Wikipedia:Reference desk/Archives/Science/2011 September 21

= September 21 =

Highest internal temperature of cold blooded animals
What is the highest internal temperature cold blooded animals (Ectotherms) can tolerate from their external environment and can warm blooded animals tolerate a higher internal and external temperature? --DeeperQA (talk) 00:49, 21 September 2011 (UTC)


 * I would expect that cold-blooded animals can withstand a higher internal temperature. After all, they are designed to handle a wider range of internal temperatures.  However, that doesn't necessarily mean they can withstand higher external temps, since warm-blooded animals may have more effective cooling methods, like sweating. StuRat (talk) 02:54, 21 September 2011 (UTC)
 * Okay, so what would be the dividing line? At what temperature would warm blooded survive and cold blooded would not? --DeeperQA (talk) 04:08, 21 September 2011 (UTC)
 * There isn't really a strong dividing line; animals like the sloth tend to blur it. --  T H F S W  (T · C · E) 05:14, 21 September 2011 (UTC)


 * It sounds like the question is more relevant to Poikilotherm and Homeotherms rather then cold or warm blood. In particular this image. Vespine (talk) 05:45, 21 September 2011 (UTC)


 * If I'm reading that chart correctly, mammals do better than reptiles with internal temperatures over 35°C, reptiles go dormant at 37°C, and mammals go dormant at 42°C (but, in the case of mammals, the exterior temp could be quite a bit higher before their internal temp would reach that). So, that seems to say that mammals can tolerate both higher internal temps (which surprises me) and external temps (which doesn't). StuRat (talk) 03:31, 22 September 2011 (UTC)


 * You might like to read Boiling frog, though the article doesn't really answer any questions.   D b f i r s   08:40, 21 September 2011 (UTC)


 * It depends on your definition of animal; extremophile lists some simple invertebrates that can live in extreme situations; the tardigrade can survive temperatures up to 151 C. --Colapeninsula (talk) 14:14, 22 September 2011 (UTC)

You've got to figure that the very few reptiles and arthropods that can be active at the peak of day in the desert will have the highest active body temperatures. μηδείς (talk) 01:44, 26 September 2011 (UTC)

Moment magnitude conversion
How can I convert a Molment Magnitude measure into a richter scale measure?
 * See the article Moment magnitude scale. For any medium sized earthquake (from say 3.0-6.0 or so) the scales are almost identical.  The Moment Magnitude scale is more accurate for measuring small and large earthquakes than the Ricter scale, so the two scales diverge at either end.  -- Jayron  32  02:32, 21 September 2011 (UTC)


 * When the moment magnitude scale was set up it was intended to match the Richter scale exactly at lower magnitudes, but provide more accurate magnitudes above about magnitude 7 as the Richter scale tends to saturate at around this value. This is because of the measuring technique, with the Richter scale and the related surface wave magnitude and body wave magnitude scales, using relatively short period (i.e. high frequency) waves, while modern seismometers use a wide range of frequencies, capturing the full energy output of the earthquake. Mikenorton (talk) 15:35, 21 September 2011 (UTC)

Earthquake question
It is known that Earthquakes occur when several tectonic plates move relative to each other.The boundry between them are large areas.Then why we say about the points like hypocenter or epicenter and not large areas? — Preceding unsigned comment added by 49.244.180.209 (talk) 02:10, 21 September 2011 (UTC)


 * Because the "slips" happen in relatively isolated locations. Rocks seem very rigid, at least on a human scale, but when measured in continent sized chunks they have some elasticity to them (scientists call this Elastic modulus).  You can think of it this way: When you tear a paper, you don't tear it all at once, you tear it one little point at a time.  An earthquake is generally one little tear happening in one location.  The rocks don't break all along the fault, they tear along it.  -- Jayron  32  02:30, 21 September 2011 (UTC)


 * If the plates moved smoothly past, there would be no quakes. But they "snag" at certain points.  When these break free, you have a quake, centered around the snag. StuRat (talk) 03:08, 21 September 2011 (UTC)

