Wikipedia:Reference desk/Archives/Science/2015 September 24

= September 24 =

Animals dying after mating
Why do some animals, such as bees, die after mating? — Preceding unsigned comment added by 24.207.79.50 (talk) 04:07, 24 September 2015 (UTC)


 * It is widely believed by evolutionary biologists that most examples of deadly mating habits either have a purpose or once had a purpose. In the case of some species of bee, the male reproductive organ detaches and is left behind inside the queen, with the supposed purpose being to prevent semen from leaking out of the queen's reproductive tract. Death inevitably follows for the drone. See Drone_(bee). Someguy1221 (talk) 04:17, 24 September 2015 (UTC)


 * It's 'benefit' rather than 'purpose' (which suggests ID) manya (talk) 04:37, 24 September 2015 (UTC).


 * This general issue is discussed at Semelparity_and_iteroparity. Many organisms reproduce only once before dying. In plants, this is much more common, e.g. annual plants. The evolutionary and ecological forces that lead this situation are well-studied, but research in to life history theory and evolution of life history traits is still ongoing. Generally, semelparity is considered to be a beneficial tradeoff in some situations where the species can have higher population growth (and higher fecundity) via a semelparous strategy than an iteroparous one. See also r/K selection. SemanticMantis (talk) 14:31, 24 September 2015 (UTC)


 * Oh, I should also mention that bees are a bit of a special case - the impacts of haplodiploidy mean that male bees don't have a father, female bees are more related to their sisters than their potential offspring, and all other sorts of weird stuff that has probably strongly influenced their evolution to the current state of eusocial insects with few reproductives and drones that are essentially long-lived sperm. So if you want to understand semelparity more generally, you might be better of thinking of a salmon or an octopus as a more representative species that commonly has a semelparous life history. SemanticMantis (talk) 14:31, 24 September 2015 (UTC)


 * The above is all correct, but in brief layman's terms, animals die after mating because their chance of living to a second mating season is so low that they are better off using all the energy they can to mate and produce offspring during the first season rather than hold back and risk not breeding to their full potential now or living to make it to a second breeding season. This goes for animals like ephemeropterans, salmon and drone bees.  In some animals, like the antechinus it is theorized the males die rather than compete with their mates for food the females need in order to raise the young. μηδείς (talk) 20:44, 24 September 2015 (UTC)
 * Hm. Well, that fits for some critters. But salmon can take anywhere from one to several years to mature before they decide to spawn. Atlantic_salmon discusses a bit of this variation and how it is beneficial. SemanticMantis (talk) 20:50, 24 September 2015 (UTC)
 * The issue is that they breed once. At least the ones that go to sea and swim back up stream do--they are better off at that point using all their energy to spawn, since only like one in a million make it back upstream to spawn the first time.  There are also precocious parr, which are otherwise immature males which haven't yet been to sea but who mate with returning females, "cheating" the system. μηδείς (talk) 22:29, 24 September 2015 (UTC)
 * In short, the r strategists. Antechinus (and some other dasyurids) are also special cases, because only the males are semelparous, while the females are iteroparous. In cases like this, it's because the males devote all their energies to sperm production and the act of mating itself.-- O BSIDIAN  †  S OUL  23:46, 24 September 2015 (UTC)
 * Besides "putting all available resources into maximizing reproduction, at the expense of future life" (as pointed out in Semelparity_and_iteroparity) by dying the reproducing organism also instantly makes place for his offspring and thus prevents to become an competitor of his offspring for the same resources. --Kharon (talk) 21:55, 24 September 2015 (UTC)
 * Yes, like the antechinus as mentioned above an hour ago. μηδείς (talk) 22:29, 24 September 2015 (UTC)

Waterproof light fixtures
For the upcoming Jewish Succos holiday, I want to put some fluorescent light fixtures in my succah (succah is like a treehouse on the ground, sort of). I had special outdoor encased fixtures, but they broke, and now I can't find any in stores. The various stores around only offer fixtures for indoors or outdoor ones that are hard wired, and I'm no electrician. A guy at the local store suggested using an indoor fluorescent fixture that I attach to a board of wood that extends past the light fixture on all sides to prevent any rain from entering the fixture by extending around the entire periphery, and painting it with waterproof paint. What do you think?  DRosenbach  ( Talk 13:19, 24 September 2015 (UTC)
 * You still have the risk of rain drops running along the wood, or of being blown/splashed directly onto the light itself, which is dangerous if the light is of the sort where the bulb is exposed and water can get into the contacts. If it's just something relatively temporary, "site lights" might be your best bet (that's a British website, but hardware stores in any country should have them). These are generally powerful, portable, waterproof and very strong – at the cost of being ugly – but once Succos is over you can also use them in your garage, on camping trips, etc. You can even get ones that hang from the ceiling. Smurrayinchester 14:14, 24 September 2015 (UTC)


