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July 18

Air conditioning

Hi all - I live in a two-story apartment with central air conditioning. However, the second floor (where the two bedrooms and the bathroom are) is a converted attic, so it has no A/C vents. The result is that my downstairs level gets air conditioned perfectly, but the upstairs remains practically as hot as if I had the A/C turned off - it's basically a sudden transition right at the top of the stairs. Basically, I'm looking for some MacGyver-esque solution to circulate the A/C to my upstairs as well. Unfortunately, the circumstances make a couple of the more obvious solutions impossible or suboptimal:

Each of the upstairs rooms only has one window, so I don't really want to get a window unit and lose all window functionality in one of them
There is no overhang over my windows, so I can't do anything that involves leaving windows open without risking getting everything drenched when it rains

So far, the best I've come up with is to buy a really big box fan and place it on the stairs facing upward, hoping it will circulate enough cold air to the upstairs to make a difference. Does this seem likely to work? And are there any other options I'm not thinking of? Thanks. -Elmer Clark (talk) 06:00, 18 July 2015 (UTC)[reply]

Not very MacGyver, but they do sell portable AC units that sit inside and have only a minimal window footprint (e.g. [1]). That wouldn't obstruct much of the view. They also start with an okay window opening shield and with a little MacGyver-ing you could improve that. If you really want full-on MacGyver, running some interior duct work could help (more than a fan at the base of the stairs anyway). Ducts that runs along the interior ceiling of the stairwell might work. Assuming your construction options are limited (e.g. rented apartment), you'd probably end up with some fairly obvious and ugly looking exposed ducts, but depending on taste, that might be acceptable. Dragons flight (talk) 06:44, 18 July 2015 (UTC)[reply]

According to some tests I've read (Consumer Reports, IIRC) those indoor AC units with the ducting to outside are expensive and don't work all that well. Anything you can do to improve air circulation would likely be more cost effective. It would be interesting to get a length of that expandable aluminum duct used for clothes dryers and try forcing air through it. But ordinary box fans would probably be more practical. Short Brigade Harvester Boris (talk) 23:36, 18 July 2015 (UTC)[reply]

Funnily enough I was looking in to portable ACs about a week ago since I came across them and was confused how they work as most pictures are highly misleading and show the AC without any ducting. Anyway during my research I came across [2] which does suggest they aren't generally very good. Nil Einne (talk) 15:02, 19 July 2015 (UTC)[reply]

Who pays for the electricity? Can you put a box fan at your door as well as at the bottom of the steps? Have you talked to your landlord, or checked with the local housing board about relevant regulations? μηδείς (talk) 23:26, 18 July 2015 (UTC)[reply]

Thanks for all of the responses so far everyone! Sounds like a couple of box fans might be my best bet. I was mostly just concerned that they wouldn't circulate the air well enough to make any difference if I didn't have any windows open. To answer Medeis's questions: I pay for the electricity, but am ok with paying more during the summer as long as it's not outrageous. My landlord was very upfront about this before I moved in, and frankly I'm not sure I'd even want them to "properly" set up the central A/C for the upstairs if there's another alternative...my rent is quite a bit lower than average for the area and I suspect this is a big part of why. And there's no legal requirement to provide any air conditioning at all where I live so they're already going well above and beyond the legal minimums. -Elmer Clark (talk) 00:33, 19 July 2015 (UTC)[reply]

StuRat might be the one to consult here on the physical whatnots. I have normally paid for my own electricity when I have rented apartments in NYC, but when i have rented rooms it was included in the rent. In either situation, buying an efficient AC for $200 has made sense. It's a matter of budgeting, so you have to decide, since we can't calculate your electric charges. My experience has been that if the house is AC'ed and you can put a box fan in your window, simply blow the hot air out of your room and the cold air will rise into it. That borders on professional legal, electrical, and housing advice, so I'd still look in to it with the local housing authority. μηδείς (talk) 02:24, 19 July 2015 (UTC)[reply]

Problems I see:

1) The hot air is up high, where it wants to stay, and the cold air is down low, where it wants to stay. Had the reverse been true, then a couple box fans blowing the cold air down the stairs might work.

2) The total cooling capacity might not be enough, even if you were able to evenly distribute it.

My suggestions:

A) Use box fans in the upstairs windows, one blowing out, and one in, both doors open, to cool the upstairs with outside air, when it's cool and dry out (usually at night). I've made masks for my fans, cut out of plastic sheeting, so that only a circular hole the diameter of the fan blades is open, with the rest of the window blocked. This prevents backflow of air, keeps out some rain, and provides a bit more privacy. The fan blowing out is likely fine even in the rain, but the one blowing in you will need to monitor. And no, you can't just have fan(s) blowing out, or the negative pressure in the house will do bad things, like suck exhaust back down your water heater chimney. You can place something waterproof on the floor by the fans, as an extra protection against rain. Total cost should be under $50.

B) Add a downstairs sleeping area. This can just be a fold-out couch, for example. There will be times when it's too hot, humid, or rainy out to use the fans upstairs, and on those few occasions, you need a way to sleep in the air conditioned portion of the house. StuRat (talk) 02:43, 19 July 2015 (UTC)[reply]

I should also add my personal experience. I have a window A/C unit in my bedroom, and am currently trying to cool the entire floor with it. I am using two box fans, one to blow cool air out of the bedroom into the hall, and another to blow it out of the hall into the dining room. This is only slightly effective. It's currently cool in the bedroom but 82° F where I am, far from it. And this is without fighting the elevation difference you have. So, this is why I don't think your approach will work. StuRat (talk) 17:08, 19 July 2015 (UTC)[reply]

Another approach (if you'd otherwise consider it) is to diet for weight loss - this tends to lower metabolic rate, making warm temperatures more bearable. But IMHO the idea that you can't leave your windows open but you can run AC all the time is one of those crazy things that give developed countries a bad name! Surely there must be something that can be rigged to deal with a little rain, and then you can enjoy some peace and quiet. Though really, window-ology can be pretty complicated ... you can get a lot out of them if you can open and close them at the right times. Maybe, in the interest of world peace, someone has to invent a plastic fold-up shade that can be hung outside the window, closes when it is wetted, and can be set to close on a timer also. If you could throw in some of that variable silvering (to block direct sunlight) that is only used now by Boeing so that passengers no longer get to decide when they want to look out the window, you'd be golden. Get cracking, MacGyver... Wnt (talk) 12:31, 20 July 2015 (UTC)[reply]

You need to circulate the air. So, you need one spot where air moves freely from upstairs to downstairs and another where it moves freely in the opposite direction. It sounds like you have one opening between the two floors. You need two. Then, you need at least one (I suggest two) fans to force the air to circulate. This will get the process started, but it will take time to adjust the air flow to get all the rooms upstairs in the cool air current. Why won't one box fan work? Assume you set it to blow the cold air from downstairs to upstairs. It is like blowing up a balloon. You can only blow so much air in there until the walls need to expand to take more. The walls of the house won't expand, so you will hit a point that the fan spins, but the cold air is just forced right back downstairs again. The same thing happens if you try to blow the hot air downstairs. It hits a point that it just turns around and heads right back upstairs. With two holes, you feed cold air into the upstairs while pull hot air out. If you go this route, I suggest getting variable speed fans. They change speed every couple seconds and help break up the current of air. That creates turbulence, which helps get the cold air into the corners. 209.149.113.45 (talk) 13:42, 20 July 2015 (UTC)[reply]

What happens there isn't back pressure - it's just that the cold air is cooler than the warm air and so is denser and will naturally sink and pool where it can, which may involve running back down the steps again. Anyone who's burned something on the oven has probably seen how stratified the layers of air in a room can be. Anyway, I *think* that by fine-tuning fan design, you might be able to increase or decrease the amount of turbulence produced, so that hypothetically you could shoot a nearly laminar flow of air up to the upper room's ceiling, then have it mix thoroughly with the uppermost layer of air, and as mixed lukewarm air it doesn't sink back again so you haven't wasted any power. Has anyone engineered such applications? (though honestly I don't know who would, or why) Wnt (talk) 13:51, 20 July 2015 (UTC)[reply]

The closest you can purchase "off the shelf" is a box fan specifically designed for this purpose. It looks like any other box fan, but the speed of the fan keeps changing. I had one when I lived in a townhouse. It was clearly effective. Just place it at the top of the stairs and the temperature upstairs was better. Then, I cut a hole in the floor in the corner of both upstairs rooms and placed a vent cover in them. I cut a hole in the ceiling of the rooms below and placed a vent cover in there (I duct-taped them to a small section of duct to keep the bottom one from just falling out. This allowed air to flow better. Then, the temperature upstairs was the same as the temperature downstairs by feel. According to the thermometer upstairs and downstairs, upstairs was 2 degrees F hotter during the day, but the same temperature at night. I then began turning off the fan at night because it wasn't really needed and the constantly changing fan speed kept me awake. 209.149.113.45 (talk) 14:12, 20 July 2015 (UTC)[reply]

Thanks again all. Sounds like there's not likely to be any particularly good solution that doesn't involve blocking off at least one window. I'll probably grab a couple of box fans and do some experimenting...worst case scenario, I can just use them as regular fans I suppose. -Elmer Clark (talk) 00:04, 21 July 2015 (UTC)[reply]

Also, in case you don't know it, window A/C units can be removed when not in use. I only have mine in for June, July , and August. The rest of the year I have full use of those windows. (I suggest sealing them in an airtight box when not in use, because experience tells me they are full of spiders which I don't want coming out into my home. 9 months later, when I am ready to install it again, the spiders are all dead.) StuRat (talk) 14:32, 21 July 2015 (UTC)[reply]

What else do I need for a virtual way to touch a dragon?

