Wikipedia:Reference desk/Archives/Science/2013 June 16

= June 16 =

Conscious control of breathing
In our aquatic ape hypothesis article is the claim that "humans also have a considerable amount of control over their breathing, which is an involuntary reflex for most terrestrial mammals.[21][27]" I can't access either of the two references, so how do scientists know whether other animals can consciously control their breathing? It's not as if we can talk to a dog and ask him to hold his breath. --50.125.164.7 (talk) 07:07, 16 June 2013 (UTC)


 * The sentence you quote doesn't imply that other animals cannot consciously control their breathing. It's an "involuntary reflex" for humans too. Many terrestrial mammals (including dogs as well as the numerous aquatic mammals) are excellent swimmers, which requires control of the beathing.--Shantavira|feed me 07:45, 16 June 2013 (UTC)


 * I think the study specifically refers holding one's breath, to enable submersion. Plasmic Physics (talk) 08:00, 16 June 2013 (UTC)


 * Even so, I know of diving dogs. Plasmic Physics (talk) 08:00, 16 June 2013 (UTC)


 * A few points. It might be partly an involuntary reflex for humans, but not entirely. If I'm in a pool and I know I'm going to put my face in the water, I will consciously hold my breath. Some dog's certainly do it too. But the real marine mammals such as seals, whales and dolphins have a bigger advantage. They can close their nostrils. Kinda wish I could do that. HiLo48 (talk) 08:25, 16 June 2013 (UTC)
 * @HiLo48 buy yourself a noseclip. Roger (Dodger67) (talk) 11:05, 16 June 2013 (UTC)
 * To parallel what a seal can do I'd need one with telepathic controls. HiLo48 (talk) 12:09, 16 June 2013 (UTC)
 * I can close my nose if I inhale hard and quick enough. Of course, inhaling hard underwater isn't smart. An electronic remote controlled noseclip would work nearly as well, I suppose, and more easily than telepathy. InedibleHulk (talk) 21:42, 16 June 2013 (UTC)
 * Just because animals like dogs can swim, doesn't mean that they have conscious control of breathing - it could just be an involuntary reflex to the face getting wet. Our Mammalian diving reflex article says this explicitly: "Every animal's diving reflex is triggered specifically by cold water contacting the face – water that is warmer than 21 °C (70 °F) does not cause the reflex, and neither does submersion of body parts other than the face.  Also, the reflex is always exhibited more dramatically, and thus can grant longer survival, in young individuals." - and our Primitive_reflexes article says that human infants can swim from birth using only reflexive behaviors...and Reflex says that the diving reflex is present in all humans.
 * Moreover, dogs can easily be observed to inhale sharply before barking - and barking certainly appears to be a conscious decision because you can train a dog to bark on command. You could argue, perhaps, that they make a conscious decision to bark - and that the necessity of taking a breath first is still an involuntary matter - but if you get into the realms of "in order to perform some conscious act, the involuntary systems must first intervene" - then it becomes hard to decide what is truly a conscious act and what isn't - even in humans.
 * Worse still, it all becomes a fuzzy line anyway. There is no sharp line between the conscious and the involuntary reflex:  I decide (consciously) that I wish to walk across the room - but I don't consciously consider how to shift my balance and move my feet to do that.  So walking has become as subconscious as breathing.
 * But what about driving to work? I don't consciously think about how to move my feet to operate clutch and gas pedals when shifting gears - I don't think I consciously consider when to shift gears either.  I certainly haven't "evolved" to develop special brain circuits for driving a car - and at one time, back when I was learning to drive, this was an entirely conscious activity.  So what I choose to have conscious control over - and when - is a learned behavior and being in the right gear for my car to operate optimally can now occur at a subconscious level.   When I was teaching my son to drive stick-shift, I found myself unable to explain the precise sequence of pedal actions when shifting gears without first watching myself do it!
 * Sure, conscious behavior *can* take over those things - but mostly, my conscious mind can be thinking about something entirely different while my subconscious takes control of the mundane tasks.
 * The aquatic ape hypothesis is widely regarded as a load of hogwash - so the things it claims do not have to be rationalized! SteveBaker (talk) 13:20, 16 June 2013 (UTC)


