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May 26[edit]

Mammals that sexually mature later than humans?[edit]

What mammals reach sexual maturity later than human beings? I'm counting both the ability to sire/bear offspring and also having reached more or less adult size.Naraht (talk) 02:03, 26 May 2017 (UTC)

The elephant, for one. ←Baseball Bugs What's up, Doc? carrots→ 02:51, 26 May 2017 (UTC)
Great White Sharks may be the latest, possibly as late as 26ish. --Jayron32 02:54, 26 May 2017 (UTC)
Except they're not mammals. But if that's the latest reproductive age of any creature, that puts a boundary around it. ←Baseball Bugs What's up, Doc? carrots→ 03:00, 26 May 2017 (UTC)
I don't think elephants is the correct answer. The elephant article does not mention when they achieve sexual maturity but mentions musth, which is not the same thing. Unfortunately I am at work and our connection is very slow so I can view Google results and Wikipedia but not much else. So Google provided the following results when I put in Mammals that sexually mature later than humans and that seems to indicate that humans are the latest. The partial result for the Quora site looks interesting. Then using Google to ask Sexual maturity elephants gives interesting results with this looking good. But exactly CambridgeBayWeather, Uqaqtuq (talk), Sunasuttuq 07:32, 26 May 2017 (UTC)
Actually, the article on elephants says sexual maturity is at about 9 years for a female, and 14-15 years for a male (several of the larger mammals have a similar difference between the two genders). That does not mean that a 15 year old male elephant would get a chance to mate, as it is competitive and the older, stronger males would dominate. That would imply that male elephants reach sexual maturity later than male humans - but not the females. Wymspen (talk) 11:48, 26 May 2017 (UTC)
I'm surprised that I missed that when I looked earlier. CambridgeBayWeather, Uqaqtuq (talk), Sunasuttuq 12:24, 26 May 2017 (UTC)
Nine-year-old male elephants have been known to mate if all the big males have been killed by poachers. Abductive (reasoning) 17:46, 28 May 2017 (UTC)
Are they less interested in almost menopausal elephants when they start to like girls just like humans? Sagittarian Milky Way (talk) 19:21, 28 May 2017 (UTC)
It seems that female elephants have lifelong fertility --Digrpat (talk) 11:58, 29 May 2017 (UTC)

Exocrine system + endocrine system =?[edit]

What is the title name for endocrine system + exocrine system? In another language that my friend speaks they are called "secretion system" but in English the term secretion system is different and it is about proteins in Gram-negative bacteria. (talk) 08:08, 26 May 2017 (UTC)

I believe the term glands encompasses both of those and also excludes other systems. --Jayron32 10:52, 26 May 2017 (UTC)
You can call it the glandular system, glandular being the adjective from gland. Wymspen (talk) 15:38, 26 May 2017 (UTC)

How does a creature adapt to city life?[edit]

What are the characteristics that a creature must have to live in the city? I presume size is important. Anything too big can easily be spotted by humans. The city has cement, asphalt, and concrete, not soil. I think some plants can slide in among the cracks of sidewalk. There may be parks, separated by tall buildings and desert-like cement floors. And fast-moving objects on wheels with humans inside roam the streets with big, shiny, blinding lights. Then, there are bright lights right next to the moon, so bright that they block out the stars. How do rats survive in the city? What other kinds of creatures can adapt to city life or farm life or face extinction because of habitat loss? (talk) 18:59, 26 May 2017 (UTC)

One obvious example is the Rock Dove, which finds the sides and roofs of tall human buildings just as habitable as the cliffs and caves of its wild habitats.
(But whatever birds lived in the trees that were growing there before the city was built, might be out of luck.) ApLundell (talk) 19:05, 26 May 2017 (UTC)
Rock doves of course would be the common pigeon. The infrequent pure white variety looks very dovey. Sagittarian Milky Way (talk) 07:31, 27 May 2017 (UTC)
Habitat loss is not really about cities, e.g. in the USA our city cores all combined are still tiny compared to the vast expanses in between them. Habitat loss is mostly due to agriculture and deforestation with suburban sprawl playing a much more minor role. Animals that do well living around humans are called synanthropes. We have articles on urban forestry and urban wildlife that describe what sorts of species live around our cities, and you can look in to each of them to see what traits they share in common. Our article on rats explains a lot about how they do so well in some human settlements. Other common urban/suburban animals of North American include squirrels, mice, ground hogs, deer, flies, snails, slugs, ants, mosquito, sparrows, cardinals, blue jays, mourning doves, robins, anoles, geckos, skinks, frogs, etc etc. Tons of stuff lives all around us. See also urban ecology for further reading and references. SemanticMantis (talk) 19:13, 26 May 2017 (UTC)
By my personal observations, Urban foxes are persistent and common in UK towns and cities – driving home through Gosport last week I saw four or five, and had to slow down and flash my headlights at one before it would deign to vacate the carriageway. In the same town's pedestrianised high street, my friend (who lives there) was walking home late one night eating a bag of chips when a fox stopped in front of him, clearly soliciting a handout. When he paused, it walked up to him and tugged gently at his trouser leg, whereupon it was rewarded.
Badgers are also not uncommon in the area (which includes the cluefully named Fort Brockhurst), though they are somewhat shyer and are most often seen crossing cycle paths. (The same friend once cycled into one and broke his wrist – the badger was doubtless unscathed.) {The poster formerly known as} (talk) 01:21, 27 May 2017 (UTC)
While some areas in big cities may give the famous impression "the city never sleeps" most areas are in fact almost completely free of human activity during night hours. Animals instinctively use these hours to wander from one green or hiding zone to another. In fact most animals seem to have much better natural planning and mapping capabilities regarding their living area than humans. They know when and where to move savely and unnoticed. --Kharon (talk) 04:16, 27 May 2017 (UTC)
Animals adapted for cliff-dwelling do well in cities. Animals adapted to forest edge and open woodland habitats do well in city parks. Abductive (reasoning) 17:48, 28 May 2017 (UTC)