I'm throwing a party for my nephew. He's a fan of dragons. So I have an idea to set up an impressive show for his birthday party where he'll be able to touch a dragon. I know that touching pressurized air can feel like a solid object, when a hand makes contact with it. So in addition to pressurized air, what else do I need for the virtual touching of a dragon? NPham2005 (talk) 07:32, 18 July 2015 (UTC)[reply]

Looking online, it appears that once again it is possible to buy pet baby alligators. It only makes sense that a young human should get a young dragon, no? And when it gets too big and mean to keep in the house you can always flush it down to the sewers.... :) Wnt (talk) 20:03, 18 July 2015 (UTC)[reply]

Where is Count Iblis? μηδείς (talk) 02:17, 19 July 2015 (UTC)[reply]

Count Iblis agreed to selfban themselves from the RD. As it came on the heels of an ANI discussion, the selfban can only be lifted if they apply to AN//I as per their agreement. See Wikipedia:Administrators' noticeboard/IncidentArchive890#Proposal to Topic-Ban User:Count Iblis from Reference Desk for more. So please don't discuss Count Iblis further here, and particularly don't link to them, since it's unfair to ask someone who is unable to easily respond. Nil Einne (talk) 14:57, 19 July 2015 (UTC)[reply]

How old is your nephew ? If he's young enough, I suggest a lizard of some type. You can just tell your nephew "he's a baby dragon who hasn't grown his wings yet". Now, where to rent a lizard might be a problem. Not sure if a pet store would be willing to do that. I suppose you could always buy one, at a place with a generous return policy, then return it later. (If this makes you feel guilty, you can buy something else to assuage your guilt.) StuRat (talk) 02:49, 19 July 2015 (UTC)[reply]

Yes, these suggestions are much easier to arrange than the virtual option of a holographic image with jets of air, but don't rent a Komodo dragon. Dbfirs 06:31, 19 July 2015 (UTC)[reply]

Holographic image with jets of air? That's perfect! The thing is, though, how do I set up the hologram? NPham2005 (talk) 11:31, 20 July 2015 (UTC)[reply]

See holography. But you do realize this is all rather ambitious for a birthday party, don't you ? I see weeks of work to set it all up, at least. StuRat (talk) 13:22, 20 July 2015 (UTC)[reply]

I was a programmer for a job similar to this in 2009. It was a "proof of concept". The hologram was just a rolling apple. The equipment to create the hologram was as cheap as possible, because it was only a proof of concept. In the end, it was just shy of $800,000. Are there cheaper holograms? Yes, but not 360 degree open air holograms. Shining laser pointers in fog is cheaper, but looks terrible when you are close enough to touch the image. As for the exact equipment used? I cannot say. It was paid for by a very rich illusionist who keeps it as a "toy" on one of his personal islands and I had to sign a NDA to work on the project. I can discuss that it was done, but not how it was done. I do not know how much the two engineers were paid. I was paid $30,000 to program the animation of the apple rolling, which wasn't too difficult. Then, I was paid $90,000 to program the interface to interact with a hand sensed by IR sensors and the moving hologram. Also, I had to keep the virtual shadow on the LCD table under the apple. I spent three months working on aligning the air jets with the apple, but some things simply couldn't be done. The air jets must be placed around the perimeter. If you curl up your hand, it is impossible to blow air through your fingers to your palm. I can only mention that particular problem because it wasn't solved. So, it only worked well if you kept your fingers perfectly straight. I assume that you don't plan to spend around $1,000,000 for something like a rolling apple display. You want something much more complicated and, likely, in far less time than the two years spent developing the apple. As with all development, you can get it done faster if you throw more money at it. So, I figure it will cost closer to $4,000,000. That is a lot more than the cost of renting a "baby dragon" lizard. 209.149.113.45 (talk) 13:33, 20 July 2015 (UTC)[reply]

Thanks for lending some numbers to my assertion that this is not a feasible project for a kid's birthday party. StuRat (talk) 00:16, 21 July 2015 (UTC) [reply]

pipeline spill

Regarding Long Lake oil line spill,why doesnt the flow detection system stop the pumps before 5 milion litre,s has gone by — Preceding unsigned comment added by 70.69.144.57 (talk) 07:43, 18 July 2015 (UTC)[reply]

It should have been detected; they don't know yet what went wrong. --174.88.133.35 (talk) 22:04, 18 July 2015 (UTC)[reply]

Magnitude 9 megaquake

According to the New Yorker, if there was a magnitude 9 earthquake, a tsunami would hit Seattle and Portland afterwards. How is that possible, given that Portland is inland? Also, wouldn't Seattle be shielded by puget sound? Wouldn't the puget sound be too shallow for huge tsunamis to occur?— Preceding unsigned comment added by 24.207.79.50 (talk) 11:23, 18 July 2015 (UTC) I also saw an online video from fox about this. — Preceding unsigned comment added by 24.207.79.50 (talk) 11:45, 18 July 2015 (UTC)[reply]

Neither place would see significant harm from a tsunami, but both cities would have issues with soil liquefaction and collapse of unreinforced masonry buildings, as well as transportation and utility disruptions. See this article [3] in Slate for a critical discussion of the New Yorker article. Acroterion (talk) 12:05, 18 July 2015 (UTC)[reply]

The New Yorker article discusses the possibility of a magnitude 9.2 or larger earthquake on the Cascadia subduction zone. Our article gives a good description of the processes that would come into play. Note that such an earthquake would be twice as strong as the 2011 Tōhoku earthquake and tsunami. Portland is on the Columbia River, with the lowest parts barely above sea level. If you have seen Youtube videos of the tsunami flowing up Japanese rivers, you can get some sense of what could happen. Looie496 (talk) 13:38, 18 July 2015 (UTC)[reply]

What does it mean area of significant slip?the article on cascadia subduction zone shows a map and the shade represents an area of significant slip.Also, I seem to be getting two contradictory answers from the refdesk — Preceding unsigned comment added by 24.207.79.50 (talk) 19:23, 18 July 2015 (UTC)[reply]

The experts are going to disagree on hypothetical questions like this, as much of it depends not only on the size of the quake but the precise location and depth. As for a shallow bay, that can make a tsunami worse, as all the oceanic water pushed into it must raise in elevation due to the shallow bottom. StuRat (talk) 20:32, 18 July 2015 (UTC)[reply]

But there's islands separating puget sound from the strait of juan de fuca.— Preceding unsigned comment added by 24.207.79.50 (talk) 21:12, 18 July 2015 (UTC)[reply]

You'd need more than a few islands to stop a tsunami, you would need a strip of land high enough that the tsunami can't go over it, so maybe 50 feet high, and contiguous, so the tsunami can't go around it. Think of it as a river. Could you stop a river with some stones sticking up out of the river ? StuRat (talk) 15:36, 19 July 2015 (UTC)[reply]

I wonder if Vancouver would get hit by a tsunami. — Preceding unsigned comment added by 24.207.79.50 (talk) 09:30, 20 July 2015 (UTC)[reply]

Assuming that you mean the Canadian city, Vancouver island would provide considerable protection, but water could still flow up the straits to cause damage. Dbfirs 14:07, 20 July 2015 (UTC)[reply]

Space time creation

If I alone suddenly popped up out of nowhere/nothingness into my own empty universe, How much spacetime would I create on my own?--81.147.170.83 (talk) 17:14, 18 July 2015 (UTC)[reply]

What a bizarre question. HIGHLY hypothetical and lacks real valid substance. To answer your question: "you would create the amount of space-time that you displace relative to your mass". I am not qualified but thought I'd give it ago. Who knows maybe the great nimur or jayron will take some time to answer this. Void burn (talk) 17:35, 18 July 2015 (UTC)[reply]

Sorry, I don't know how to answer this question except to tell you that it isn't well formed. My advice is pretty much the same as always for this type of question: the best way to really understand weird modern physics is to start with a solid formal education in conventional physics. This is hard work; but it's absolutely necessary. A lot of people get really enthusiastic about weird and exotic cosmology - probably because they read a popular science article or watched a documentary - and they want to dive into details... but, they haven't yet learned (and perhaps they are not capable of learning) the formalisms that allow us to study these details scientifically. Many people want to go straight to big bang cosmology, but they want to skip over ten years of basic math and physics! The OP's question is a perfect example of this. They are using some words that are related to science ("universe," "spacetime") and there is a hint of some question about cosmological origin concept - but the OP's question is so distant from anything we can answer scientifically, all I can conclude is that they are very confused. These words have meaning in physics, but the OP has not formed a coherent problem-statement out of the words. It's ... almost echolalic.

Our articles on cosmology may interest you. It will help your understanding if you get a good book; and in the future, the OP would get more mileage by asking us for help finding good resources (instead of playing imaginative games or asking for answers to brain-teasers). There are many places where unrestrained imagination has merit; but not in physics: in science, you have to learn the basics before you can just let your mind run wild. After you have mastered the basics, then you can apply your imagination to do something productive. If you don't like thinking in this way - tempering your creativity using learned rules - then maybe science isn't for you. Nimur (talk) 08:09, 20 July 2015 (UTC)[reply]

What units of space and time do you want the answer in? AndyTheGrump (talk) 17:42, 18 July 2015 (UTC)[reply]

I think we can closely approximate the answer if we model spacetime as wood, creation/"popping" as chucking, OP with a woodchuck. Wnt (talk) 20:06, 18 July 2015 (UTC)[reply]

Approximate answers? Pah! I can give an exact answer... How much spacetime? All of it. AndyTheGrump (talk) 20:07, 18 July 2015 (UTC)[reply]

Ah, so if I can arrange to pop out of nowhere/nothing somewhere other than this universe, I would have all the space I always wanted and all the time to do everything I wanted in my universe? --81.147.170.83 (talk) 16:30, 19 July 2015 (UTC)[reply]

As long as breathing is not required. ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:32, 19 July 2015 (UTC)[reply]

Would you care to join me?? At least that would shut you up!!--81.147.170.83 (talk) 16:35, 19 July 2015 (UTC)[reply]

You're the one that raised the absurd premise. ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:18, 19 July 2015 (UTC)[reply]

Richard Owens west Canada expedition

19:00, 18 July 2015 (UTC)66.192.172.132 (talk)What is known of Owens west Canada expedition? What is known of M.W.Bartlett who was an agent for Owens on the west Canada expedition?

