Welcome to the science section
of the Wikipedia reference desk.

Select a section:

WP:RD/S

Want a faster answer?

Main page: Help searching Wikipedia

How can I get my question answered?

Select the section of the desk that best fits the general topic of your question (see the navigation column to the right).
Post your question to only one section, providing a short header that gives the topic of your question.
Type '~~~~' (that is, four tilde characters) at the end – this signs and dates your contribution so we know who wrote what and when.
Don't post personal contact information – it will be removed. Any answers will be provided here.
Please be as specific as possible, and include all relevant context – the usefulness of answers may depend on the context.
Note:
- We don't answer (and may remove) questions that require medical diagnosis or legal advice.
- We don't answer requests for opinions, predictions or debate.
- We don't do your homework for you, though we'll help you past the stuck point.
- We don't conduct original research or provide a free source of ideas, but we'll help you find information you need.

Ready? Ask a new question!

How do I answer a question?

Main page: Wikipedia:Reference desk/Guidelines

The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.

February 15

Diabetes type 2 - mechanism of the problem

What is the problem of diabetes type 2? I've said it because the pancreas don't secret enough insulin, and my teacher said it's not because of secretion of the pancreas since the pancreas secretes normal insulin levels but the problem is with the cells that they receptors for the insulin are covered by fats. He added that diabetes type 1 has to do with the fact that the pancreas don't secret enough insulin but in diabetes type 2 the pancreas does secrets enough insulin. Then I've asked him again, why diabetic type 2- patients used to take insulin if they have enough insulin in their body and he answered me that it is given to the patient when the diabetes is progressive after some years that the pancreas is already out of function. Now all this information is really against what I was told in the past by another teacher (that said what I did). What's true? 93.126.88.30 (talk) 00:11, 15 February 2017 (UTC)[reply]

There are many variations of diabetes. See brittle diabetes and insulin resistance, for example. StuRat (talk) 02:24, 15 February 2017 (UTC)[reply]

Our article Diabetes mellitus says that your teacher is correct-- type 1 is due to a bad pancreas, while type 2 starts with the cells' bad insulin reception but can eventually involve the pancreas going bad as well. Loraof (talk) 02:27, 15 February 2017 (UTC)[reply]

Yes, the article answers the question quite well. Type 2 diabetes begins with insulin resistance, where cells fail to respond properly to insulin. Now, as the disease progresses this can lead to pancreatic dysfunction, as the pancreas attempts to produce more insulin to compensate for this insulin resistance, and some type 2 diabetics can eventually require insulin administration. I get the feeling the original questioner is not a native English speaker. Wikipedia is available in many languages; if you have trouble understanding the English article, see if there are articles in your native language(s). --47.138.163.230 (talk) 03:49, 15 February 2017 (UTC)[reply]

The best person to discuss this with is an endocrinologist. My general practitioner put me on insulin due to my A1C, and I put on 30 lbs. I changed to a different doctor who sent me to an endocrinoogist, who said that not only was the insulin a bad idea, but that it would eventually cripple my pancreas. He put me on various non-insulin medicines, and I lost the gained weight, and then some. I had bariatric surgery Jan 20, an am totally off all DMII meds (I had been taking three pills and a shot a day), and have lost another 30 lbs. So obviously my pancreas has not shut down yet. Seek professional advice. μηδείς (talk) 22:29, 16 February 2017 (UTC)[reply]

By which mechanism sex is considered a risk factor for arteriosclerosis?

I listened today to a lecture in which the lecturer has said that there are 6 risk factors for arteriosclerosis: 1. food. 2. smoking 3. high blood pressure 4. obesity. 5. age 6. sex. I really don't have an idea on what it's based, because after googling I didn't find source for that. But my question is about sex. What does it mean that it's a risk factor and by which mechanism sex can be a risk factor for arteriosclerosis? (Maybe he wanted to say that they are general risk factor for life rather than for arteriosclerosis. It's not clear) 93.126.88.30 (talk) 00:25, 15 February 2017 (UTC)[reply]

Apparently, men are significantly more susceptible to it than women are. My source for that is this article.[1] Google the subject and there should be plenty of entries. ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:30, 15 February 2017 (UTC)[reply]

(edit conflict) Right, here "sex" means the sex of the person, not how much sex s/he has. Our article arteriosclerosis does not mention risk factors, but the related article Atherosclerosis#Risk factors does mention being male as a risk factor, with a citation. Loraof (talk) 02:21, 15 February 2017 (UTC)[reply]

long tangent not relevant to the OP

The following discussion has been closed. Please do not modify it.

- This might be why "gender" is used more and more instead of "sex". ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:24, 15 February 2017 (UTC)[reply]
  - OSHA form: Q:"number of employees, broken down by sex?" A: "None (booze is more of a problem for us.)" -Arch dude (talk) 06:11, 15 February 2017 (UTC)[reply]
  - No, thats wrong. It's because gender has social components, while sex (the property, not the act) is biological (if not always binary). --Stephan Schulz (talk) 14:14, 15 February 2017 (UTC)[reply]

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ - Yes, thanks. The worst part is when people who should know better use "gender" as a sort of euphemism for "sex". SemanticMantis (talk) 15:27, 15 February 2017 (UTC)[reply]

That's precisely the point. Whether Schulz likes it or not, "gender" is often used as a synonym for "sex". In addition to the "broken down by sex" joke, there's this old one-liner with many variant punch lines, where someone's filling out a form, and where it says "sex" they respond with something like "3 times a week." ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:11, 15 February 2017 (UTC)[reply]

Wiktionary's article "Gender" points out that the meaning "sex" goes back hundreds of years, but the use with that meaning has been declining, especially in academia, for the past 50 years. Our article Sex and gender distinction says The sex and gender distinction is not universal. In ordinary speech, sex and gender are often used interchangeably.[3][4] Some dictionaries and academic disciplines give them different definitions while others do not. Loraof (talk) 16:40, 15 February 2017 (UTC)[reply]

The use of "gender" to mean sex, or even social roles correlated with sex, used to be seen as a sort of humorous intentional error, the word "gender" being properly restricted to grammar. I think what's happened in recent decades (much less than fifty years, maybe twenty or thirty) is that non-grammatical meanings have become accepted as fully legitimate. At the same time, "gender" in the non-grammatical sense may also have shifted away from biology and towards social roles. --Trovatore (talk) 16:49, 15 February 2017 (UTC)[reply]

According to Etymology online [2] the "gender as grammatical construct" sense is older, but the "gender as synonym for sex" is pretty damned old too. The grammatical meaning dates from the "late 14th century" while the gender-as-sex meaning dates from the early 15th century. It does say that the preference for using gender to mean "male or female" sex dates to the 20th century, but the meaning is almost as old as the grammatical one. Basically it only almost always meant that, at least in equal measure, to the word "sex". --Jayron 32 19:05, 15 February 2017 (UTC)[reply]

But it was a disfavored meaning; that's my point. It wasn't considered precise speech. --Trovatore (talk) 19:15, 15 February 2017 (UTC)[reply]

It was an old meaning of gender: "A class of things or beings distinguished by having certain characteristics in common; (as a mass noun) these regarded collectively; kind, sort." (OED) from the fourteenth century that was used occasionally for the class of males or the class of females as in " His heyres of the masculine gender" (1474) and "Has thou oght writen there Of the femynyn gendere" from the Wakefield Mystery Plays (1460?). In 1945, the American Journal of Psychology defined gender as "the socialized obverse of sex". Dbfirs 20:36, 15 February 2017 (UTC)[reply]

Perhaps. But it was considered jocular, imprecise, or otherwise inferior in the mid-to-late 20th century. --Trovatore (talk) 20:48, 15 February 2017 (UTC)[reply]

Was that because psychologists and sociologists began using it with a different meaning? Dbfirs 21:19, 15 February 2017 (UTC)[reply]

I suppose it's conceivable. I seem to recall that William Safire wrote in opposition to the non-grammatical usage. If someone could find his essay/chapter/whatever, it might give some insight.

But mostly it just always struck me as something Gomer Pyle would say; definitely not scientific prestige usage. --Trovatore (talk) 22:11, 15 February 2017 (UTC)[reply]

@Trovatore:What? Where? I was taught in middle school, in the late 20th c., that sex is biological and gender, though overlapping in usage, is a social concept. In essence, the "socialized obverse" from Dbfirs source. All my continued education, high school through PhD has supported that same general distinction, though detailed specifics of the definitions may vary. This is certainly true in biosciences, but also in my experience with sociology, psychology and the humanities. ('gens, gentis', from the Latin, type or kind, especially of people, underlies gender, but also genus, gentile, generate, genetics, etc. That itself comes from a PIE root *gene- "to produce, give birth, beget,") Granted, I was not around in the mid 20th c, but you should provide some sources for your repeated claim of "humorous intentional error", etc. I agree it is not proper to use "gender" to mean "biological sex" in a contemporary scientific context, but I really don't know what you're getting at for the rest. SemanticMantis (talk) 22:14, 15 February 2017 (UTC)[reply]

Well, this was the way I heard it anyway. There's a hint of it in the EO link that Jayron gave, though it doesn't put a date on it. As I say, I think there's something by Safire somewhere, but I don't have it to hand. --Trovatore (talk) 22:19, 15 February 2017 (UTC)[reply]

I don't have access to the Saffire opinion, but the OED says: " In the 20th cent., as sex came increasingly to mean sexual intercourse (see sex n.1 4b), gender began to replace it (in early use euphemistically) as the usual word for the biological grouping of males and females. It is now often merged with or coloured by sense 3b" [and 3b, with cites from 1945 onwards, is "Psychol. and Sociol. (orig. U.S.). The state of being male or female as expressed by social or cultural distinctions and differences, rather than biological ones; the collective attributes or traits associated with a particular sex, or determined as a result of one's sex. Also: a (male or female) group characterized in this way."] Dbfirs 22:30, 15 February 2017 (UTC)[reply]

Viagra does cause delayed back ache. Perhaps these phenomena are related? μηδείς (talk) 22:19, 16 February 2017 (UTC)[reply]
- Maybe related to this oldie: "If you don't swallow it quickly, you'll get a stiff neck." ←Baseball Bugs ^{What's up, Doc?} carrots→ 08:40, 18 February 2017 (UTC)[reply]

Our article Testosterone and the cardiovascular system explains one potential issue - the sex hormone testosterone is linked to increased incidence of arteriosclerosis.

The body makes testosterone in response to the arousal stage of a sexual encounter. I'm not sure if that's enough to increase your risk of atherosclerosis.