May 27[edit]

Feynman Lectures. Exercises PDF. Exercises 4-1...4-16[edit]

I have a general question. In exercises for Lecture 4 a principle "if system is in balance it is reversible machine" is used. But why is it true?
If a reversible machine is balanced it doesn't mean that anything else balanced is a reversible machine.
If Feynman uses this argument, then why doesn't he say that frankly in Lecture 4 (He says only "If we say it is just balanced, it is reversible and so can move up and down")?
But even with this argument there is a problem: at the moment of Lecture 4 we do not know that balanced system is a system without acceleration, because we do not know what acceleration is yet. Therefore, we can't know what a "balanced system" means. So we can't say is the reversible machine in Fig. 4–1 balanced or not at each moment of its operation.

We have:
1) Statement "balanced system is reversible machine" is unproven.
2) Statement "reversible machine is balanced system" is unproven.
3) Statement "if all reversible machines are balanced then all balanced systems are reversible machines" lacks logic. Username160611000000 (talk) 08:10, 27 May 2017 (UTC)

That part isn't quite as clear as the rest, but it does make sense. If you have a "machine" in the classical sense, specifically an inclined plane, with weights on the incline and vertically, then if one end pulls down i.e. it is unbalanced, it is not reversible. Presumably this is in the sense that once the one weight hits the ground, its energy is dissipated and (by conservation of energy) there's no way to reset the whole thing how it was without putting some energy back in. He is taking conservation of energy on blind faith, to be sure. Now, if you have the same machine and it is precisely balanced, then you can push it either way as you like, because, well, I think that's what balanced means. But ... yes, balanced is an imprecise term. After all, a screwdriver can be balanced on its tip, and in theory, you could have it sitting like that and with a push send it one way or the other, yet that is not reversible. The key distinction there though is that the screwdriver doesn't stay balanced. The inclined plane example, in theory, you can give it a little teeny weeny itsy bitsy push, and if it's a perfectly reversible machine, watch it creep down or up, one way or the other, over months and years and whole precessions of the earth, and yet, if you give it a little more push, or push it a little back the same way, it will then go at that new rate the same way. And so you see there that because it remains continually balanced, it never is in the point of giving up its energy, i.e. it does no mechanical work on the weights to get them moving this way or that, beyond what you yourself have put in. Wnt (talk) 20:12, 27 May 2017 (UTC)

Typical revolutions per minute of a fidget spinner[edit]

Not a specialised one designed to go ridiculously fast. Just a normal, hand-spun one. What sort of ballpark are we talking? 10rpm? 1000rpm? Amisom (talk) 21:05, 27 May 2017 (UTC)

This is still a very new field of research so there won't yet be much published literature on this particular aspect.----Seans Potato Business 21:57, 27 May 2017 (UTC)
A Fidget spinner is a type of stress-relieving toy. A video of children playing with the toy shows it spins at a rate a child can easily start and stop, apparently similar to a Gramophone record i.e. 16 to 78 r.p.m.. Blooteuth (talk) 22:55, 27 May 2017 (UTC)
A fidget spinner is hand spun to about 1000rpm in this YouTube video (1:06 minutes in). --Modocc (talk) 23:01, 27 May 2017 (UTC)
About 20,000 rpm or more to get failure. Count Iblis (talk) 23:54, 27 May 2017 (UTC)

Is there any pattern to warning symbols?[edit]

I see sometimes common warning symbols in orange squares or white diamonds with red outlines or yellow triangles with black outlines or white triangles with red outlines. Is there some situation where one is preferred? Can an nuclear trefoil, for example, be put in any of these?

