Wikipedia:Reference desk/Archives/Science/2019 February 24

= February 24 =

Jenny (not Lind)
Did the Curtiss Jenny have a pilot-adjustable mixture control in the cockpit, or did its engine run in full rich at all times? 2601:646:8A00:A0B3:1924:14C4:1666:AB35 (talk) 08:47, 24 February 2019 (UTC)
 * Almost certainly both. They made an awful lot of them, and this was just the time that such a pilot-operated control for mixture was appearing. So I think your question would convert to "Which engine and carburettor model introduced it?". Sadly I'm in the UK, my US sources are thin. Andy Dingley (talk) 11:16, 24 February 2019 (UTC)

Subspecies and gender identification for two images (WP:FP related)


The first image is a featured picture that is up for delisting because it is not used in any articles. It is potentially salvageable if we knew what subspecies and gender it was - Pied Kingfisher now documents a couple of subspecies and genders are identified. Geolocation indicates Israel, and if this is C. r. syriacus the image can be reinserted and FP status retained because it conveys different information than any other image in the article.

Similarly, the second image could be nominated as a replacement for the existing FP File:Giraffe08 - melbourne zoo edit.jpg. A subspecies and gender identification would add to its value in the article. MER-C 13:31, 24 February 2019 (UTC)
 * For the latter photo, can't you just email the Melbourne Zoo and ask them which species their giraffes are? Eliyohub (talk) 16:40, 24 February 2019 (UTC)
 * Based on the photos here, it looks like the Melbourne Zoo has Rothschild's giraffes on exhibit, but I'm not certain. Could also be the reticulated giraffe. I can't find anything on the web that states definitively what they have on display - and it could be the case that they have more than one subspecies mixed together. Rothschild's and reticulated are the two most common giraffes to be found in zoos, so either would be possible. Agreed that the head-shot from our article is not as good as this one. Matt Deres (talk) 19:32, 24 February 2019 (UTC)


 * The Pied Kingfisher is definitely a female from the lack of a near continuous dark patch across the breast or a thin dark line below that as described here. As to the subspecies, C. r. syriaca may not be currently recognised as a true subspecies, as it's based entirely on wing size - see here, which means that it would likely be the nominate subspecies C. r. rudis. Mikenorton (talk) 20:22, 25 February 2019 (UTC)

Smallpox infection and eradication
After reading smallpox and the WHO website, it's still unclear to me whether smallpox eradication is merely disruption of the transmission route via herd immunity due to continuous vaccination (where Variola virus itself may still persist somewhere in the nature) or, in the true sense, the physical elimination of the virus itself. Or does it mean that due to vaccination the virus died out because of continuous inability to find a host after vaccination?

Also, our article and the WHO site itself do not say how the virus is transmitted to the first infected person in the chain, only stating that it's "person-to-person contact". Apparently, if it's person-to-person contact, then the first person rather gets it from the wild, but this exact source is not specified. Thanks. 212.180.235.46 (talk) 15:41, 24 February 2019 (UTC)


 * The smallpox virus is 100% extinct everywhere in the world except for a couple of Biosafety level 4 laboratories. And no, the first person did not get it "from the wild". Unlike, say, Ebola, Smallpox only lives in humans. There are no animal or insect sources and there is no no carrier state (a person who carries the disease but is not sick) Before smallpox was eradicated, the disease lived only through continual person-to-person transmission. --Guy Macon (talk) 19:13, 24 February 2019 (UTC)
 * Our smallpox article says [t]he date of the appearance of smallpox is not settled. It most likely evolved from a terrestrial African rodent virus between 68,000 and 16,000 years ago. This seems like a classic chicken-and-egg problem.  When the rodent virus jumped the species barrier, you would probably not have called it smallpox; its descendant virus in the 20th century is definitely smallpox; there is no precise moment in the middle where it changes from not-smallpox to smallpox, and therefore no well-defined "first person" to have smallpox.  But humanity in general got it from "the wild", yes, or at least any alternative hypothesis would need extraordinary proof. --Trovatore (talk) 00:11, 25 February 2019 (UTC)
 * Right. Humanity obviously got whatever species the ancient ancestor of small pox was from somewhere. It is logically possible that when the first pre-human became a human -- another fuzzy line -- he/he already had it, but that's not the way the evidence seems to point. Thus that "somewhere" was most likely an animal, and the thing that first human "got" was most likely not smallpox but rather a species that was the ancient ancestor of small pox, and which differed from smallpox in at least one important way -- it infected something other that humans. Smallpox doesn't. The bottom line is that the line of reasoning "the first human got smallpox from an animal and therefore smallpox cannot possibly be a human-only disease" is flawed. Smallpox is a human-only disease. --Guy Macon (talk) 16:56, 25 February 2019 (UTC)
 * As noted in Cowpox, there are many related viruses, some of them transferable and not so dangerous. Given how quickly microbes can evolve, it wouldn't be at all surprising if the ancestor of smallpox came from a non-human. But the many millennia that have passed since then would make it very hard to pin down. ←Baseball Bugs What's up, Doc? carrots→ 17:55, 25 February 2019 (UTC)