 * Note that the sentence quoted by the OP doesn't use the word "conscious" -- for good reason, it's really irrelevant in this context. The practical issue is simply whether various animals are capable of holding their breath, that is, inhibiting breathing while closing off their air passages.  Whether they can do it in response to instructions is not relevant to their ability to dive. Looie496 (talk) 13:38, 16 June 2013 (UTC)
 * The article may not make this clear - but the original aquatic ape hypothesis uses this "conscious control of breathing" idea to explain all sorts of things - such as our ability to talk. We needed to evolve to swim in order to switch to a fish-based diet, we needed conscious control of breathing in order to do that, we were better able to develop speech with conscious breath control.  But that's really nonsense on several levels - firstly that conscious control of breathing is necessary for swimming (it's not - the mammalian dive reflex provides a means to do that reflexively) or that mammals in general don't have this conscious control ability (watch a dog barking to realize that they do). SteveBaker (talk) 00:43, 17 June 2013 (UTC)
 * Actually I'm quite fond of the aquatic ape idea in a weaker form. The Okavango Delta is part of an ancient lake in a region with dramatic yearly climate change.  Part of the year it is dry desert, part of the year it is a vast area of waist-deep flooding.  Chacma Baboons learned to stand upright there.  Lechwe antelope developed elongated feet (like ours?).  Every year there are massive fires that leave behind cooked meat, for those clever enough to avoid them.  The place seems like the mold that humanity could have been stamped from, and part of that is dealing with life largely in the water for part of the year. Wnt (talk) 01:25, 18 June 2013 (UTC)

electron spin reversal
in a direct current circuit that is initiated by a plasma field why does the circuit preform its normal circuit path ,but also operate on a one wire system in the off position and when operating in the one wire off position the batterys in the d c circuit seem to recharge themselves the question is ,are the characteristics of the diode changing or is the a reversal of polarity happening in the battery cell material itself causing this unusual characteristic  50.93.30.1 (talk) 18:46, 16 June 2013 (UTC) or are both conditions of the circuit changing .50.93.30.1 (talk) 19:11, 16 June 2013 (UTC)
 * I'm not sure I understand your question, but I think by "electron spin" in the question title, you're not actually referring to the quantum mechanical spin of an electron, but rather an apparent reversal of the flow of electrons within the circuit in question. If I'm understanding you correctly, I think you're asking why the battery appears to become somewhat recharged when you switch off the normal flow of current in a circuit containing a battery and a gas-filled tube acting as a diode.  There wouldn't actually be a reversed current flow in such a circumstance, since no current flows around an open circuit.  Rather, I think what you are seeing is the voltage recovery effect that some types of batteries have, in which the battery appears to regain a bit of its charge when the battery goes for a little while without a current being drawn from it.  The effect is most pronounced after drawing a large current from the battery, as would be the case if you're discharging the battery through a forward-biased diode without using a resistor to limit the current.  I unfortunately can't seem to find a Wikipedia article discussing the recovery effect in batteries, but you can read an excerpt from a book that briefly mentions the effect if you click on this link and scroll down a bit to the section entitled "Battery Peculiarities: Voltage Recovery".  Red Act (talk) 02:31, 17 June 2013 (UTC)

what makes earths seasons
QBold text — Preceding unsigned comment added by 68.115.48.41 (talk) 22:28, 16 June 2013 (UTC)


 * Mainly the axial tilt of Earth which during a year changes the time from sunrise to sunset when you are not on the Equator. See more at Season. PrimeHunter (talk) 22:39, 16 June 2013 (UTC)


 * The angle of the sun to the ground makes a huge difference to how much heat it provides. That's why it's hotter at the equator than at the north and south poles - and why the middle latitudes are somewhere between those extremes.  At the equator, the sun is almost vertically overhead around noon - but when you're closer to the poles, it scarcely rises above the horizon.   The seasonal variation is caused by the fact that the earth's axis of rotation is tilted.  So at some times of year, the northern hemisphere is tilted towards the sun during the day and the southern hemisphere is tilted away.  That makes for summer in June/July/August in the northern hemisphere when those are the winter months in the south.  Six months later...in December/January/February, the earth has moved around to the opposite side of it's orbit and the positions are reversed making it winter in the north and summer in the south.  That axial tilt simply makes the sun be higher or lower in the sky depending on the time of year - which accounts for the temperature variation.  Some seasons are rainier or drier than others  SteveBaker (talk) 00:37, 17 June 2013 (UTC)

Nosecones on airliners and fighter jets
I suddenly wondered why the difference between nosecone shapes on passenger and fighter jets - the article says the simple cone is easier to construct, but hints that it isn't very aerodynamically efficient - seems odd, since companies that makes fighter jets have money to burn... Is it possible they use the simple cone because it looks more badass? The friendly ellipse or whatever it is of passenger jets is certainly less weaponish in appearance... Adambrowne666 (talk) 22:44, 16 June 2013 (UTC)