See the article about [Hazard symbol]s. Their use of hazard symbols is often regulated by law and standards organisations who direct different colors, backgrounds, and borders. The radiation Trefoil symbol was originally majenta on a yellow or blue background but is now internationally recognized drawn in black, see Hazard symbol#Ionizing radiation trefoil warning symbol. See the article Warning sign about national traffic hazard signs. Blooteuth (talk) 22:44, 27 May 2017 (UTC)
See also Globally Harmonized System of Classification and Labelling of Chemicals and GHS hazard pictograms. Also Hazchem used in some Commonwealth countries. Alansplodge (talk) 23:18, 27 May 2017 (UTC)

May 28[edit]

If babies are never weaned, then will they be able to digest lactose at later ages?[edit]

I know babies are weaned from breastmilk. But what happens if they are never weaned? Will babies continue to feed on breastmilk and be able to digest breastmilk at later ages? (talk) 02:07, 28 May 2017 (UTC)

Most people can digest milk their entire lives. Why would this matter? --DHeyward (talk) 02:28, 28 May 2017 (UTC)
It may be true in D's country, but it is not true in general that "most people can digest milk their entire lives". -- (talk) 02:40, 28 May 2017 (UTC)
Agreed. Most people of the world live in Asia, and Asians, with exceptions of North Asians, are largely lactose-intolerant. (talk) 03:22, 28 May 2017 (UTC)
Fine, but the question seems to be, if they never stop drinking milk, can they avoid the onset of lactose intolerance? I think the answer is "no", but I'm not really sure, and it's an interesting question. --Trovatore (talk) 03:39, 28 May 2017 (UTC)
I agree I think the answer is no. First, I don't see any reason to think breast milk will make a difference so without ruling it out, I'll let someone else look for any evidence about that. While I couldn't find a source specific placesspecifically commenting on the issue, remember in plenty of places cow milk consumption is fairly common from weaning or before. Most sources like [1] [2] discussing lactose intolerence refer to differing ages of onset etc. They don't say anything about how people can avoid it if they make sure they always consume milk. Note that although people who regularly consume milk may have less symptoms of lactose intolerance [3], according to [4] which is from the dairy industry of Canada, there's no evidence that this is due to increased lactase production and actually they acknowledge they don't know for sure why there seems to be this adaptation, but just that there is evidence does. This doesn't rule out a higher level of lactase production in people who have always consumed milk (nor for that matter that there really is no increased production in people who start to later regularly consume milk even if they lack the various known lactase persistence alleles), still it makes it seem less likely. Nil Einne (talk) 04:26, 28 May 2017 (UTC) 07:04, 28 May 2017 (UTC)
If I'm reading your question right, you're not talking about any old milk (like from cows or goats) but from human breastmilk. ←Baseball Bugs What's up, Doc? carrots→ 09:46, 28 May 2017 (UTC)
There is a specific gene (MCM6) which has the role of switching off lactase production after weaning: it generally kicks in when the child is about four, and had an evolutionary advantage, in that it prevented the older child from hogging the mother's milk, and let the next baby get its share. The mutation which changed Europeans, and some other populations, means that this gene does not work: we continue to produce lactase, so can continue to digest lactose. Without that mutation, the gene is going to switch of lactase production: a child will stop wanting to breast feed because it will start getting bad tummy aches. Wymspen (talk) 10:26, 28 May 2017 (UTC)

Actually re: my answer above, I intentionally didn't link to or check out our articles because I assumed the OP had read them. It seems this was a mistake and I'm now assuming they didn't. While Lactose intolerance isn't that helpful (that I noticed), we also have an article Lactase persistence which specifically covers the issue "While a variety of genetic, as well as nutritional, factors determine lactase expression, no evidence has been found for adaptive alteration of lactase expression within an individual in response to changes in lactose consumption levels.[1]". I haven't checked the source, so I'm not sure if it specifically comments on continuous lactose consumption, I think the evidence is now fairly strong that it's unlikely it will ward of the development of lactose malabsorption/intolerance.

About your comment, I believe we covered the question of why lactase nonpersistence is the norm recently. While it's possible it did provide an evolutionary advantage in some species including humans, for the reasons you stated, I would be careful about assuming that this is a significant factor. Lactase nonpersistence seems to be the norm in most mammal species so it's not clear that preventing older offspring from hogging the milk would be a significant factor.

Nil Einne (talk) 11:32, 28 May 2017 (UTC)

Reading a bit more, I see I missed this part:

Multiple studies indicate that the presence of the two phenotypes "lactase persistent" (derived phenotype) and "lactase nonpersistent (hypolactasia)" is genetically programmed, and that lactase persistence is not necessarily conditioned by the consumption of lactose after the suckling period.[11][12]