Scientists who deal with earthquakes precisely do not really talk about epicenters. They talk about fault mechanics. For example, this research group, Crustal Deformation and Fault Mechanics, uses geophysical data to model the actual rock behavior more accurately than just a point-source earthquake. You can see some illustrative diagrams of their research; including some nice 3D diagrams of earthquake data. Here is some more work from another researcher, shear dynamics. Today's journalists find a dot on a map easier than a thorough scientific analysis, but if they did a little research, they'd see that earthquakes are actually very complicated, dynamic, volumetric events. Nimur (talk) 23:48, 21 September 2011 (UTC)

why are the pictures of actual size molecules are countable?
how is it that we know so much about the structure of molecules (numbers of atoms (from various kinds in it) or their aesthetic arrangement) but we haven't really see them (i know of only 2 photos of molecules in "reality".

i would like to know about a text-book who contains photos of molecules, i must look in it. i believe that there aren't such photos here in Wikipedia in molecule only because of copyright problems. thanks. 109.66.42.35 (talk) 10:17, 21 September 2011 (UTC)


 * There aren't any photographs possible. Visible light has too long a wavelength to resolve detail on that scale. All that is possible is either a CGI constructed using data obtained by non-optical nanoscopes, or a translated image using an xray crystallography. Plasmic Physics (talk) 10:33, 21 September 2011 (UTC)


 * We can't take photographs of molecules because they are too small compared to the wavelength of visible light, so we have to use indirect methods to infer the details of their composition and structure. Some of these methods are described under Molecular geometry determination in the molecular geometry article. Gandalf61 (talk) 10:37, 21 September 2011 (UTC)


 * One can create images of atoms using a scanning tunneling microscope. That doesn't use light either, but you can definately image individual atoms using the technique.  -- Jayron  32  15:16, 21 September 2011 (UTC)


 * indeed!, we can see individual atoms.. as we all can see in the article atom. so why are the photographs of molecules are so countable (1-2), you could use google to see this 2...thanks. 81.218.145.251 (talk) 15:34, 21 September 2011 (UTC)


 * There are no photographs of individual atoms or molecules. What you see are images created by taking the output from some very fancy electronics and doing a lot of complicated signal processing on it. Gandalf61 (talk) 22:39, 21 September 2011 (UTC)


 * Which is to say, we get into unusual and counterintuitive definitions of "seeing" when we start talking about things the size of atoms or molecules. It's a fair point to say we can visualize them; it's also a fair point to note that this is an especially mediated/manipulated form of visualization. --Mr.98 (talk) 02:03, 22 September 2011 (UTC)


 * Infact I used an AFM just the other day. Plasmic Physics (talk) 23:14, 21 September 2011 (UTC)


 * Thinking: if you're not actually perceiving visually the nanometric objects, then is still right too call it microscopy or nanoscopy? Why not call it micrography or something similiar? Plasmic Physics (talk) 03:10, 22 September 2011 (UTC)
 * There is this, the picture part way down is the letters "IBM" arranged out of individual atoms, I can't find if there is a wiki article about it. Vespine (talk) 03:26, 22 September 2011 (UTC)


 * Still not a photograph. Plasmic Physics (talk) 10:26, 22 September 2011 (UTC)

redundant rails
When travelling on mainline railways I often find that there are long sections of rusty rails between the rails in use. What are the purposes of these? Difficultly north (talk) 11:49, 21 September 2011 (UTC)
 * In the UK it's common to leave old rails (or cut off rails) in the track bed, or next to the track when they have been replaced - this is a management/cost issue where the effort/equipment does not exist to recycle the rails.. (or it is more cost effective to allow this wastage)
 * In some cases what appears to be two rusty rails will be seen between the running rails - these may be fixed to the sleepers (railroad ties) across a rail expansion joint - they are added to add stability keeping the track in allignment at points were there is a gap in the connectivity of the running rails. (I'm assuming you wouldn't have confused what you saw with Gauntlet track).Imgaril (talk) 12:15, 21 September 2011 (UTC)
 * No not Gauntlet track. I am often seeing it anywhere on the National Rail network. Simply south...... creating lakes for 5 years 18:42, 21 September 2011 (UTC)
 * Rails left in the track bed tends to be a temporary thing, either delivered and not yet installed or the old rails awaiting uplift. More often than not, somewhat counter-intuitively, the rusty rails are the new ones. --Tagishsimon (talk) 16:54, 21 September 2011 (UTC)
 * Okay. I'll take a photo of what I mean tomorrow but I think yours sounds more sort of what I'm referring to. Simply south...... creating lakes for 5 years 18:42, 21 September 2011 (UTC)
 * Yup, I'm fairly confident we're talking about the same thing. Installing long welded rail takes time, and track possession times are short, so the job gets broken down into delivery, assembly, installation, dismantling, uplift, etc. --Tagishsimon (talk) 22:45, 21 September 2011 (UTC)