 * For a short lasting events such as this – the power efficiency of fluorescents does not really matter. I would go with  festoon lights. . They look pretty, are weather resistant, and can be used on other occasions  to illuminate the yard for  barbecues, garden party’s etc. Being of different colours, they mix to  produce an acceptable white ambient light. Also the juxtaposition  of these different coloured  bulbs give a richer light (in high-lights and shadows) than just white bulbs would do alone. P.S. Also purchase an earth leakage trip. This is a must. Do you hear. Also, including a  light from a naked flame ( say an oil lamp) can give that little  bit of atmosphere to provide a  visual reminder  to the early beginnings. Or you could go ultra modern and European and use exterior waterproof LED strips that one can run off an automotive  battery for days and  days on just one charge.  5m Waterproof 3528 LED Warm White Strip Lights with Power supply--Aspro (talk) 18:03, 24 September 2015 (UTC)


 * For indoor lighting in a temporary structure the advantages of low voltage Track lighting are:


 * the only parts that must be kept in a dry, insulated and earthed metal box are the on/off switch and transformer
 * there is no shock hazard from the cables and/or track that carry low voltage to the lamps, even if they are exposed to moisture
 * you have a wide choice of low voltage lamps including incandescent (such as car lamps), fluorescent with inverter and various LED lamps. It's only necessary to match their voltage (typically 12V) and total current requirements to the output rating of the mains transformer. LED lamps are the most economical to run but need to have a DC supply which a circuit regulates from the AC output of the transformer.


 * In case of a mains failure, the low voltage lighting can be kept alight by connecting a vehicle lead-acid battery as backup power supply. 84.209.89.214 (talk) 18:06, 24 September 2015 (UTC)
 * If I understand it correctly, it's really a "portable" waterproof fixture with an attached power cord that you want? Maybe ask around for someone who can connect the two? Connecting the fixture would take only a few minutes, the time to open it up, connect three wires, and close it again. You could use a (three-wire) extension cord of suitable length (cutting of the unneeded socket), it would save the trouble of having to attach a plug at the other side (and in my experience, an extension cord from a discount store is usually cheaper than buying a cable and a plug from an electrical supply).
 * Or you could opt for the alternatives suggested above by other editors. But don't use an indoor fixture outside, that is compromising electrical safety. Probably no ground wire, not waterproof, needs an extension cord, which, if you want to do it safely, would require an "outdoor power cord protect box", etc...  Ssscienccce  (talk) 18:25, 24 September 2015 (UTC)

Try LED strings - low voltage, so not really a problem, and some can run on solar power (legit during Succoth I think) which means no actual power cords. And very safe. Collect (talk) 19:49, 24 September 2015 (UTC)


 * I'd go a bit further and use LED flashlights/lanterns, hopefully with rechargeable batteries. You can recharge them in the house every day and use them at night.  Best of all, there is absolutely no risk of electrocution.  And isn't the point not to have all the luxuries of home ?  Fluorescent overhead lights sound like overkill, to me.  StuRat (talk) 03:50, 25 September 2015 (UTC)


 * Thanks to all!  DRosenbach  ( Talk 00:09, 25 September 2015 (UTC)

Why are salt pans and dry lakes flat?
I was reading the "endorheic basin" article, which states: "Thus endorheic basins often contain extensive salt pans (also called salt flats, salt lakes, alkali flats, dry lake beds or playas). These areas tend to be large, flat hardened surfaces and are sometimes used for aviation runways or land speed record attempts, because of their extensive areas of perfectly level terrain." Why would salt pans, dry lakes, etc., be flat terrain? —SeekingAnswers (reply) 14:24, 24 September 2015 (UTC)

To clarify my question, I would also like to know the direction of causation: whether salt pans and dry lakes are flat because because the process of drying away of water somehow made them flat, or whether they were already flat and that was why water "sought" them out. —SeekingAnswers (reply) 14:46, 24 September 2015 (UTC)