To clarify - is this the Richard Owens after whom the Owens Valley is named? I'm afraid we don't have an article on him - all we have is brief details of his military career at California Battalion#Battalion Organization. But this may assist others in finding more information. Tevildo (talk) 20:43, 18 July 2015 (UTC)[reply]

We also have Owens Peak who seems to be the same man; "an Ohio born explorer (aka "Owings"), who accompanied John C. Frémont on his third expedition to California (1845–1946). Fremont also named a valley, river and lake for Owens, whom he considered 'cool, brave and of good judgment'. Owens served as Captain in Fremont's California Battalion during the Mexican-American War, and was California's Secretary of State during Fremont's brief tenure as Governor (1847)". Unfortunately, the link that references the last sentence doesn't go to the right page any more. Kit Carson Days, 1809-1868: Adventures in the Path of Empire, Volume 2 by Edwin Legrand (p. 926) says, "He is reported as doing a merchandise business in Santa Fe in the Fifties; and a Richard Owens was the last auditor (1850) of the territory of New Mexico under military rule. The place and date of Owens' death seem not to be of record". However, this Richard Owens seems to have made his name in California rather than Canada. Alansplodge (talk) 16:30, 19 July 2015 (UTC)[reply]

According to this article, William Fitzwilliam Owen published two books, one under the name "Richard Owen", and one under the name "William Fitzwilliam". Could he be the OP's "Richard Owens"? There are, of course, several other Richard Owens to choose from, but none of them obviously associated with exploration. Tevildo (talk) 18:02, 19 July 2015 (UTC)[reply]

baby spots

Some animals are born with spots but lose them: e.g. some deer, some cats. Is there a word for that phenomenon? —Tamfang (talk) 21:04, 18 July 2015 (UTC)[reply]

One term is Moulting. Cats are listed, deer are not. However, this referred to the process in deer as mo(u)lting. ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:34, 18 July 2015 (UTC)[reply]

We don't seem to have an article on juvenile coloration (I may be wrong, there should be one). There are several reasons for it. Spotting is usually to camouflage young that sit still in shade-dappled areas, like fawns and lion cubs. Some birds simply lack the adult coloration that marks (especially male) gender. Many primates have blondism in juveniles or red hair, including humans, gibbons and Silvered leaf monkeys, which seems to elicit caring behavior and perhaps deter aggression from sexually mature males. See also the colored gape of many bird chicks. μηδείς (talk) 23:21, 18 July 2015 (UTC)[reply]

Biotech Research- please help!

Hello! I am working on a self-issued biotech project for fun. After one of my friends wondered out loud whether or not sci-fi-esque suspended animation is possible, I set out to find an answer.

To cut to the chase, does Wikipedia contain articles on non-solid nutrirional options, esp. nutrient mixes, calorie paste or an othersuch item, IV systems, and a list of the body's compatability with intravenous compounds/objects?

Thanks you for any help you can give! 12.204.242.133 (talk) 23:34, 18 July 2015 (UTC)[reply]

Medical food and Parenteral nutrition might be useful starting points. Tevildo (talk) 23:59, 18 July 2015 (UTC)[reply]

Liquid breathing, cryoprotectant and machine perfusion may be of interest. And we do have an article on suspended animation. Graeme Bartlett (talk) 00:04, 19 July 2015 (UTC)[reply]

July 19

Does shaving your armpits make them smell less bad?

^Topic Malamockq (talk) 01:08, 19 July 2015 (UTC)[reply]

See [4] AndyTheGrump (talk) 01:17, 19 July 2015 (UTC)[reply]

Lesbians

Does the "lesbian bed death" theory change depending on whether the couple are composed of both lipstick lesbians, both stone butch, or a lipstick lesbian and a stone butch? — Preceding unsigned comment added by 147.91.1.41 (talk) 01:54, 19 July 2015 (UTC)[reply]

Can someone who's good with WP:AfD explain which criterion would be best for deleting this 30+ year-old fringe nonsense based on the "work" of one rather un-noteworthy author? Thanks. μηδείς (talk) 10:08 pm, Today (UTC−4)
- See WP:GNG and WP:NTEMP. According to the guidelines, if it was notable 30 years ago, it's still notable today. Tevildo (talk) 15:51, 19 July 2015 (UTC)[reply]
According to the article you've just linked, it is a fringe theory which has been fairly thoroughly debunked by mainstream sociologists who study these things seriously. So, the answer to your question is "the answer doesn't matter because the theory itself isn't sound". --Jayron 32 02:51, 19 July 2015 (UTC)[reply]

That's a really dismissive and unhelpful approach. The guy specifically asked whether the theory changed based on those factors - in other words, does the theory/its adherents postulate that those factors matter. You might as well answer a question about Aristotle's theories on gravitation with "it doesn't matter because he was wrong." -Elmer Clark (talk) 05:14, 21 July 2015 (UTC)[reply]

If civilisation collapsed, could humanity have another industrial age?

Have we drilled and mined all the oil and coal within easy reach that if society collapsed and humanity went into a primitive state the industrial revolution could never happen again? 2.102.184.233 (talk) 06:58, 19 July 2015 (UTC)[reply]

At the top of the page, it says "We don't answer requests for opinions, predictions or debate." Ian.thomson (talk) 07:15, 19 July 2015 (UTC)[reply]

I'd mine rubbish tips for plastic to burn. Also a great resource for other raw materials. I'd guess that a charcoal fuelled industrial economy would be possible, but would not be easy. However, knowing the answers in advance helps a lot.Greglocock (talk) 07:39, 19 July 2015 (UTC)[reply]

Statement of the obvious, but we use fossil fuel because it's cheaper, not because it's the only energy source. There's no reason other than the economics of extraction that industries tend to run on fossil fuels—Brazilian industry runs on sugarcane and the nation hasn't fallen apart yet. There are plenty of potential natural sources of oil that wouldn't require processing to be usable in an non-industrial society—palm, rape, soy, even whale. – iridescent 08:52, 19 July 2015 (UTC)[reply]

But the question is if any of those energy sources would be available in the quantity needed to fuel an industrial age, keeping in mind that our current production methods for many of them rely on fossil fuels. I'm sure you can harvest some of those using traditional farming methods (plowing with draft animals, etc.), but the quantity would likely be way less. StuRat (talk) 18:35, 19 July 2015 (UTC)[reply]

Why would humanity need another industrial age? If "society collapsed" there would be certain problems which would have to be addressed. But there would likely be certain knowledge retained from prior to the "collapse". The presence of that knowledge would imply a different path forward than the path previously taken by humanity prior to the industrial age. A collapse of society is a possibility but a complete loss of information is unlikely. Bus stop (talk) 19:07, 19 July 2015 (UTC)[reply]

The question was whether it would be possible, not desirable. --174.88.133.35 (talk) 04:59, 20 July 2015 (UTC)[reply]

It would be possible but it would differ from the previous industrial age because information would be available that was not available the first time around. Bus stop (talk) 05:04, 20 July 2015 (UTC)[reply]

It's not just information that is needed. For example, they may have plans for a nuclear power plant, but they still can't build one without massive resources, like money, skilled manpower, tools, raw materials, roads, ports, etc. StuRat (talk) 13:18, 20 July 2015 (UTC)[reply]

He probably meant we would aim for electricity and not an inefficient steam engine and then use that for a few decades and later recapitulate the entire 19th century. If we did that and there were literally no civilization it would take thousands of years for someone to think of the stirrup. Sagittarian Milky Way (talk) 17:13, 20 July 2015 (UTC)[reply]

The more interesting/immediate question is whether the planet will survive. In a "collapse of civilization", does it ever become truly infeasible for small local entities and barbarian regimes like ISIS to extract shale oil and such to power their local and longer-range wars? I don't know. If we could manage to roast the Earth in a runaway greenhouse effect we wouldn't have to worry about the next cycle. Wnt (talk) 12:19, 20 July 2015 (UTC)[reply]

Engineering in business

Is engineering in the workplace less mathematical than engineering in college and academia? 176.27.11.220 (talk) 11:35, 19 July 2015 (UTC)[reply]

Yes. In the workplace, an engineer's skill with math is used more to comprehend the math that others have used in explanatory documents than in actually applying math to solve problems. The other major change when transitioning from academia to the workplace is the increased use of written language. In academia, engineering students don't get a lot of practice at written language but in the workplace engineers are using written language on a daily basis to explain and persuade. Many graduate engineers initially display inadequate skills with written language. Dolphin (t) 13:16, 19 July 2015 (UTC)[reply]

In the workplace engineers tend to 'specialize' and not need the wide verity of mathematical skill they learnt in university. However, across the whole of industry I would say that it is on par with academia. The two can't be separated, as industry also performs its own R&D. Its from this feedback process that collages get feedback as to exactly what courses to offer the next generation of future ~~slaves~~ graduates and where to direct resources into their own university’s blue skies research. On balance, collage just bring 'the knowns' to a wider audience. So to answer you question. Yes, math is as widely used in the work place as in hallowed institutions.--Aspro (talk) 15:01, 19 July 2015 (UTC)[reply]

Many engineers - even those who specialize in areas other than computer design - spend a lot of time performing computer programming. To quote Edsger Dijkstra, one of the founders of modern computer theory, programming is one of the most difficult branches of applied mathematics.