Is there a place in the world in which in July or August it's colder than its temperature in other times?
Is there a place in the world in which in July or August it's colder than its normal temperature in other times? I mean to ask about existence of a country in which has winter in the time that the most of the world have summer time. It means that this country has an a lower temperature in July August while while in the most of the world it's considered summertime. 93.126.116.89 (talk) 20:50, 24 February 2019 (UTC)
 * Most of the southern part of the southern hemisphere is like that. See for example Climate of Launceston, Tasmania. Graeme Bartlett (talk) 21:20, 24 February 2019 (UTC)
 * Linking Southern Hemisphere in case the OP doesn't know what it is. ←Baseball Bugs What's up, Doc? carrots→ 23:27, 24 February 2019 (UTC)
 * Although I'm not the original-poster, I'm curious to know why that is. The Earth goes around the sun in an ellipse. So when the Earth is closest to the sun, shouldn't both hemisphere be warmer, and when the Earth is at the farther points of the ellipse, shouldn't both hemispheres be colder? Or is summer/winter not defined by proximity to the sun. 67.175.224.138 (talk) 20:32, 25 February 2019 (UTC).
 * See Effect of Sun angle on climate. Mikenorton (talk) 20:37, 25 February 2019 (UTC)
 * Nothing surprising at all. It is the same as January and February being the coldest months in the northern hemisphere. Ruslik_ Zero 20:50, 25 February 2019 (UTC)
 * See also Apsis Nil Einne (talk) 21:59, 25 February 2019 (UTC)


 * The lowest temperature ever recorded on the Earth's surface was −89.2°C at Vostok Station, Princess Elizabeth Land, Antarctica on 21 July 1983. Since its "Winter" in Antarctica around that time i assume this counts as a Place. --Kharon (talk) 22:19, 25 February 2019 (UTC)


 * The ellipse traveled by Earth is relatively close to being a circle, so the point of closest approach to the Sun (perihelion) is not much nearer than the point farthest from the Sun (aphelion). What counts is Earth’s axial tilt – the angle by which Earth’s north-south axis deviates from perpendicular to its orbital plane – which is about 23°. When the northern hemisphere of Earth is tilted toward the Sun, the southern hemisphere is titled away from the Sun, and vice versa. That’s why summer in the northern hemisphere coincides with winter in the southern hemisphere and vice versa. Loraof (talk) 00:47, 26 February 2019 (UTC)
 * So for half a year where the Earth is at perihelion, is that summer for Northern or Southern hemisphere? 67.175.224.138 (talk) 01:40, 26 February 2019 (UTC).
 * Not "half a year" but a point in time along a cyclic scale. Perihelion comes in early January, aphelion comes in early July. And whether you're in the northern or southern hemisphere, the height of summer can get pretty hot. As Loraof suggested, the difference in the distance extremes (91.4 vs. 94.5 million miles) is not very much, only about 3 percent. ←Baseball Bugs What's up, Doc? carrots→ 04:12, 26 February 2019 (UTC)
 * Perihelion is actually a moveable feast.  The year from perihelion to perihelion is longer than the time it takes the sun to complete a circuit of the stars which in turn is longer than the cycle of the seasons.   All these periods are virtually the same length (365 1/4 days give or take a few minutes). 2A00:23C4:7939:B000:74D4:2AD4:6C84:C5F2 (talk) 13:20, 26 February 2019 (UTC)