Wikipedia:Reference desk/Archives/Science/2013 February 7

= February 7 =

New Horizons photos of Pluto
The most recent photograph of Pluto taken by New Horizons that I've been able to find is this one, from September 2006. Since the probe is now at a little over 5 AU from the dwarf planet, I'm wondering why I've not been able to find more recent pictures. New Horizons took many photographs of Jupiter and its moons during a flyby in 2006, so it seems that they would have also planned to photograph Pluto and Charon during the approach, and not just during flyby in 2015. I've not done the math to calculate what kind of angular diameter Pluto would have from New Horizons' current location, but I have to imagine that any image taken from the probe right now would provide better detail than the embarrasingly-blurry Hubble composite (though I admittedly know little about the technical specs of the cameras on board). Evanh2008 (talk&#124;contribs) 00:08, 7 February 2013 (UTC)


 * Here's a photo of Pluto, taken by LORRI, released from January 24, 2008. There's no need to remain in the dark: the science payload description contains detailed descriptions of each camera on board.  Right now, the spacecraft is in the interplanetary cruise phase, so it isn't actively taking photos very often.  It's pretty easy to know what the photos would look like: LORRI, the highest-spatial-resolution camera, has a 20.8 cm aperture, so you can trivially compute the farthest distance before Pluto will resolve to anything more than a single pixel.  (About 500 million miles from Pluto, which is ... still a little ways to go).  Space is very big!  Nimur (talk) 00:20, 7 February 2013 (UTC)


 * Using a camera entails risks of damage, so taking lots of low-res pics is a bad risk-versus-reward option. They might take a pic occasionally, just to ensure that the camera is still working, but that's it, 'til they get closer. StuRat (talk) 00:27, 7 February 2013 (UTC)


 * A single pixel? According to my research (which consists of watching detective shows on network TV), you can expand a single pixel into a high-resolution picture. Just tell the technician "enhance!"... (Note to the humor impaired: no, I am not being serious) --Guy Macon (talk) 06:14, 7 February 2013 (UTC)


 * One of the most impressive enhancements can be seen in Blade Runner :) Reflectionsinglass (talk) 09:11, 7 February 2013 (UTC)


 * The ones that annoy me the most are when the technician sitting at the keyboard apparently doesn't think of enhancing the picture until the non-technical guy looking over his shoulder says "Can you enhance that?"..."Oh! Yes! I can! I'm glad you suggested that!"...Star Trek is frequently guilty of this one. SteveBaker (talk) 14:10, 7 February 2013 (UTC)


 * And, in the audio field, you had to love the original Star Trek episode where they detected the presence of an extra person on the ship by turning the ship's microphones way up and listening for heartbeats. I was worried that Spock would fart and permanently deafen them all. StuRat (talk) 16:31, 7 February 2013 (UTC)
 * Did you notice that, while their pulses were at all sorts of phases with respect to each other, the whole damm lot of them had the exact same clock-steady pulse rate? It doesn't happen that way in practice. In any group of healthy people, you get rest pulse rates anywhere from below 60 to as much as 75 or even more. Surely someone in the ship actually getting some physical exercise would have a varied rate?  And some people past about age 40 or so may have the odd ectopic beat now and then.  Wickwack 58.167.247.139 (talk) 00:35, 8 February 2013 (UTC)
 * Ack. That's why I don't like most Star Trek episodes. Their 23rd century is so clean and shiny that their Schroedinger's cat is 100% alive and even their Black Holes are actually only an unusually dark shade of gray.
 * And Spock doesn't fart. He simply holds it back till it comes out the other end as pseudoscience. - ¡Ouch! (hurt me / more pain) 17:17, 9 February 2013 (UTC)


 * http://tvtropes.org/pmwiki/pmwiki.php/Main/EnhanceButton --Guy Macon (talk) 17:28, 7 February 2013 (UTC)


 * Don't forget that, while with only a single frame or still picture, you can't enhance beyond what the pixels provide, in a video you can, to a limitted extent. If the subject, sized so that it/he/she covers only a few tens of pixels in any one frame, and it/he/she moves in a straight line a fraction of a pixel per frame (or a non-integer multiple of the pixel pitch), it can be enhanced.  By means of computer software that moves it back at the same rate, in effect the number of pixels is increased, as edges in the subject cross from one pixel to another in a sort of picket fence effect.  The improvement is not dramatic however - those movie simulated enhancements remain impossible.  Two factors limit how good it is: 1) it cannot overcome optical blurring, and 2) the subject does not restrict their movements to convenient precise speed straight lines.  Wickwack 58.167.247.139 (talk) 00:08, 8 February 2013 (UTC)


