Wikipedia:Reference desk/Archives/Science/2014 July 22

Science desk
< July 21	<< Jun | July | Aug >>	July 23 >

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

July 22

Can anyone identify this bird?

I would like to upload this somewhat accidental pic I took to Commons, but I can't identify the bird. It's the eye colour that defeats me. Can anyone help? It was taken a few weeks ago a couple or miles or so inland from one of the wilder reaches of the west coasts of the EU on an old train embankment in a wooded area. The eye colour is natural as I wasn't using fill-in flash. Help really appreciated. Coat of Many Colours (talk) 00:07, 22 July 2014 (UTC)

I think it's a Tit. Not sure which one, though. --Jayron32 00:39, 22 July 2014 (UTC)

Indeed there are some red-eyed Tits around, thanks for that. Coat of Many Colours (talk) 01:06, 22 July 2014 (UTC)

It's a Dunnock — quite common in that part of the world! MeegsC (talk) 01:26, 22 July 2014 (UTC) (from WP:BIRDS)

Brilliant! That's it exactly. I had no idea they had red eyes. Not exactly twitcher event of the year thus, but still it gives me pleasure. He was just perched a metre or so away from me and quite unafraid and at last I was able to get decent shot of a bird. Thanks so much. Coat of Many Colours (talk) 06:24, 22 July 2014 (UTC)

Happy to help. They're brilliant little birds. And it's always fun to get a great shot! MeegsC (talk) 12:00, 22 July 2014 (UTC)

Life flashing before one's eyes

Is there a term for it? Is it covered somewhere? I don't see it being covered in near-death experience. Anna Frodesiak (talk) 00:28, 22 July 2014 (UTC)

Life review, though I haven't looked at the article. Huge admirer of your user page by the way. Coat of Many Colours (talk) 00:36, 22 July 2014 (UTC)

This also might interest. Coat of Many Colours (talk) 00:39, 22 July 2014 (UTC)

Wow! Sooooooooo spooky. Thank you kindly. I expanded the description and made a couple of redirects. And thank you for the compliment about my userpage. :) Anna Frodesiak (talk) 00:51, 22 July 2014 (UTC)

Pleasure. Coat of Many Colours (talk) 01:04, 22 July 2014 (UTC)

Skyglobe replacement

I want an application that will serve the same as Skyglobe, but I don't know what to call it, so I can't run a decent Google search; all I've been able to find so far is stuff such as Terrestrial Planet Finder, which obviously is not a program I can use to figure out what's in tonight's sky. Any ideas? I downloaded and extracted the ZIP file for Skyglobe, but upon telling it to run the Windows version (I have Windows 8) of the program, all I got was a message of "this program cannot be run on your computer", so I need something else. Nyttend (talk) 02:57, 22 July 2014 (UTC)

The only one I'm familiar with is RedShift (planetarium software) — (current version 7) –There are several others listed on Planetarium software; and a more complete list can be found here, on AstronomyOnline.org (neither list mentions Win8, however).  ~:71.20.250.51 (talk) 06:04, 22 July 2014 (UTC)

I'm not sure I've got all the nuances of your question, but Stellarium (computer program) is a tremendous program. I run it on Windows 7 but it claims to run on Windows XP or greater. (BTW I've recently discovered Google Sky Map for Android). Thincat (talk) 21:23, 22 July 2014 (UTC)

Starry Night runs on windows 8 (but not W8 RT). I've found the cheapest version to be excellent. As Thincat says, if you want something for free, google sky map on a smartphone or tablet is brilliant. Hold it up to the sky and it shows you an annotated image of the section of sky you're pointing it at - and as you move the phone the image moves too. Richerman (talk) 14:00, 24 July 2014 (UTC)

Base hydrolysis

Do thioethers and alkyl arsenides/arsenates undergo hydrolysis in concentrated alkali solution? (For that matter, do amines do so?) Thanks in advance! 24.5.122.13 (talk) 04:07, 22 July 2014 (UTC)

Answer to question 1. --Jayron32 04:14, 23 July 2014 (UTC)

Thioethers, not thioesters (I already know the latter hydrolyze readily). In case you're wondering, here are my three reasons for asking. (And just so you know, my educated guess would be that alkyl arsenides and thioethers hydrolyze, but amines don't -- but I can't find reliable info to either confirm or refute it.) 24.5.122.13 (talk) 09:11, 23 July 2014 (UTC)

Identification of the species

Species name?