 * I think you're talking about guard rails. They are there to make sure the train doesn't go to the side if it derails. You see them mostly on bridges and other sturctures where a train leaving the track during derailment could cause a lot of damage to nearby structures. Here's a good picture: []. BTW, I remember going through this tunnel as a kid when my folks would take me to New York. The tunnel is in Nay Aug Park in Scranton, PA. Dominus Vobisdu (talk) 16:14, 21 September 2011 (UTC)
 * Sorry, I'm not referring to guard rails. Simply south...... creating lakes for 5 years 18:42, 21 September 2011 (UTC)


 * Did you mean like these ? or these  ?? or even these  ??? . Imgaril (talk) 18:49, 21 September 2011 (UTC)


 * I see loose rails here too, but never on the tracks, that would just be dangerous. They usually lie next to the tracks. Plasmic Physics (talk) 23:11, 21 September 2011 (UTC)
 * I'm not sure anyone has alleged they're on the tracks (meaning on the rails), so much as on the track bed. The first two photos in Imgaril's post are them. --Tagishsimon (talk) 23:15, 21 September 2011 (UTC)


 * I meant track bed. Those rails in the photo clearly serve a purpose. I may not know what it is, but I do know that steel is expensive, and it wouldn't be used if there was no reason. Plasmic Physics (talk) 01:02, 22 September 2011 (UTC)
 * The 'purpose' is explained in the text in the links - the rails are awaiting installation, or waiting to be taken away - as Tagishsimon described. (Unless you meant the photo above right)94.72.237.125 (talk) 01:10, 22 September 2011 (UTC)

How sealed plastic soda bottle tops are attached
I guess this is an engineering-related question. When you first get a bottle such as a 2-liter bottle of soda, the screw-off top is one with the ring that stays at the base of the neck after purchaser rips the cap/ring connection by twisting the cap. How is that cap/ring piece initially attached? Is it rammed on with high force, with the threads of the bottle and the threads on the inner side of the cap just temporarily distorting as they rub past each other? I've also seen metal cap/ring pieces on glass bottles, but metal would seem to be less elastic than most plastics. 20.137.18.50 (talk) 17:39, 21 September 2011 (UTC)
 * The rings have little plastic "wings" on the inside which allow them to be threaded on, but which "catch" when threaded off, thus allowing the ring-and-cap assembly to be put on the bottle, but preventing the ring from coming off when twisted the other way. -- Jayron  32  17:55, 21 September 2011 (UTC)
 * A ratchet effect then?
 * Yes. 70.91.171.54 (talk) 19:02, 21 September 2011 (UTC)
 * I'm fairly certain that the metal ones are placed on as oversize caps, and then cold formed to a tight fit (I'm sure there will be a video of this on youtube, but can't find one as yet). There's an article on these metal ones Screw_cap_(wine) - the links have more info about how they are attached.Imgaril (talk) 18:14, 21 September 2011 (UTC)