 * Because gravity would cause erosion on any slopes. -- Jayron 32 14:35, 24 September 2015 (UTC)
 * Hm, this is of course appropriate, but not the whole story. Why are there hills by my house if gravity and erosion should take them away? Of course the answer is that they are slowly eroding, and there is also uplift in some areas, recent glaciation, and other things that cause topography. I think gravity is important, as is the self leveling of water, but I think a complete explanation must draw on some other factors that I can't think of right now. SemanticMantis (talk) 14:41, 24 September 2015 (UTC)
 * Because the material that makes the hills by your house is not the same as the material that makes up salt flats. The cohesive forces holding together different soil and rock types varies widely.-- Jayron 32 14:52, 24 September 2015 (UTC)


 * User:SemanticMantis, with the edit comment "non-helpful", self-deleted his own response wherein he wrote, "Sure, but it's not clear that erosion is the dominant feature in flattening of salt flats. Mikenorton has it as an accreting process rather than an ablative process." I thought it was a helpful comment and makes a valid point. —SeekingAnswers (reply) 15:32, 24 September 2015 (UTC)
 * The lack of hills in the areas of salt flats is why there isn't as much erosion. It's not that there were hills, and they salt eroded down into flat areas, so much as the lack of slopes in the area is why water collected in basins and evaporated into flat salt pans.  Had there been slopes, the water would not have collected in depths necessary to form salt flats.  -- Jayron 32 15:43, 24 September 2015 (UTC)


 * Because "water seeks its own level." Oddly enough, I can't find a WP page that simply addresses this concept and common phrase. It occurs in Pressure, along with lots of math and derivations for why this is the case. SemanticMantis (talk) 14:41, 24 September 2015 (UTC)
 * "Water seeking it's own level" is a folk expression which scientists call Hydrostatic equilibrium. -- Jayron 32 14:53, 24 September 2015 (UTC)
 * "Water seeking its own level" and hydrostatic equilibrium explain why the surface of water bodies would be flat; it does not explain why salt pans and dry lakes (the bottom floor) would be. —SeekingAnswers (reply) 15:30, 24 September 2015 (UTC)


 * As to causation, water (and the salts that it carries in solution) collects in the topographically low areas that are now salt pans. Repeated cycles of filling and evaporation will produce that flat surface. Mikenorton (talk) 14:56, 24 September 2015 (UTC)
 * Piles_of_Salt_Salar_de_Uyuni_Bolivia_Luca_Galuzzi_2006_a.jpg tried to make an analogy of filling a bowl of salt water, then waiting for the water to evaporate. The problem with that analogy is that it won't always work - depending on the rate of evaporation and the salt concentration, you may get a nice flat surface, or you may get large crystals or mounds, like in the picture at right SemanticMantis (talk) 15:20, 24 September 2015 (UTC)
 * (Those appear to be manmade. However, you're right that salt flats aren't always flat) Smurrayinchester 15:23, 24 September 2015 (UTC)
 * Hm, I guess it doesn't say explicitly that they are natural, but the photo does claim to be taken at the world's largest salt flat Salar_de_Uyuni. SemanticMantis (talk) 15:29, 24 September 2015 (UTC)
 * From the image description: "Salt is harvested in the traditional method: the salt is scraped into small mounds for water evaporation and easier transportation, dried over fire, and finally enriched with iodine." Smurrayinchester 15:59, 24 September 2015 (UTC)
 * D'oh! Thanks. I'll amend the caption, other good pics of natural salt pillars in your links above. SemanticMantis (talk) 16:25, 24 September 2015 (UTC)


 * (Edit conflict) To expand a little: rain will fall on the salt pan and dissolve some of the salt (and also carry the insoluble sediments). Gravity will then pull it to the lowest point, where it will pool until it dissolves, leaving the salt behind. By this process, salt and other sediment is transported from the highest points to the lowest, which gradually flattens the pan. That said, salt pans aren't always smooth - Devil's Golf Course is very rough indeed, because rain in Death Valley is virtually unknown and instead crystalisation effects predominate. Smurrayinchester 15:22, 24 September 2015 (UTC)
 * Agree. Salt lakes form in endorheic basins, closed drainage basin that retains water and allows no outflow to other external bodies of water, such as rivers or oceans, but converges instead into lakes or swamps, permanent or seasonal, that equilibrate through evaporation. Climate changes with time, I assume that in the past, rain would wash sediment down from the surrounding heights, and over time sediment deposition would cause the bottom of the lake or marshes to become fairly flat. The thickness of the salt layer of the Bonneville Salt Flats for example reaches only 5 feet near the center. Ssscienccce  (talk) 15:31, 24 September 2015 (UTC)