Can someone help me with the identification of the species? Thanks in advance. Nikhil (talk) 05:40, 22 July 2014 (UTC)

So, from your image title, I'm guessing that this specimen was found in "Blossom International Park" - about 3 Km from the town of Munnar in India. (That kind of information *REALLY* helps with identification problems). I did a Google Image search on the name of the park and got a bazillion photos of various flowers...I hoped to find a picture of the flower in your photo which someone might have helpfully labelled - but no such luck. Sadly, the park is renowned for the enourmous range of exotic flowers it has...which isn't exactly helpful! If you have a picture of the plant from further back - so we can see the general shape of the plant - that might help. SteveBaker (talk) 14:53, 22 July 2014 (UTC)

Where in the world was this taken? Was it a garden or wild? When was it taken? How tall was the shrub? Answers to these questions will help identify the flower. As it stands, I might guess a white azalea, but that's just a guess. SemanticMantis (talk) 14:38, 22 July 2014 (UTC)

• @SemanticMantis Thanks for the response. It was taken in Kerala, India. It was taken in a flowers park, sort of exhibition for all the flowers. Shrub was about 1 to 1.5m tall. Nikhil (talk) 14:51, 22 July 2014 (UTC)

Reaction

If p-aminophenol is reacted with acetic anhydride, what is the product? Is the amino group acylated or the hydroxy group? 49.183.254.235 (talk) 06:36, 22 July 2014 (UTC)

The hydroxyl group is more reactive, so it should be acylated preferentially. So the product will be mainly the acetic ester, with possibly a small amount of the amide. (Note that in the presence of an acidic catalyst such as aluminum trichloride, yet another reaction can occur, placing the acyl group on any of the four remaining aryl positions, but preferentially (but not exclusively) ortho to the amino group -- so you'd now end up with a total of up to four different products!) 24.5.122.13 (talk) 08:35, 22 July 2014 (UTC)

Although the article Paracetamol disagrees with me, giving the amide as the main product. Maybe this depends on the reaction conditions? 24.5.122.13 (talk) 08:51, 22 July 2014 (UTC)

Is the amino group more electronegative? 49.183.254.235 (talk) 09:49, 22 July 2014 (UTC)

As a rule, oxygen is more electronegative than nitrogen. 24.5.122.13 (talk) 00:05, 23 July 2014 (UTC)

"More reactive" is always dependent upon the context (what sort of reaction?). Here, you are talking about as a nucleophile. Generally speaking, neutral amines are more nucleophilic than alcohols. And this reaction is a reversible or chemical equilibrium or interconvertable among the products. Generally speaking, amides are more stable than the esters, so over time, some ester than might form would also convert to the amide rather than the opposite. DMacks (talk) 16:08, 26 July 2014 (UTC)

Inertia Simple expiation needed thank you.

Confused my self on it. Please be patience with me thank you. Inertia and what it means is driving me crazy.

Ok my question is: if Inertia is the property of mater and for the sake of argument that it is stationary. lets call this first object a tree stump. Then if another object comes along moving at high speed (velocity right?) Then should this moment be called inertia? or momentum? or energy? I'm missing something here. Am making a book and trying find the correct word, and have been stuck on using inertia correctly, I tend to think backwards on some things if that makes an sense.