Most importantly, men usually have higher circulating testosterone levels then women all the time, regardless of their level of sexual activity; they're important to development and maintenance of Secondary sexual characteristics such as beard growth. As the our article Testosterone and the cardiovascular system shows, this explains the higher incidence of arteriosclerosis and heart disease in men.

So, the answer to your question is being of the male sex definitely increases your risk of atherosclerosis because testosterone is linked to that disease process. The level of testosterone increases during sex due to how arousal triggers increased testosterone output but I don't know having more sex increases your prone-ness to atherosclerosis. loupgarous (talk) 01:36, 19 February 2017 (UTC)[reply]

Feynman Lectures. Lecture 48. Ch.48-4 . Refractive index < 1, phase speed > c [3]

...
In other words, for the slowest modulation, the slowest beats, there is a definite speed at which they travel which is not the same as the phase speed of the waves—what a mysterious thing!

— Feynman • Leighton • Sands, The Feynman Lectures on Physics, Volume I

What does he mean by "slowest"? Very low frequency of modulating wave?

A part from words Let us see if we can understand why to the end of the chapter is also obscure.

Now because the phase velocity, the velocity of the nodes of these two waves, is not precisely the same, something new happens. -- He considers x-rays. X-rays have a speed $v_{\text{x-rays}}=c/n$ . How could it be that phase velocities are different? Even in the glass (or carbon) two x-ray waves must propagate with equal speed.

$\definecolor {myorange}{rgb}{0,0.38,0.52}\color {myorange}dk/d\omega =1/c+a/\omega ^{2}c$ -- When I express the formula (48.14) like this: $\omega ={\tfrac {1}{2}}(ck\pm {\sqrt {(ck)^{2}+4a}})$ and differentiate, I get: ${\tfrac {d}{dk}}\omega ={\tfrac {d}{dk}}{\tfrac {1}{2}}(ck\pm {\sqrt {(ck)^{2}+4a}})={\tfrac {1}{2}}(c\pm {\tfrac {c^{2}k}{\sqrt {(ck)^{2}+4a}}})$ . But Feynman got ${\tfrac {c}{1+a/\omega ^{2}}}$ . Why? Username160611000000 (talk) 07:52, 15 February 2017 (UTC)[reply]

Group velocity might help you. Tigraan^{Click here to contact me} 13:58, 15 February 2017 (UTC)[reply]
- The images in the article show group speed ≠ phase speed. This case is not explained by Feynman yet.
- I assume next: with frequency $\omega _{2}=8\pi$ (Fig. 48–1) the refractive index will be $n_{2}=1-{\tfrac {Nq_{e}^{2}}{2\epsilon _{o}m(\omega _{_{2}})^{2}}}=1-{\tfrac {a}{(\omega _{_{2}})^{2}}}$ . So the phase speed will be $v_{p;2}=c/n_{2}$ .
  And by analogy for $\omega _{1}=10\pi$ we have $v_{p;1}=c/n_{1}<v_{p;2}$ .
  Is it that what Feynman meant?
  Username160611000000 (talk) 18:00, 15 February 2017 (UTC)[reply]
- WRT formula :
  
  ${\tfrac {1}{2}}(c\pm {\tfrac {c^{2}k}{\sqrt {(ck)^{2}+4a}}})={\tfrac {1}{2}}(c\pm {\tfrac {c^{2}({\tfrac {w}{c}}-{\tfrac {a}{wc}})}{\sqrt {(c({\tfrac {w}{c}}-{\tfrac {a}{wc}}))^{2}+4a}}})={\tfrac {1}{2}}(c\pm {\tfrac {cw-{\tfrac {ca}{w}}}{\sqrt {(w-{\tfrac {a}{w}})^{2}+4a}}})=$
  $={\tfrac {1}{2}}(c\pm {\tfrac {cw-{\tfrac {ca}{w}}}{\sqrt {w^{2}+{\tfrac {a^{2}}{w^{2}}}-2a+4a}}})={\tfrac {1}{2}}(c\pm {\tfrac {cw-{\tfrac {ca}{w}}}{\sqrt {w^{2}+{\tfrac {a^{2}}{w^{2}}}+2a}}})={\tfrac {1}{2}}(c\pm {\tfrac {cw-{\tfrac {ca}{w}}}{\sqrt {(w+{\tfrac {a}{w}})^{2}}}})=$
  $={\tfrac {1}{2}}({\tfrac {cw+{\tfrac {ca}{w}}\pm cw\mp {\tfrac {ca}{w}}}{w+{\tfrac {a}{w}}}})={\begin{cases}{\tfrac {cw}{w+{\tfrac {a}{w}}}}={\tfrac {c}{1+{\tfrac {a}{w^{2}}}}}\\{\tfrac {\tfrac {ca}{w}}{w+{\tfrac {a}{w}}}}={\tfrac {c}{{\tfrac {w^{2}}{a}}+1}}\end{cases}}$
  
  It's strange, but second answer doesn't fit ...
  Username160611000000 (talk) 20:16, 15 February 2017 (UTC)[reply]

What type of person makes all the factory parts and programs them to work?

In a factory, everything seems to be automated. What type of person invents all the factory parts and programs them to work properly to create lots of things in a relatively short period of time? What skills and knowledge are needed? Are there any books about this matter? 166.216.159.7 (talk) 15:42, 15 February 2017 (UTC)[reply]

Designing machines is done by engineers. --Jayron 32 16:26, 15 February 2017 (UTC)[reply]

Also, to expand on that, no one single person would be expected to design an entire factory all by themselves. Hundreds of engineers working in teams would do that. --Jayron 32 16:29, 15 February 2017 (UTC)[reply]

See Manufacturing engineering and Industrial engineering. Loraof (talk) 16:31, 15 February 2017 (UTC)[reply]

Well, also it should be noted that, depending on what the factory is making, there would be a dozen or more engineering sub-disciplines involved. After all, the robot itself may be designed by a mechanical engineer, while wiring would be done by an electrical engineer. If (for example) it was a chemicals factory, there would be chemical engineers to handle designing reaction vessels. It goes on and on. No one person would be expected to do all of those jobs, it would require many dozens of engineers from a wide variety of disciplines. --Jayron 32 16:47, 15 February 2017 (UTC)[reply]

Design of things is still the design of things, whether they're made by hand, by manually-controlled machine or by fully-automated robot. Many of the design issues, either the aesthetic design of them or their engineering design is still much the same.

Manufacture by automated machine relies on the CAD / CAM / CNC cycle. One might use CAD to draw something that's then made entirely by hand, one might begin to design for robot manufacture by using a pencil and paper, but somewhere along the route an automated manufacture involved moving into the CAM / CNC world.

The first CNC began with punched cards and punched tape, first for the Jacquard loom and later for milling machines. These are powered, manually controlled machines, where their hand controls are replaced by power controls under the direction of the tape's instructions. G-code (from the 1960s) was an important step for this (it's still around today) where very simple instructions are given to a dumb machine in the form "move this control so far, move that control a little". Writing G-code was long recognised to be a long and tiresome task, using much the same skills as a manual machinist used for manual machining.

CAD has been around for as long as computers were available. It could be said to begin in the 1940s, but this was theoretical modelling of complex engineering (nuclear engineering, aerodynamics and fluid dynamics for gas turbines) rather than an interactive "design" process. CAD, as we'd know it now, begins in the late 1970s with graphical terminals and minicomputers.

CAM joins up the design and control aspects of this: it embodies the machinist's knowledge of how to use a machine to make a shape. CAM becomes increasingly sophisticated and automated: from an early beginning in checking the low-level and error-prone G-code for validity, or generating batch machining tasks (e.g. remove 0.5" of material in repeated 0.025" steps, starting from the same place), through to modern 3D printing. 3D printing can specify a solid shape by CAD, but the CAM not only works out how to move the print head to make the shape but can also transform the hand-drawn solid automatically into a hollow honeycomb, saving material and print time.

Factories are also about more than machining. I spent much of my career making production line machines to assemble or test assemblies, particularly in car factories. These didn't look like "robots", or even robot arms, they mostly resembled a conveyor belt with workstations for each task. An operator might manually place a gear on an axle, some screws are automatically fed from a magazine screwdriver and driven home, then a power press drives a bearing into place. Finally a rotating shaft measures the force needed to turn the assembly and if this is within the expected limits, to check that everything turns freely. Skills for this (a good job market) ranges from general mechanical engineering design, specific production engineering (there are college degrees in that speciality), electrical work, PLC programming and (my part) general computer programming for connecting user interfaces (see SCADA) to machinery and usually doing some statistical processing for tasks like SPC. Some projects were purely for testing, such as engine test cells and dynamometers.

There is a massive literature and training organisation around these industries. Andy Dingley (talk) 18:42, 15 February 2017 (UTC)[reply]

Its almost never only one person. Naturally its not obviouse to outsiders how many problems need to be solved to build a working, reliable factory. Experts on automation may seem like the real core of designing a factory but they only have basic knownledge of for example electrical installations, architecture, work security, workflow or finances.

Ofcorse, if you plan a multimillion investment like a factory you want to make shure for example some machine gets placed on a proper solid floor that can withstand all the forces and also doesnt get you in trouble if some oil leaks on to it. Just imagine some goverment inspector who wants ot check out your "factory" slipping and braking his arm on some oily patch next to a machine you just put there thinking what could go wrong. You have to think of everything and ofcourse thats even a challenge for a team of experts, let alone one who is specialized on Automation. --Kharon (talk) 02:05, 17 February 2017 (UTC)[reply]

I worked in the body panel press shop at Pressed Steel Fisher in Swindon for one job. The steel sheets (maybe 6' square) are greased before they go into the presses. The floor was of wooden blocks. As usual, I was wearing a suit and tie - the few concessions were that the tie was a clip-on, I wore Doc Martens and I kept a large boilersuit handy if I actually had to climb into a machine. In Swindon though, this wasn't enough - that plant was filthy, in a clean sort of way. The grease from the sheets got everywhere, including the wooden floor. I had to nip out at lunchtime and buy myself a set of hobnailed boots just to stay upright. I also purchased a picnic set - clean plastic table, clean chairs and a picnic umbrella, which I set up as a computer workstation alongside the machine for whilst I was in there. Naturally I set the umbrella up too - I'd paid for it, I was having it!

