Science desk
< July 8	<< Jun \| July \| Aug >>	July 10 >

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

July 9[edit]

Non-human neurobiology, memory cues, and episodic memory[edit]

For some reason, certain objects around me trigger a specific episodic memory. The house always reminds me of the time when I literally drew a picture of it with colored pencils. When traveling to a destination by car, my spatial memory allows me to find a specific location. Then, I remember how elephants can migrate and remember exact locations, provided that humans allow them to migrate beyond the borders of nature parks and countries. Could it be that episodic memory evolved because it enabled creatures to remember specific things, like a watering hole or abundant food source during a specific time of year, and to recognize patterns? 50.4.236.254 (talk) 02:23, 9 July 2017 (UTC)[reply]

Absolutely. The memory of "what did I do the last time I was in this situation and was it the best choice" is vital to survival, and thus passing down genes. Of course, other animals won't think of it in those terms, and may only recall fear when they encounter an animal that wounded them in an earlier encounter, and then back off from the confrontation because of that fear.

As far as experiments to show this, there's the ever popular mouse running a maze experiment. The more they do a particular maze, the more they remember of which way to turn at each intersection, etc., and the quicker they get to the food at the end. Then there's Ivan Pavlov's dogs, which learned to associate a bell with food.

Incidentally, this type of memory may take up lots of space, so animals with larger brains may have substantially more of it, perhaps more than humans. StuRat (talk) 02:28, 9 July 2017 (UTC)[reply]

Also interesting: you may remember smelling when winter or spring comes and being overwhelmed by pleasant memories. There are strong links between olfaction and memory (also more at Olfaction). Other animals also obviously rely much more on scent than we do. —Paleo Neonate - 14:29, 9 July 2017 (UTC)[reply]

Can a person distinguish Greenwich mean time and coordinated universal time when setting a clock manually?[edit]

A request for an argument by a known sockpuppet, rather a genuine question.— Preceding unsigned comment added by Dbfirs (talk • contribs) 16:42, 10 July 2017 (UTC)[reply]

This article Reaction time suggests that they can't. 81.131.180.213 (talk) 07:29, 9 July 2017 (UTC)[reply]

Yes, because the difference is sometimes greater than the 200ms reaction time, and, with a bit of practice, I used to reduce the reaction time when setting my watch from the time signal to less than 100ms. I had to reset my accurate watch every time there was a leap second. I agree that most people are not that fussy about a fraction of a second, and most clockwork and quartz clocks cannot maintain the accuracy necessary. Devices that self-adjust from a GPS or long-wave time signal will certainly show a difference between mean solar time and Coordinated Universal Time. "GMT" can be used for either of these times, depending on context. Dbfirs 07:43, 9 July 2017 (UTC)[reply]

This seems to be something of an oxymoron. Greenwich mean time has been around since 1840. Coordinated universal time has been around since 1960. The various scientific terms have precise meanings - if your claim that GMT can be used for UTC is correct one would expect that UTC can be used for GMT. Do you have a reliable source for your assertion? 81.131.180.213 (talk) 08:02, 9 July 2017 (UTC)[reply]

UTC has a precise definition, unlike "GMT" which is used in two differing ways, though the difference is always less than a second and most people don't care about the difference. As timekeeping becomes more accurate, terms adjust their meaning, as stated in our article Greenwich mean time. I agree that for navigational purposes, GMT might retain its mean status. Dbfirs 12:26, 9 July 2017 (UTC)[reply]

The claim that GMT "is used in two differing ways" did not appear in your answer as originally posted. Neither of your responses provides references, although all refdesk answers are supposed to include them. The only reference you've provided is a Wikipedia article, which is not a reliable source. Are your answers simply your own personal opinion (something which is not allowed on the refdesk)? "Terms adjust their meanings" is another oxymoron - the adjustment is done by people. Science being a precise discipline I find it rather far - fetched that scientists, having gone to the trouble of providing precise definitions for different timescales would then use the names indiscriminately. Back in the 1920s "Greenwich Mean Time" did have two meanings - the civil meaning of "mean solar time at the Greenwich meridian counted from midnight" and the scientific meaning of "mean solar time at the Greenwich meridian counted from noon". In 1925 the civil timescale and the scientific timescale became identical (measured from midnight) and the astronomers started using the snappier title "Universal time", something which did not catch on with the general population, who continued to call the timescale "Greenwich mean time". In 1960 the civil atomic timescale was given the name "coordinated" to distinguish it from the rotation - based "mean". Are you saying the convention has changed? 86.159.235.7 (talk) 16:22, 9 July 2017 (UTC)[reply]