Here is where I'm having a problem:

Ignoring him she continues to sprint over the surfaced of the lake! Half way into the lake, making a v-turn and going up a hill. And then they go through another valley. Near a long mountain range she lets go of his hand. - Inertia propels her forward - into a stump near by with a bone-crushing smash! Parcival runs over to her. Hurriedly kneeling down afraid to touch her.

Ignoring him she continues to sprint over the surfaced of the lake! Half way into the lake, making a v-turn and going up a hill. And then they go through another valley. Near a long mountain range she lets go of his hand. - The momentum propels her forward - into a stump near by with a bone-crushing smash! Parcival runs over to her. Hurriedly kneeling down afraid to touch her.

Ignoring him she continues to sprint over the surfaced of the lake! Half way into the lake, making a v-turn and going up a hill. And then they go through another valley. Near a long mountain range she lets go of his hand. - Her energy propels her forward - into a stump near by with a bone-crushing smash! Parcival runs over to her. Hurriedly kneeling down afraid to touch her.

So what one of these three is correct? Thank you so much if you decide to help me. I should know this stuff my by now, but guess I've forgotten what it means exactly. Help please. — Preceding unsigned comment added by 173.18.147.198 (talk) 15:43, 22 July 2014‎

None are correct. If she were a rocket, circling the Earth, with no propellant left in the tanks, she would not be propelled by it. So she is not propelled by inertia, momentum, nor force, but merely continues moving relative to the ground. Wnt (talk) 17:27, 22 July 2014 (UTC)

A better example is this: "...she lets go of his hand, but continues moving forward. Why? She has inertia." Inertia means resistance to change. --Bowlhover (talk) 18:20, 22 July 2014 (UTC)

As pointed out above, "propel" is a problematic word, because propulsion is a matter of accelerating an object via the application of a force, but you're trying to describe the behavior of an object in the absence of a net force. And "energy" provides an insufficient explanation of the behavior, because energy is a scalar quantity, so the conservation of energy alone doesn't preclude the possibility of the object changing direction while maintaining the same speed; see kinetic energy. The full behavior of the object continuing in a straight line at a constant speed can be described as either being an example of the law of inertia, or as being an example of the conservation of momentum. Red Act (talk) 20:26, 22 July 2014 (UTC)

The usual phrase is "her momentum carries her forward". Dbfirs 20:49, 22 July 2014 (UTC)

Your problem is that you want to describe something we easily understand, a painful collision of a running lady with a tree stump, but have introduced technical terms of physics such as inertia momentum and energy in your narrative. I think it is unnecessarily pedantic to analyse the collision in these terms but here are their rôles in the collision:

• Inertia is the resistance of any physical object to any change in its state of motion, including changes to its speed and direction. The lady has forward inertia. In non-technical storytelling I don't object to "Her inertia propelled her forward into a stump..". This is just the literary device of making an active verbal statement where as Wnt points out, there is no actual propellant. However general readers tend to associate inertia more with absence of movement than persistence of movement, which is not the right association here.
• Momentum is the product of the mass and velocity of an object. The lady has forward momentum. This means the same as inertia except that momentum is a numerical vector quantity. Likewise it's possible to say "Her momentum propelled her forward into a stump..". However the resulting collision is not the elastic type that conserves momentum so you are using the word colloquially, not technically.

Momentum is always conserved; an inelastic collision loses energy, not momentum. —Tamfang (talk) 17:51, 26 July 2014 (UTC)

• Energy is a numerically calculable property of matter that comes in many forms. In the story, the lady has Kinetic energy ${\begin{smallmatrix}{\frac {1}{2}}mv^{2}\end{smallmatrix}}$ until she meets the stump. That energy then converts into other forms of energy such as heat, noise, vibrations and bone fracture. Such analysis does not make for good storytelling.

It would be simplest to forget the exact physics, write "She broke free from his grip and flew into a stump with a bone-crushing smash" and get on with the rest of your book. 84.209.89.214 (talk) 21:30, 22 July 2014 (UTC)

There is some subtlety to this description. Newton says that objects remain in their state of motion unless disturbed by a force. So she keeps on moving because that's what things do if you don't go sticking a tree-stump in front of them! In terms of the physics, nothing special is happening to her as she continues to move. Her constant state of motion is due to the LACK of any other influences. We don't need a name for what changed - because nothing changed.