Does the sedimentary pile-up process resulting in flatness, described in the above responses, apply only to salt pans and dry lakes with their repeated cycles of evaporation, or would it apply to bodies of water in general, so that even (non-dry) lakes, seas, and even oceans have flat bottoms? (Are lake, sea, and ocean bottoms generally flat?) Why or why not? —SeekingAnswers (reply) 15:41, 24 September 2015 (UTC)
 * For the oceans, abyssal plains are pretty flat. But you also have e.g. Marianas trench. SemanticMantis (talk) 15:43, 24 September 2015 (UTC)
 * Trenches and ridges are the result of tectonic processes, as the plates move together or apart. Ignoring tectonic effects the ocean bed looks like a big step. Near land, you have the flat continental shelf (produced by water flows called turbidity currents), and the ocean you have the also flat, but much deeper abyssal plain, with a big drop between them. Smurrayinchester 15:59, 24 September 2015 (UTC)
 * is a nifty chart of the distribution of altitudes on Venus, Earth, Moon and Mars. Note the bimodal distribution on Earth. —Tamfang (talk) 08:28, 25 September 2015 (UTC)


 * See also Lake.  Ssscienccce  (talk) 20:29, 24 September 2015 (UTC)

Physics question (unsure how else to describe)
This has been something I've been wondering since I was young, especially since my grasp on physics isn't the best: Say you're traveling in a closed car or other vehicle on a straight stretch of highway at 100 km/h, and you toss a ball straight upwards into the air of your car interior. Why doesn't the ball remain positionally stationary relative to the car, and careen into the car's back window as the car continues traveling forward? ᴅʀᴀᴄᴏʟyᴄʜ - ✉  ✎  14:53, 24 September 2015 (UTC)


 * Inertia. Its frame of reference is the same as yours. Although you are throwing it upwards, It has the same forward momentum as you and the car have. So, when you throw it up, it is moving forward at the same speed you are. 217.158.236.14 (talk) 14:55, 24 September 2015 (UTC)


 * It does remain stationary relative to the car. The car is moving 100 km/h relative to the road, and the ball is too. Thus, they are (horizontally) stationary relative to each other. AlexTiefling (talk) 15:25, 24 September 2015 (UTC)


 * Here's a nice cartoon illustration from the UCLA physics dept. SemanticMantis (talk) 15:26, 24 September 2015 (UTC)


 * If your car is accelerating as you throw, the ball will probably hit the back window (or the front windscreen if the car is braking harshly, or the side window if cornering). When accelerating, braking or cornering, the car is changing its inertial frame, so the ball no longer remains matched to that frame once it is in the air. An interesting experiment is to take a helium balloon in a vehicle to see how it behaves.  Newton's First Law applies to your ball in a car at constant velocity.    D b f i r s   15:44, 24 September 2015 (UTC)
 * If the car is travelling at constant speed and is tall enough and the ball is thrown upwards hard enough, surely it would eventually hit the rear window. Imagine a car 100 feet tall and you throw the ball so it would attain that height. Air pressure acting on the front surface of the ball will eventually slow its forward motion, so that the rear window catches up to it and collides. That air pressure on the front surface must be offset by the pressure acting on the rear surface due to the window pushing air ahead of it. Nevertheless, at some point on its upward or downward travel, the window and ball must collide. So although the answer is that the forward motion of the ball at the instant it leaves the passenger's hand keeps on carrying it forward, the phenomenon is apparent only because of the limited height to which the ball can be thrown in a conventional car. Akld guy (talk) 21:19, 24 September 2015 (UTC)


 * No, it has nothing to do with height. In the reference frame of the constantly moving car there simply is no net force that would push the ball either forward or backward. Just like in everyday life we do not experience the motion of the Earth's rotation (even if we jump really high), the ball inside the car cannot 'feel' in which direction the car is moving. - Lindert (talk) 21:31, 24 September 2015 (UTC)