 * Those kinds with anti-tamper or lock rings are called PP (pilfer-proof) screw caps. Like Jayron said, notice the teeth inside the bottom-most portion of the cap (the bank) which is only loosely attached to the top. They are all pointing in one direction. When you screw them on, they are flattened against the skirt of the cap, thus offer no resistance. But once they reach the end of the threads, they encounter an open space underneath a flange, and they pop out, pointing against the thread. Screwing it off will now make the teeth catch on the lower rim and it will instead break along the pre-cut stress points and be retained. And yes they are screwed on by machines. From labor-intensive ones for small-scale production to fully automatic ones.--  Obsidi ♠ n   Soul   19:11, 21 September 2011 (UTC)
 * Actually I used to have a job putting the tops on 2litre bottles of milk - a machine filled them, but humans screwed the tops on... The trick is to hold the top steady and rotate the bottle by pulling.. Working inside a fridge in the middle of summer and all the milk you can drink - paradise. (they probably have a machine now - that was 20 years ago when milk in plastic bottles, in metric quanities was still a novelty) These were the "ratchet type", a bit like File:Milk jugs in a row.jpg. The clicking of the rachetting action is quite a pleasurable sound. Imgaril (talk) 00:49, 22 September 2011 (UTC)
 * Heh, I imagine it would have been very dreary. :P And yeah. There's a dairy (for water buffalo milk) nearby, and they use small machines that still require a person to hold the bottle up to it, but the actual spinning of the cap into it are all done by the machine very quickly.--  Obsidi ♠ n   Soul   06:33, 22 September 2011 (UTC)
 * Unrelated but quite wonderful. Bus stop (talk) 23:36, 21 September 2011 (UTC)

Where do I go wrong in this statics problem?
Problem: If the load has a mass of 3.0Mg with its center of mass located at G, determine the horizontal and vertical components of reaction at the pin C when x = 3.9m

See a diagram here: http://postimage.org/image/358oy4cxw/. Image text: The jib crane is supported by a pin at C and rod AB.

I understand that there are essentially three unknowns (the magnitude of the force along the rod and the vertical and horizontal components of the force at the pin) and three equations (the sum of vertical and horizontal forces and the sum of moments must be zero):

$$\sum F_x = \mathrm{pin}_x + \mathrm{rod}_x = 0$$

$$\sum F_y = \mathrm{pin}_y + \mathrm{rod}_y - 3000 \mathrm{kg} * 9.8 \mathrm{m/s^2} = 0$$

$$\sum M = 4\mathrm{m} * \mathrm{rod}_y - 0.2 \mathrm{m} * \mathrm{rod}_x - 3.9 \mathrm{m} * 3000 \mathrm{kg} * 9.8 \mathrm{m/s^2} = 0$$

$$\frac{-3.2 \mathrm{m} * \mathrm{rod_x}}{4 \mathrm{m}} = \mathrm{rod}_y$$

I solve this with matlab like this:

The results are pinx = 33.72kN, piny = 2.421kN (and rodx = -33.72kN, rody = 26.98kN).

However when I enter the answer to the online system I got the problem from it says "Term 2: Not quite. Check through your calculations; you may have made a rounding error or used the wrong number of significant figures." Term 2 refers to pin_y. The system is very lax with rounding and accepts any answer as long as the relative error is below a few percent. The value of g the system uses is exactly 9.8m/s^2.

Since I can enter the answer an unlimited number of times I varied pin_y in steps of .01kN a few steps to both directions until the message went away. That suggests that while pin_y might be close to correct pin_x is not. I've been thinking about this for a few hours and just cannot see my error. It's getting very frustrating. I'd appreciate if you could check that I have solved at least something correctly. If you can think out of the box and tell what is the real problem my online system wants answered it would be great. --19:49, 21 September 2011 (UTC) — Preceding unsigned comment added by 145.94.77.43 (talk)


 * In your last equation, I think the 3.2m should be 3m. Also, the second argument to  is missing an "= 0", but not using Matlab I don't know if that's a bug or not. -- BenRG (talk) 22:16, 21 September 2011 (UTC)
 * Matlab solve equates to zero by default, I failed to add a ' = 0' when copypasting. That 3.2 - .2 part was it. Thank you! This was a shamefully huge help. --145.94.77.43 (talk) 23:31, 21 September 2011 (UTC)