If you want to be scientifically pedantic, then having a "high speed" is the correct terminology. A "high velocity" is a rather meaningless term because velocity is speed combined with direction - and "high" versus "low" is hard to say when a direction is included. So, actually, "speed" might be the better word.

But then, we could invoke relativity and say that it's not even meaningful to talk about the person's velocity/speed because it is equally valid to state that she is "stationary" and it is the tree stump that is moving "at high speed"...and then the only true description is to say that the person and the tree are moving relative to each other at high speed.

When viewed like that, you can't even say which object has kinetic energy, or momentum or inertia - it's all a relative matter. From the perspective of the tree, the person has lots of kinetic energy and is moving pretty fast. From the perspective of the victim, the tree stump has kinetic energy and is moving alarmingly quickly.

Fortunately, in a location such as the surface of the earth, we have a convenient verbal convention, which is to discuss motion in a frame of reference in which the earth is stationary...but its' only a verbal convention - and if you're discussing the motion of (say) the moons of Jupiter - it would be singularly perverse to do so with the earth-is-stationary frame of reference.

It follows that when we discuss how someone flies through the air and whacks into a tree stump, we put enough verbal short-cuts into the explanation to keep things comprehensible. Trying to sound more 'scientific' brings with it some fairly extreme inconveniences.

SteveBaker (talk) 04:39, 24 July 2014 (UTC)

The relativity being invoked is Galileo's and Isaac's and not Albert's. The term its' seems a peculiar contribution to the English used on this planet where we owe a budding author a competent explanation rather than bad examples that demand expiation. 84.209.89.214 (talk) 20:15, 24 July 2014 (UTC)

Help identifying a dragonfly

File:Unidentifed dragonfly.jpg

Can anyone identify this dragonfly. Taken in Yellowknife, Northwest Territories. Wasn't able to measure it but they are about 150 mm (5.9 in) long. The black item behind it is a tyre. Thanks. CBWeather, Talk, Seal meat for supper? 16:58, 22 July 2014 (UTC)

It must be from the Anax genus. It resembles Anax imperator, the Emperor dragonfly, but our article suggests that they are smaller, and unlikely to be found in Australia. AndyTheGrump (talk) 17:15, 22 July 2014 (UTC)

Well, it's a good thing this dragonfly was photographed in Canada then... --Jayron32 17:17, 22 July 2014 (UTC)

Doh! Sorry, brain slipped out of gear... AndyTheGrump (talk) 17:34, 22 July 2014 (UTC)

CBWeather, are you quite sure about the size? I can't find evidence of any species that big being found in Canada. Incidentally, I may have been premature in identifying it as Anax - it could be another of the Aeshnidae family - possibly Aeshna. AndyTheGrump (talk) 19:09, 22 July 2014 (UTC)

Just asked my daughter, she was there as well, and after a few comments about my eyesight and age it is more likely to be 75 to 100 mm (3.0 to 3.9 in) long. I noticed that in the Emperor (dragonfly) article that the males are difficult to approach but these were easy to get up to. Is it possible it is some variety of darner, Aeshnidae or Aeshna? CBWeather, Talk, Seal meat for supper? 04:22, 23 July 2014 (UTC)

Yeah, that seems likely, looking into this further - though apparently the darners can be very difficult to positively tell apart. I think it may possibly be Aeshna eremita, the Lake Darner - see the image here [1] AndyTheGrump (talk) 06:06, 23 July 2014 (UTC)

Thanks. I'll ask User:Dger as he is the one who uploaded the image in the article. 22:38, 23 July 2014 (UTC)

