Wikipedia:Reference desk/Archives/Science/2017 May 29

= May 29 =

What is shame from an evolutionary perspective?
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. 50.4.236.254 (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. 50.4.236.254 (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)


 * Dogs are social, but behave much differently if raised by dogs instead of humans. Human-like behavior (such as the puppy-dog eyes) doesn't happen in the wild. Around humans, dogs learn very quickly that specific behavior results in preferential treatment. Humans reward human-like behavior, so dogs exhibit human-like behavior without any need to fully comprehend what that behavior means. 209.149.113.5 (talk) 11:47, 30 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)
 * Personally I've become suspicious that shame is simply the physical sensation of vasoconstriction somewhere near Broca's area, curtailing verbal communication, and further that the facepalm might be a physical reaction to this. I meant to try to figure out if facepalms had a left-side bias for this reason, but there are, well, some issues with trying to figure that one out. ;) Wnt (talk) 16:56, 30 May 2017 (UTC)

Domestic irradiator instead of a refrigerator?
Could an irradiator be an economically-viable alternative to a refrigerator? Would it require too much shielding? --78.148.98.254 (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. Tigraan Click 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)

Deinococcus radiodurans would have 37% viability after a 15,000 Gray dose. Then it would spoil the food. Edison (talk) 17:59, 30 May 2017 (UTC)


 * Looking at food irradiation I'm not feeling the idea is all that far-fetched. I mean, anywhere from 1000 Gy to 25000 Gy whether the intent is to hinder spoilage a little or to sterilize, with some apparently nontoxic damage to the food at higher levels.  Some bacteria may be selected to thrive in the niche but they ought to be containable, or at least, have low odds to be good pathogens.  A key distinction between commercial irradiation and home irradiation would seem to be that you don't have to do it all in a few minutes at home; you can apply that 1000 Gy over the course of a day, and if you keep the food 25 days, then you've given it more of a sterilizing dose.  So I'd think you can settle on a dose that is not that high and can be sustained in your chamber pretty much as long as desired.  Now to be sure, 1000 Gy a day is still more than 40 Gy an hour, which is lethal, and more than 0.5 Gy a minute - it is highly disapproved to linger in front of the irradiator mulling over what to eat today.  Still, it might make for a laugh riot if folks in a postapocalyptic film use the elevator to the surface as a storage space to keep their food fresh. ;) Wnt (talk) 18:28, 30 May 2017 (UTC)


 * While it wouldn't wholly replace a fridge, it might be a useful device to have in addition. Great for those of us too lazy to go to the market every other day for fresh fruit. ...But it's not going to happen any time soon.
 * The equipment to do this sort of thing is dangerous and tightly regulated. You simply couldn't make a safe one.
 * here is an accident report about someone who was fried in a large-scale device, but it also gives a good overview of how the machines work. They use Cobalt-60 which you absolutely should not have in your house.
 * Imagine all the problems that would come from mass-producing a device with Cobalt-60 in it. Firstly, the amount of cobolt-60 in use would go up dramatically, increasing the risk of accidents in production.  Then, the manufactured machines would be shipped to appliance stores all over the world, some of these would be destroyed in shipping accidents. Once they were in consumer homes, any fire, earthquake, or other disaster would risk destroying the machines, presenting a significant risk to residents and first responders. A certain number of them would break down and, no matter how many warning stickers you put on them, some idiots would decide to try to fix them, with bad results.  And finally, five-to-ten years later, when people want to upgrade to a newer, more stylish model, you'll have a serious waste disposal issue. (You'd need to replace or reload the machine at least once a decade anyway. But the old,used Cobalt-60, would be far from "dead".)
 * As handy as they might be, I don't see it becoming practical any realistic time soon.
 * Food irradiation is one of those things that has to be done by professionals or not at all.
 * The Goiânia accident involved a medical irradiation machine, but it's an illustration of how badly things can go wrong when such machines are left unattended. ApLundell (talk) 14:38, 31 May 2017 (UTC)

Cobalt-60 is a poor choice for irradiating food at home. Better to use X-Rays.

It isn't all that hard to build your own X-Ray source suitable for irradiating food. You can easily cast a lead enclosure from lead salvaged from old car batteries. By placing your irradiation chamber inside a refrigerator or large freezer, you can have long exposure times, which allow for a weaker X-Ray source. --Guy Macon (talk) 20:16, 31 May 2017 (UTC)
 * How to Build an X-ray Machine
 * How to X-Ray
 * An Inexpensive X-ray Machine
 * Homemade X-ray Machine


 * I was thinking lead shielding might develop induced radioactivity, but apparently unless it contains antimony or certain other elements and the beam is >8 MV, this shouldn't be a serious problem. Wnt (talk) 11:47, 1 June 2017 (UTC)

Help with understanding a U-series dating method
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  leads to the product,  (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)
 * Aha. They are measuring 234U in the ice, where ice is defined as "not dust." There are 3 ways a 234U atom can find its way into (non-dust) portion of the ice: it's in the precip already, or it decays from the 238U in the precip, or it gets kicked out of a dust particle when a 238U atom in the dust fissions. -Arch dude (talk) 01:39, 30 May 2017 (UTC)
 * Yes, that seems to be it. I think that's clear enough that I can use it in the article with a clear conscience.  I still don't know what "recoil age" means, but I don't think it matters for the purposes of the ice core article. Mike Christie (talk - contribs -  library) 02:25, 30 May 2017 (UTC)