Nil Einne (talk) 11:36, 28 May 2017 (UTC)
Decades ago I read a book about a European's life among the Inuit. It may well have been "Arctic Adventure" by Peter Freuchen. In it the author told of a custom among the local Inuit of mothers continuing to breastfeed their offspring into adulthood, such that a grown man would proudly take a suck from his old mother's breast. I wonder if lactose intolerance is common among the Inuit? (PS) I found the actual passage, confirming what was stored in my memory from 50 years ago! [5]. Edison (talk) 13:09, 28 May 2017 (UTC)
Hmmmm... I may have contributed to confusion here before. I went on recently about lactase being inducible in humans, being sure I'd read something to that effect, yet now as you say there are sources being cited to the contrary. Looking at it this time, I ran across a curious bit of data: [6] says that "The mean level of lactase activity among subjects with C/C-13910 genotype was 6.86 ± 0.35 U/g, with C/T-13910 genotype 37.8 ± 1.4 U/g, and with T/T-13910 genotype 57.6 ± 2.4 U/g protein" So at this key genetic locus, it is less than a ten-fold difference in level - and homozygotes and heterozygotes, differing by 2-fold, are taken to be essentially the same. That paper also concludes that lactase levels have to be less than 10 U/g for lactase intolerance to occur. Now that strikes me as a really small difference in enzyme activity, when we consider that some of us are afraid to put milk in coffee and others of us will kill an entire container of ice cream in no time! I also ran across an indication that intestinal flora contribute to lactase levels in rats [7] but haven't looked into this further. There's something I don't understand here... Wnt (talk) 00:10, 29 May 2017 (UTC)

Effect of bovine milk and human milk on human babies[edit]

Humans probably agree that human babies should be fed human milk. But in case the mother dies in childbirth, has HIV, or (A) just doesn't want to or can't breastfeed for some reason, (1) how good is unpasteurized, grass-fed, raw bovine milk as a replacement for human breast milk? (B) Human breast milk may be flavored with whatever food the mother eats. So, (2) does that mean if the mother eats crappy doughnuts and soda, the child will grow up to eat crappy doughnuts and soda? (C) And if the mother eats fruits and vegetables, then her veggie-flavored or fruit-flavored breast milk will cause the child to eat fruits and vegetables and reject crappy doughnuts and soda because they are too sweet to be palatable? (3) What about the breast milk of the biological mother compared with the breast milk of the adoptive mother or wet nurse? (talk) 17:17, 28 May 2017 (UTC)

[I have lettered your premises and numbered your questions to facilitate others' who may wish to address them. Please be aware that (A) elides the fact that many mothers find themselves unable to breastfeed their infant(s), no matter how much they'd like to – glossing over this fact can cause offense and distress. {The poster formerly known as} (talk) 20:07, 28 May 2017 (UTC)]
I made small adjustments by adding the word "can't". (talk) 20:23, 28 May 2017 (UTC)
(1). Cow's milk compared to human breast milk contains too little iron, retinol, vitamin E, vitamin C, vitamin D, unsaturated fats or essential fatty acids for human babies. It also contains too much protein, sodium, potassium, phosphorus and chloride which may put a strain on an infant's immature kidneys. In addition, the proteins, fats and calcium in whole cow's milk are more difficult for an infant to digest and absorb than the ones in breast milk. United States Centers for Disease Control report 148 outbreaks, 2,384 illnesses (284 requiring hospitalizations) as well as 2 deaths due to unpasteurized dairy products between 1998 and 2011.
(2) There is no evidence of eating habits being inherited through breast milk.
(3) What about it? Wet nursing is not widely practiced now. A more acceptable substitute is screened, pasteurized, expressed milk (or especially colostrum) donated to milk banks, analogous to blood banks. Blooteuth (talk) 19:40, 29 May 2017 (UTC)

What does the word "refractory" in "refractory period" refer to?[edit]

I know what it means "refractory period" (both, absolute and relative) in the action potential graph, but I don't understand what the meaning of "refractory" in this context is. What is it refractory for? (talk) 12:49, 28 May 2017 (UTC)

See refractory. Refractory is an adjective usually used around high-temperature resistant materials, indicating that they are unaffected by outside influences, such as heat. This is extended by analogy to physiology, to where there is a time period during the potential graph, during which this too is unaffected by further outside stimuli. Andy Dingley (talk) 13:07, 28 May 2017 (UTC)
Also see meaning 4 in the Wiktionary entry: wikt:refractory. Looie496 (talk) 14:05, 28 May 2017 (UTC)
Thank you. I found the answer here. "After repolarization there is a period during which a second action potential cannot be initiated, no matter how large a stimulus current is applied to the neuron. This is called the absolute refractory period, and it is followed by a relative refractory period, during which another action potential can be generated, but only by a greater stimulus current than that originally needed. This period is followed by the return of the neuronal properties to the threshold levels originally required for the initiation of action potentials." (talk) 14:45, 28 May 2017 (UTC)
  • This is really a language question. The word "refractory" means "very difficult to change." See refractory (disambiguation) for several non-metallurgical examples.-Arch dude (talk) 22:45, 28 May 2017 (UTC)

Re: whale death due to ship strike. Why not attach a beeping horn to the ships bow to provide warning to whales in imminent danger?[edit]

Blue whale gets hit by big ship and dies. Question: Would some kind of underwater horn that emits a warning sound towards the area of travel help whales avoid getting hit by the ship? My guess is, this would have been tried already and found to be unhelpful. But I'd like to know why it wouldn't work?