I still preferred it to the BMC A-Series engine cylinder head machining line. They were made from a particularly graphitic grade of cast iron, which threw a haze of conductive black dust into the air. That got everywhere and caused no end of short circuits. Our computers had to be IP66 waterproof to survive. Andy Dingley (talk) 15:06, 17 February 2017 (UTC)[reply]

Walking on the moon

If I applied the same forces with my feet as I do on earth, but was skipping (like the astronauts did) on the moon's surface, how high off the surface would I be jumping? --31.92.250.145 (talk) 18:17, 15 February 2017 (UTC)[reply]

It would depend on how high you could jump on earth. ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:34, 15 February 2017 (UTC)[reply]

Quick approximation is that the lunar gravity is 1/6th that of Earth. You're also going to jump less well encumbered by a space suit, and carrying the extra weight of a space suit, rather than just running shorts.

But (comparing your performance on Earth whilst carrying the weight of a spacesuit) you could jump to six times the height you could reach on Earth. Andy Dingley (talk) 18:44, 15 February 2017 (UTC)[reply]

The relevant equation is

E=mgh

, where

E

is the amount of energy you put into the jump,

m

is your mass (plus that of anything you're carrying),

g

is the gravity of the planet or moon you are on, and

h

is the height you jump. This can be re-arranged to

h={\frac {E}{gm}}

. Assuming you can apply the same amount of energy into the jump (it will be over shorter period), then, as, Bugs said, the height you jump is inversely proportional to the gravity. LongHairedFop (talk) 19:33, 15 February 2017 (UTC)[reply]

Yeah but the astronuts didnt seem to be jumping that high: only say 150cm. They should be diong a few feet at least.Also, why are the in slow motion?31.92.250.145 (talk) 22:07, 15 February 2017 (UTC)[reply]

My guess would be that they had been trained to jump slowly and gently, to avoid going too far or too fast. Even in low gravity, inertial mass and momentum remain unchanged, so collision injury is just as serious. The apparent "slow motion" is a direct result of acceleration from the moon's gravity being only one sixth of that on Earth. Dbfirs 22:22, 15 February 2017 (UTC)[reply]

They also had to be careful, because if they were to trip and fall, they could damage the suit or the equipment pack, which could be fatal. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:32, 15 February 2017 (UTC)[reply]

I seem to remember at least one of the moonwalkers falling over with no apparent ill effects. Anyway, why do you have to bounce around in low gravity? And what was the mass of the spacesuits etc compared to their unsuited body mass?31.92.250.145 (talk) 22:56, 15 February 2017 (UTC)[reply]

There are videos of astronauts falling (see this). In photos, Buzz Aldrin has dirt near one knee, but I think that he said that he didn't remember falling down. As far as jumping on the Moon, the space suit is restrictive. It also added 200 pounds on Earth, but if an astronaut weighed 175 pounds on Earth, that would be like (175+200)/6 = 62.5 pounds on Earth. If the spacesuit were completly flexible (it wasn't) then you should be able to jump nearly three times as high (with the added weight) as you can on Earth. The reason that they appear to be moving in slow motion is because of the acceleration of gravity and his first law of motion, F=ma, and the equation for how far a body falls under gravity. If you work through the math, it takes about 2.5 longer for something to fall the same distance on the Moon as on Earth. The same thing applies when something is going up. And bouncing around was the best way to move. During the Apollo 11 moonwalk, Aldrin demonstrated several methods of moving. Bubba73 ^{You talkin' to me?} 00:07, 16 February 2017 (UTC)[reply]

Some time in the last 50 years I have read [sorry, no specific reference yet found] that the skipping or 'galumping' gait adopted by the lunar astronauts was what they quickly found to be the surest method of progression in the conditions. The lower gravity means both that a given muscular effort causes a greater rise, and that foot/ground friction is much reduced. Many of us will have experienced the advantage of 'galumping' when proceeding downhill at speed (somewhat comparable to the lower gravity situation), and also of the adjustments necessary when walking on slippery ice; the combination of the two is out of most people's experience. Our article Apollo 11, under 'Lunar surface operations', includes the following text – note the last sentence:

"Armstrong said that moving in the lunar gravity, one-sixth of Earth's, was "even perhaps easier than the simulations ... It's absolutely no trouble to walk around."^[36] Aldrin joined him on the surface and tested methods for moving around, including two-footed kangaroo hops. The PLSS backpack created a tendency to tip backwards, but neither astronaut had serious problems maintaining balance. Loping became the preferred method of movement."

The best gaits to use in various gravity strengths (and on various surfaces) is a difficult matter to research, although experiments (as preparation for possible human exploration of Mars, whose gravity is about 1/3 ours) have been done by suspending subjects by sprung wires, sometimes from an overhead travelling framework – relevant videos I have seen may be findable on the usual sites, here are a couple new to me:

https://www.youtube.com/watch?v=LvnDIDqcfGI

https://www.youtube.com/watch?v=5MraTpKa7a8

As yet there has not (to my knowledge) been a conclusive finding for Martian surface gravity (approximately 1/3 of ours). The poster formerly known as 87.81.230.195} 90.203.118.169 (talk) 04:11, 16 February 2017 (UTC)[reply]

The lunar gait was described as hopping or kangaroo hopping, rather than skipping. The point is that under the low gravity they found it easy to hop with both legs together, but that as the suit limited movement of each leg going past the other, it was much easier to hop with both together.

When falling over they tried to either fall forwards onto one knee (under the low gravity this would be low risk) or else to fall backwards. The PLSS rear pack was much more robust than the front equipment and cameras, also it left the astronaut lying on top of the PLSS rather than under it, making it easier to get up again. Andy Dingley (talk) 10:08, 16 February 2017 (UTC)[reply]

One light controlled by two switches

Sometimes there are two switches in different locations for one light. When you turn off the light with one, you can turn it back on with the other. Is there a diagram somewhere that shows how this is done? Is it somewhere at Multiway switching? I can't imagine how it could work. Many thanks, Anna Frodesiak (talk) 23:12, 15 February 2017 (UTC)[reply]

Yes, Multiway switching#Traveler system is the usual way. Andy Dingley (talk) 23:15, 15 February 2017 (UTC)[reply]

Thank you, Andy! I saw that and didn't get it, then stared at it for longer and now I totally get it. Cheers. :) Anna Frodesiak (talk) 23:27, 15 February 2017 (UTC)[reply]

(asside) When I was a child, my uncle, an engineer showed me how two switches do this. He challenged me to figure out how to do it with three switches. I couldn't do it. The third switch has to be a different type. Bubba73 ^{You talkin' to me?} 19:20, 16 February 2017 (UTC)[reply]

February 16

Hiding numbers in a crossed-eye stereogram.

I'm making a bunch of puzzles for an Escape Room. These puzzles need to be mildly difficult to solve - but not impossibly so. My particular need is to creatively hide a 4 digit number "in plain sight" to open a combination lock as one step in a multi-stage puzzle.

I had an idea for way to hide a number in a "crossed eye stereogram" (see Stereoscopy) like this one:

(You cross your eyes until one picture overlays the other - then it all pops out in 3D - you can try it out if you sit back a ways from your monitor).

What I'm ultimately wanting to do is to place a grid of random numbers into just the right-hand image (perhaps have them written on a chalk-board inside the photo) then to place the red pattern into the corresponding place on the chalk-board in the left-hand image.

When you 'fuse' the two images into one, I hoped that the red circles would highlight four of the numbers with the lines between showing the order they go in. When you put something in one image and not in the other, it kinda looks transparent or something. You'd only be able to figure out the combination by crossing your eyes or using a 3D viewer which I'd leave lying around someplace else.

I've never seen this trick done for hiding numbers, so to test out my idea, I made this super-simple test case:

My hope was that when you viewed the image by crossing your eyes (possibly by using a Stereoscope) to align the two pictures into one - the red pattern would indicate the four numbers in the grid that you need to open the combination lock.

What actually happens is really weird and totally not what I expected! A fuzzy region around the red pattern seems to "erase" the nearby numbers in the right-eye image!

Swapping the left and right images produces the exact same response (so it's not like the effect is caused by "left-eye dominance" or anything).

So two questions:

What is happening? (I'm curious!)
Is there anything I can do to make it work the way I'd hoped it would?

SteveBaker (talk) 04:23, 16 February 2017 (UTC)[reply]

That's your blind spot - the "scotoma" or "optic nerve disk." The actual physiology is a bit complex - suffice to say that all humans have a spot in the almost-exact-center of each eye's visual field in which there is no visual perception, and your brain just "blips" it out so you don't notice it! It is the enabler for many an optical illusion, and it's also described in the PHAK as a risk: you can't see tiny dots in the sky when you stare straight at them! In your set-up, your circles draw the viewer's eye directly to the number, causing it to fall in to their blind spot. In the PHAK, they do the exact same thing with a diagram of an airplane, demonstrating how you might not see something that's flying right toward you unless you make a concerted effort to constantly scan your visual field.

You need a "bigger" number field - the actual scotoma is tiny, so if your numbers (and circles) are even a bit larger, you won't have the problem. Or you can try to train or instruct your viewers to visually scan off-center...

Nimur (talk) 05:05, 16 February 2017 (UTC)[reply]

I don't think it's the blind spot. When I close one eye, the image the other eye is pointed at returns to normal. I suspect the culprit is that the images are too dissimilar. It's difficult to keep them aligned, and the brain may be blinding you to incongruous parts of each image. Someguy1221 (talk) 05:13, 16 February 2017 (UTC)[reply]

With Steve's setup, he's forcing the number into the blind spot by requiring you to align and focus your eye in a specific location. The instant that you close one eye, saccade occurs, and your brain and eye work together to scan over the whole visual field, moving any specific location out of your optic disk for at least part of the time - helping your brain to fill in the little blip.