 * (ec) In the hypothetical situation being described in the original question the car is closed. Assuming that there is no air blowing into or out of the car, then the air in the car is moving at the same speed as the car and so there is no "air pressure on the front of the ball" to slow its motion as the air pressure is equal on all sides. Of course if you start to introduce variables such as air blowing through the car then the whole situation is different and you are looking at the effects of air movement rather than inertia. Richerman    (talk) 21:35, 24 September 2015 (UTC)
 * Yes but no mention was made that the car was a totally closed, sealed car. We were led to believe that this was an ordinary car, which as everyone knows has air leaks even when the windows are closed. You're talking about a hypothetical situation with a sealed unit, something that would exist only in a lab experiment. Akld guy (talk) 21:57, 24 September 2015 (UTC)
 * It says "Say you're traveling in a closed car or other vehicle". The small amount of air leaking into the car with the windows closed would be coming from various points and would not just act on the front of the ball. Richerman    (talk) 23:31, 24 September 2015 (UTC)
 * You know, I had a feeling I'd get a satisfactory answer within a couple of minutes, then come back in a day and find hypothetical situations like 100-foot-tall cars... oh, REFDESK. Don't ever change. Face-grin.svg ᴅʀᴀᴄᴏʟyᴄʜ - ✉  ✎  18:11, 25 September 2015 (UTC)


 * There are three separate things going on here. Inertia, drag and turbulence.
 * If we imagine driving along on the moon (no air, so no drag and no turbulence), you'd toss the ball up in the air and it would land right back into your hand.
 * Down here on earth, we have a bunch of air - which is (mostly) stationary as the car smoothly slices through it. If your car was perfectly aerodynamic (so we have drag, but no turbulence), then from the perspective of someone inside the car, the ball would go backwards exactly as far as it would have gone if you were standing still in a 100 mph headwind and tossed the ball up into the air.  However, from the perspective of someone standing beside the road, the ball would land a little way ahead of where you tossed it - but mostly, it would land pretty close to where you were when you threw it.  A lot depends on the mass and smoothness of the ball.
 * However, there are no perfectly aerodynamic cars - so the air is going to be swirling around it - some going up, some down, some sideways - but MOSTLY going backwards. So when you toss the ball...it's anyone's guess where it'll end up...it depends entirely on very subtle details of airflow and car design.  But...predominantly - it's going to end up somewhere close to the perfect aerodynamic case would have left it.
 * SteveBaker (talk) 18:43, 25 September 2015 (UTC)
 * Now you've totally lost me. The question was "Say you're traveling in a closed car or other vehicle on a straight stretch of highway at 100 km/h, and you toss a ball straight upwards into the air of your car interior" so where does "the ball would go backwards exactly as far as it would have gone if you were standing still in a 100 mph headwind and tossed the ball up into the air" come into it? Richerman    (talk) 19:43, 25 September 2015 (UTC)


 * Your thought experiment is very similar to the one used by Galileo to justify the principle of relativity: Galileo's ship. -- BenRG (talk) 19:50, 25 September 2015 (UTC)
 * SteveBaker totally lost me too. Some responders seem to think that the ball will return exactly to the thrower's hand as if it had never slowed. In an absolutely sealed car that admits no air (a hypothetical, unreal car), it would. In a real car that leaks air through various crevices, there will be an air flow through the passenger compartment that will slow the ball's forward motion. This air flow may be imperceptible to the car's occupants. The slowing effect is far too small to be observable when the ball can be thrown only a couple of feet in the air, hence my analogy of the 100-foot tall car, which the OP apparently found funny and mocked. Richerman apparently believes that 'closed car' in the posed question means one that admits no air, when the OP did not indicate anything of the sort and we were left with the assumption that the windows were simply wound up and the doors were shut. Akld guy (talk) 21:18, 25 September 2015 (UTC)
 * Oh - yeah, I'm sorry - if it's a closed car, then the ball drops right back into your hand. Special relativity guarantees that. SteveBaker (talk) 22:27, 25 September 2015 (UTC)
 * ... and it's true that if you open some vents at the front, and air leaks out at the back, then there will be a slight backwards pressure on the ball, but the air flow will not be linear, so there might be some positions where the ball would move slightly forward relative to the car. In practice, it is not possible to guarantee throwing the ball exactly vertically, so this error will mask any slight air pressure effects.   Some cars are almost airtight, so that you have to open a window to be able to close the last door easily (the old VW Beetle had that problem).  Fitting an air vent with an outlet to the rear of the car might give a slight forward motion to the ball, with higher air pressure to the rear, but these effects are very slight and were not, I think, what the OP was asking about.    D b f i r s   22:45, 25 September 2015 (UTC)
 * Well, yeah - but there could just as easily be airflow from the cars' heater or A/C fans - and those are going to be the same no matter your forward speed...and if you're going to get stupidly picky, the effect of your own breath will alter the trajectory, so will vibrations in the air due to the noise from the engine...I really don't think that's at all relevant here. The question is about frames of reference and airflow due to motion, not micro-details about the trajectory of balls due to small airflow disturbances.  At constant velocity (ie constant speed and direction), from the perspective of the occupants the ball behaves identically no matter how fast the car is moving. SteveBaker (talk) 15:23, 26 September 2015 (UTC)