Thanks, --InverseSubstance (talk) 15:48, 28 May 2017 (UTC)

  • Ships already make a large amount of noise, and whales not only have excellent hearing but also have natural sonar. The problem is that the whales make little or no attempt to avoid being hit by ships.[8]. The currently favored technology to reduce whale strikes is a combination of reduced ship speed,[9] routing shipping lanes away from where whales are most common,[10] and sonar and other alarms so that the ships can avoid the whales.[11] --Guy Macon (talk) 18:31, 28 May 2017 (UTC)
Whales evolved for tens of millions of years in an environment which did not include large, hard, fast counter-current-moving surface objects. They likely lack the cognitive ability to understand the ramifications of such objects, in the same way that many land mammals fail to cope with the characteristics of motor vehicles and end up as roadkill. Some of the latter may to some extent be evolving instincts helping to avoid traffic, but are evolutionarily aided by greater numbers and shorter generation lengths. {The poster formerly known as} (talk) 20:17, 28 May 2017 (UTC)

The research papers are helpful. Thanks for that. I agree, the whales that avoid ships will be selected in, and the ones that don't will get selected out. There are deer whistles sold that one puts on the front of one's truck, and its supposed to warn deer to get out of the way. Maybe just another gimmick, eh? I have an idea! How about a giant airbag that inflates at the front of the ship to cushion the blow? Or maybe some powerful jets of water to give a warning? Just thinking out loud here... --InverseSubstance (talk) 20:34, 28 May 2017 (UTC)

Whalebags? Sagittarian Milky Way (talk) 20:42, 28 May 2017 (UTC)
Its very, very unlikely whales collide with ships because the oceans are really huge areas and shipping lines only use a tiny tiny fraction of the space. Also whales, especially as in this case a blue whale, usually avoid humans. Strangely in this case there are no reports about evidence like huge wounds or broken bones, far as i have read. So i wonder how this "ship collission"-Story made it to the news. Would not shock anyone if it turned out that someone boldly made it up just to fill some space and everyone else started copying it, would it? --Kharon (talk) 20:45, 28 May 2017 (UTC)
See here: "The entire left side of the whale was damaged from a boat strike, and the whale had 10 broken ribs and 10 fractured vertebrae from close to its tail to mid-body, according to Halaska. The whale was identified through photographs of its tail in a database of the Cascadia Research Collective. It was spotted 11 different years beginning in 1999, most often off Santa Barbara. The carcass will be left on the beach to decompose and be eaten by birds. A reef along Agate Beach would make towing the carcass back out to sea difficult." Count Iblis (talk) 00:30, 29 May 2017 (UTC)
[12] mentions "“It’s an unhappy coincidence,” Irvine says. Over a 2-week period in 2007, for example, at least three blue whales were killed by ships striking them near California’s Channel Islands. (Two other blue whale carcasses were spotted during the same 2 weeks, but the scientists weren’t able to study them.)" So actually it seems in the more reliable sources at least, when they say struck by a ship they mean we studied the carcass and decided it was most likely struck by a ship. This blog [13] by someone who seems to be a nature photographer is similar circumspect, it does have the photos if you want to check them yourself. Although interesting, the author does specifically note it was in an area with high shipping traffic. That was in Sri Lanka and [14] notes it's particularly an issue there (the claim is it's a leading cause of death). The first source suggests it is possible but less certain, it's also problem along the Californian coast. (Although the certainty may relate more to who's talking since one was a scientist studying whales whereas the other is an advocacy group.) I suspect some of the sources linked above by others before you posted also discuss the evidence blue whales are being struck by ships. Nil Einne (talk) 07:11, 29 May 2017 (UTC)
I think that a ship coming into port with a dead whale draped over its Bulbous bow is pretty good evidence that ships hit whales. -Guy Macon (talk) 14:47, 29 May 2017 (UTC)

There's several obvious flaws in your hypothesis. First, you can't say random chance is unlikely simply by saying the ocean is big, you need to determine what percentage of the ocean is covered by blue whales (in general) over a defined time period, e.g. ten years. If it's something like 0.00000001% then yes, random chance seems unlikely. But even at 0.1% it's starting to seem possible. Maybe you have some idea what this is based on evidence but that hasn't been presented here. And while I admit it seems likely it'll be small to me, you need to actually have some evidence (even OR) before you can just assume random chance isn't enough.