Just like the diagrams in the textbook, Steve's setup is actually working against your physiology and visual perception system, forcing a specific alignment, and encouraging your eye not to scan the target-object out of its blind spot. Nimur (talk) 05:22, 16 February 2017 (UTC)[reply]

No, I just used one of those diagrams to locate my blind spot. It is not remotely close to where my eyes are focusing while overlaying the images. Someguy1221 (talk) 05:53, 16 February 2017 (UTC)[reply]

At first sight, I liked the blindspot explanation - but on reflection, I don't see how it can be true. Why should the numbers always disappear and the red diagram not? Flipping the entire image left/right doesn't change the results. On the face of it there is symmetry everywhere - so why is the red diagram clearly visible while the numbers always fade out? SteveBaker (talk) 13:32, 16 February 2017 (UTC)[reply]

In general, your brain can't overlap disparate images very effectively - rather than seeing one combined image, you see both simultaneously. For an example, see the film Goodbye to Language, which is in 3D but sometimes uses totally different images in the left and right channels. You never see these overlap - rather, they "pop" against each other, and your attention is always drawn to sudden movements or bright/sharp objects. You're getting a similar effect here - I suspect the reason that the red circles are so visible is that they have sharp edges and clear details while the numbers just form a wall of noise, so your brain always focuses on them. Smurrayinchester 08:57, 16 February 2017 (UTC)[reply]

That does seem to be the case here. I probably need to do some more experiments. SteveBaker (talk) 13:32, 16 February 2017 (UTC)[reply]

Bear in mind that some people, myself included, can't 'see' stereograms. Have never been able to. I guess in your escape room scenario there will be a group, and most people will be fine, but still. 131.251.254.154 (talk) 10:47, 16 February 2017 (UTC)[reply]

OFF-TOPIC: Stereoblindness is a well-understood phenomenon - and if both of eyes work then it's possible to cure it. (See Stereopsis recovery). The good news for people with stereoblindness is that brain plasticity often allows people recover the capability. People who do this (See Susan R. Barry), claim to see the world in an entirely new and richer way! So I encourage you to seek out an expert.

From the escape room perspective, stereoblindness affects about 5% of the population and our problems are designed to be solved by a team. The smallest team allowed is usually 4 and the largest is 8. The odds of four of them all being stereoblind is vanishingly small (5% x 5% x 5% x 5% = 0.0006%). We don't shy away from problems that colorblind people can't solve for the same reason - and a reasonably good IQ is needed to be successful too! SteveBaker (talk) 13:20, 16 February 2017 (UTC)[reply]

Perhaps not what you have in mind, but personally I find it much easier to combine overlapping images by putting one on top of the other and holding them up to a strong light. Of course, then you wouldn't be using the stereoscope, etc. I wonder if a flip book or zoetrope would be any more effective? Though again that would require a different approach. Dragons flight (talk) 11:09, 16 February 2017 (UTC)[reply]

Note that the image of the polar bear is made for parallel-eye viewing, not crossed-eye viewing. If you try it with crossed-eye viewing, the depth is reversed. And I never managed parallel-eye viewing without a stereoscope, although I've no difficulty with crossed-eye.

If, in the image with the yellow squares, I look with my left eye at the number field or with my right eye at the red lines, from a reasonable distance from my monitor, the other feature falls into my blind spot. It's far enough from the centre of my field of view not to interfere with the overlapping images. But strong features, like the red lines on yellow background, override weak features, like a wall of numbers. Furthermore, the images have too little in common. When I don't focus on the edge between the yellow and the grey areas, I can't keep the images aligned. On the other hand, I often see those "Find the 10 differences"-images on yoghurt bricks and the like, and I can easily solve them by overlapping both images. I can see the differences blink whilst the rest of the image is static.

If you want to do something with stereograms, what about hiding the numbers in the third dimension of an autostereogram? I prefer them with crossed-eye viewing (so that's the opposite of most examples in that article), but even if you view them the wrong way, the depth is just reversed but the numbers should still be readable. PiusImpavidus (talk) 11:38, 16 February 2017 (UTC)[reply]

I had already planned to use an autostereogram to provide an instruction for another puzzle. A decent escape room needs maybe ~30 puzzles to solve in order to keep a group of 4 to 8 people busy for an hour - so there is room for all kinds of sneakiness. The thing about autostereograms is that people would completely expect to have to view them to get the answer - this one would be a little more subtle (if it actually worked!).

I never understand the difference between "parallel viewing" and "crossed-eye viewing" - it seems that what I have to do is to relax my gaze and let my eyes cross in order to see the polar bear...and when I do that, it seems to have the correct depth information.

What started me off on this is that McDonalds are currently giving away a Batman-themed stereogram viewer with their "Happy Meals" and one of them got abandoned at my house by the grandkids. Since my escape room is themed as "Escape from toyland" having a children's viewer present seemed like an opportunity too good to miss! The polar-bear image works in their viewer - so I guess that "parallel viewing" is what I mean here.

SteveBaker (talk) 13:20, 16 February 2017 (UTC)[reply]

"Crossed eye" means that a line drawn out from the pupil of each eye would cross, while parallel means they go off to infinity. "Relaxing" your gaze makes your eyes parallel. Guess: The catch I think is that some people have eyes further apart then others, and the ones with their eyes furthest apart find existing parallel eye stereograms easiest to read, so they make more... for people like them. The ones who are narrower aren't programmed to have their eyes point apart in two different directions, so they never have a chance. Wnt (talk) 14:40, 16 February 2017 (UTC)[reply]

I believe you have encountered the effect known as binocular rivalry. It is well known in perceptual psychology and has been studied quite extensively. It has nothing to do with the blind spot. Looie496 (talk) 14:09, 16 February 2017 (UTC)[reply]

I agree - as the article describes, I saw the numbers blotted out by the shape, then perfectly visible with the shape also. The catch though is that the numbers don't seem to blot out the red lines so intensely, so it is entirely possible for me to find the circled numbers - IF there are enough cues to line the shapes up accurately. Also, there is a sort of "lasso area" around the red line figure that blots out the numbers, but further away there is no interference, and the way in which that area is delineated is likely to be intensely interesting. This could be fun to look up further. Wnt (talk) 14:27, 16 February 2017 (UTC)[reply]

Fair gambit! I can concede that this may be a purely psychoperceptual illusion, like binocular rivalry, and that may even be a better explanation for the effect than positing a physiological cause like the optical disk blind spot - besides, I can't see what you see, so maybe we're seeing (and explaining) different effects! This raises some fun questions about testability and falsifiability as it pertains to visual illusions: how could we test the root cause? If it's your blind spot, scanning the field should make it go away (and does, for me at least). I'm not certain that proves very much, though!

At the very least, psychological and perceptual illusions can coexist with real physiological visual artifacts - it could be a combination of all of the above!

Nimur (talk) 06:57, 17 February 2017 (UTC)[reply]

@Nimur: I don't understand how you can look at that image and think the blind spot is anywhere near what you see. I mean, the images in each eye that don't superimpose are somewhere near the blind spot, but I can remove them from play simply by holding up my hands as a frame so that those images are blocked out, and the superimposed parts still look exactly the same as they did. Wnt (talk) 20:53, 18 February 2017 (UTC)[reply]

I'd like to suggest that you use a rather complex image for the stereograph, but then make the hidden message different in the two eyes. When looking at a stereograph, any details that don't "match" stick out like a sore thumb. You notice this when using vintage stereo cards that have a scratch or something on them. It feels like the scratch is flashing as your two eyes fight over what version of the image is 'correct'. (You can intentionally exploit this effect to quickly solve one of those 'spot the differences' puzzles they sometimes print in newspaper comic pages.) ApLundell (talk) 17:27, 16 February 2017 (UTC)[reply]

 ASCII-art stereogram:

 Here is an ASCII stereograms.  View with a monospace font.
 To see the 3d effect, you need to focus your eyes such that the two
 adjacent "X" characters at the top look like three. Once you've done 
 that, wait a few moments for your eyes to get used to it, then slowly 
 look down at the rest of the image.

                             X         X
 .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .
  .   .   .   .   .   .   .   .   .   .   .   .   .   .   .   .   .
    .    .    .    .    .    .    .    .    .    .    .    .    .
    .     .     .     .     .     .     .     .     .     .     .
      .      .      .      .      .      .      .      .      .
  .       .       .       .       .       .       .       .       .
       .        .        .        .        .        .        .
    .         .         .         .         .         .         .
 .          .          .          .          .          .          .
 |          |          |          |          |          |          |
 |          |          |          |          |          |          |
 |          |          |          |          |          |          |
 |          |          |          |          |          |          |
 |          |          |          |          |          |          |
 |          |          |          |          |          |          |
 .          .          .          .          .          .          .
    .         .         .         .         .         .         .
       .        .        .        .        .        .        .
  .       .       .       .       .       .       .       .       .
      .      .      .      .      .      .      .      .      .
    .     .     .     .     .     .     .     .     .     .     .
    .    .    .    .    .    .    .    .    .    .    .    .    .
  .   .   .   .   .   .   .   .   .   .   .   .   .   .   .   .   .
 .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .

--Guy Macon (talk) 19:06, 16 February 2017 (UTC)[reply]

When I look at the image with yellow background, I get the stereo effect, but the red circle's pattern does not "lock" on the random numbers. Circle's pattern kind of vibrates in horizontal position. Even then, I can see that the area of red circles overwrites the background numbers. But I noticed, with some efforts, I can see the numbers but this make the circle kind of disappear. I was able to focus on either on circle or on number at a time, and was able switch focus as desired. Therefore, to get images in locked state, I thought I need a matching pattern in remaining part of both images. Then actually I cut the red circle's pattern and pasted on the right side of bear on the left bear image, and random number pattern on similar position on the right bear image. And then when I looked, I got the circle pattern nicely locked on the numbers. And in stereo view, I could still focus on either circle and on number, and flipping the focus revels the desired numbers! Give it a try. manya (talk) 05:36, 17 February 2017 (UTC)[reply]

If you don't mind it not being a proper stereogram (like the one with the polar bear), there's something called SIRDS (single image random dot stereogram.) There are generators for that kind of thing on the internet if you google. They take an image that contains a mask and create a "Magic Eye"-type image that contains the outline of what was in the original image. When viewed properly it will appear embossed Asmrulz (talk) 17:06, 17 February 2017 (UTC)[reply]

Here's a random one from google search results: http://pictureimage.whak.com/signs/stereogram/?text=123

It takes a string of text and generates a SIRDS image with the string hidden in it. I personally couldn't "acquire lock" on the image but I think it's because I'm viewing it on a monitor. It'll work if you print it out (perhaps scale up a bit) Asmrulz (talk) 17:14, 17 February 2017 (UTC)[reply]

Identify a tadpole shrimp (Triops)

Is this photo a Triops granarius or a different species? Found in an ephemeral pond near Victoria West, Northern Cape province, South Africa. The image in the article is too small and unclear to properly compare it. Roger (Dodger67) (talk) 07:42, 16 February 2017 (UTC)[reply]

Hmmm, a quick search online yields an essay suggesting that there is some work needed on the taxonomy. [4] I thought someone must have looked at the DNA, so I went to PubMed and found this, which should be useful. But I'm a bit reluctant about using Sci-Hub from this location, and who the heck has access to "Zootaxa"? So I'll leave it to you to go over what they say about the two other species they think they can distinguish there. Wnt (talk) 14:35, 16 February 2017 (UTC)[reply]