 * I don't see any fighter aircraft with true "cones" (ie simple, circular cross-section, straight-sided) - they all seem to have curved sides to some degree. The optimum shape is a symmetrical "volume of revolution" - and the exact shape depends on the speeds that the aircraft is expected to travel and whether top speed or best fuel economy is the goal.  Nose cone design goes into this in incredible detail.  That said, not all aircraft have optimal drag coefficient as a goal - some have to accommodate equipment such as cameras and radar gear in there - others have to be stealthy and have a minimal radar profile.  There are dozens, perhaps hundreds of variables determining the best shape, so it should be no surprise that there is a wide variety of shapes out there.  However, I'm very sure that "looking badass" isn't one of them - and "ease of construction" is an unlikely goal compared to all of the other things (such as engines and instrumentation) that cost so much to manufacture. SteveBaker (talk) 23:28, 16 June 2013 (UTC)


 * I don't think the article suggest this. The shape may deviate from the ideal in order that is protects the avionics but the reasons are never to make the aircraft look badass. It is not the 'look' of a fighter aircraft that makes it effective but its actual in combat effectiveness. Consider the Fairey Swordfish. Saw service in during WWII and it was a biplane. Yet, it could spoil your whole  day if it dropped its load on you.--Aspro (talk) 23:31, 16 June 2013 (UTC)


 * @Aspro: from the article: A very common nose cone shape is a simple cone. This shape is often chosen for its ease of manufacture, and is also often (mis)chosen for its drag characteristics. - but I was assuming the fighter jet nosecone is a simple cone, which SteveBaker points out it isn't.Adambrowne666 (talk) 23:36, 16 June 2013 (UTC)


 * The fundamental reason for different shapes is the intended operating speed. Airliners operate at subsonic speeds, where a 'blunt ellipse' is the optimum shape, whereas jet fighters are designed for transonic and supersonic speeds, where a more pointed shape is better. AndyTheGrump (talk) 23:40, 16 June 2013 (UTC)


 * Thanks, Andy - yes, that makes sense - I thought I was onto something - some semiotic reason for the pointy tip on fighters... Adambrowne666 (talk) 23:55, 16 June 2013 (UTC)


 * “This shape is often chosen for its ease of manufacture” A defence contractor usually gets a contract based on development cost plus 20% profit. “Ease of manufacture” doesn’t come into it at all. If it is technically feasible they will push to  incorporate it. Flight duration and max  speed  is a very important parameter.  The tax payer then pays for it. So it is shaped... however the aircraft designers (defense contractors) think it should be shaped. Passenger aircraft (with exception of Concord) are sub or transonic. So they don't benefit from these type of cones.  Don't believe everything you read on Wikipedia. Take it from me, I know some of the editors that contribute!--Aspro (talk) 02:22, 17 June 2013 (UTC)


 * The whole "to make them look more badass" idea is probably upside down. They only look like noses of planes which are known to be badass. If the planes which featured this kind of nose had not been successful, we wouldn't associate their shape with speed, nor any other kind of badassitude (is that a word???) - ¡Ouch! (hurt me / more pain) 10:19, 17 June 2013 (UTC)


 * If it's not a word, it SHOULD be! How does one nominate a word for "Best New Word of the Year"? 24.23.196.85 (talk) 20:06, 17 June 2013 (UTC)
 * It's not even the best I can think of. I should go ahead and post some on my user page - unless a WP: rule says I cannot do that. Then my talk page will have to do. - ¡Ouch! (hurt me / more pain) 07:06, 18 June 2013 (UTC)
 * The technology concealed within will often lead to some rather odd shapes. I believe that the Hawker Siddeley Harrier GR3 had a forward looking infrared sensor, while others have air-to-air radar scanners. Alansplodge (talk) 12:53, 17 June 2013 (UTC)
 * Our F-106 and F-4 fighters also had FLIR sensors installed along with the normal air-intercept radar, but that didn't influence the shape of their nosecones in any significant way. 24.23.196.85 (talk) 20:09, 17 June 2013 (UTC)


 * You can find all sorts of weird nose cones out there - the F117 nose...erm..."wedge" for example is an aerodynamic disaster area - but it keeps the aircraft stealthy - and that's what matters most. Curved surfaces are a very bad thing for keeping a low radar cross-section, and nose cones are amongst the worst offenders. SteveBaker (talk) 13:14, 17 June 2013 (UTC)