Now that we have cheap and omnipresent calculating machines, it is unlikely that an employed engineer will need to perform arithmetic very often. However, engineers conduct mathematics every day. After you study more engineering mathematics at the university tiers, the distinction (and the relationship) between arithmetic and mathematics will become more clear. Nimur (talk) 17:22, 19 July 2015 (UTC)[reply]

Disagree on one little point. Programming is one of the most exciting branches of applied mathematics. After all. One doesn’t climb Mount Everest just because it difficult (only masochists do that). It is the human drive, to willingly suffer those hardships to reach the highest peak. That is the reward. To stand upon top -with the rest of the world below you.--Aspro (talk) 23:18, 19 July 2015 (UTC)[reply]

The answer is, it depends. I have had to learn quite a lot of additional maths in both of my specialisations (NVH and vehicle dynamics) , but equally there is a quite a lot of my university maths I don't use at all. However the average oompa loompa (http://www.urbandictionary.com/define.php?term=Oompa+Loompas+of+Science) seems quite happy not to bother with anything beyond excel used/misused at a fairly basic level. Iimagine there are many engineers who use statistics at a fairly advanced level compared with what they learned in university. Greglocock (talk) 01:53, 20 July 2015 (UTC)[reply]

Yes, I can agree with the above. When one specializes one uses one skill to go beyond what one was taught. Nimur comment puzzles me a little though. Does he mean arithmetic long hand. i.e., with pencil and paper? I went on to learn (not very well) log tables (and on entering industry), slide rules (which, over forty years on, still work without having their batteries replaced even once) and then big desk top calculating machines with nixie tube displays. What ever means ones uses to perform arithmetic, one is still performing arithmetic.--Aspro (talk) 21:21, 21 July 2015 (UTC)[reply]

Hybrid cars: Nickel-Metal Hydride or lithium-ion battery?

How does it come that the nickel-metal hydride battery was chosen for the Prius (until 2015 at least)? As I understand, when you brake, the car stores the energy into the battery. However, are nickel-metal hydride batteries appropriate for this kind of fast loading? And besides price, does nickel-metal hydride have any advantage in comparison to a lithium-ion battery? And what was the reason of the newly introduction of a lithium-ion battery for the Prius 2015?--Yppieyei (talk) 15:55, 19 July 2015 (UTC)[reply]

NiMH are far less likely to undergo the infamous venting with flames that lithium batteries are famous for. See Plug-in electric vehicle fire incidents, Lithium-ion battery#Safety and Nickel–metal hydride battery. Nil Einne (talk) 16:28, 19 July 2015 (UTC)[reply]

NiMH batteries also have less of a tendency to degrade when recharged in hot temperatures, as anyone who lives in a hot climate and buys a phone or laptop with a non-replaceable lithium battery generally finds out within a couple of years. – iridescent 16:32, 19 July 2015 (UTC)[reply]

Also note that, while that would qualify as fast charging if it all went into a single cell, that it's spread out over all the batteries in the entire car, so that it's not much charging at all into each. I suppose they could also use a flywheel or capacitor to store the energy temporarily, to slow the charging even more (or reuse it directly from those sources). StuRat (talk) 18:30, 19 July 2015 (UTC)[reply]

The LiOn, used in mobile phones, tablets and notebooks are known to be usedful for three years. To keep it useful for longer time the Prius operats its battery between 40 to 90 percent charge, only. Do you known an owner of a Prius who needed to renew the battery? --Hans Haase (有问题吗) 20:08, 19 July 2015 (UTC)[reply]

There are lots of Prius' owners renewing the battery. You can find loads of used Prius batteries on eBay, and even buy a single module of it. The Li-ion battery is new, as said by the OP, so there are not many of this around yet. --Scicurious (talk) 03:14, 20 July 2015 (UTC)[reply]

Checkout BMW i3 and Tesla Model S.--Phil Holmes (talk) 12:54, 20 July 2015 (UTC)[reply]

Singularities

If singularities are in fact impossible in our universe, then each black hole must excrete its matter somewhere. Does this excretion have to be in this universe or can the matter be ported to another universe?--81.147.170.83 (talk) 16:34, 19 July 2015 (UTC)[reply]

You have stated a premise as if it is a fact: if a then b ...

You have not shown a; why do you believe singularities are impossible?

You have not established the validity of the logical implication: why do you believe that this implies black holes must excrete matter somewhere?

It is not efficient to start chasing down a logical consequence when neither the truth of the statement, or its premise, has yet been established.

So, let's start over... where are you reading about black holes? How have you reached the point where these questions even come up? Have you started by reading our article, black hole, and then following up with the reference material in that article?

To study black holes meaningfully, you need to learn a lot of prerequisite mathematics and physics. This way, we can quickly refer to preestablished concepts, like the conservation of mass flux or the mass-energy equivalence or the complicated geometry of spacetime that follows from a treatment of gravity in general relativity. If you haven't mastered these concepts first, it will be hard to efficiently communicate about black holes with any scientific merit. For example, we will want to determine whether mass, or mass flux, is a conserved quantity - and whether this statement is true in the exotic circumstances near a black hole. That's a complicated scenario! As a prerequisite, are you already familiar and able to work with these quantitative concepts in non-exotic scenarios?

Nimur (talk) 16:44, 19 July 2015 (UTC)[reply]

As far as black holes excreting matter, this seems to happen in our own universe, from each black hole, but over a very long time frame (except for micro black holes). See Hawking radiation. StuRat (talk) 16:51, 19 July 2015 (UTC)[reply]

While Hawking radiation is a real phenomenon, it is not directly a consequence of the original premise ("singularities are impossible", a premise which is neither confirmed nor refuted by the existence of Hawking radiation). This is important: scientific hypotheses must be precise and testable, and our conclusions must be commensurate to the evidence. Nimur (talk) 16:57, 19 July 2015 (UTC)[reply]

Most if not all physicists would agree with "singularities are impossible". But I don't know how you got from that to "each black hole must excrete its matter somewhere". -- BenRG (talk) 19:09, 19 July 2015 (UTC)[reply]

I understand what they are saying: "Matter can not forever go in one direction (into the black hole) without ever going the other way". I'm not sure that I agree with that argument, though, as it could forever go into the black hole at an ever decreasing rate, or perhaps just stop going anywhere at some point. StuRat (talk) 20:58, 19 July 2015 (UTC)[reply]

Black holes grow larger and more massive as they accrete matter. They're no different in that regard from any other gravitationally bound object. The matter doesn't have to go anywhere; it's just there. -- BenRG (talk) 00:31, 20 July 2015 (UTC)[reply]

I could see someone coming to this conclusion based on the peculiarities of space in a black hole. Specifically, that standing still over a period of time is impossbile - the future is down, and all that. One might conclude that if matter can't sit still, but it is blocked from moving down, it must go somewhere else. Someguy1221 (talk) 05:17, 20 July 2015 (UTC)[reply]

The matter actually is excreted, via Hawking radiation. The OP is grasping toward the ongoing theoretical question of whether information (as well as mass) gets destroyed in a black hole, or if it comes out in some way in the Hawking radiation. I think current belief is that things fall into a black hole, they get thoroughly disassembled, but they do come back out after a very long time. Wnt (talk) 12:16, 20 July 2015 (UTC)[reply]

Ok let me put this more simply without any assumptions. Where does all the matter that falls into a black hole go?--81.147.170.83 (talk) 14:50, 20 July 2015 (UTC)[reply]

In plain English, the matter goes near the black hole. This plain English description would also apply to matter that falls onto a planet: if a meteorite falls onto Earth, the meteorite (and all the fragments and gases and matter) all ends up going "near" Earth. The plain English description - "near" - is not precise enough to capture the details that make black holes different from ordinary stuff.

To measure where something goes, you must define position (and distance) using some coordinate scheme. To understand black holes, you must recognize that in general relativity, gravitation manifests as a distortion of the coordinates. As mass accumulates, the warping of space and time increases: the measurement of position becomes more complicated. When and where you make the measurement becomes much more important. Your answer is dramatically different if you are within a certain distance from the "center" of the accumulating matter - the Schwartzchild radius.

Conceptually, there is no "hole": there's just a big massive object. But, unlike other big massive objects you are familiar with, this object is so massive that the effect of its gravity changes the definition of position in a way we cannot ignore. The best way to describe this change accurately is to start writing out equations. Are you looking for a resource that will walk you through those equations?

If you would like to look at how we could formalize the defintion of "position," you can read our more technical articles on black holes. For example, take a look at the radial distance element in our article, Eddington–Finkelstein coordinates. This tells us about the path that an object would travel for one simplification of a black hole. Do you know how to use a differential path element to work with position, distance, and trajectory? Does this math make sense to you? You will probably need to spend some time reviewing algebraic geometry and calculus; and that's just to understand the result. To understand the derivation - in other words, why this is the answer - you will need to study some fairly difficult physics, too.