The bigger flaw though seems to be in assuming random chance. It's possible shipping lanes and the areas blue whales tend to swim in overlap for some reason e.g. favourable ocean currents or location near but not too near certain coasts. Maybe also favourable feeding/fishing grounds (yes I know blue whales are filter feeders but krill etc are eaten either directly or indirectly by some of the fish we eat); although shipping lanes was mentioned above I'm not sure if it's certain this was a cargo vessel (and of course if there is, it would be because the wounds etc have been carefully studies, as it seems they have been per Count Iblis). Maybe size would make it unlikely to be one but some Factory ship aren't exactly small. And these are a lot of assumptions, how well have you considered each one. To give a related example, if I see my neighbour on the bus in the morning on my way to work/uni/whatever regular activity and then see them on the way back as well, and then see them again tomorrow; thinking stalker is generally (but not always) silly regardless of there being many buses in Auckland. An even closer example, it's no surprise that whale watching ships can encounter whales somewhat regularly.

Also [citation needed] for the claim that "especially" blue whales avoid humans, I briefly looked but couldn't find any source discussing this. And what is meant by humans? Swimming humans? Large ships? There's a fair chance the whales aren't going to see these as the same thing, as others have indicated. (Actually the view including from people who actually study blue whales seems to be the opposite, blue whales don't avoid ships.)

Nil Einne (talk) 06:55, 29 May 2017 (UTC)

P.S. Especially in light of my other comment above, I should also point out if shipping lanes and the grounds some blue whales tend to inhabit overlap in at least one instance, it's interesting but ultimately irrelevant when it comes to considering the likelihood of collisions; why there's this overlap. Nil Einne (talk) 07:16, 29 May 2017 (UTC)

So you mean, That's a Whale of a Story! --InverseSubstance (talk) 20:49, 28 May 2017 (UTC)

I agree with Guy Macon: the ships are already really noisy. Underwater noise pollution is widely thought to contribute to deaths from cetacean stranding and so forth. The ship could start beeping when it detected a whale, but how would a whale understand that is in reference to it? Still, the wildcard here is whale language. If someone can figure out something to play that means "MOVE IT!", and broadcasts that when a whale is detected, maybe you have a winner. But without the experiment, that's just pure hot air on my part. Wnt (talk) 00:17, 29 May 2017 (UTC)
[15] Sagittarian Milky Way (talk) 19:21, 29 May 2017 (UTC)

The interested reader may find the following to be helpful; Amazon has a bunch of reviews of the book How to Avoid Huge Ships by those who have successfully avoided huge ships (and a few cautionary tales by those who failed to do so). The reviews are here:[16] --Guy Macon (talk) 15:00, 29 May 2017 (UTC)

  • There are about 9,000 blue whales in the world. About 2,900 of them hang out off the California coast. Containerships from China usually visit Los Angeles and then Oakland before heading back to China, so there are a large number of very large ships in these coastal waters. On my only containership trip in these waters (in 2009), we saw two Blue whales fairly close up, and the officers said that this was routine: they see them more often than not. For some reason 2017 appears to be a record year for whale sightings. Containerships travel at 20 knots or more. Their enormous propellers are directly coupled to the engines and rotate very slowly at 100 RPM or so. -Arch dude (talk) 21:30, 29 May 2017 (UTC)

May 29[edit]

What is shame from an evolutionary perspective?[edit]

It seems to me that a large part of shame has to do with the fear of social rejection. So, one requirement may be that the organism needs to be able to predict the future or remember the past. Another requirement may be that the organism needs to fear social rejection. Another requirement may be recognition of the self. Ay, there seems to be so many factors that I wonder if humans are the only creatures that can experience shame. (talk) 02:24, 29 May 2017 (UTC)

Well, dogs show behaviors that look a whole lot like it. Looie496 (talk) 03:01, 29 May 2017 (UTC)
That makes sense. Dogs are social animals. I bet one of the requirements of shame is fear of social rejection. An animal can remember the past and be self-aware, but does not really depend on social approval and acceptance. (talk) 03:32, 29 May 2017 (UTC)
Your bet is as good as ours. ←Baseball Bugs What's up, Doc? carrots→ 04:40, 29 May 2017 (UTC)
Social systems in the natural world involve a pecking order, so I would guess that it evolved to help to assess if your current position is at risk of being challenged. Count Iblis (talk) 05:54, 29 May 2017 (UTC)
Why speculate when there is Google?
Evolutionary Neurobiology of Shame
Why humans evolved to feel shame
On the biological and cultural evolution of shame
Evolving Concepts of Evolution: The Case of Shame and Guilt
A little bed-time reading. Alansplodge (talk) 17:55, 29 May 2017 (UTC)
Charles Darwin, in his book The Expression of the Emotions in Man and Animals, described the effects of shame. Roger Scruton, in "Modern Sex: Liberation and its Discontents" wrote "the real purpose of shaming is not to punish crimes but to create the kind of people who don't commit them". See the article Shame that suggests the emotion stems from comparison of the self's state of being with the ideal social context's standard. Blooteuth (talk) 19:09, 29 May 2017 (UTC)
@ Your question is an interesting one, but one which had led to anthropomorphic and anthropocentric answers. Most ethologists today would accept that vertebrates and some invertebrates are conscious and therefore may experience emotions. However, this is just about where the agreement stops, mainly because of our human inabilities to ask questions of animals about these matters in a scientifically robust and biological meaningful way. DrChrissy (talk) 20:47, 29 May 2017 (UTC)