Thanks Wnt, leaving the taxonomic fights aside, it seems that granarius (by whatever name) is the common species in the area concerned. Roger (Dodger67) (talk) 16:59, 16 February 2017 (UTC)[reply]

does exercise oxidize us

does exercise oxidize us? Is this unhealthy somehow? — Preceding unsigned comment added by 31.4.145.73 (talk) 15:42, 16 February 2017 (UTC)[reply]

This may be useful for your research. --Jayron 32 15:47, 16 February 2017 (UTC)[reply]

In the literal sense, yes, because the food you eat is oxidized to release energy for your body to use. As with anything, extremely excessive physical activity can be bad for your health, but the health benefits of reasonable amounts of exercise are well-documented. If you live in the developed world, you're at much greater risk of not getting enough physical activity, which can lead to all kinds of health issues. See also oxidative stress for the general topic of cell damage caused by oxidation reactions. --47.138.163.230 (talk) 01:56, 17 February 2017 (UTC)[reply]

We can read a lot about this subject in scientific articles and our own articles as mentioned above. But we need to consider here that our understanding of the processes involved here is still quite new while the biological processes are very ancient, many of these date back to the time that organisms first started to use oxygen about 2 billion years ago. Evolution has led animals that have made the best out of all these processes, so a naive way of thinking that heavy exercise may not be healthy due to the large amount of oxidation, probably does not reflect reality. The opposite, taking a lot of anti-oxidants has been put to rigorous tests, with typically negative outcomes, e.g. taking a lot of vitamin C impairs recuperation after heavy exercise. Count Iblis (talk) 02:26, 17 February 2017 (UTC)[reply]

^{[citation needed]} for your last claim, preferably with a WP:Medrs compliant source if you can. It's not mention by the ref linked by Jayron32 above. Nor in vitamin C which only mentions "A study in rats and humans suggested that adding Vitamin C supplements to an exercise training program lowered the expected effect of training on VO2 Max. Although the results in humans were not statistically significant, this study is often cited as evidence that high doses of Vitamin C have an adverse effect on exercise performance. In rats, it was shown that the additional Vitamin C resulted in lowered mitochondria production.[40]". I assume we're talking about humans not rats since the OP clearly is and in any case I don't think this single study really belongs in our article (but that's something for the article talk page). And "It has not been shown effective in prevention or treatment of the common cold, except in limited circumstances (specifically, individuals exercising vigorously in cold environments).[25][needs update][26]".

I'm not suggesting that vitamin C supplementation after or before heavy exercise has any benefit. Rather most likely there is no benefit nor negative, e.g. as mostly suggested by this (non medrs) source [5], e.g. "The overwhelming consensus of a fairly large number of well-conducted investigations is that vitamin C has no ergogenic effect in persons who are not vitamin C deficient" and "The overwhelming consensus of the literature is that long- or short-term supplementation with vitamins E or C has no ergogenic effect on submaximal exercise performance, aerobic capacity, or muscle strength". Yes this only talks about ergogenic effect but it's silly to think they wouldn't have mentioned if there was a well supported ergolytic effect.

Note this doesn't mean it's a good idea to supplement as some people claim because it probably has no significant negative effect. Since you have no reason to think it has a positive effect either nor to think a positive effect is more likely, that doesn't make sense. And there is the minor (presuming you aren't talking about extreme amounts) stress you're putting on your body excreting all that excess vitamin C.

Nil Einne (talk) 06:28, 17 February 2017 (UTC)[reply]

How do I make a factory?

I really like watching How It's Made series on YouTube. Everything is automated. There are machines that control everything in high speed! I wish I can make my own factory. What skills and knowledge and how much money do I need to build my own factory? How many subjects in physics and chemistry do I have to learn about before I can make my own factory? How do I extract metal ore from the ground? How do I convert metal ore into usable pieces of metal? How do I make a wire? Where do I start in the process of making an automated machine? 66.213.29.17 (talk) 19:51, 16 February 2017 (UTC)[reply]

Are you the same person who asked the question about factories a few days ago? If so, the answers are there still. To reiterate: One person does not make a factory. Hundreds do. It is beyond the scope of ability and knowledge and time and resources for a single person to handle the entire thing. Please scan up this page for responses to this question the last time it was asked. If there are more specific questions that you need answered, we'll try to help as well. --Jayron 32 20:01, 16 February 2017 (UTC)[reply]

#What type of person makes all the factory parts and programs them to work?

For the historical aspects, some good reads are John G. Landels'. Engineering In the Ancient World. and L T C Rolt's. Tools for the Job.Andy Dingley (talk) 20:24, 16 February 2017 (UTC)[reply]

We have articles on mining, ore and metalworking. I recommend typing some of your keywords in to our serach box, and then reading the articles. We can help you read up on these things, and answer questions about them, but we can't teach you the entire field of industrial engineering and design of factories. SemanticMantis (talk) 21:52, 16 February 2017 (UTC)[reply]

"How do I make a factory?" is not a science question. It should be asked on another page. DrChrissy ^(talk) 21:58, 16 February 2017 (UTC)[reply]

The same IP user posted this question about a factory. Blooteuth (talk) 00:44, 17 February 2017 (UTC)[reply]

For a factory on the human scale I might recommend RepRap and other rapid prototyping and 3D printing. For a chemistry factory, microfluidics is a growing field that carries out whole reactions in a tiny module. While these technologies currently have significant limitations relative to conventional methods, they seem to have great potential, and they allow new methods - for example diazomethane can be produced and used in a microfluidic set-up, even though a traditional chemist might not dare to come within sight of a flask of it. Factories have largely shed their human workers for machines; arguably the next step is to make those machines tiny, and the factories to match. Wnt (talk) 12:46, 17 February 2017 (UTC)[reply]

February 17

Plant from Bangladesh

Which plant is farmed here? I've never seen such fruits.--Sascha GPD (talk) 13:45, 17 February 2017 (UTC)[reply]

Hard to tell. The fruit resembles durian or maybe jackfruit or maybe breadfruit. --Jayron 32 14:22, 17 February 2017 (UTC)[reply]

Amongst other things, the leaves look wrong for all 3 of these to me. Nil Einne (talk) 15:01, 17 February 2017 (UTC)[reply]

Doing more google searches, other spiky green fruits include guyabano, or some species of cucumber, such as a luffa or Marah (plant) (aka manroot). --Jayron 32 16:37, 17 February 2017 (UTC)[reply]

I'll admit the first thing I did was take a quick look at the breadfruit article... then I realized this would be hard. I suck at botany, but my notion is that the first thing you do is fire up the glossary of leaf morphology and open the image to full resolution. At center-right far-top there's a little clearing and you can see the leaf beneath it, and various others, have branching leaf veins and jagged edges, with the veins apparently running to the narrowest parts of the edges. So I would say these are simple leaves (our redirect just takes you to leaf). The margin I would call "dentate" rather than "serrated" because the "teeth" seem symmetrical, and not "crenate" because they seem roughly zigzag. I think the shape of the leaf is "heart-shaped" = "cordate" - not to be confused with a chordate! In places the vein branching matches our figure for "dichomatous", in others "palmate" - I'll let someone else take a bite at that apple. And while the perspective confuses me a bit, I think I can see there are long stems supported on a framework that have leaves branching "alternately" in each direction, toward and away from us. So I am going to suggest that additional searches include dentate cordate alternate ... and I'll hope for a miracle. ;) Wnt (talk) 19:35, 17 February 2017 (UTC)[reply]

I should mention I did have a look at various other Artocarpus, none of them seem to have similar leaves. So perhaps either a speciesly less commonly cultivated or somethign else. Nil Einne (talk) 03:24, 18 February 2017 (UTC)[reply]

My guess is some member of the family Cucurbitaceae, superficially it resembles Echinocystis lobata but it seems that species is not cultivated. Most likely it is of the genus Cucumis (same as cucumbers) Cucumis zeyheri has similar morphology but appears to grow on the ground rather than as a climbing vine. Hope this helps. 204.28.125.102 (talk) 00:31, 18 February 2017 (UTC)[reply]

Is abstract thinking unique to Homo sapiens?

--IEditEncyclopedia (talk) 14:19, 17 February 2017 (UTC)[reply]

Wikipedia has an article on Animal cognition which would be a good starting point for your research. --Jayron 32 14:24, 17 February 2017 (UTC)[reply]

Is there non-circle Neanderthal geometric art? Like squares or triangles? If there isn't then maybe yes. Or maybe not. Even were that 100% foolproof maybe there were millions of Neanderthals in all time and only one had abstract thought and we've just never found his drawings of cubes and icosahedrons. Sagittarian Milky Way (talk) 14:31, 17 February 2017 (UTC)[reply]

And what do you call a 1/8th homo sapiens who had the smarty genes from her homo sapiens great-grandparent and the ability to bench press hundreds of pounds from her 7 Neanderthal great-grandparents? Sagittarian Milky Way (talk) 14:45, 17 February 2017 (UTC)[reply]

Apparently John Urschel ;-). --Stephan Schulz (talk) 15:56, 17 February 2017 (UTC)[reply]

It would be difficult to test for animals fully understanding abstract thought, so we might do better to test for their understanding of things like scale models first. For example, show them a scale model of a room with a treat hanging out of a box, then take them to the full-sized room and see if they check out the full-sized box first (don't actually put a treat in it or they might smell it). If they don't understand scale models, there doesn't seem to be much hope for them understanding more complex abstract concepts. StuRat (talk) 16:33, 17 February 2017 (UTC)[reply]

Yes, it is difficult, but a cursory search shows that a number of scientists have designed a range of test for assessing abstraction on non-humans, and then published the results in peer-reviewed studies. Science is often difficult, but that is no reason things can't be studied and understood. I wonder- how long did you look for references on this? SemanticMantis (talk) 18:33, 17 February 2017 (UTC)[reply]

If you can find animals that can handle scale models, then the next step is to make it a scale model, except that it's a mirror image, and see if they can handle that, then start changing details, like make it a different type of chair and box in the room. Then perhaps try a photo of the room, then a map. At this point, we are getting into fully abstract thought, or we can identify precisely where each animal falls short. StuRat (talk) 22:23, 17 February 2017 (UTC)[reply]

This being the science desk, I don't think abstract thought has a definition sufficiently precise to qualify for use in the question posed, which is Is abstract thinking unique to Homo sapiens? Bus stop (talk) 17:06, 17 February 2017 (UTC)[reply]

There are certain terms which have more precise meaning in psychology and philosophy which may be more precise, such as metacognition and theory of mind. We even have an article titled Theory of mind in animals and Animal consciousness, although both of those suffer from the same issues as human definitions as noted in hard problem of consciousness. --Jayron 32 18:24, 17 February 2017 (UTC)[reply]