Nimur (talk) 15:57, 20 July 2015 (UTC)[reply]

For more reading: our article on Gullstrand–Painlevé coordinates includes a worked example-problem for an object falling into a black hole. Again, the reader is expected to have a very strong background in mathematical physics. The equation solutions are not very difficult; but their derivations, and the conceptual implications, are quite complicated. Nimur (talk) 20:36, 20 July 2015 (UTC)[reply]

I may not actually understand ~~all~~ any of the above, but I remember reading that Hawking radiation could be thought of as a quantum tunneling effect for particles at the singularity. Searching Google delivers various hits for this idea (mainly Arxiv papers of, to me, unknown canonicity), including our own article. So we say that particles that fall into a black hole fall "into" the singularity, but in truth a particle isn't at any one particular place; there is variation in where it really is by measurement. Very, very rarely this variation in measurement is so far that it is outside the black hole entirely. Now one of many things I don't know is if anyone has a way to measure Hawking radiation and see if it matches theory for all the particles sitting at the center of the hole, rather than (say) sitting in a shell just under the event horizon or whatever, in which case I assume there'd be more Hawking radiation. There's some kind of comparison to Unruh radiation but I think that kind of begs the question if there were some structure inside the hole we don't know about. Wnt (talk) 21:35, 20 July 2015 (UTC)[reply]

Radio-frequency identification

The IT media keep telling us about the promised advantages of clothing with computers woven in to them but why doesn't clothing have cheap RFID chips already? !!! The poor (and understaffed) Northumbria Police are having ask members of the public for information to solve the mystery of a Beach Towel stolen in broad daylight. Had the owners been able to buy a Beach Towel with such a RFID chip woven in, these scums (beach bums), would by now have been apprehended by now -as soon as their motel scanner registered that they where carrying a Beach Towel that had been taken without the owner's consent. Isn't that more useful that a pair of computerized Bermuda shorts that can instantly give you the value of $π$ to 10⁶ decimal places?--Aspro (talk) 19:46, 19 July 2015 (UTC)[reply]

Your external link doesn't work for me. This one does. Rojomoke (talk) 19:55, 19 July 2015 (UTC)[reply]

Thanks. Both links work for me, so perhaps my link only works in the UK. I can't see how the newsindex in the URL makes and regional difference. Can any geek shine light on this? --Aspro (talk) 20:29, 19 July 2015 (UTC)[reply]

Huh, now yours works. Must have been a temporary glitch. BTW, I'm in the UK. Rojomoke (talk) 21:55, 19 July 2015 (UTC)[reply]

Uhm. Wondering, that as it was Sunday night, the website may have been under going a little weekend maintenance? That can make normal access problematical.--Aspro (talk) 23:30, 19 July 2015 (UTC)[reply]

So you want to install RFID readers in every room, all linked to a central database, at a cost of millions, to catch beach towel thieves ? Also consider the loss of privacy ("Looks like Mrs. X's panties ended up in MyMr. Y's bedroom again !"). Please tell me you asked this question as a joke. StuRat (talk) 20:54, 19 July 2015 (UTC)[reply]

Well... So OK... You are honest enough to admit that My Y's bedroom frequently gets littered with Mrs. X's panties, but RFID could be of use to Mr X (who bought her knickers in the first place) and wants to get his property back (these days - designer panties don't come cheap – ask any woman). Is this not, the position the beach towel owner found themselves in? Fortunately, here in the UK, we have a police force that leaps into action in order to maintain zero tolerance. If ever these guys get caught they are facing at least three life sentences. --Aspro (talk) 22:37, 19 July 2015 (UTC)[reply]

This is I suspect not a serious question, but I will say that there are much simpler ways to mark clothes - you can order embroidered or printed name tags for a few pence each from various online shops, or just write the name on using a wash-fast marker pen - and they're about as difficult to remove from a piece of clothing as an RFID tag would be (since you can just snip it out or whack it with a magnet to mess up the chip). Some clothes and bags do already have chips sewn into their labels (I had a coat that caused me massive problems when a stock-checking tag sewn into the pocket lining somehow reactivated and began triggering alarms in every shop) but these are for stock-tracking, shop security and luggage tracking, rather than protecting later owners from theft. Smurrayinchester 09:06, 20 July 2015 (UTC)[reply]

Yeah, but it's harder to have a drone fly over and keep constant surveillance over what every laundry tag says. See [5] for an idea. Why do you think the spy-industrial complex wants to put a "short-range" radio connection in everything you use, if they couldn't read it at short range? Wnt (talk) 12:13, 20 July 2015 (UTC)[reply]

Hotel towels with RFID chips starting hitting the media about 2011. It's worth a quick google if you want to find out more. shoy (reactions) 18:30, 20 July 2015 (UTC)[reply]

In NZ it hasn't been uncommon for jackets and coats sold in some shops to have RFID tags, probably for over 10 years. It's not so fun when as Smurraryinchester mentioned, store security systems get triggered by them, even stores which have never and are never likely to sell these items because they are a house brand of another store. Of course even worse than a coat/jacket is a reusable shopping bag which again may be housebranded but active security systems in stores not owned by the same company, but perhaps not the store you purchased it from. As Summaryinchester mentioned, these RFID tags are intended for the store use and I'm totally sure they actually have a unique per item identification. Nil Einne (talk) 20:10, 20 July 2015 (UTC)[reply]

July 20

What's the formula that predicts telephonic traffic? Is there one for humans instead of phone calls?

I saw in a math book long ago that there's a formula that predicts phone traffic between US city pairs by population and distance and people hardly ever called from Seattle to Miami compared to between Baltimore and DC or something because it's exponential or something with distance. I wonder what it was. Maybe there's one for transportation of humans or even Internet traffic? Sagittarian Milky Way (talk) 01:20, 20 July 2015 (UTC)[reply]

Teletraffic engineering involves much math, but particular city pair predictions, whether for telegrams or airline flights, are mostly based on recent traffic, with the predicting part being mainly guessing at future growth rates. Jim.henderson (talk) 01:49, 20 July 2015 (UTC)[reply]

Well I'm sure actual data would be more accurate but there's got to be a formula that fits the data points closest. Also, few people would get to the airport 2 hours before to fly a short distance so adding highway traffic would probably make a better formula (though one fit for airlines might fit well for long distances). Sagittarian Milky Way (talk) 02:05, 20 July 2015 (UTC)[reply]

Yes, IIRC this formula was important in a wider scope than just telephony. You might get a better response at Computing or Mathematics. μηδείς (talk) 16:00, 20 July 2015 (UTC)[reply]

Public events like cricket (FIFA World Cup) or similar events on TV may cause phone usage behavior like no calls and many calls in the break, advertising gaps and when a team has won. --Hans Haase (有问题吗) 20:15, 20 July 2015 (UTC)[reply]

Coronal sulcus and foreskin of penis

Why is it that some normal foreskins retract over the head and past the coronal sulcus and others only go over the head but not past the sulcus? What determines how far down the foreskin goes and why is it different for different people? 94.14.154.30 (talk) 20:57, 20 July 2015 (UTC)[reply]

Human_variability. SemanticMantis (talk) 21:14, 20 July 2015 (UTC)[reply]

For the last question, see Frenulum_of_prepuce_of_penis. SemanticMantis (talk) 22:39, 20 July 2015 (UTC)[reply]

As an uncircumcised male, I challenge the premise that any healthy adult male can not retract their foreskin past the coronal calculus. I think it's borderline a medical condition if you can't do that after puberty, but it's not really something I want to search for references on this comptuer. Vespine (talk) 22:51, 20 July 2015 (UTC)[reply]

I guess it depends on what is considered "healthy" - phimosis is a real thing, not clear to me that that in and of itself is an illness. From the article "Normal developmental non-retractability does not cause any problems. Phimosis is deemed pathological when it causes problems" (emphasis mine). SemanticMantis (talk) 23:08, 20 July 2015 (UTC)[reply]

So it's not a problem unless it's a problem? :) Sounds like an argument for circumcision. ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:22, 21 July 2015 (UTC)[reply]

Your leg is not a problem until it is a problem? Sounds like an argument for amputation. Fgf10 (talk) 11:31, 21 July 2015 (UTC)[reply]

Could be! ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:54, 21 July 2015 (UTC)[reply]

If it wont go, it needs stretching -- continually!!--81.147.170.83 (talk) 15:26, 21 July 2015 (UTC)[reply]

Possibly aided by a motor, such as the Wankel engine. ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:40, 22 July 2015 (UTC)[reply]

July 21

Can sound travel through Mars' atmosphere?

Imagine this situation. Two people at a distance are shouting over the surface of Mars (ignore the habitability). Could they hear sound? --IEditEncyclopedia (talk) 04:35, 21 July 2015 (UTC)[reply]

Here is a webpage from NASA JPL about Mars Polar Lander's acoustic microphone. This 1999 space probe was lost and could not operate its instruments atthe Martian surface. But, you can read what planetary scientists expected to hear!

After the loss, the Planetary Society tried to piggyback their experiment on another spacecraft, the NETLANDER probe. That mission never launched; CNES did not fund it. I don't recollect any more recent serious scientific effort - attached to NASA or any other space exploration agency - to place a microphone on Mars. (Here's the project webpage, hosted at Berkeley's Space Sciences Laboratory: Mars Microphone). "Sound on the surface of Mars is expected to be similar to that on Earth, except much fainter because the atmospheric pressure is much less than on Earth. Martian atmospheric pressure is about 7 millibars (as on Earth, this is altitude-dependent), which is less than 1% of the Earth's."

Even if the Martian atmosphere could transfer sound waves - perhaps at very low amplitude - it is unlikely that any such sound would be audible to unassisted human ears. Human ears don't work very well in extremely low ambient pressure. The technical term is "barotrauma": exposing your ear to such low pressure that is not at equilibrium with the rest of your body can cause temporary or permanent damage, including hearing loss. Here's a recent research article: Predictors of ear barotrauma in aircrews exposed to simulated high altitude. We know from experiments like this (and from terrible accidents) that humans don't deal well with low pressure: high altitude air crews and astronauts on the Martian surface are both, for practical physiological purposes, essentially in total vacuum; they must be provided a safe and controlled pressurized environment. If you're interested in "trying it out for yourself" just to see what it's like to expose your ears to near-vacuum conditions, the FAA and the Air Force work jointly to open up their high altitude physiology and safety training program to civilian members of the public every once in a while. You can find details at American Flyers, a commerical facilitator. A friend of mine flew up to Beale for this course some years ago: the effects of severe low pressure were, in his words, quite unpleasant. In addition to physical discomfort, there are also profound psychological effects.