condensation in lungs
the inside of lungs is a fairly damp environment I presume, so does condensation form on the inside of the lungs when breathing cold air? If it does, where does all the liquid go? Does the person need to cough it out later? Googlemeister (talk) 21:11, 21 September 2011 (UTC)
 * Cold air contains very little moisture. Drying out would be a bigger problem. The inside of the lungs is warm enough to hold a lot of moisture, which is respirated. Remaining excess moisture would either be expectorated or be absorbed by the lung tissue. Dominus Vobisdu (talk) 21:17, 21 September 2011 (UTC)
 * Well cold air does not have to be dry. I was thinking where it was near freezing but foggy.  Googlemeister (talk) 21:20, 21 September 2011 (UTC)
 * Even extremely humid cold air contains little moisture. Cold air can hold far less moisure than warm air can. When near freezing cold air with 100% relative humidity is warmed up to body temperature, it becomes very dry warm air. Dominus Vobisdu (talk) 21:31, 21 September 2011 (UTC)
 * Without directly answering: inhaled air is humidified and warmed by the upper airway, so that the partial pressure of water in alveoli is a fairly uniform 47 mmHg.). See Alveolar gas equation, Pulmonary gas pressures, Nasal concha. - Nunh-huh 21:22, 21 September 2011 (UTC)


 * Condensation forms when you have warm air and a cold surface. The situation you are describing is the reverse of that, so there shouldn't be any significant condensation. Looie496 (talk) 21:27, 21 September 2011 (UTC)


 * Well, it is possible, if you have air significantly hotter than body temperature at 100% relative humidity (or even supersaturated). I think I've had that happen in a hot shower, with the door closed, where it seems to become difficult to get enough oxygen.  Opening the door solves the problem.  A sauna might be another place where this might be an issue.  Note that these same conditions would tend to cause hyperthermia, as well, although that seems to take a bit longer.  StuRat (talk) 00:29, 22 September 2011 (UTC)


 * Pulmonary alveoli absorb moisture into the body along with oxygen; they have to do the former to be able to do the latter. When they fail to do so adequately, bronchitis results. 70.91.171.54 (talk) 22:37, 21 September 2011 (UTC)

Can you tell me something about vultures?
Do we know how intelligent vultures are, compared to humans and other birds? --95.150.167.139 (talk) 23:10, 21 September 2011 (UTC)


 * "humans and other birds"? ←Baseball Bugs What's up, Doc? carrots→ 23:39, 21 September 2011 (UTC)


 * It would depend on deciding on a definition of intelligence that could be validly applied to both birds and humans. Even if you restricted it to just birds, there are many different "intelligences" that could be looked at. HiLo48 (talk) 00:20, 22 September 2011 (UTC)


 * Well, way above chickens, below parrots, and well below humans, for a start. StuRat (talk) 00:34, 22 September 2011 (UTC)


 * Vultures seem to be good at finding food, which is more than I can say for some humans and other birds. ←Baseball Bugs What's up, Doc? carrots→ 00:43, 22 September 2011 (UTC)


 * Here in the US, humans appear to be way too good at finding food. :-) StuRat (talk) 06:44, 22 September 2011 (UTC)


 * We have bad definitions of "intelligence" even for just human beings. But a rough estimate in comparing species can be found using the brain-to-body mass ratio and/or the encephalization quotient. I haven't been able to easily locate the numbers for a vulture. But that's what I would look for, anyway, to figure out where vultures in particular stand. Humans rank about twice of any animals for EQ. Some birds — especially corvids — have relatively high EQs. Most birds do not. I know very little about vultures in particular. --Mr.98 (talk) 02:00, 22 September 2011 (UTC)

There's plenty of videos of other birds (crows in particular) showing surprisingly high intelligence/problem solving skills - http://www.youtube.com/watch?v=dbwRHIuXqMU and http://www.youtube.com/watch?v=riqtFvZg1mI&feature=related for example. I've no idea about vultures relative to crows though.ny156uk (talk) 06:57, 22 September 2011 (UTC)

One way vultures do have distinctive brains is in respect to the olfactory lobe. Most birds have very poor senses of smell (even by human standards), but vultures are highly developed in this regard. They also have some interesting communication and sharing behaviors. You know how you see 1-3 vultures circling for hours? That is to tell other vulture that food is to be found. It makes evolutionary sense to share when food comes in large amounts, but rarely (other species can also 'listen in' on this signal). Thus, they will circle for much longer over a bison than they would a rabbit. Whether these features count as 'intelligence' is up to you :) SemanticMantis (talk) 15:44, 22 September 2011 (UTC)