No. Not according to some definitions and some research. See e.g. Visual categorization: accessing abstraction in non-human primates [6] and A non-human primate test of abstraction and set shifting: An automated adaptation of the Wisconsin Card Sorting Test [7]. Both articles are freely accessible, you can look at the prior work they cite, and you can use google scholar to look at other articles that cite these works. SemanticMantis (talk) 18:32, 17 February 2017 (UTC)[reply]

First of all, I'm not entirely sure that I use the term "abstract thought" in the same way that others do here, so forgive me if I go off on a tangent. There were some famous observations by Wolfgang Kohler which may be relevant here. Kohler had a large enclosure containing several chimps. There was a bunch of bannanas hanging very high in the enclosure, and on the ground there were various items, including several crates and sticks. The story goes that one day, a chimp piled 3 crates on top of each other (without trying to get the bannanas between stacking crates). After the third crate had been stacked, the chimp grabbed a stick,climbed the crates, and reached up with the stick to get the fruit. One account of this is here[8]. There are a couple of other terms used in this area of ethology which might be helpful for research. These include "gestalt" or "gestalt thinking", or the Eureka moment. DrChrissy ^(talk) 18:58, 17 February 2017 (UTC)[reply]

I wouldn't call that abstract thought, it's tool use. Visualizing how to stack the boxes is not abstract, but rather a concrete thought process. Similarly, crows use tools [9], and any bird building a nest or perhaps spider building a web is using similar concrete thought processes. StuRat (talk) 19:08, 17 February 2017 (UTC)[reply]

Oh yes, it could be classified as tool use - it could be placed in several other categories of behaviour - perhaps cognitive trial-and-error. What do you mean by a "concrete thought process" - this is not an ethological term I have encountered before. DrChrissy ^(talk) 19:20, 17 February 2017 (UTC)[reply]

side conversation, no references, open at your own time-wasting peril SemanticMantis (talk) 23:40, 17 February 2017 (UTC)[reply]

Perhaps tangible is a better word for it then. I mean thought processes which can be visualized physically, like the stacking of blocks, as opposed to an abstract concept like "honor", which can't be. StuRat (talk) 22:20, 17 February 2017 (UTC)[reply]

But this is now becoming circular. You are using words which can not be defined for non-human animals, such as "honour". If we can't define it, or at least develop a working definition, we can't test it. DrChrissy ^(talk) 22:34, 17 February 2017 (UTC)[reply]

This is part of the problem. It's difficult to even define what abstract thought in animals would be, much less test for it. But it's not being able to visualize how to stack blocks. From what we know about humans with no language skills (who later developed them so they could describe what it was like before, like Helen Keller), they thought in terms of pictures, making abstract thought an impossibility. If animals also think this way, then they would have similar limitations. Of course, animals do have some language skills, but they seem to be rather rudimentary. StuRat (talk) 22:57, 17 February 2017 (UTC)[reply]

I'm sorry but this is going off on tangents which have nothing to do with the OP. You are throwing in terms such as "tangible", "concrete", "visualise" with no definition and in ways that simply do not relate to my understanding of ethology. This is really not helping the reader. DrChrissy ^(talk) 23:12, 17 February 2017 (UTC)[reply]

@StuRat:. Why don't you try reading a bit about the topic? I have given two very relevant references, each of which contains working definitions of abstraction, and each of which cites many additional scholarly works. The ones I posted are freely accessible, but some of the works they cite are not. If you would like to read some of them and do not have access, just let me know, and I will be happy to provide copies if I can. This is not a desk for you to approach a field from an ignorant position, and hope to work things out from first principles. This is a reference desk, where our goal is to serve our patrons with references. Since you clearly don't know much about this topic, and cannot (or will not?) supply any suitable references, try reading some of the references provided - try to learn from the experts, rather than stumbling around the topic like a chihuahua in a sock. SemanticMantis (talk) 23:39, 17 February 2017 (UTC)[reply]

I think that referencing a "chihuahua in a sock" is borderline WP:NPA. It's uncalled for. A questioning of the term abstract thinking is appropriate to the question asked in this thread. Even the distinction between abstract thinking in humans and non-abstract thinking in humans is a worthwhile discussion and, in my opinion, not entirely irrelevant to the the question posed in this thread. Bus stop (talk) 04:18, 18 February 2017 (UTC)[reply]

Hopefully this def of abstract thought, which contrasts it with concrete thought, will help you understand the difference better and will help us define, and hence answer, the OP's Q: [10]. StuRat (talk) 23:39, 17 February 2017 (UTC)[reply]

This being the science desk, I don't think abstract thought has a definition sufficiently precise to qualify for use in the question posed, which is Is abstract thinking unique to Homo sapiens? Bus stop (talk) 17:06, 17 February 2017 (UTC)

By abstract thought, I mean the ability to hypothesize. To create ideas about different things such as God, moon, sun, rainfall, thunderstorm etc. Humans created abstractions about these things, which are gradually evolved with new knowledge. At first, humans thought sun and moon to be planets revolving around Earth. Do other animals have this ability to create ideas about things? --IEditEncyclopedia (talk) 07:58, 18 February 2017 (UTC)[reply]

According to Gorilla#Intelligence, "Some researchers believe gorillas have spiritual feelings or religious sentiments". Does religious feelings count as abstract thought? --IEditEncyclopedia (talk) 08:25, 18 February 2017 (UTC)[reply]

I , for one, am getting completely lost in the moving goal-posts of this almost totally anthropocentric thread. How can we possibly discuss whether non-human animals "think" about God when so many humans would deny his/her existence? Then on the other hand, do animals have abstract thoughts about rain. I don't know whether they have abstract thoughts about rain, but I know that many, many animals react to rain and many animals appear to be able to predict rain. Going back to anthropocentrism and God. Here comes my bit of OR. I have two cats. They have a collection of toys which I tend to keep all lumped together. One of my cats regularly, without any prompting, goes to this pile of toys and brings back the same toy each time for me to throw for him. Anthropocentrism means we are essentially locked in our human skin. How can I possibly know what my cat is thinking when he walks to the toy pile to get his favourite toy. Perhaps he believes it is a God in the same way that some humans have an abstract thought about God? DrChrissy ^(talk) 10:59, 18 February 2017 (UTC)[reply]

Perhaps some animals will weigh in on this question... Bus stop (talk) 14:48, 18 February 2017 (UTC)[reply]

Several already have - we refer to them as editors. DrChrissy ^(talk) 15:42, 18 February 2017 (UTC)[reply]

So, the question restated is "Is abstract thinking possible in humans?" Bus stop (talk) 16:15, 18 February 2017 (UTC)[reply]

Well not really, you are asking a completely different question. DrChrissy ^(talk) 16:25, 18 February 2017 (UTC)[reply]

A related question is whether animals and birds are required to obey the Ten commandments, and whether they are aware that they sin by disobeying. I regularly watch birds eating thrown-out bread, and it's not at all unusual to see one of them stealing a piece that another bird is eating, when there are plenty of unclaimed pieces on the ground. It's obvious that not all humans obey the commandments at all times, indicating free will to sin or not sin and guilt if they do. If the commandments are universal, we could conclude that animals also experience guilt when they disobey one. Akld guy (talk) 19:50, 18 February 2017 (UTC)[reply]

The survival instinct often overrides everything else, in both humans and non-humans. ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:53, 18 February 2017 (UTC)[reply]

@ Akid guy. I can not agree. Even if the 10 commandments were universal, this in no way means we can conclude non-human animals experience guilt if they violate one of these. I feel guilt if I find a £10 note in a shop and decide to keep it for myself rather than find the owner. There are many persons in our prisons who feel no guilt at having committed serious crimes against others. Even within our own species we would be pushed to conclude that the feeling of guilt due to violation of the 10 commandments causes guilt throughout our species. DrChrissy ^(talk) 21:22, 18 February 2017 (UTC)[reply]

My username is AKLD guy. Akld is one of the abbreviations in NZ for Auckland. Akld guy (talk) 23:41, 18 February 2017 (UTC)[reply]

Apologies for mis-reading your username. DrChrissy ^(talk) 00:03, 19 February 2017 (UTC) [reply]

Now, if your name was aphid guy you could weigh in authoritatively on this question pertaining to animal intelligence... Bus stop (talk) 00:58, 19 February 2017 (UTC)[reply]

Spider and snake

About this video: http://videos.elmundo.es/v/0_ynih8y9m-esta-arana-acaba-con-una-serpiente-10-veces-mas-grande?uetv_pl=virales&count=1 What kind of spider is this and what is she planning to do with the snake, eat it somehow?? Thanks, --ZygonLieutenant (talk) 16:39, 17 February 2017 (UTC)[reply]

I tried three times on two different browsers, and got a "connection error" on the video every time. If you can find another copy of the video hosted elsewhere, or can tell us where it originally appeared, that might help.

However, there's a decent chance you saw this video [11] of an Australian redback spider attacking a snake, though the version I link ends before the snake is clearly dead. The video clip is understandably very popular, and has been shooting all around the internet the past few days, so I think that might be what you saw. SemanticMantis (talk) 19:36, 17 February 2017 (UTC)[reply]

_{Ummm yes it's the same video and it's faked. Blooteuth (talk) 19:03, 17 February 2017 (UTC)}[reply]

Is that your opinion, or do you have some reference to support the claim? Are you claiming it's not a spider? Or not a redback spider Or not a snake? Or that it is a spider and a snake but the spider is not at Can you explain what you mean by that, and give references if possible? Also, you have interjected you comment in the middle of my post, in violation of WP:THREAD. Please follow our guidelines, they help us keep things intelligible and organized here. Rather than move all the related comments around, I will simply sign again above, but please don't make extra work for us. SemanticMantis (talk) 19:08, 17 February 2017 (UTC)[reply]

I was just about to reply supporting Blooteuth. My opinion, and it is only opinion, is that the video is likely to be faked. I lived in Australia for 12 years and have plenty of experience of red-backs. The one in the video looks absolutely ENORMOUS. Our Redback spider states "Females have a body length of about 10 millimetres (0.4 in), while the male is much smaller, being only 3–4 mm (0.12–0.16 in) long." The beast in the video looks very much larger than this. DrChrissy ^(talk) 19:15, 17 February 2017 (UTC) [reply]