Which plant?
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)
 * This |Zimbabwe-based seed company says that "the most popular bean varieties are of the speckled sugarbean type." We do have an article on sugar beans, but it's just a re-direct to general Lima/Butter beans, and not much specific on the speckled sugar bean grown in Africa. This page discusses several bean varieties grown in Zimbabwe. Here's |a nice pamphlet on growing sugar beans from N2AFRICA, "a large scale, science-based “research-in-development” project focused on putting nitrogen fixation to work for smallholder farmers growing legume crops in Africa. SemanticMantis (talk) 02:34, 30 May 2017 (UTC)

Frequency of solar eclipses at a given place
"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)
 * Totality is more common in the Northern Hemisphere than the South because the June solstice is almost aphelion. Maybe the peak is somewhat north of the 0th parallel? Sagittarian Milky Way (talk) 06:56, 30 May 2017 (UTC)

Solar eclipse at the poles
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)
 * Yes, these effects cancel. The sun is visible (weather permitting) at the poles about half the time, the same as at other latitudes. It's just that that "half the time" is 24 hours a day for half the year, rather than an average 12 hours a day for all the year as in most of the world.  (Other latitudes in the Arctic or Antarctic are intermediate between the two cases.)  It's not exactly half, because the Earth's orbit is not circular, but close enough. --69.159.63.238 (talk) 06:10, 30 May 2017 (UTC)
 * So does foreshortening cancel? An x "milligamma" slice of the Earth will be less miles of Earth's surface wide at 0 gamma because it isn't foreshortened but it'll be longer. Sagittarian Milky Way (talk) 06:39, 30 May 2017 (UTC)
 * A recent one. Count Iblis (talk) 22:17, 29 May 2017 (UTC)

I'm thinking that at a zero-order approximation, the risk should be the same. I mean, every point on Earth is, on average, in the sun half the time, and on average, the risk of a moon shadow crossing the point is random at any given time and place. So if a polar area is bent away from the passing shadow and have less likelihood of being hit by any given pass, when a pass does hit its shadow should go a long way along the ground, like you're looking at your shadow at sunset. If you want to do a higher order simulation, you have to model the exact north-south distribution of the moon in its orbit, the exact reach of the cone of the umbra and how the Earth's curve away from it decreases the chance of totality and so on. That is a big project. There's also the wildcard of whether any kind of precise repetition could emerge at high level number crunching of the periodicities of eclipses - see - so far as I know at the highest level it is just considered "secular variation" i.e. everything is hit eventually, but maybe there's some kind of NSA astrology you can do to show that there's no real randomness in the long run? It'd be funny if there turns out to be some spot in South America that never gets eclipsed because of a 9040:17337 resonance with Jupiter or something. ;) But I know of absolutely no such thing! Wnt (talk) 18:41, 30 May 2017 (UTC)
 * A place being immune seems about impossible since Saroses make ~36 slices from highest gamma to lowest or vice versa then die, there are many Saroses at the same time, and Earth's rotation is delayed by 32*centuries2 seconds, a rate which itself varies with isostatic rebound (24 hours minus 1.7 milliseconds/century long day now, 2.3ms/century if the Ice Age had never happened). Sagittarian Milky Way (talk) 22:20, 30 May 2017 (UTC)

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


 * While a good paper for an introduction to 4D wormholes, that paper doesn't answer many questions. It explains the questions. I have one answer. I've been Googling to see if I can find the thesis that used this specific method of explaining it, but I can't find it anywhere. So, here is a plagiarized answer until I find the proper attribution: Imagine time is a highway. We are all driving down the highway in the same direction side by side. Now, you create a wormhole in the highway by bending the road so it curves and hooks up with itself. Suppose you get mile marker 100 to join with mile marker 50 in a big loop. Now, at mile marker 75, you purposely sideswipe another vehicle. No problem. You just take the loop at mile 100, go back to mile 50, and this time you don't sideswipe the other vehicle when you get to mile 75. This works if time is like it is in the movies. Every time you take the loop, all the cars are back in the same position and travel from mile 50 to mile 100 again. But, what if that isn't the case. What if when you branch off at mile 100, all the other cars continue driving down the highway? You loop back to mile 50 and an entirely new set of cars is there. You can't go back in miles and kill yourself. You can't change events that happened on a previous trip. You simply merge into an entirely new set of traffic. The causality argument vanishes because, if we go back to time travel, going back in time doesn't let you meet your younger self. It lets you meet an entirely different universe traveling on the same timeline, just traveling behind ours. 209.149.113.5 (talk) 16:47, 30 May 2017 (UTC)
 * Would'nt a wormhole swallow itself aka one end "jump" to the other aka implode in the first femtosecond of its existence? --Kharon (talk) 18:26, 30 May 2017 (UTC)
 * In ER=EPR entangled particles are connected via wormholes. But also the wormhole connection lengthens at the speed of light. So don't expect any useful communication. Graeme Bartlett (talk) 01:32, 31 May 2017 (UTC)