Why is the Baja California Peninsula a desert area?
Why is the Baja California Peninsula a desert area? The article list of North American deserts points out that the Rocky Mountains, Sierra Madre Oriental, Sierra Nevada, Transverse, and Peninsular Ranges are responsible for casting the rain shadows that account for most of the nearby deserts (the Sonoran Desert, the Chihuahuan Desert, the Great Basin Desert, and the Colorado Plateau), but rain shadow does not seem to explain the Baja California Desert. The Peninsular Ranges form the "spine" of Baja California, but those mountains shouldn't cast a rain shadow when Baja California is surrounded on both west and east by water. The areas on the west should be able to get rain from the Pacific Ocean, and the areas on the east should be able to get rain from the Gulf of California. —SeekingAnswers (reply) 15:54, 24 September 2015 (UTC)
 * The primary winds over Baja are the Trade winds, which blow east-to-west, the opposite as the direction over the U.S.; so Baja is in the rain shadow of the Sierra Madre Occidental mountains. See the map to the right.  -- Jayron 32 16:02, 24 September 2015 (UTC)


 * See Orographic lifting for rain shadow. I believe most of the rain comes in the eastern Pacific tropical storm season. --DHeyward (talk) 16:09, 24 September 2015 (UTC)

Which uses, overall, the least amount of water, almond milk, soy milk, or rice milk?
Have there been any studies made comparing them? Of course it may vary a lot within any one of the three industries, like perhaps one soy milk producer using way more water than another, especially if that producer is in a region with less expensive water, but on average, is one of almond soy, or rice much less water intensive? Furthermore, are there potential production designs that could in the future save more water in that industry than in the other two industries? Thanks.Rich (talk) 16:19, 24 September 2015 (UTC)


 * It takes almost 300 liters of water to make 1 liter of soy milk, see table 2 here . A key term to help in other searches is water footprint. You are correct that it will vary within an industry due to production methods. An obvious source of variation is whether the soy is irrigated or produced via rainfed agriculture. In the corn belt of the USA, most of the corn is alternated with soy, and irrigation is relatively rare in that area. However the study linked above seems to have also averaged in the water usage from some irrigated soy. SemanticMantis (talk) 16:28, 24 September 2015 (UTC)


 * Here is a study for Soy Milk. Here is a discussion of Almond production in general, though it does not go into the additional water needed for making almond milk.  I can't find anything specifically on rice.  Note, that finding good, scientific studies on Almond Milk is a bit trickier, since the popular press has blown up in recent years calling almond milk the devil; and then responses from other parts of the popular press saying almond milk is NOT the devil.  Mostly because almonds come from California, and California is under a drought, and almonds use water to grow.  -- Jayron 32 16:29, 24 September 2015 (UTC)
 * To avoid wasting time - we both linked the same document for soy, just with different URLs and file names. SemanticMantis (talk) 16:41, 24 September 2015 (UTC)
 * On the topic of California's drought, and its impact to commercial agricultural tree nuts, the economics are even more subtle and insidious. Because deciduous trees are perennial plants and they take a long time to mature, farmers may not opt to let the orchard "fallow" during drought years.  Once planted, the orchards are committed to a multi-year, intense water budget.  For more information, here is the University of California's agricultural program to study optimization of resource use for deciduous tree crops, which I found from the website of the UC Davis Fruit and Nut Agriculture program.
 * Among the many resources, these pages include summaries of scientific studies on water use and its effect on, say, almond tree irrigation efficiency.
 * Unlike many other crops, California tree farmers can't make the decision to not water their orchards this year - even if the economics of nut prices make the water costs a net financial loss; even if the natural resource experts know the Central Valley has not enough water for this agriculture this year. The orchards will die if they are not watered; and that will cause an economic impact over the span of several decades.  So, it is more efficient to opt to keep the trees alive (at an economic loss) and not to plant other, more profitable crops - provided that those other crops' life cycles don't recur over many years.  Contrast this with, say, alfalfa: if this year's market is poor, an alfalfa farmer can simply choose not to plant, and not to use any water on a fallow field.  They can just pick right back up where they left off next year, (hopefully) when the water is more plentiful.
 * The point of all this discussion is to emphasize that "water budget" is not as simple as one number. The entire agricultural economy, and the natural resource landscape, is full of complex interdependency.
 * Nimur (talk) 16:46, 24 September 2015 (UTC)