I have no strong opinion on this specific video, but have no problem believing such a thing could happen, given the descriptions in the ref I just posted below. I agree the spider looks a bit bigger than 10mm, but the angles are odd, and there is considerable variance in female size [12] SemanticMantis (talk) 19:18, 17 February 2017 (UTC)[reply]

Oh, I agree this behaviour could happen, I'm just not sure about this particular video. It's a shame there were not more objects in the background to help judge size and perspective. Or better still, a person in a white lab coat placing a ruler by the side of the spider, perhaps with a running commentary about how many of her mates she had eaten in the last month! ;-) DrChrissy ^(talk) 19:52, 17 February 2017 (UTC)[reply]

As for the second question: some spiders can and do eat snakes sometimes. The spider venom of some species can act to essentially liquify the interior of prey, letting the spider suck out all it wants (some additional info here [13]). See here [14] for a similar example. SemanticMantis (talk) 18:18, 17 February 2017 (UTC)[reply]

re the Daily Mail story: I'm not sure I have heard of red-backs throwing their web at potential prey. I know some spiders hunt a little like this (see bolas spider) but I always thought the red-back was a sit-and-wait character. DrChrissy ^(talk) 19:07, 17 February 2017 (UTC)[reply]

Yeah, I wouldn't vouch for anything the DM says with respect to biology. However, this review article [15] says, with additional reference "Latrodectus hasselti spiders enjoy a varied diet, trapping some 60-70% of beetles as well as other kinds of insects, spiders, small mice and occasionally lizards which blunder into their sticky trap lines." It continues to describe how the spider incapacitates prey by "squirting a swathe of viscous silk over its target." The article does not specifically describe snakes being caught in this manner, but to me, it's not hard to believe that a spider that can catch lizards can also catch a small or even (perhaps rarely) medium-sized snake. SemanticMantis (talk) 19:17, 17 February 2017 (UTC)[reply]

Great reference - thanks very much. DrChrissy ^(talk) 19:25, 17 February 2017 (UTC)[reply]

The video got an article on National Geographic's website. [16] 209.149.113.5 (talk) 19:50, 17 February 2017 (UTC)[reply]

Thanks! They don't seem very skeptical... SemanticMantis (talk) 20:17, 17 February 2017 (UTC)[reply]

Looks like there's a fishhook holding the snake in place. Justin15w (talk) 20:12, 17 February 2017 (UTC)[reply]

February 18

What is the difference between IS:733 and IS:736

Dear all, Kindly clarify what is the difference between aluminum alloy standards as mentioned in Indian standards Is:733 and Is:736. for example i am giving manufacturing drawing for a milled box sizing 60x60x40 mm. Should i mention material to be as per IS:733 or IS:736. Ex: 1.Material:Aluminium alloy To IS:(733 or 736),Grade:64430-T6 Please clarify SD — Preceding unsigned comment added by Sameerdubey.sbp (talk • contribs) 03:55, 18 February 2017 (UTC)[reply]

Please note: Someone here might be able to tell you something about the difference between the standards, but you should understand that we cannot tell you what you "should" do. We're not here to give advice, only information, and legal advice is something we have specifically decided we're not competent to give. We are very unlikely to have someone around with real competence regarding technical points of Indian law, and even if someone here says they do, we have no way to verify he is telling the truth. Wnt (talk) 10:04, 18 February 2017 (UTC)[reply]

One is for aluminium bars, rods and sections - the other is for aluminium plate. Use the one relating to the type of aluminium that will be used to manufacture whatever you are designing. If you start with aluminium sections (which would seem probable if your box is milled), it will be 733 - if you start with aluminium plate, it will be 736. Wymspen (talk) 12:29, 18 February 2017 (UTC)[reply]

Scientific coincidence

The Titius–Bode law is an example of a scientific coincidence. Are there other examples of scientific coincidence apart from it? --IEditEncyclopedia (talk) 15:09, 18 February 2017 (UTC)[reply]

I am a little confused. What is the difference between "scientific coincidence" and "coincidence"? DrChrissy ^(talk) 16:05, 18 February 2017 (UTC)[reply]

The OP may be looking for other examples of apparent scientific laws that have turned out to be rules that don't really apply. An example is Vitalism, the notion that living organisms are fundamentally different from non-living entities because they contain some non-physical element or are governed by different principles than are inanimate things. It was discredited by Friedrich Wöhler's discovery in 1828 that Urea can be produced from inorganic starting materials. See the article about Superseded scientific theories for other examples. Blooteuth (talk) 17:09, 18 February 2017 (UTC)[reply]

Dirac large numbers hypothesis may be of interest. Loraof (talk) 17:38, 18 February 2017 (UTC)[reply]

A famous example is that a total solar eclipse is just possible. Solar eclipse#Types says: "The Sun's distance from Earth is about 400 times the Moon's distance, and the Sun's diameter is about 400 times the Moon's diameter. Because these ratios are approximately the same, the Sun and the Moon as seen from Earth appear to be approximately the same size". It has been called a sign that God designed it. If you believe more in science and an old universe then the Moon is moving slowly away from Earth so the coincidence is the current distance. PrimeHunter (talk) 18:05, 18 February 2017 (UTC)[reply]

Did you know total solar eclipses would be impossible if the orbits were perfect? An averagely far Sun is 0.533° wide and the closest you can get to an averagely far Moon makes it 0.527° wide (both sea level and in an aircraft). The only thing making total solar eclipses possible at low Earth orbit or below is that the Moon is sometimes closer than average (less often, the Sun being further than average is sufficient) Sagittarian Milky Way (talk) 19:51, 18 February 2017 (UTC)[reply]

See also Mathematical coincidence#Fine-structure constant. The article mentions other examples from the physical world but they rely on units invented by humans. PrimeHunter (talk) 18:13, 18 February 2017 (UTC)[reply]

Can dogs and cats eat cooked foods?

What happens if they are fed cooked foods? Are they really carnivores? Why do packaged pet foods contain fruits and vegetables? Can they be fed peas and carrots? 166.216.159.13 (talk) 15:40, 18 February 2017 (UTC)[reply]

Regarding dogs. Please read our article Dog food. Dogs are usually classified as carnivores but contrary to popular use of the term, as the article Carnivore explains, this does not mean they eat only meat, rather, carnivores get their requirements from a diet consisting mainly or exclusively of animal tissue. Dog food also explains dogs can eat cooked meat - most tinned dog food is cooked. They can also be fed a vegetarian diet. DrChrissy ^(talk) 15:59, 18 February 2017 (UTC)[reply]

Regarding my Cat. 1) Eats it, asks for more and never says thank you. 2) He's a facultative carnivore not an obligate carnivore, but why bother hunting prey when master serves Cat food (see article) that may indeed contain some plant matter, just as long as no one seriously expects to convert this cat to Vegetarianism? Blooteuth (talk) 16:52, 18 February 2017 (UTC)[reply]

Why are you stating the cat is a facultative carnivore when there is a multitude of scientific papers stating they are obligate carnivores, e.g. [17]? DrChrissy ^(talk) 17:03, 18 February 2017 (UTC)[reply]

Yes, CATS ARE OBLIGATE CARNIVORES. IT IS COMPLETELY INCORRECT TO SAY THEY ARE FACULTATIVE CARNIVORES, AS SHOWN BY NUMEROUS RELIABLE SOURCES LINKED ABOVE AND BELOW. Please forgive my typographic emphasis - this is important, and an issue of animal welfare, so I wanted to make it unmistakably clear for any casual reader :) SemanticMantis (talk) 23:26, 18 February 2017 (UTC)[reply]

This vegan cat food site admits "Some cats have a more difficult time adapting to a vegan diet than others". Note that domestic cats know only what they like and not what is good for them, which is why they are liable to ingest things that do them no good, such as Melamine in wheat glutin (see 2007 pet food recalls) and lactose in cow's milk that gives pussy Diarrhea. See also. Blooteuth (talk) 17:29, 18 February 2017 (UTC

I really don't think it is appropriate on a sci-ref desk to try and counter my RS with information from web-site advertisements. Please could you provide an RS that states cats are facultative carnivores. DrChrissy ^(talk) 18:10, 18 February 2017 (UTC)[reply]

Cats are natural carnivores which occasionally eat some vegetable matter such as grass. ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:26, 18 February 2017 (UTC)[reply]

Dogs also eat plant matter but they are classified as carnivores. Cats are classified as "obligate carnivores" for a scientific reason. If we are going to bend or misuse these scientific terms on this REFERENCE desk, the least we owe our readers are RS to support the terminology we use when this clashes with other RS. RS please. DrChrissy ^(talk) 18:31, 18 February 2017 (UTC)[reply]

Both cats and dogs are members of the order carnivora, but that is an evolutionary classification that does not necessarily have anything to do with current culinary requirements or preferences. Cats are obligate carnivores because they rely on external sources of arginine and taurine. Arginine is primarily sourced from meat, and AFAIK there is no significant natural vegan source of taurine. If a cat's nutritional needs are met, they can, of, course, eat some additional plant food. Most of that is not poisonous to cats, it just does not meet their requirements. Dogs, on the other hand, can live on a mostly vegetarian diet - indeed, some of the key genetic differences between wolves and dogs relate to the efficient digestion of starchy foods in dogs. --Stephan Schulz (talk) 19:07, 18 February 2017 (UTC)[reply]

Our article on taurine says that about 3,000 tons of it are synthesized annually for addition to pet foods. I may not be a fan of veganism but I can't say no to a good chemistry experiment on animals. ;) Wnt (talk) 19:40, 18 February 2017 (UTC)[reply]

Point taken and qualifier inserted above. --Stephan Schulz (talk) 19:44, 18 February 2017 (UTC)[reply]

I feel it is required to point out that cats are obligate carnivores, as any reliable source will tell you. This means forcing them into a vegan or even vegetarian diet is highly unnatural at best, and really can only be described as animal cruelty. It will lead to deficiencies in taurine (causing retinal degeneration and cardiomyopathy), arginine (causing dangerously high blood ammonia levels), arachidonic acid and other essential fatty acids (causing problems with liver, kidney, skin and more), and other essential nutrients such as iron, calcium and phosphorus. Lack of meat also screws with cats' urine pH, possible causing kidney stones, and the high carbohydrate nature of vegetarian/vegan foods puts them at risk of diabetes. Vegan diets would need extensive supplementation to be even remotely healthy for a cat. The link provides by User:Blooteuth is incorrecnt. The company is either lying for the economic benefit of their company, or incredibly ignorant. Dogs are of course essentially omnivores, and are much more flexible when it comes to diets. Fgf10 (talk) 20:52, 18 February 2017 (UTC)[reply]