Nimur (talk) 05:11, 21 July 2015 (UTC)[reply]

Just to be clear, sound clearly exists on Mars. It has an atmosphere, which can transmit vibrations. That's all sound is: matter which vibrates. The Martian atmosphere, though quite thin by Earth standards, is real, and thus can really transmit sound waves. You are correct that it is unlikely humans could hear the sound, for a variety of reasons, but the sound clearly would exist, and be detectable, just not by unaided human ears. --Jayron 32 05:31, 21 July 2015 (UTC)[reply]

Be careful, you'll have the philosophers spouting their "If a tree falls in a forest..." nonsense here before too long!. Entirely correct answer though. Fgf10 (talk) 11:29, 21 July 2015 (UTC)[reply]

Ermmmm...wouldn't they be wearing helmets, so they would not be able to the shouts! Sorry! I think Jayron is correct.DrChrissy ^(talk) 14:15, 21 July 2015 (UTC)[reply]

Let's be clear- there are two distinct definitions for sound - see Sound#Definition. One definition is based on physics, and that works fine on Mars, as per Jayron. However, the second definition requires Auditory sensation evoked by the oscillation - So Nimur's perspective is also valid. To go back to the old saw about trees falling that Fgf10 mentions, the solution is very clear - from a physics perspective, sound is just vibration and energy, and of course the tree makes a sound. From a music theory or audiological perspective, sound needs a hearer, and so there isn't a sound if there's no perceiver. SemanticMantis (talk) 14:33, 21 July 2015 (UTC)[reply]

I don't think, even under that definition, sound needs somebody to actually hear it, but just needs to be something somebody could hear, if they were present. In that way it's similar to other human perceptions. We don't theorize that the forest entirely ceases to exist when nobody is looking at it, after all. (I suppose you could, but both would violate Occam's razor, so you would need to explain exactly why it changes depending on the presence or absence of an observer. We do get some things in quantum mechanics that seem to follow that pattern, but that's very different from macro objects.) StuRat (talk) 15:25, 21 July 2015 (UTC)[reply]

No, that's not how the definition works. It doesn't say "capable in principle of being heard", it says "auditory sensation." Using that definition, it's not a sound if nothing hears it. You don't have to use that definition if you don't want to :) SemanticMantis (talk) 15:57, 21 July 2015 (UTC)[reply]

I think it is clear enough that if you could put your ear to a railroad track on Mars, you would hear the oncoming train about as far as on Earth. So the question is how well the sound travels through the Martian air, complicated by the impedance mismatch at the astronaut's helmet (and perhaps at the source, if the source is, say, another astronaut with a smashed radio screaming at a White Ape). I think that the specifics of the helmet are going to matter a lot. But apart from that, well, the sound can be simulated; it's just, alas, that these bastards seem to be holding out on us. Wnt (talk) 19:40, 21 July 2015 (UTC)[reply]

Quick calculation for viability of camping turbine project

I had an idea to turn such a fan as this into a turbine to charge electronics when camping. It's IP55 waterproof.

I'm trying to calculate whether this is viable. I figured if applying 270 mA at 12 V gives a flow of 89.4 CFM (cubic feet per minute) and the wind speed is 5 m/s then the flow rate through the fan blades is 5 m/s x 60 s/min x pi x (0.014 m)2 = 185 litres which is only 6.5 cubic feet. Even if the wind was 10 m/s which is not unlikely but 8m/s is most likely, it's still not going to be producing much power. Am I right in declaring this idea to not be viable? ----Seans Potato Business 14:03, 21 July 2015 (UTC)[reply]

Another reason why it's impractical is that windmill blades need to be far from the ground or anything else that will slow the wind, so you would need to carry a mast with you while camping, too. Alternatively, I like the idea of a flexible solar panel on the top and back of your backpack, so it can charge your devices (in your backpack) while you walk. StuRat (talk) 14:42, 21 July 2015 (UTC)[reply]

It's Scotland so there's plenty of wind, particularly in the hills but not so much sun! 7-8 m/s is a reasonable expectation on the hills. --Seans Potato Business 15:38, 21 July 2015 (UTC)[reply]

On the ground ? StuRat (talk) 15:44, 21 July 2015 (UTC)[reply]

I've no idea. It gets windy enough to make conversation difficult. --Seans Potato Business 16:33, 21 July 2015 (UTC)[reply]

Another option might be piezoelectrics in your shoes to charge things as you walk. That would involve a wire going up each leg, though, into your backpack. StuRat (talk) 15:46, 21 July 2015 (UTC)[reply]

While we're on a digression, I should add that camping frequently involves the availability of free fuel. I don't know if there is a mini steam engine you can carry with you to recharge your electronics, but searching for "camping thermocouple" I found a few links like [6] which sort of make me think there must be a way to recharge items quietly and easily from a campfire. But I'm a bit shy of finding the genuine article at the moment. Of course, if you don't have fuel available you could always find out where the New Horizons mission control replica is and heist its power supply. :) (Fallout... what's a little fallout?) Wnt (talk) 18:02, 21 July 2015 (UTC)[reply]

Here's a review of that product [7]. Here's a review of several off-the-grid chargers, ranging from hand cranks to solar to various combination devices [8]. SemanticMantis (talk) 18:43, 21 July 2015 (UTC)[reply]

Yeah, the general suckiness of thermocouples and the lack of some solid state gizmo that works as quietly, but with the efficiency of a Carnot engine... that strikes me as one of the most gaping holes in our current technology. In this century there are not supposed to be compressors and combustion chambers and fans everywhere, dang it! Wnt (talk) 19:46, 21 July 2015 (UTC)[reply]

And this appears to be the product you're looking for, although if you're prepared to pay a fortune (for the UK you're looking at £300-£500) the Trinity Wind Turbine is a lot cooler (the whole thing folds down into a neat little cylinder about the size and shape of the cardboard tube from a toilet roll). – iridescent 22:05, 21 July 2015 (UTC)[reply]

This guy demonstrates the concept. I think the most practical idea is to use lightweight foldable solar panels. They'll produce some power even in cloudy Scotland though of course much less than in bright sunshine. You probably won't be able to charge something power-hungry like an iPad but it should be possible to charge a radio or maybe a mobile phone. Here are some reviews. Short Brigade Harvester Boris (talk) 05:08, 22 July 2015 (UTC)[reply]

Do people ever make birth control for male nonhuman animals?

I watched a nature documentary that reported that African elephants were confined to nature conservation parks, which had limited space, because human beings were taking over the land for agriculture or something related to the expansion of human development. The elephants thrived in the park too well, and hunting them was no good, because they bereaved the dead. So, a viable option was to invent birth control for the female elephants. This reminded me of the fate of the North American deer and how birth control was invented for the female deer. Do people always make birth control drugs for female animals and not male animals? Is it ever possible to temporarily make infertile a male animal? 140.254.226.190 (talk) 14:08, 21 July 2015 (UTC)[reply]

At least a handful of places have sterilized male squirrels in an effort to control the squirrel population - Santa Monica here [9], UC Davis here [10], Britain here [11]. Many of them use Gonacon - more on that here [12]. SemanticMantis (talk) 14:15, 21 July 2015 (UTC)[reply]

Oh, Gonacon is just a redirect to Wildlife_contraceptive, and doesn't have good info. From the Telegraph article above, "The vaccine stops ovulation and lactation in female squirrels, while halting testicular development in males." The ecoworld article says " Once injected, the animal in question is sterile for 2-4 years." The same article says it can also be used on Feral hogs, horses, deer, cats, and dogs. So the answer to your question is "yes" - Gonacon only started being deployed in the wild fairly recently, but it works on males and females, and will probably increase in usage over the next decade. SemanticMantis (talk) 14:27, 21 July 2015 (UTC)[reply]

I suspect that the question was directed at non-surgical methods, but let's not forget castration.DrChrissy ^(talk) 14:35, 21 July 2015 (UTC)[reply]

Castration changes the physiology and behaviour of male animals, thus vasectomy is the preferred surgical option.

http://www.biodiversityscience.com/2012/12/11/vasectomy-elephant-longer-term/

Roger (Dodger67) (talk) 15:44, 21 July 2015 (UTC)[reply]

Yes it is common practice in the UK (and probably other countries too) to neuter male cats and dogs. --TammyMoet (talk) 17:59, 21 July 2015 (UTC)[reply]

I'll also add that sterilizing females is more effective than sterilizing males, at least for most species. population biology, sexual selection, and fecundity usually work out for mammals such that the number of viable females is the limit to population growth. If you sterilize say 20% of males, you still might find that 100% of viable females give birth that season. But if you sterilize 20% of females, then only 80% can give birth that season. This is why control of wild populations usually targets females or both sexes, and not just males. SemanticMantis (talk) 18:37, 21 July 2015 (UTC)[reply]

Is the correct answer. One human male produces enough sperm to get every woman in the world pregnant in a few weeks. Elephants tend to live in herds of females, with calves, and bulls either solitary or in small groups. The herds and bulls only normally come together to mate. It would only need on rampant bull elephant to mess up the park's program. I suspect the park would want to control the population at a stable level, and keep genetic diversity and family groups. So putting e.g. half of the cows in each herd on the pill would be the best way to achieve population control, whilst retaining diversity. Martin451 16:38, 22 July 2015 (UTC)[reply]