 * In general, if your concern is to have the least environmental impact, then the cheapest generic item is the best, since this will normally mean the lower the costs in materials and transportation to produce it and bring it to market. As long as all the costs are all factored into the price (there is no government subsidy or additional penalty) and the item is not one bought for its brand name, whichever has the lowest price should have had the least cost in production.  There will always be a bunch of hidden factors, but that's going to be the case no matter how you do your calculations. μηδείς (talk) 20:22, 24 September 2015 (UTC)

NOx in diesel vs NOx in gasoline engines
Why is NOx production higher for diesel engines/a problem to be dealt with? --Scicurious (talk) 19:03, 24 September 2015 (UTC)


 * Diesel engines are designed to operate at significantly higher pressures and temperatures. This is necessary given the characteristics of diesel fuel and allows for greater energy efficiency, but it also has the side effect of creating much more NOx.  Dragons flight (talk) 19:12, 24 September 2015 (UTC)


 * Infact the effords to reduce CO2 emissions from combustion engines - what todays politics focus on to prevent global warming - have lead to higher NOx emissions. On top this lowered combustion engines performance because exactly a high CO2 emission makes an effective combustion. The clue to the riddle is the simple fact that mono-nitrogen oxides (NOx) are formaly not Greenhouse gas but Carbon dioxide (CO2) is. --Kharon (talk) 21:34, 24 September 2015 (UTC)
 * Not only are NOx's not greenhouse gasses, according to NOx they actually cause global cooling and help to counteract the effects of CO2 on global warming. However, they are nasty in a wide variety of other ways (they cause acid rain, smog and can irritate lungs), so keeping their atmospheric concentrations low is important. SteveBaker (talk) 18:31, 25 September 2015 (UTC)

A few questions about prison hooch
I usually buy peaches and bananas a handful at a time, and find this often means they all ripen and then quickly go bad. I was curious about brewing prison hooch as an experiment. Everything I have read on line says you need actual brewer's yeast as an ingredient, that you need to keep the brew warm, and that you need to use an airtight container which you must burp to expel excess gas. I would like to know:


 * (1) Is store-bought yeast necessary? The peaches I buy almost always have a rather obvious yeast blush on the day they become ripe.  Or am I running the risk of getting mold instead?
 * (2) How warm does the brew need to be? Would a black bag plastic bag in a sunlit window be good enough if the room averaged, say, 70 degrees?
 * (3) Would an oversized jug with a pinhole in the lid be good enough as an "airtight" container? I've had friends brew beer and lose half the batch to explosions, and I definitely don't want exploding hooch.  I just don't know if the pinhole will interfere with the fermentation, assuming the brew is producing gas.

Thanks. μηδείς (talk) 20:13, 24 September 2015 (UTC)
 * You do understand that pruno is part of the punishment, right? I hope this is just a chemistry experiment and you're not actually planning to drink the stuff.  I guess you could save it for Lent.  --Trovatore (talk) 20:42, 24 September 2015 (UTC)
 * Sounds like someone has never had the pleasure of sipping some delicious and inexpensive homebrew :P SemanticMantis (talk) 20:52, 24 September 2015 (UTC)
 * Who, me, or Travatore? I have had home made wine (dad added too much sugar) and home brewed beer using both hops and hemp.  I am assuming what I will get is something between wine and very cheap vodka, and do intend to drink it but will dilute it with OJ if it's that bad. μηδείς (talk) 22:16, 24 September 2015 (UTC)
 * Comment was to Trovatore, as per WP:INDENT. I think it sounds like a fun project and I wish you luck - I've had great hooch but never made it myself :) SemanticMantis (talk) 01:12, 25 September 2015 (UTC)