This reference is a very accesible analysis of why dogs are classified as "carnivores" and cats as "obligate carnivores"-VERONIQUE LEGRAND-DEFRETI. Proceedings of the Nutrition Society (1994), 53, 15-24. Differences between cats and dogs: a nutritional view. DrChrissy ^(talk) 20:57, 18 February 2017 (UTC)[reply]

Excellent link, should have looked for something like that, rather than type out that whole rant. Much obliged for the reference. Fgf10 (talk) 21:06, 18 February 2017 (UTC)[reply]

Absolutely no problem at all - that is what this ref-desk is for. Your post was not a rant - it was a clearly informed contribution to the discussion which is always welcome. DrChrissy ^(talk) 23:45, 18 February 2017 (UTC)[reply]

You can feed your pets some vegetables as snacks, but there are some you should never feed them. The ASPCA has a decent list here: link EvergreenFir (talk) 17:09, 18 February 2017 (UTC)[reply]

Cats are obligate carnivores, but vegetable products are added to cat food to provide fiber and nutrients that they would get in the wild from animal sources. For example, they get fiber from hair and feathers, but that is replaced with plant fiber in cat food. They also require a lot of fat in their diets, and can be harmed by garlic, onions, and other ingredients commonly added to human food. Also, they do not require vitamin C in their food, as their body manufactures it and unlike humans, they need complete proteins in their diets as they cannot manufacture them from amino acids. That's why you should not feed cats table scraps. Dogs are much closer to humans in their diets, which is why dog food is different from cat food. TFD (talk) 20:38, 18 February 2017 (UTC)[reply]

I don't understand people who try to feed their cats a vegan diet. Is it an UMC thing? Lady, if you need to virtue-signal to your SWPL friends, adopt a baby from Africa or something, just stop abusing the cat Asmrulz (talk) 23:39, 18 February 2017 (UTC) [reply]

This post is absolutely no help whatsoever to this thread and I ask an uninvolved editor to strike it or perhaps place it in a collapsible box. DrChrissy ^(talk) 23:57, 18 February 2017 (UTC)[reply]

You should discuss this on the user's talk page rather than screwing around with his edit here. ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:12, 19 February 2017 (UTC)[reply]

To address some of the other Q's:

1) There's nothing in being a carnivore which requires eating raw food.

2) As for adding fruits and vegetables, they may provide needed dietary fiber. In nature, eating a mouse would likely include it's (vegetarian) intestinal contents, so a bit won't hurt. Also, such a pet food may sell better, if people think it's better for their pet, regardless of if it really is. In the past, they've included things like sawdust for fiber, sometimes disguised as "cellulose", but that just sounds bad and turns off potential buyers. StuRat (talk) 23:55, 18 February 2017 (UTC)[reply]

Scientific American "Veggie Cat Food? Why Not All Cats Need Meat" The vegetarian pet debate is a contentious one among vegetarian pet owners and veterinarians and is one not likely to go away anytime soon.

Web MD says If you are considering a vegan or vegetarian diet for your dog or cat....Only consider or feed commercial diets that have gone through feeding trials and meets the requirements for AAFCO (Association of American Feed Control Officials) compliance.

In some medical cases (allergies, liver or bladder disease) veterinarians use specially formulated pet foods only available by prescription that are made from nonmeat protein sources (egg or soy, for example). Blooteuth (talk) 00:11, 19 February 2017 (UTC)[reply]

Antidepressant vs recreational drugs

In as much as I understand it, most, but not all, antidepressants focus on serotonin—I do not profess to know the mechanism. However, recreational drugs seem in most, but not all, cases to focus on dopamine. Why the discrepancy?--Leon (talk) 18:28, 18 February 2017 (UTC)[reply]

They're different neurotransmitters that do different things. See Neurotransmitter#Examples_of_important_neurotransmitter_actions for a cursory overview. Shock Brigade Harvester Boris (talk) 19:24, 18 February 2017 (UTC)[reply]

Yes, but both antidepressants and recreational drugs are used for, in very broad terms, to help people "feel better", or at least "less bad". So one might expect them to work with the same neurotransmitters in more cases than not.--Leon (talk) 19:36, 18 February 2017 (UTC)[reply]

It depends on what neurotransmitter you want to mess with. Some depressed patients in a clinical setting respond positively to Dopamine reuptake inhibitors others need Norepinephrine–dopamine reuptake inhibitors. Some street drugs mess with your serotonin levels and druggies choose, MDMA, aSerotonin releasing agent.

I believe that in many cases where your split (in antidepressant/serotonin and recreational drug/dopamine) is wrong. — Preceding unsigned comment added by Hofhof (talk • contribs) 20:03, 18 February 2017 (UTC)[reply]

So, if someone needs serotonin but not dopamine, does that suggest, albeit weakly, that they may not enjoy e.g. heroin?--Leon (talk) 20:18, 18 February 2017 (UTC)[reply]

If someone is low on serotonin to a pathological level, he will enjoy heroin and can get easily addicted to it. Heroin messes with a lot of neurotransmitters, including serotonin. Source: [18]. Also remember that depressed people can have panic attacks or not be depressed all the time. Heroin will be pretty enjoyable for them. Hofhof (talk) 20:33, 18 February 2017 (UTC)[reply]

The dirty truth that us neuroscientists don't like to say very often is that we really don't know anything about depression. The use of serotonin modulating drugs comes from observations of low levels of breakdown products of serotonin in the cerebrospinal fluid some (not all) depressive patients, and the clinical improvement some (again, not all) patients see when prescribed serotonin modulating drugs. However, we don't know why serotonin is down in some patients, we don't know how serotonin alters mood, and we don't know why some patients don't respond to serotonin modulating drugs. Of course, the pharmaceutical industry has made good money on selling their SSRIs, so will glance over these minor details. Why we don't know more is a long and ugly story, but it has a lot to do with our inability to really model depression in animals models. What we do know is that for some patients, cognitive therapy, exercise , or other drugs such as mentioned above, work a lot better than SSRIs. Hell, in some trials even placebos work as well.

As for dopamine and recreational drugs, dopamine is crucial for the reward system in the brain. It is thus involved in 'pleasure' and positive reinforcement. Fgf10 (talk) 21:04, 18 February 2017 (UTC)[reply]

Interesting on all counts...

Perhaps a slight digression: I've read conflicting accounts on the possibility of not enjoying opioids. Some people believe it is almost impossible because "everyone" likes dopamine, but some people seem to dislike opioids. How is it possible if dopamine feels good?--Leon (talk) 21:11, 18 February 2017 (UTC)[reply]

Also Fgf10, whilst you are explicit on some points, it is not at all clear on what you or the establishment has to say about the role of serotonin. Is it necessary for the feeling of pleasure, or not?--Leon (talk) 21:34, 18 February 2017 (UTC)[reply]

The first problem with answering that question is to define 'pleasure'. Human affection is a mess of complex processes, which are poorly defined, and the neural basis for even a single of those processes is generally poorly defined. We know a lot of effects of serotonin, see for instance serotonin syndrome. You'll note everything mentioned in that article is a physical property, such as body temperature and pupil diameter, which are easily measured. How do you measure pleasure? In humans, this is normally done with questionnaires, which are a poor measure of anything. To directly measure the effects of serotonin on pleasure (whatever your definition), you'd have to drastically alter the levels and measure the effects. This is essentially impossible in healthy humans (for practical and ethical reasons). Therefore we usually do these experiments in animals and try to extrapolate the results. However, if measuring 'pleasure' in humans is difficult, try doing it in animals. We're stuck with poor proxy measures such as (an)hedonia, measured by preference for sweet foods etc. Long story short, we don't really know how serotonin affects mood. That is does seems true, as raising serotonin levels in depressive patients often elevates mood. Your question perfectly illustrates how seemingly simple questions are still really difficult to asnwer. Good things they are, or I'd be out of a job! Fgf10 (talk) 23:08, 18 February 2017 (UTC)[reply]

Killing a tree without copping it down

Would drilling a hole into a tree and pouring weed killer into the hole kill it? — Preceding unsigned comment added by 189.201.241.54 (talk) 19:22, 18 February 2017 (UTC)[reply]

Check out girdling. EvergreenFir (talk) 19:27, 18 February 2017 (UTC)[reply]

You would probably need to drill several holes at various points around the circumference to have the same effect as girdling. Both glyphosate and hormone weedkillers such as 2,4-Dichlorophenoxyacetic acid can be used to kill trees in this way. Another method is a circle of copper nails. Dbfirs 20:54, 18 February 2017 (UTC)[reply]

Stage of development when freezing developing humans

Up to what stage (and why not further) can you freeze a developing human? I assume that's past being a zygote, but before turning into a baby. Where and how can you determine the limit?--Hofhof (talk) 20:10, 18 February 2017 (UTC)[reply]

This is just a guess but I would imagine it is the point just before when cells need chemical signals to instruct them to start specializing into liver cells, brain cells, arms and legs etc., (thalidomide interferes with the chemical instructions needed for newly forming cells).--Aspro (talk) 21:40, 18 February 2017 (UTC)[reply]

Embryo cryopreservation may be a good starting point. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:40, 18 February 2017 (UTC)[reply]

Illnesses from indirect accidental consumption of animal faeces during outdoor activities

Are there a lot of known cases of people who do outdoor activities in first world countries becoming ill from indirect consumption of animal faeces? For example they touch something with traces of animal faeces (maybe touching equipment which has touched it) and consume food with their hands. 2A02:C7D:B957:3B00:74AC:C58F:30BC:44E2 (talk) 23:52, 18 February 2017 (UTC)[reply]

Define "a lot". Foodborne illness often results from consuming something contaminated with fecal matter, though I'm not sure this has any particular correlation with "outdoor activities". There are reasons other than fecal contamination to wash your hands; your hands can carry other pathogens such as influenza and bacteria that can infect wounds (like ones you might get from outdoor activities). --47.138.163.230 (talk) 00:29, 19 February 2017 (UTC)[reply]

February 19

I'd like to have my car tires vulcanized .......... by Buster Keaton's mechanic

youtu. be/UWEjxkkB8Xs?t=2m31s

In an unnamed Buster Keaton movie, bad guys are after him and he tries to hitch a ride by sitting on a car's rear spare tire. The car drives away and Keaton finds himself remain in the same place. The spare tire is actually used as a roadside sign placed behind the car with a cardboard saying "Vulcanizing" and an arrow pointing to the shop.

Did people of the 1920s really have to have their car tires vulcanized by someone? -- Toytoy (talk) 01:55, 19 February 2017 (UTC)[reply]