Domestic irradiator instead of a refrigerator?[edit]

Could an irradiator be an economically-viable alternative to a refrigerator? Would it require too much shielding? -- (talk) 12:43, 29 May 2017 (UTC)

Irradiator is supposedly a device that heat things instead of cooling them? Ruslik_Zero 13:37, 29 May 2017 (UTC)
No - I imagine it is a machine using beta or gamma radiation as a means of food preservation - Food irradiation. I don't think I would want one in my kitchen. Wymspen (talk) 14:07, 29 May 2017 (UTC)
Well then, first step would be to know whether food irradiation is comparable to refrigeration as a way to preserve food. Our article on decomposition seems to say that abiotic decomposition is possible. TigraanClick here to contact me 16:02, 29 May 2017 (UTC)
Then this might be why this was not tried in the 50s. Sagittarian Milky Way (talk) 18:22, 29 May 2017 (UTC)
Irradiating food to preserve it between uses (which is what we use refrigerators for in kitchens) would require an impractical amount of shielding, yes. According to our article Food irradiation, 1000 Gray is considered a "low dose" for food irradiation, while a 5 Gray dose of whole-body radiation is considered lethal to humans within 14 days.
Apart from that, it's not just microbes responsible for food spoilage which are changed by food irradiation. While a one-shot dose of gamma radiation retards spoilage of food enough to permit, say, fresh produce to be economically shipped very long distances (between continents) for sale, repeated irradiations intense enough to keep food from spoiling between uses (in the way we, say, keep a jug of milk in the refrigerator to keep it from spoiling) would also change many foods enough to make them not taste good. Milk and eggs are good examples of complex foods we refrigerate and which would not survive many irradiations without being made unpalatable. loupgarous (talk) 18:26, 29 May 2017 (UTC)
Indeed, spoilage is not a purely biological process, but also a chemical one. Irradiation will e.g. do nothing to reduce the rate at which fats go rancid. Cooling reduces the rate of chemical reactions. As a rule of thumb going from 24°C (not an implausible temperature for a room or the environment) to 4°C (a typical fridge temperature) will reduce the rate of reactions by a factor of 4, and thus keep food fresh longer. --Stephan Schulz (talk) 21:07, 29 May 2017 (UTC)

Help with understanding a U-series dating method[edit]

I'm working on ice core, and have found a reference in Landais 2012 (p. 192) to a U-series dating method, cited to Aciego 2010. The latter is an appendix to the proceedings of a conference, without much discussion, but the reference in Landais, which just calls it "a promising study", makes it worth a one-sentence mention (and I've seen it cited elsewhere in introductions to journal articles on this topic). However, I don't understand the method and was hoping someone here could enlighten me -- I don't want to cite something I don't understand. It looks like Aciego et al are discussing U-series decay in dust that falls on the ice core, but what exactly are they measuring, and how does it determine age? Thanks for any help. Mike Christie (talk - contribs - library) 14:17, 29 May 2017 (UTC)

It looks like they are discussing uranium-uranium dating and uranium-thorium dating. Double sharp (talk) 14:47, 29 May 2017 (UTC)
You may find this paper useful. Mikenorton (talk) 15:35, 29 May 2017 (UTC)
That does help, but I'm not sure what Aciego is referring to by "recoil products from dust into ice". Is she saying that the alpha decay in dust grains of 238
leads to the product, 234
(or a later alpha daughter product in the decay series) recoiling into the ice, and that analysing the ice itself for daughter products, eliminating the dust, can be used to determine the age via the given equation? I looked through Mike Walker's Quaternary Dating Methods to try to get a better understanding of how U-series dating works, and it looks like it depends on an event that causes a disequilibrium, which can be dated by determining the extent to which the decay has returned to secular equilibrium. I don't see what is going on here that would allow that method to work. Mike Christie (talk - contribs - library) 16:10, 29 May 2017 (UTC)
"Recoil products from dust into ice" seems to refer to an impact. Meteor (especially bolide in the geological sense of the term) impacts in parts of the Earth where uranium is relatively abundant in the mantle which release much dust into the atmosphere could create such a disequilibrium. See Uranium–lead zircon systematics in the Sudbury impact crater-fill: implications for target lithologies and crater evolution by Petrus et al for an example of studies of such phenomena which use uranium dating. loupgarous (talk) 19:48, 29 May 2017 (UTC)
I don't have access to the paper, but from the abstract I don't think that can be the explanation. Aciego is talking about dust in ice cores with miles of ice below them; there's no possibility of an impact being on anything but ice. Micro meteorites are found in ice cores, but that doesn't seem to be it either. Mike Christie (talk - contribs - library) 20:09, 29 May 2017 (UTC)
  • Does ice exhibit a phenomenon like a Radiohalo? (The Radiohalo is a real phenomenon. The whacko creationist stuff is pseudoscience.) With a radiohalo, you detect a physical change in the substrate instead of attempting to detect the daughter product itself. -Arch dude (talk) 21:11, 29 May 2017 (UTC)
    I've never read that it does, but it's possible. Aciego doesn't use the term. The calculations Aciego gives is this: The activity of 234U in the ice is due to (1) the recoil out of the dust plus (2) the decaying initial 234U dissolved in the precipitation plus (3) the accumulation from the decay of 238U dissolved in the precipitation. These three terms are functions of t, the time since deposition; she re-arranges to isolate t and calls t "the recoil age of the ice". I can see that if you can measure all three of those terms you can solve for t, but what is "the recoil out of the dust", and why does she call t "the recoil age"? Mike Christie (talk - contribs - library) 21:36, 29 May 2017 (UTC)