On the contrary, the reference desk is for directing enquirers to appropriate Wikipedia articles. I suspect that you are continuing an old argument, so I will not respond further. Dbfirs 20:24, 9 July 2017 (UTC)[reply]

This is becoming rather murky. On 24 April 2015 the lead included the statement

Coordinated Universal Time is kept within 0.9 seconds of GMT.

The statement was referenced, and having read the book I can confirm that it is properly sourced. On that day Dbfirs added the unreferenced claim

GMT is very close to Western European Time, and is often considered to be identical to Coordinated Universal Time in the UK.

The same evening he added this referenced claim:

GMT is now UT1 or UTC.

The reference did not support the claim (it didn't mention coordinated universal time, as you can see)[1] so the "BRD" cycle continued with the changes being reverted and an explanation provided in the edit summary. The next step should have securing agreement on the talk page. Instead Jc3s5h decided to tag - team by starting an edit - war backed by another reference which was not easy to verify as no URL was provided. When it was checked it nowhere stated that Greenwich mean time is now identical to coordinated universal time, as claimed. To add insult to injury, he removed a reference dating from 2014 with the spurious edit summary claim that it was 39 year[s old].

On the talk page it was pointed out that Seago, Seidelmann and Allen [a source cited in the article] confirm that

UT1 ... is a precise astronomical measure of the rotation of the Earth on its axis, synonymous with mean solar time at the meridian of Greenwich, sometimes known simply as Greenwich mean time (GMT).

Dbfirs didn't respond but instead made the counter - claim that the British government "seems to think that GMT has been the same at [sic] UTC since 1972". Examination of the source [2] shows him using synthesis to push his POV.

On 7 June 2015 the claim

Today GMT is considered equivalent to UTC for UK civil purposes (but this is not formalized)

was added, and the reference provided, when examined, was found not to mention Greenwich mean time at all. It appears that Dbfirs has some explaining to do - perhaps this is why he has disengaged from the discussion.

The great thing about Refdesk participation is that you don't have to give a damn about all these Wiki behavior issues and can just focus on the facts. The most basic one is that "GMT is a time zone and UTC is a time standard". [3][4] According to that site, GMT does not change with daylight savings silliness; instead, Britain (and presumably Greenwich ... what an indignity!) change to British Summer Time. Someone on stack overflow claims that computer systems may switch on GMT, but he got a downvote ... I'll take it as a faint warning. NOAA says [5] that UTC is simply the new name for GMT, and the time servers, by saying that GMT is a time zone and giving UTC+0 times for it, seem to be implying the same thing. This site [6] says that some astronomers still use a pre-1925 definition of GMT that is ... somehow... different than the current. So far, I'm not seeing the 0.9-second thing coming out in the top search hits, apart from Wikipedia and those derived from it, but I can't say it's not true. Wnt (talk) 20:21, 11 July 2017 (UTC)[reply]

According to StackExchange, one (Greenwich Mean Time) is derived from the sun - it's the one sundials show (after adjusting for the equation of time). It's the one marine chronometers (and hence ordinary clocks and watches) aspire to. The other (coordinated universal time) is measured from an atomic clock. The sun is not a perfect timekeeper (it runs slow - see Delta T) so to keep coordinated universal time from wandering too far from sun time the occasional leap second is added to rein it in. 81.151.129.198 (talk) 20:43, 11 July 2017 (UTC)[reply]