 * Thanks for the replies, everyone! And especially Nimur and StuRat! Evanh2008 (talk&#124;contribs) 14:30, 8 February 2013 (UTC)


 * Hehe, putting that tag on an answer is like asking "what could possibly go wrong?" Here you go:  Wnt (talk) 16:52, 11 February 2013 (UTC)

biology
Assume there exists a 13 year old girl, capable of reproduction but still in the process of developing secondary sex characteristics, and she got pregnant. Will the girl continue developing? When will she continue developing? If she still lacks underarm hair, will her body produce such hair even if she got pregnant? — Preceding unsigned comment added by 49.145.4.37 (talk) 09:27, 7 February 2013 (UTC)


 * Have you seen any 40 or 50 year old women that appear to have stopped developing secondary sex characteristics at the age of 13? --Guy Macon (talk) 18:39, 7 February 2013 (UTC)
 * How is your posting even remotely responsive to the question? Or was it just intended as humor?75.34.25.6 (talk) 19:54, 7 February 2013 (UTC)
 * The post did answer the question. The more direct answer is, pregnancy does not halt puberty. thx1138 (talk) 20:27, 7 February 2013 (UTC)

Think. The end of puberty is commonly considered to be reproductive capability and achievement of maximal height. It is not "final attainment of secondary sex charateristics" because things like androgenic hair changes continue throughout life. Breasts increase size and change shape with both pregnancy and obesity. So yes, it is possible for a girl to be ovulating while she still has an inch of growth left, but both of those things are dependent on estrogen and are unlikely to be discordant. Pregnancy results in a further jump in estrogen levels and would bring growth to a close faster. alteripse (talk) 23:50, 7 February 2013 (UTC)


 * The above opinions are interesting. But do we have any biologers or farmists here who might be able to refer to scientiary sources that actually discuss whether pregnancy causes growth or stunting in immature animals? μηδείς (talk) 11:36 pm, 7 February 2013, last Thursday (3 days ago) (UTC−5)
 * The question was about girls, not animals, so I gave an answer about girls, not animals. Puberty is different enough in humans that even primates are not necessarily going to help with this, let alone farm animals. The following facts are not "opinions" and are actual data gathered on American girls about 50 yrs ago. Average bone age at menarche: 12y6m  Average remaining growth at menarche: 2" if no pregnancy occurs. Many, not all, girls will ovulate within the first months after menarche. Some even do it once before menarche. Here are some citations on what happens to growth when pregnancy occurs before growth is complete. http://www.ncbi.nlm.nih.gov/pubmed/8262493 http://ajcn.nutrition.org/content/60/2/183.long Look for a farmer or biologist if you like, but there is no type of person more professionally qualified to answer this question than a pediatric endocrinologist.   alteripse (talk) 22:23, 8 February 2013 (UTC)
 * Interesting source, but the specific fact I was asking about was the difference in final height between girls who do and do not have a pregnancy while still growing. That paper was largely about fetal weight, and did not seem to compare the two populations--unless I missed it.  You say 2" inches is expected after menarche with no pregnancy--doo you have the figure for how many inches are expected after menarche if there is a pregnancy? μηδείς (talk) 01:47, 9 February 2013 (UTC)
 * No, because it will depend on how much remaining growth when she gets pregnant. I know of a pregnancy that occurred even without menarche (i.e, the first ovulation was fertilized) in an 11 yr old mildly precocious girl who had about 3" of remaining growth by bone age prediction at the beginning of the pregnancy. The recent reports of the 9 yr old Mexican girl and of course Lina Medina are examples of more than 2" of remaining growth potential at the time of pregnancy, but i have seen no data for them on height at impregnation and height eventually attained. For obvious reasons, pregnancies in girls with significant amounts of remaining growth are rare and usually terminated, so it is typically difficult to find good data. The closer to average timing the girl's puberty is, the more likely that bone age and menarche will be concordant, and the likely height loss less than an inch. It is in a girl whose puberty is precocious that there may be more chance of losing height growth, but these are less likely to carry to delivery, and the average doctor's office height measurement is only accurate to the nearest inch in many cases, making it difficult to detect changes of growth potential unless by chance there had already been an endocrine evaluation. The camden paper discussed nutritional limitation of fetal growth and confirmed that at least some height growth continued in the girls, though measured stature was compromised by the lordosis of pregnancy so they were assessing growth by knemometry. They did not try to assess the difference between bone-age-based height prediction at diagnosis of pregnancy and eventual attained height well after delivery, which is not exact but would be the best way to answer your question. The reason we can assume that there would be at least a little height loss from estrogenic acceleration of bone maturation is that pregnancy estrogen levels are comparable to those used to accelerate bone maturation and attenuate adult height in girls thought to be too tall or in the Ashley treatment. The more common situation in which this issue comes up is when oral contraceptives are being considered in a girl who has not finished growing; potential height loss is one of the factors weighed. alteripse (talk) 02:15, 9 February 2013 (UTC)
 * Thanks for the detailed answer, I had assumed some stunting would be the likely case, but figured paradoxically there might be a growth spurt. The effect of oral contraceptives makes sense. μηδείς (talk) 02:26, 9 February 2013 (UTC)

