Wikipedia:Reference desk/Archives/Science/2018 December 21

= December 21 =

claws, hooves, nails—or not?
Does any tetrapod with distinct digits – thus excluding (e.g.) snakes, whales, sea turtles – not have keratin structures thereon? —Tamfang (talk) 04:26, 21 December 2018 (UTC)


 * Probably frogs, see Frog, except for some burrowing frogs, which have "keratinized tubercles".--Wikimedes (talk) 04:38, 21 December 2018 (UTC)

Thank you! Any mammals? —Tamfang (talk) 05:45, 22 December 2018 (UTC)

Danger, danger, danger
Statistically speaking, what is more dangerous: attempting to beat the water speed record, or fighting in the Soviet Army as an infantryman at the Battle of Stalingrad? 2601:646:8A00:A0B3:4C8F:175D:BDAF:23EC (talk) 08:14, 21 December 2018 (UTC)
 * You could compute it by dividing the fatalities in each by the total participants in each. ←Baseball Bugs What's up, Doc? carrots→ 09:06, 21 December 2018 (UTC)
 * That's what I thought, but can you point me to the sources for these numbers? 2601:646:8A00:A0B3:0:0:0:A5A2 (talk) 09:52, 21 December 2018 (UTC)


 * They only fought Stalingrad once. Many of the major names for water speed records kept repeating their record attempts until it did finally kill them.  One of the safest boats (in terms of successful runs) was Bluebird K7. Yet this was finally the boat that Campbell was killed in. It's little appreciated afterwards how old the boat was, and how long a successful career it had had beforehand.
 * So the figures for "risk per attempt" and "risk per racer" would be quite different. Andy Dingley (talk) 10:35, 21 December 2018 (UTC)


 * This Quora thread has casualty rates for Stalingrad. The German figure (94%) must include prisoners, although very few of those lived long enough to go home. Alansplodge (talk) 13:45, 21 December 2018 (UTC)
 * Thanks, everyone! So in terms of risk per racer, it's not even close -- even in the infantry, even on Hill 102, you were still much safer than if you decided to take up record-breaking as your full-time career (especially if you managed to survive your first day on the battlefield).  But in terms of risk per attempt, that's a different story! 2601:646:8A00:A0B3:0:0:0:A5A2 (talk) 01:14, 26 December 2018 (UTC)

cox proportional hazard regression v multiple logistic regression
Hi all, I'm trying to learn about medical statistics but the difference between cox proportional hazard regression and multiple logistic regression is unclear to me. From what I've read: Cox proportional hazard regression model is used in survival analysis, e.g. it is used to determine the effects of variables such as smoking status on the survival of a group of people over a period of time.

In terms of multiple logistic regression, I'm not really sure what it is, the wikipedia article on it is Greek to me! According to one of my textbooks, it could be used in a retrospective study following an outbreak of a disease to identify factors (e.g. temperature on arrival to hospital, sex of patient) that might be associated with an increased risk of death. I'm aware that temperature is a continuous outcome measure where as sex of patient is binary.

To me, these 2 different medical statistics seem like the same thing, there must be some difference but I don't understand it...

If anyone can help with a brief explanation of the difference(s) between them I'd be very grateful. Please don't include formulas in your response if at all possible(!) as I am definitely not mathematically minded, I had enough trouble learning about T-tests! Thank you. RichYPE (talk) 09:30, 21 December 2018 (UTC)


 * Courtesy links: Proportional hazards model and Logistic regression. Loraof (talk) 20:50, 21 December 2018 (UTC)


 * The proportional hazards model asks what is the probability that something happens at a certain time. Logistic regression can ask that same question, and in a different context it can ask what is the probability that something falls into one of two possible categories. Loraof (talk) 23:27, 21 December 2018 (UTC)

Many thanks. RichYPE (talk) 11:23, 23 December 2018 (UTC)

Is honey vegan?
is honey vegan? Blingeapper (talk) 12:22, 21 December 2018 (UTC)
 * (ec) No, assuming that you mean "can honey be used or eaten by vegans". Vegan means abstaining from the use of animal products. Honey comes from bees, and bees are animals. Bazza (talk) 12:37, 21 December 2018 (UTC)
 * And this is the mainstream vegan view, honey is not vegan. Abductive  (reasoning) 14:57, 21 December 2018 (UTC)
 * And by "products" they include the result of an animal's labor, arguing that we would be enslaving the animal. IOW if you trained an animal to pick apples, those particular apples would not be vegan.
 * A further subtlety: for some vegans it isn't actually animals that are forbidden. They are concerned with suffering so the rule is "nothing with a central nervous system." Thus they are allowed to eat yeast and jellyfish. Others don't allow alcoholic beverages as being the product of yeast. Some use health-based arguments, arguing that plants are healthy to eat and animals not. That particular brand of vegan would reject fully synthetic meat that was never part of an animal. --Guy Macon (talk) 18:04, 21 December 2018 (UTC)
 * When I hear these debates about what "truly" vegan is about, I'm reminded of a colleague who considered himself a vegan, yet was a significant cigarette smoker. ←Baseball Bugs What's up, Doc? carrots→ 18:40, 21 December 2018 (UTC)