A good reference for discussions of GMT vs. Universal Time is an upcoming paper by Seago and Seidelmann with abstract at http://sot2016.cfa.harvard.edu/SoT2016/cgi-bin/TXT/Invited/Invited_SeagoJohnH.txt_N.html where they analyze the difference between mean solar time at Greenwich and Universal Time. With many more computations and diagrams they come up with the same answer that Sadler got in 1954 http://adsabs.harvard.edu/abs/1954ONRAS...3..103S Steven L Allen (talk) 22:37, 11 July 2017 (UTC)[reply]

Rare events predicted by a "theory of everything"[edit]

For example, most grand unified theories predict proton decay with a very long half-life, something not predicted by the standard model. Are there any extremely rare events predicted by a theory of everything that are not predicted even by a GUT, let alone the standard model? Surprisingly, I can't seem to find an answer in our articles on theory of everything, string theory, or M-theory. PeterPresent (talk) 14:36, 9 July 2017 (UTC)[reply]

The "theory of everything" does not exist yet. --AboutFace 22 (talk) 17:55, 9 July 2017 (UTC)[reply]

https://arxiv.org/abs/hep-ph/0703221 Count Iblis (talk) 20:09, 9 July 2017 (UTC)[reply]

Thanks for that paper! So, according to that paper, a prediction of string theory is that the universe will transition into an "exactly supersymmetric" universe with different properties. Is this actually a novel prediction of string theory though? Aren't there GUTs or other theories (e.g. Minimal Supersymmetric Standard Model) that also predict this phenomenon? PeterPresent (talk) 01:50, 10 July 2017 (UTC)[reply]

I think that within string theory it's harder to get around the exact supersymmetric ground state than within effective field theories such as the Minimal Supersymmetric Standard Model where you can introduce all sorts of terms in the Lagrangian to change the predictions. Count Iblis (talk) 21:27, 10 July 2017 (UTC)[reply]

The biggest criticism of string theory / M-theory is that it hasn't offered any testable predictions that distinguish it from other theories. There are a few possibilities that aren't very testable. Some versions of M-theory allow for other "universes" parallel to our own but whose gravity can still affect our universe (and sometimes identified with dark matter). Finding evidence of that would be exciting, but you can also have M-theory without that element (or with other universes so distant as to be completely undetectable). Similarly, string theory allows for compact extra dimensions. Evidence of such extra dimensions could show up in particle accelerators, or the extra dimensions could be a billion billion times too small to be seen with current accelerators. So, if you find them, it would be good evidence, but not being able to find them proves nothing. String theories can also give rise to a wavelength-dependent variable speed of light and time-variation of fundamental constants, though neither concept is exclusive to these theories, nor are the effects required to be remotely large enough that humans are likely to be able to observe them any time soon. These theories sometimes also predict non-trivial internal structures for black holes (e.g. fuzzball (string theory) and might have implications for Hawking radiation, but it is unclear if those ideas are testable even in principle. Dragons flight (talk) 08:08, 10 July 2017 (UTC)[reply]

Sometimes, a theory can make a prediction that some extremely rare event may occur. For example, although most predictions of GUTs would in practice require experiments in the GUT scale, most GUTs predict that protons decay - something that could occur not at all in the GUT scale - but only very rarely. I'm interested in predictions like that. Does string theory / M-theory / TOE predict some extremely rare phenomenon - even on normal energy levels - that is not predicted by our current theories of even GUTs. PeterPresent (talk) 08:24, 10 July 2017 (UTC)[reply]

A theory of everything is needed to unite gravity with quantum mechanics, which is believed to be the last stage in connecting the various known forces in the universe. Pretty much any particle physics process imaginable, such as proton decay, can already be predicted in some GUT theory without the need for gravity. Where a TOE makes new predictions, to the extent that any of them do, is in areas like gravitation, dark matter, black holes, etc. I already gave you examples of those. Dragons flight (talk) 08:53, 10 July 2017 (UTC)[reply]

Our article on gravitons (which emerge in many quantum gravity and string theories) has a quite entertaining discussion of how rare the interaction between gravitons and matter would be, and how large a detector you'd need to see one (spoilers: the required neutrino shield would be so large it would immediately collapse into a black hole). Smurrayinchester 08:59, 10 July 2017 (UTC)[reply]