Unseen effects on water when going down a drain
What causes water to swirl when going down a drain? Does it rotate in one direction in the northern hemisphere and the other direction in the southern? Question from Sir Lar Feb. 7,2013 Payson Az. 85541 — Preceding unsigned comment added by Sir Lar (talk • contribs) 10:29, 7 February 2013 (UTC)


 * There's a nice discussion of this here: Coriolis effect. Basically, unless conditions are very carefully controlled, the effect of any initial movement of the water or irregularities in the container will predominate over the Coriolis effect, which is what would cause the rotation to be the opposite direction in each hemisphere. Equisetum (talk &#124; contributions) 11:44, 7 February 2013 (UTC)


 * The business of clockwise versus anticlockwise sink/bathtub swirl in the northern and southern hemispheres is a complete and utter myth. It's quite amazing to me that so many people believe this when the most trivial of experiment will demonstrate that it's clearly not true - just watch your bathtub and sinks for a few days - you won't see any consistency whatever in which way they swirl.  The magnitude of the coriolis effect is vastly too small to produce this effect.  Even the slightest motion of the water or irregularity in the shape of the container or the drain will easily overwhelm it.  Coriolis only has an effect for things that move LONG distances in the north/south direction - things on the scale of ocean currents, hurricanes.


 * The interesting part of this question (and I don't immediately see an answer) is why water swirls as it goes down the drain at all.
 * SteveBaker (talk) 14:04, 7 February 2013 (UTC)


 * had one of those deeply mystical latenight college discussions on related topics once. our final decision was that spirals and/or helices are the normal state, straight lines and circles are the singular variations on the general theme. Consider; with repeating subunits, whether physical or force, there is always an angle between the new vector and the previous, which can be projected onto a vector parallel with the original, and a vector in a plane perpendicular; i.e. a forward motion, and a rotation. if the former is 0, it's a circle. if the latter is zero, it's a straight line. otherwise, a helix. thus the helical config of proteins, DNA, etc., is just an intrinisic feature of repeating subunits, not anything specificall evolved. in this case, you could sort of imagine a centripetal force, as in this case due to the "perpendicular plane" being a bowl, sort of reminiscent of Einstein's rubber sheet space topology, it's a spiral in/down, really a shallow helix/spiral combo. Gzuckier (talk) 15:09, 7 February 2013 (UTC)


 * I'd say spiral water flow down a drain is a result of both an unbalanced downward force and an unbalanced inward force. The downward force is easy enough to visualize, as the open drain leaves an unsupported column of water above it, which then falls down the drain.  This then leaves a gap in the water, and water pressure then pushes the water in from the sides, providing the inward force.  In reality, they don't happen in distinct steps like that, and the water is moving downward as it moves inward, so you never quite replace all the water, at least if the distance from the drain to the surface is small, leaving an indentation in the surface of the water, possibly extending all the way down to the drain.  As for which way it chooses to rotate, I agree that any minor asymmetry can start it going one way or the other.  StuRat (talk) 16:25, 7 February 2013 (UTC)