Wild animal photos

Wikipedia:Help_desk#Wild_animal_photos Can someone identify two animal species if provide the photos?Lbertolotti (talk) 20:30, 21 July 2015 (UTC)[reply]

Without seeing the photos, we have no way of knowing whether the species can be identified. Certainly we succeed in making positive identifications sometimes, but it very much depends on the images, and the amount of other information provided (not least the location where the photos were taken). You should note however that when it comes to insects (like the fly which is one of your subjects), it is sometimes only possible to make a positive identification of a particular species through microscopic examination and/or dissection. AndyTheGrump (talk) 20:39, 21 July 2015 (UTC)[reply]

@AndyTheGrump Ok, do you want me to use the Wikimedia uploader for this?Lbertolotti (talk) 22:17, 21 July 2015 (UTC)[reply]

I've added some other wild animals images, luckily we will identify them all.Lbertolotti (talk) 16:54, 22 July 2015 (UTC)[reply]

Bird

Well here it is.Lbertolotti (talk) 00:34, 22 July 2015 (UTC)[reply]

Hey that's a start! Is this near Anchieta,_Espírito_Santo? I can't find a WP article related to Anchieta Island. SemanticMantis (talk) 01:32, 22 July 2015 (UTC)[reply]

Anchieta Island, in the northern coast of the state of São Paulo, Brazil, famous as the site of a state prison.Lbertolotti (talk) 01:42, 22 July 2015 (UTC)[reply]

The photo is very difficult to make out, but I'm guessing that's a plover of some sort. There are a lot of plovers in South America, and many of them have dark backs and white fronts (which is all the colouration I can make out in that photo). Did the bird resemble any of the ones on that list? Smurrayinchester 08:00, 22 July 2015 (UTC)[reply]

Looks like a plover, but the bird's body proportions are different from those images. Look at the size of his legs compared to his torso.Lbertolotti (talk) 12:56, 22 July 2015 (UTC)[reply]

I was thinking it looked more like one of the stilts or avocets. SemanticMantis (talk) 14:24, 22 July 2015 (UTC)[reply]

Am I seeing things, or does the bird have a plume of feathers from the side/back of the head?DrChrissy ^(talk) 14:56, 22 July 2015 (UTC)[reply]

His head was quite smooth, unfortunately I couldn't get closer or he would have flown away.Lbertolotti (talk) 15:21, 22 July 2015 (UTC)[reply]

But there appears to be something white protruding from the side/back of the bird's head?DrChrissy ^(talk) 15:34, 22 July 2015 (UTC)[reply]

Fly

Fish

Goose

Here I was thinking about the white ones.Lbertolotti (talk) 16:54, 22 July 2015 (UTC)[reply]

Sand Dollar

Bird

Sea Urchin

Worm

How many times per day does a normal person leave their house?

Assume a democratic western country. Count things like going to work, going to the shops, walking the dog, etc but only if the person returns home between each activity. If the person does all those things but does not return home between each one, then it only counts as having left the house once. — Preceding unsigned comment added by 193.50.192.37 (talk) 19:04, 21 July 2015 (UTC)[reply]

You need to be more specific about what you mean by "normal". ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:16, 21 July 2015 (UTC)[reply]

The dictionary definition will do. — Preceding unsigned comment added by 193.50.192.37 (talk) 19:23, 21 July 2015 (UTC)[reply]

That has 21 separate definitions. ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:29, 21 July 2015 (UTC)[reply]

Along with the problems as to what is "normal" and what isn't there are too many variables for there to ever be a definitive answer. House in the city or the country? Weekday or weekend? Single person or family? etc etc. MarnetteD|Talk 19:34, 21 July 2015 (UTC)[reply]

Why is it a problem to define a norm? The question is clearly statistical - in which norms are common. 209.149.113.45 (talk) 19:39, 21 July 2015 (UTC)[reply]

I am normal and I normally leave my house once a day; sometimes I go out again in the evening but not normally.--Shantavira|^{feed me} 19:51, 21 July 2015 (UTC)[reply]

As noted by MarnetteD, one's occupation is likely to drive the answer. Someone who works in a company might well leave home just once or twice a day. Someone who works at home might go in and out of their door many times in one day - or possibly not at all. Someone who's a traveling salesman or a touring performer might go months between stays at home. So the question as it stands can't really be answered. ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:07, 21 July 2015 (UTC)[reply]

All of these concerns about what is normal, occupation, etc. could be handled by reporting a mean. Table 2 here [13] presents some data. They come up with 4.3 trips per person per day. (and to everyone else, please at least attempt to do some research or find a reference before challenging the question.) SemanticMantis (talk) 21:02, 21 July 2015 (UTC)[reply]
- It remains to be seen whether that's what the OP really wanted. ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:15, 21 July 2015 (UTC)[reply]

That's what they're supposed to be getting, though, this being the reference desk and all. I'm fairly certain they didn't ask for sophistry about their question. Ian.thomson (talk) 21:21, 21 July 2015 (UTC)[reply]

If the question is vague, it's not our fault. ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:24, 21 July 2015 (UTC)[reply]

The item linked to is only about how people travel not the number of times one might leave the house in a day so it is only a partial answer to the OPs question. This proves my point about the difficulty in getting a definitive answer. BTW my post was not sophistry. MarnetteD|Talk 22:18, 21 July 2015 (UTC)[reply]

How to reliably kill all transponders on a car

I have seen different, vague, confusing things about how many transponders are put on modern cars. In the light of this story, this is no matter a matter for vague wondering. Of course, a critical security patch is available ... the funny thing about critical security patches is, though, there's always a next one, right up to the end of the supported life of a product, no matter what the product. If a driver, hypothetically, would for some reason prefer not to find his car repeatedly running him over and over under the guidance of its parallel parking feature and rear-view camera on the same unlucky day that the North Koreans cause millions of simultaneous traffic accidents in the space of an hour, it would appear that a no-nonsense Battlestar Galactica approach is needed, and fast.

So can anyone point to resources that a) try to go through all the known types of cars and say where everything with an antenna of any kind may be hidden away at, b) give instructions how to physically destroy them, and c) can you inform whether there are any legal coercive tactics already set up to try to prevent this because of the loss of surveillance data?

P.S. this is not a personal request for advice. I have a car from 1997 and a map. :) Wnt (talk) 20:37, 21 July 2015 (UTC)[reply]

Does Paranoia not have the answers you are looking for? --Jayron 32 21:56, 21 July 2015 (UTC)[reply]

This is a real news story. The vulnerability has been known for nine months, but not that many vehicles even received the patch. Even if you believe there's no other way in and the security is perfect now, that still leaves any good group of hackers with a beautiful opportunity to make Pearl Harbor look like a kid saying boo. Wnt (talk) 22:01, 21 July 2015 (UTC)[reply]

Youtube has a very comprehensive and thorougher instructional video of how to disable, stage-by-stage any unwanted electronic car gadgets in just 4 and 35 seconds. Hope this helps.[14]--Aspro (talk) 23:03, 21 July 2015 (UTC)[reply]

Imagine the following scenario, which I think is actually FAR more likely than the above news story (I actually question how "plausible" some of the claims in the "news story" are, is it even possible to disable a car's brakes from the computer? I don't believe consumer cars have brake-by-wire yet, I know some cars can automatically APPLY the brakes, but I've not heard of a car where the pedal can literally be uncoupled from the brakes, but I'm not any kind of expert so I could be wrong.) SO, imagine you do go in and disable some "transponders" in your car, but you've also inadvertently disabled some safety feature, like Automatic braking for example, and you have an accident, and the insurance company finds out that you've "hacked" the car, I imagine you would be up a proverbial creek, all your warranties would be void and you would possibly be personally liable for any and all damages. Vespine (talk) 23:11, 21 July 2015 (UTC)[reply]

Sorry, this is the link to the real article. Note the citations to at least two other tests where brakes were disabled. Wnt (talk) 00:03, 22 July 2015 (UTC)[reply]

These are quite sensational claims! Is there any evidence that the attack could succeed against an unmodified vehicle? Have there been any independent verifications of the claims?

The story claims that the attackers demonstrated remote attacks that can disable a vehicle as it operated on a public roadway (the article says the motor vehicle was operated on Interstate 64 in Missouri when the brakes were intentionally disabled). It's alarmingly unethical - and very probably illegal - to demonstrate these vehicle failures while operating a vehicle on a public roadway in the state of Missouri.

Nimur (talk) 01:14, 22 July 2015 (UTC)[reply]

Either the main journalist is sexing the story up, and/or all three of them are complete idiots. So far as disabling all transponders goes, it would have to depend on both the model and the options fitted, there is no general solution. Greglocock (talk) 01:29, 22 July 2015 (UTC)[reply]

It seems ludicrous to risk actual harm to uninvolved individuals, when the technical merits of these claims could be equally-well demonstrated on a closed course - or even on a non-moving vehicle! To me, this irresponsibility suggests a serious lack of integrity - and causes me to doubt the veracity of the claims.

Besides, even if we wish to accept the claims exactly at face value... so what are the actual implications? Are we supposed to start panicking because a psychopathic attacker who wishes to destroy vehicles and harm humans can cheaply and anonymously attack a vehicle's brakes? The attacker could throw rocks at cars, or drop caltrops on the freeway, too... there are thousands of ways that a person can wreak harm on unsuspecting soft targets. This particular harm-by-cyberattack is difficult to execute, and depends on specific details in specific incarnations of certain technologies ...so, where is the novelty?

