demand to support a large number of drive through sites, nor may there be the infrastructure (parking lots, open areas) to build impromptu drive-through testing sites as is done in most of the rest of the U.S. As means of data 55 % of New Yorkers own no car and of those that do, many still use public transportation for getting around the city. --Jayron 32 16:44, 19 October 2021 (UTC)[reply]

Agricultural science

What is commercial Farming Advantage of commercial farming — Preceding unsigned comment added by 105.112.33.245 (talk) 15:24, 15 October 2021 (UTC)[reply]

What do you mean? ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:04, 15 October 2021 (UTC)[reply]

If you mean industrial farming, economies of scale spring to mind. Clarityfiend (talk) 03:35, 16 October 2021 (UTC)[reply]