 * I kinda suspect some kind of conservation of angular momentum thing going on here. The huge body of water has a certain angular momentum just due to random motion in the container - but as it heads down the drain, the flow is straightened out.  The conservation law might therefore imply that the angular momentum ends up being concentrated in a smaller and smaller mass of water - so the rotation rate has to go faster and faster as the container empties.  That's a guess - but it might explain why the swirl goes faster and faster as the water flows away. SteveBaker (talk) 17:25, 7 February 2013 (UTC)
 * No need to speculate: this is a standard homework problem in any fluid-mechanics class. Here's a nice website from MIT: Conservation of Angular Momentum (in the context of an aerospace fluid mechanics class).  If you refactor this as part of a flow equation, you can easily see that angular momentum effects an equivalent pressure that "pushes" the water away from the center of a vortex.  This is analogous to effective gravitational potential.  You can refactor the law of conservation of momentum so that in the equation, it looks like it's creating a net force, or a net pressure, or effectively creating an energy barrier, to keep the water from flowing in to the center of the vortex, in contraposition to gravity (which wants to make the water fall into a lower position, in the vortex).  (This pressure is the ensemble effect of the "fictitious" centrifugal force on each fluid molecule).  That's how you can sustain a "vertical edge" to the water.  Nimur (talk) 01:14, 8 February 2013 (UTC)
 * Yes, any large body of gas or liquid will have some small random net spin (the chance of it not is astronomical) and hence, due to conservation of angular momentum spin faster as it contracts. μηδείς (talk) 19:02, 7 February 2013 (UTC)


 * Could Cyclic cellular automaton explain the inevitable evolution of spiral movement?--Digrpat (talk) 22:48, 7 February 2013 (UTC)
 * It's not really necessary to go beyond the mere fact that any mass of randomly moving particles is going to have some sort of net spin. The only way it wouldn't would be if every particle's motion miraculously happened to cancel out.  Either there will be a small amount of particles on the right moving faster toward the drain, or on the left, and voila, a vortex starts spinning. μηδείς (talk) 01:35, 8 February 2013 (UTC)


 * Right - so (naively) if (say) 60 liters of water in an idealized 2 meter diameter cylindrical bathtub is rotating at a leisurely one revolution per minute (almost too slow to notice) then when it's drained down to the last liter, it'll be spinning at one revolution per second - and as the last 1/10th liter disappears, ten revolutions per second. But real-world bathtubs have a smaller cross-sectional area at the bottom - so when the water is spinning around in a 10cm circle centered on the drain-hole, it'll be zipping around at 100 revolutions per second!  Obviously this is a very naive estimation because friction, viscosity and the irregular shape of a typical bathtub would change all of that - and also, the entire body of water isn't rotating at the same speed and some residual angular momentum surely resides in the water as it heads down the drain.  But you can easily see how that rotation can go from negligable to dizzying as the water drains out.  This also explains why the speed of the swirl is so much lower in a handbasin than in a bathtub.


 * Hmmmm....now I want to watch a swimming pool drain out! SteveBaker (talk) 17:39, 8 February 2013 (UTC)
 * The vortex will, of course, reach some sort of terminal velocity, because it's no an ideal fluid in a frictionless environment. μηδείς (talk) 21:27, 10 February 2013 (UTC)

Should I get the shingles shot?
-- Jayron  32  00:03, 8 February 2013 (UTC)

Reventazón River vs. Reventado River in Costa Rica
First of all, feel free to move this to the Miscellaneous desk if geography isn't science-y enough. So, my question. There's the Reventazón River in Costa Rica. This river is not covered in Library of Congress Subject Headings, but LCSH does have a "Reventado River (Cartago, Costa Rica)." I suspect these both refer to the same river. I looked up Lake Cachí in Google Maps, and it's within Cartago Province. So it doesn't seem likely that two rivers with such similar names would be in the same province. Our List of rivers of Costa Rica doesn't mention a Reventado, nor does its equivalent in Spanish Wikipedia. I suspect the LCSH term is an older name for the river, but I'm trying to confirm this. I'm waiting to hear back from the Library of Congress about this, but I'm impatient. --BDD (talk) 21:59, 7 February 2013 (UTC)
 * Michigan has eight Pine Rivers and seven Black Rivers. Name similarity is a poor standard. Rmhermen (talk) 23:13, 7 February 2013 (UTC)
 * For posterity's sake, I heard back from the Library of Congress, and these are indeed different rivers. --BDD (talk) 17:14, 11 February 2013 (UTC)