Swarms of Antarctic krill

The introduction to the Antarctic krill article notes that its swarms can reach a density of 30,000 individual animals per cubic metre, and that the animal itself can grow to a length of 6 cm. Given that there are 1,000,000 cubic centimetres in a cubic metre, and that the image shows the length as several times the other two dimensions (let's guess 5mm height and width), we're left with something like 45,000 of those 1,000,000 cubic centimetres being occupied by the krills' body volume. How do all of them survive, let alone go anywhere in the swarm? Imagine a huge room in which 5% or more of the volume is occupied by humans (e.g. the ceiling is just tall enough for an average-height human, so we can pack the whole volume without stacking people): there's not going to be anywhere near enough food to eat (after all, krill don't have supermarkets or pizza delivery), and without verbal communication, those humans are going to have a massively hard time going anywhere all together, especially if we remove the walls and ceiling. How are krill able to do it better than humans? Nyttend (talk) 23:51, 22 July 2014 (UTC)

To me a "swarm" isn't the density at which they normally live, any more than a "crowd" of humans is how we normally live. Presumably they just pack together occasionally for certain purposes, like mating.

Also, since they are filter feeders, their food is delivered by the water itself, so they don't need room to farm, herd, etc., like people do. Now, if you had a cubic kilometer with them all at that density, then I would expect that the center of that cube would starve, but if spread out over long "tendrils", they should have more access to food washing in from the sides. StuRat (talk) 23:57, 22 July 2014 (UTC)

The article said that "swarm" was the term for their schools, so I was imagining something like schools of bigger fish, a massive "blob" (large in all three directions) of fish all actively swimming together, rather than a group mating but not going anywhere or a massively long string or otherwise essentially 2-D group. Did I have the wrong idea? Nyttend (talk) 00:07, 23 July 2014 (UTC)

Consider that krill in large groups don't have to deal with the problems of body heat, sore legs and the various mammalian (and distinctly human) social anxieties that come with those, like a crowd of people do. If someone's in their way, they can far more easily go around, over or under. Water is cool that way. InedibleHulk (talk) 03:13, 23 July 2014 (UTC)

Of course, when you're moving as a unit, the problem of people in your way isn't so common. Compare marching soldiers to a similarly sized concert audience. I'd assume time moves slower for those tiny krill, so what may be seen as rapid commotion by our eyes should be much more relaxed on their level. If you've never seen a giant cloud of bats leave a cave, I recommend it. Almost unbelievable how they don't all crash and die. InedibleHulk (talk) 03:22, 23 July 2014 (UTC)

@Nyttend:Several benefits of Schooling_(fish) apply to krill as well as fish. Flocking_(behavior) gives some clues as to how this is accomplished by organisms without much of a brain or communicative capacity. Basically, all each one has to to is swim vaguely in the direction of another that it can perceive, and (modulo some tuning of parameters), coherent motion is achieved as an emergent process (see also Self-organization, and perhaps ant mill).

Contrary to your notion that the swarm has less food, aggregation can serve to increase feeding efficiency. It can also serve to reduce predation by slightly larger organisms, though of course whales and such take advantage of the swarms to increase their feeding efficiency. These concepts are elaborated in the schooling article. Another thing to keep in mind is that water "feels" much different to krill compared to cod or humans, because of the differences in Reynold's number. This means it's really hard for krill to bump into each other. Does this explanation make sense?

To your follow-up question, my understanding is that the density quoted is something like a seasonal max. Not all krill are always 'swarmed', and not all swarms achieve that density. But many swarms exist as coherent aggregations at any moment. I'm not an expert on krill, but that's my reading as a biologist.

Finally, is 5% by volume really that dense? If we take average human volume to be 0.0664m^2 and average human height to be 1.6m (via wolfram alpha [2]), then that puts ~120 people in a room with dimensions 10mx10mx1.6m. Looking only at area, that's ~0.83 m^2 per person, which is far less crowded than a modern lecture hall or a bus at rush hour, to my estimation. SemanticMantis (talk) 14:56, 23 July 2014 (UTC)