Which plant?[edit]

Which plant is this?

--Pyrophyt (talk) 16:43, 29 May 2017 (UTC)

To my eye, it resembles some type of bean plant. Alansplodge (talk) 17:46, 29 May 2017 (UTC)
I agree that it's probably a legume, the location and date of the photo might help narrow down the possibilities. Roger (Dodger67) (talk) 18:41, 29 May 2017 (UTC)
Google suggests that the "Father Richert Farming Project" is at St. Rupert Mayer's High School, Makonde in Zimbabwe. Alansplodge (talk) 23:47, 29 May 2017 (UTC)
And it ain't alfalfa, clover, pea, lentil, lupin bean, mesquite, carob, soybean, peanut or tamarind, which pretty much leaves beans in the legume department, as far as I can tell. Alansplodge (talk) 23:52, 29 May 2017 (UTC)

Frequency of solar eclipses at a given place[edit]

"Total solar eclipses are rare events. Although they occur somewhere on Earth every 18 months on average, it is estimated that they recur at any given place only once every 360 to 410 years, on average."

So, do we know whether there's a place in the inhabited part of the world that has historically experienced more solar eclipses (not necessarily total) than any other place? And what would explain this? Sorry if this has been asked before. -- Jack of Oz [pleasantries] 21:44, 29 May 2017 (UTC)

Barring Viganella, which can't experience a solar eclipse in the winter because it can't see the sun in the winter at all (and probably experiences fewer in the summer, since the mountains hide the sun before sunset and after sunrise), I'd point you to the map in my question just down below. It looks like eclipses are most common in equatorial regions. Nyttend (talk) 21:52, 29 May 2017 (UTC)

Solar eclipse at the poles[edit]

Attempting to answer the eclipses-in-Toronto question led me off onto yet another rabbit trail: solar eclipses in general. File:Central eclipses 2001-2020.png makes it clear that during this two-decade time, they're much more common in equatorial regions, decreasing with latitude increases, and they're virtually nonexistent at the poles. But maybe that's the result of a too-small sample (i.e. a time span of 200 years would show different results from this time period of 20 years), or maybe because it's a Mercator projection that simply doesn't show the poles well. Can all parts of the world experience a total eclipse, even the poles? Nyttend (talk) 21:49, 29 May 2017 (UTC)

Yes. Total solar eclipses can occur at any latitude. The polar regions are of course smaller targets in real life than on the map. The paths being widened by foreshortening helps the poles see more umbra than they would otherwise and being further from the Moon hurts somewhat but not a ton. Maybe the fact that half the year the poles are immune to umbras being blocked by the ground and instead just stand still waiting to be hit helps them but maybe other things like never getting eclipses in winter cancels that out. Sagittarian Milky Way (talk) 21:55, 29 May 2017 (UTC)
A recent one. Count Iblis (talk) 22:17, 29 May 2017 (UTC)

Does superluminal communication through a (traversable) wormhole inherently imply time travel?[edit]

The article on wormholes mentions that "In 1988, Morris, Thorne and Yurtsever worked out explicitly how to convert a wormhole traversing space into one traversing time by accelerating one of its two mouths". But would a causality violation occur if I merely used a wormhole traversing space as a data link?

Perhaps more succinctly, is traversing a wormhole inherently a form of time travel? What if didn't accelerate either end of the wormhole?--Jasper Deng (talk) 22:19, 29 May 2017 (UTC)

That's a good question. I have no idea what the answer is, but it reminds me: how do you accelerate the mouth of a wormhole anyway? I mean, I assume if you hit it with a baseball bat you get a ... distorted baseball bat. Does the mouth of a wormhole fall like an ordinary physical object in a gravitational field? Or does the far end somehow ... apply a rigid force on it? Good question. Well, I did the web search and here it is ... now all I have to do is understand that ... give me a minute........ Wnt (talk) 22:55, 29 May 2017 (UTC)

May 30[edit]