Learning/teaching systems thinking[edit]

How can we learn or teach systems thinking? --Hofhof (talk) 19:30, 9 July 2017 (UTC)[reply]

First it needs a definition. ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:52, 9 July 2017 (UTC)[reply]

It seems to be mainly founded on logic. Learning logic is a mix of understanding the principle and then practice repeated application to achieve a lasting imprint in out memory. --Kharon (talk) 09:07, 10 July 2017 (UTC)[reply]

That makes no sense Kharon. According to the corresponding articles - systems thinking and systems science - and to a trivial logical analysis systems include any kind of field that has an effect on an issue: cognitive, society, science, math. I'd bet a good 'systems thinker' has broad general knowledge about the involved issues. --Clipname (talk) 16:22, 10 July 2017 (UTC)[reply]

irrelevant comment
Looks to me like you dont know how much of our world is based on logic. Maybe i can convince you with irony: Ask an economist! They are said to teach the worst in both, bending all reality to their "logic" and "making sense". --Kharon (talk) 18:00, 10 July 2017 (UTC)[reply]

This is WP:NOTAFORUM for abstract debate, my friends. The OP's question is arguably too broadly phrased for us to answer without engaging in extensive speculation (which is not the point of this space); the thread can stand for the purpose of providing references that might be useful, but not our personal opinions. On that subject, the OP may be interested in the works of Fritjof Capra, who has made a decades-long endeavour out of trying to find ways to encourage systems thinking in the mainstream. In particular, The Turning Point may be off interest, as might Mindwalk, a quasi-narrative film that is based on his works. Snow ^{let's rap} 23:42, 10 July 2017 (UTC)[reply]

By not shying away from hard core reductionism. E.g. Biology = systems chemistry, see also here and here. Count Iblis (talk) 02:07, 11 July 2017 (UTC)[reply]

What temperature range can feral pigeons survive in?[edit]

At what temperature do they start feeling uncomfortable? Do these numbers change with the seasons? If so, what are the seasonal adaptations and what triggers them? Does the climate of an area feral pigeons are introduced to selectively concentrate the subspecies and sub-subspecies most fit for that climate? (similar to how the European climate selectively concentrated white people) Sagittarian Milky Way (talk) 20:11, 9 July 2017 (UTC)[reply]

I can attest that below −20°C they start feeling uncomfortable (seeking warm place). Ruslik_Zero 20:36, 9 July 2017 (UTC)[reply]

For the last bit, sure. We have shitty sub at species sorting but if you search that and "environmental filtering", you'll find lots of research and information about how species' abundances are tied to adaptation to local climate, resources, etc., and how that ties in to natural selection Careful about using the term "most fit" though, it's not a very good term, and tends to be used by people spouting discredited social darwinism. It may be that the feral pigeons of Minneapolis have slightly different traits than those of Miami, due to natural selection, but by virtue of stably persisting, they are all equally fit as populations. I'd WP:OR not be surprised if a box of pigeons moved from WI to FL had slightly less reproductive success than their native-born counterparts, but I'm not aware of any studies on the topic, nor could I find any. This [7] recent paper has some nice discussion of the genetic variation, convergence, divergence, etc. of feral pigeons. There are also some comments on how/why local populations may differ. I only skimmed it, but if you read it carefully and look at some of the refs (and look at papers that cite this one [8]), you'll know more than you even wanted to about pigeon genetics and spatial distribution! SemanticMantis (talk) 19:10, 10 July 2017 (UTC)[reply]

Oh, and this paper [9] is all about geographic variation in pigeon size, and explicitly invokes natural selection by environmental variable acting on heritable size traits. It's surprisingly right on target for explicitly answering your question, that's rare, so enjoy :) SemanticMantis (talk) 19:13, 10 July 2017 (UTC)[reply]

Thanks. Sagittarian Milky Way (talk) 19:28, 10 July 2017 (UTC)[reply]

Also of interest may be adaptive radiation (which is very general, but also affects birds in large continuous ranges). —Paleo Neonate - 19:38, 10 July 2017 (UTC)[reply]