 * Ahah. What part of an animal did he smoke or is there some kind of a hidden point you're making in your post?--TMCk (talk) 23:15, 21 December 2018 (UTC)
 * Am guessing he smoked those humpy ones. Martinevans123 (talk) 23:29, 21 December 2018 (UTC)
 * I don't know. Luckily I was nowhere near when he would light up. But what's the point of being vegan if not to be healthy? ←Baseball Bugs What's up, Doc? carrots→ 23:36, 21 December 2018 (UTC)
 * I once bought some honey from an organic farm shop; the owner told me all about the health benefits of unblended, unheated honey, while he coughed and spluttered through his nicotine-stained teeth.... PaleCloudedWhite (talk) 23:47, 21 December 2018 (UTC)
 * "Fags are people too, you know." Martinevans123 (talk) 23:54, 21 December 2018 (UTC)
 * Baseball Bugs, if you're not already aware, our article at Veganism lists a number of reasons to go vegan, none of which are the health of the consumer. Matt Deres (talk) 14:42, 22 December 2018 (UTC)
 * It seems to have to do with harm to animals, and apparently harm to oneself is fine. ←Baseball Bugs What's up, Doc? carrots→ 06:06, 23 December 2018 (UTC)


 * Guy, I realise you're making a point about the diversity of opinion among vegans, but just to be clear: it's a very, very unusual vegan who would consider consuming a fungus like yeast to be non-vegan. They might avoid alcohol for other reasons, of course. HenryFlower 21:48, 21 December 2018 (UTC)
 * "Yeasts are people too, you know." Martinevans123 (talk) 23:27, 21 December 2018 (UTC)
 * I just did a bit more research (I had a vague memory about vegans and wine/beer) and it turn out that my memory about yeast was wrong. As you can see in our articles on Vegetarianism and wine and Vegetarianism and beer they most;ly have a problem with animal product used in manufacture -- and further searching turns up wine and beer makers who don't use animal products so they can sell to the vegan market. Thanks for helping me to clear up my misconception. --Guy Macon (talk) 23:45, 21 December 2018 (UTC)
 * Yup, it's the finings used to clarify the beer, at the end of brewing. This makes the yeast clump together, so that it can be removed. Traditionally isinglass was used, which is extracted from the swim-bladder of some fishes. In addition, some beers, such as milk stout contain adjuncts which are non-vegan. LongHairedFop (talk) 10:44, 23 December 2018 (UTC)
 * Contra Abductive, I don't think there's really a vegan consensus on honey. Some vegans accept it; some don't.  The ones that accept it presumably don't consider insects to be the sort of "animals" they're concerned about.
 * I recently saw an article that made a moral argument in favor of vegans eating, not just honey, but insects themselves. The gist of the argument was that the evolutionary purpose of suffering was longevity, and insects were too short-lived for suffering to be adaptive, so insects presumably did not suffer.  Given that vegetable farming imposes suffering on (for example) field mice, it was supposed to be better to eat the actual insects.
 * (I am not sure whether the author considered him/herself a vegan.)
 * I found the argument interesting, but not especially convincing. But the hard problem of consciousness inevitably comes up here. --Trovatore (talk) 08:40, 22 December 2018 (UTC)
 * Insects (and other invertebrates) are deliberately killed during the production of commercial food crops anyway - even organically grown ones - so any act of eating by a human, even those who consider themselves as 'pure' vegans, is likely to involve the death of animals. PaleCloudedWhite (talk) 08:57, 22 December 2018 (UTC)
 * The vegans I've met or read from who eat honey do so because beekeepers will tell you that it's an undeniably symbiotic relationship and anyone who says otherwise is either ignorant or delusional. Wild hives are inefficient crapshoots for all the reasons.  You have to divide effort between looking for food, maintaining the hive, defending the colony from wasps; build too big and weather's gonna wash it away, build too small and everyone drowns in honey; build too close to food and you're just inviting bears and wasps and insecticides to find the hive.  Human-made hives are extremely safe and reliable, are protected from predators, come with way more storage space than the bees could ever dream of, and are usually near lots of plants that the bees like.  Bee keepers do everything they can to make sure that the bees are healthy and safe, and that does include collecting the honey because bees will stuff their hives so full that everyone gets trapped inside.  Ian.thomson (talk) 06:31, 23 December 2018 (UTC)

Speculation about possible space travel
For our present understanding, even the 'closest' star is way too far to be reached with present technology within the span of a human life. However, things are not always how they seem to be. So, is there any not-yet-dismissed hypothesis that would allow human built spacecrafts, manned or not, to travel to any near star systems?--92.191.143.129 (talk) 17:37, 21 December 2018 (UTC)


 * Until somebody who knows what they're talking about comes along, try our Interstellar travel article, especially the Proposed methods section. Alansplodge (talk) 18:16, 21 December 2018 (UTC)

Atomic clock and standard time
According to atomic clock, its caesium standard is calibrated against ephemeris time, meaning an atomic clock is ultimately based on ephemeris time. But seemingly an atomic clock can also show old-school standard time for various time zones, like here. How can an atomic clock measure both of these times? 212.180.235.46 (talk) 20:03, 21 December 2018 (UTC)
 * You're conflating two different ideas. The first is the passage of time itself in your particular reference frame.  That is, the length of the second, which in any particular reference frame is invariant in that frame.  The other is the particular time any one clock should read (i.e. what should my properly calibrated clock read).  Ephemeris time and standard time and the various solar times are clock times.  These are calibrated against the standardized length of the second, not the other way around.-- Jayron 32 23:08, 21 December 2018 (UTC)

What kind of snake was put in the passenger's seat?
The clip starts at 6:30 on the YouTube video with "kDCtQcYES9Q" in the link. Thank you. 104.162.197.70 (talk) 22:42, 21 December 2018 (UTC)
 * The one in the cage looked to me to be an albino Burmese python. - Bilby (talk) 23:34, 21 December 2018 (UTC)