 * No, you don't need to buy yeast, but there's a reason brewers commonly do - it lets you control what is in there and also initial concentration. Lots of things are traditionally made with Brewing, like sourdough bread, kombucha, sour beers, kimchi, sauerkraut, yogurt, etc. But your brew will likely be more sour than if you didn't let in the things like Brettanomyces and Lactobacillus that will likely show up with spontaneous fermentation. As for temp, low temp is the easiest way to get dangerous things into yogurt or kombucha, but my kombucha goes just fine at ~78F. Not sure how much that applies to hooch. You also might be interested in doing something more like Applejack_(beverage). SemanticMantis (talk) 20:43, 24 September 2015 (UTC)


 * As I understand it, leaving even a pinhole will likely let in wild stuff, which may turn out fine, but that's why people usually want air locks. One thing you can do for small batches is cover the lid with a balloon - gives you plenty of time to let it off gas while keeping it airtight. And if you forget about it, the balloon will just pop off, not explode . SemanticMantis (talk)
 * Starting with fruit and not boiling the mixture before fermenting, there will be all kinds of stuff in it anyway. A big cotton ball in the neck of the jug as an improvised fermentation lock would suffice, I think, for keeping additional organisms and oxygen out. Ssscienccce  (talk) 21:45, 24 September 2015 (UTC)
 * Good point, I was thinking of critters that could colonize over time in a liquid that might not colonize the outer bit of a peach within a few days. But there is indeed probably more than just yeast at the start, if you're starting with old peaches exposed to air. SemanticMantis (talk) 21:50, 24 September 2015 (UTC)
 * Yes, I had thought of the balloon, and am sure I could rig an ess-neck trap for ventilation. I think from what's been said I will go with a pack of brewer's yeast, although I was kind-of hoping to work from "scratch". My understanding is that you know the process is done when the burping stops. μηδείς (talk) 22:21, 24 September 2015 (UTC)


 * You should read Yeast in winemaking. As yeast ferments the fruit it produces Co2 and alcohol as waste products. Eventually as the concentration of alcohol increases it kills the yeast, so it more-or-less drowns in its own urine! Wine and beer yeast has been selectively bred to be tolerant enough of alcohol to produce the required concentration before it stops working and to produce the flavours that the consumer finds desirable. Wild yeasts will work but they may become overwhelmed by other organisms before they have multiplied enough to begin the fermentation process, and if they do get going they will be very variable in their tolerance to alcohol and so may stop working before the required concentration has been reached - see Why Should I Use Wine Yeast? When the fermentation is going well it will produce enough Co2 to keep out oxygen and other organisms, but as it slows down towards the end of fermentation it won't - this is when an air lock comes into its own. Fermentation works best at the correct temperature  -  see:  You only get explosions if the fermentation is confined and the Co2 can't escape, such as: if the airlock gets blocked, if the drink has been bottled whilst still fermenting, or if fermentation restarts after the drink has been bottled.  Richerman    (talk) 22:36, 24 September 2015 (UTC)

Mutation of yogurt bacteria
Are the yogurt-making bacteria Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus the same as they were 500 years ago or a month ago? Do they mutate slightly? Anna Frodesiak (talk) 21:36, 24 September 2015 (UTC)


 * Almost certainly a little different than they were 500 years ago. How much depends on what you care about and how you measure. The yogurt they make is probably pretty much the same. Here is a study that specifically looked at drug resistance in Lactobacillus, and concluded that high spontaneous mutation frequencies were responsible. Even without the strong selective pressure, genetic drift also occurs. This paper  discusses the very high genetic variability in Lactobacillus spp. that live in vertebrate guts. SemanticMantis (talk) 21:46, 24 September 2015 (UTC)


 * Lactobacillus bulgaricus seems to have undergone important evolutionary changes "recently", and is still evolving rapidly. It has adapted to the dairy milk environment created by man, has lost functions not needed in that environment, and seems to cooperative with S. thermophilus in several ways.
 * "Several unique features of the L. bulgaricus genome support the hypothesis that the genome is in a phase of rapid evolution. ... has known a recent phase of important size reduction ... an extremely rare feature in bacterial genomes, may be interpreted as a transient stage in genome evolution. The results indicate the adaptation of L. bulgaricus from a plant-associated habitat to the stable protein and lactose-rich milk environment through the loss of superfluous functions and protocooperation with Streptococcus thermophilus." See source for more details.  Ssscienccce  (talk) 22:23, 24 September 2015 (UTC)


 * Very interesting. Thank you folks. :) Anna Frodesiak (talk) 01:12, 25 September 2015 (UTC)