Honestly, I am more worried about enemies and random psychopaths who would drop caltrops on roadways than I am worried about computer-enthusiast miscreants who attempt to "hack" vehicle safety and control electronics. How serious a threat are caltrops? They are so serious that they are listed as Item #1 in the CIA virtual Museum Tour (with photos!). You don't need to use advanced technology to cheaply and effectively execute anonymous attacks on public infrastructure.

So, Wnt, as you harden your security against electromagnetic threats, what preventive defenses are you taking against caltrops? How secure is your car against rock-throwers? ...Vandals who slash tires or cut wires? ... Sugar in the gas tank? ...Snipers emplaced on the roadway? How about the more mundane threat of running our of gas due to an economic denial of service atrack? Why do you choose to fixate only on one specific category of potential threats to your vehicle? In one of our recent discussions on security as it pertains information and technology, I linked to some great resources to help you consider the whole security picture - specifically, the plenum session of the President's Cyber Security summit in January 2015. Again, in a computer security question that came up in March of this year, I linked to the computer security section of the Marine Corps Physical Security manual. Your vehicle's greatest security weakness is probably not its computer system or its wireless radios. If you are so concerned about esoteric computer security threats that you would alter your motor vehicle in an effort to remove radios... perhaps you should hire a guard for your vehicle to protect against other, more perspicuous vulnerabilties.

Nimur (talk) 06:02, 22 July 2015 (UTC)[reply]

I think you're missing the point. This one brand controls (and I mean controls) 470,000 vehicles. The articles suggest others have the same problems. Now yes, two hackers playing with one vehicle is a small threat. But a group like North Korea or the Syrian Electronic Army could line up a botnet with thousands of computers, infect millions of vehicles, and SIMULTANEOUSLY crash a large fraction of them. And guess what -- if there are two hundred thousand traffic accidents on the road, you can hit your Onstar button but the cops ain't comin! Now if North Korea could put sugar in the gas tank of every car in my neighborhood, I'd want to harden against that, sure ... though even if they could, it's less distressing to have your vehicle sabotaged when you're not in it. As for ethics, well, is putting a car in neutral on the highway really that much more unethical than putting half a million cars on the road that can be tracked, spied on, and even crashed remotely? (the article skirted some obvious issues, like whether the hackers could tap into the microphone and listen to the occupants' conversations) Wnt (talk) 10:24, 22 July 2015 (UTC)[reply]

I wonder how much access they had to the target vehicle before the demonstration. Greglocock (talk) 10:38, 22 July 2015 (UTC)[reply]

I doubt that it is chicanery on the part of the Wired author. A bill was introduced yesterday in response to this [15] but the details aren't available yet at that link; from the description it doesn't sound like it goes far enough. I don't want car companies to protect their records of everywhere I've ever driven; I don't want them to have them at all. And I don't want an interface to be "secure", I want it genuinely not to be there at all. Wnt (talk) 10:54, 22 July 2015 (UTC)[reply]

How much access did they have to the vehicle? They own it. They initially connected to the Jeep using the hard-wired technician's connection. Then, they rewrote the firmware of the controller. Then, they called a friend who happened to be a writer and said, "Hey, hop in our Jeep and take it for a ride and see what we can do!" This is in no way equivalent to the headline that I saw today: "Hackers take complete control of a smart car from across the globe!" 209.149.113.45 (talk) 14:52, 22 July 2015 (UTC)[reply]

Source for this additional info? It's interesting since the Wired article seems to imply as Wnt suggested that they were able to take control over it remotely without physical access so either with the default firmware, or with new firmware they can upload without physical access but they won't reveal much more until the Black Hat conference. (However they learnt about the vunerability initially.) I presume that in reality, what they mean is that it can happen remotely, but only with special firmware that can be uploaded by someone with physical access which can then use the cars built in system to accept remote commands. Of course one thought is that as long as this can happen with access to the technician port, you could enable remote control simply by designing a device which can be plugged in and is capable of accepting remote commands. This may cost more since you need a unique device for every vehicel you target (ignoring any you recover for later use) and also has a higher risk of being noticed (although in reality, I suspect someone with sufficient resources could make a device most people are unlikely to notice unless they look very carefully and while I'm not sure where the port is on these cars, I suspect people rarely look at them), but otherwise would be just as effective. Now if the vehicle had a clear indication that the technician port was being used on the dashboard, this may be noticed, but that's presuming it can't be hidden by someone with access to the technician's port. Nil Einne (talk) 16:24, 22 July 2015 (UTC)[reply]

It is actually the lack of a reputable source that causes me to disbelieve the claims in this Wired article. Has there been any independent verification? Is there an entry in the national Common Vulnerabilities and Exposures database? What is the entry number? Which peer-reviewed computer security or automotive engineering journal has published a study of this problem? In this case, all the syndicated re-published news articles in the world are worth less than a single good technical write-up in an industry journal.

Instead we are asked to believe that two independent researchers accomplished an incredible feat. Of course it is possible that they discovered and exploited a serious oversight in production vehicles; but this is unlikely. What we need is independent verification. These researchers purport to favor complete disclosure instead of a silent behind-the-scenes security fix. Ok, great - so why didn't Wired link to a CVE entry and a technical whitepaper? Apparently the researchers do not wish to disclose their methodology or permit outside scrutiny?

This is the difference between sensational journalism that has mass appeal to uninformed users of techology, and actual computer security engineering that can be taken seriously by informed individuals. Nimur (talk) 16:56, 22 July 2015 (UTC)[reply]

This "story" is being heavily exaggerated by the media. This morning, I saw a headline "Hackers take complete of a smart car and smash it into a ditch from across the globe!" So, you have to avoid anything written since July 18, 2015. All you will find is garbage. In the original wired article by Andy Greenberg (who mysteriously becomes a woman in articles I've seen written in the past few days), he clearly states that he was given the car by the hackers and he explains that they messed with the stereo, windshield wipers, and set the transmission into neutral. Then, he went to an empty lot and they did more fun stuff. How? Go back to the previous article that Andy wrote. He explains that they sat in the back seat and were directly wired into the car. They replaced the firmware and were able to control the car. So, who are these hackers? Charlie Miller and Chris Valasek have been "hacking" the firmware of various cars for about five years. They work for IOActive and are trying to PROTECT cars from hackers, not turn the world into a global demolition derby. They are trying to perfect a method of rewriting the firmware so they can remote-control as much of the car as possible, all in an attempt to uncover and fix weaknesses. But, all they can control is what the computer controls. Does the computer control the steering wheel? No. Does the computer control the brake (not the ABS - the physical brake)? No. All of that nonsense is coming from Andy Greenberg, who obviously has a tendency to exaggerate. 209.149.113.45 (talk) 17:09, 22 July 2015 (UTC)[reply]

I agree with you, Wnt, that the risks seem to outweigh the benefits, some of which just seem silly. You can turn up the volume on your car from the Internet now, versus reaching all the way over to the radio ? Sure, that's worth making a car that can be hacked ! Here's a list of the features of the Uconnect system: [16]. Of those, several seem potentially dangerous if hacked or if they just have a bug. Turning the volume to a deafening level could cause an accident (and I had a TV where the remote kept sending the volume up signal, so this even seems possible just as a bug). Turning the heat on max on a hot summer day could be dangerous (hopefully the occupant could still open windows). The autostart feature could be used to run the car out of gas or, if in a garage (particularly attached to a house), create a dangerous build-up of carbon-monoxide. If the car isn't smart enough to check to see if the car is running before trying to start it, then that could cause something bad to happen (not quite sure what). StuRat (talk) 16:33, 22 July 2015 (UTC)[reply]

July 22

Adult Growth of Vertebrates

Mammals grow until they are adults and then stop growing, so that humans are the same height for most of their life. Birds grow until they are adults and then stop growing. Some long-lived vertebrates, including some fish and crocodilians, continue to grow. I am assuming that the difference is that mammals and birds are warm-blooded, and that so-called cold-blooded reptiles and fish continue to grow. Is that correct, and is there a reason, such as having to do with energy use in adult warm-blooded vertebrates, why growth stops for warm-blooded vertebrates? Robert McClenon (talk) 02:55, 22 July 2015 (UTC)[reply]

The truth is Robert, there's a slight adjustment to be made in the way you are conceptualizing this issue that will greatly improve your understanding of it. Specifically, most any complex organism's growth (and especially that of metazoans) will eventually plateau - these organisms simply very greatly in the length of time it will take them to reach this point, their liklihood of dying first from predation, disease, or an environmental factor and the exact nature of the interplay between environmental constraints and innate epigenetics. In a sense though, you are correct that certain clades show a preponderance for having higher populations of individuals that have stalled out in their growth; its just that the explanation for this difference is often not entirely explained by the relative difference in any two species' physiologies with regard to just things such a growth factors, cellular differentiation, replication errors, and the like, but rather also the entire sum of their genetic qualities and their environmental context (including such things as diet, space, breeding context and other factors which influence growth through epigenetics, but then also dumb luck with regard to survival). So you will find that phylogenetics only sets you up so much to understand which of these species will have great variety in ultimate sizes of individual specimens and/or what proportion of the population have begun to slow (or even have stopped) in their growth; sometimes two very closely related species will vary drastically in this regard, simply because they have a slightly different ecological niches. All of this is not to say that there aren't clades which have genetic features that allow them to grow more tissue of certain types without stalling out or to avoid cancers and other effects of senescence; it simply means that for most organisms, the situation is a little more complex than just these factors. Of course, it is true, since you specifically cite adulthood, that certain species are more likely to stop growing roughly at sexual maturity. As you observe, this trait is particularly strong in Mammalia, but you'll also find great variation in other kinds of tetrapods. Forgive the lack of citations; super exhausted here; will try to cobble together the sourcing and more complete discussion of these issues tomorrow. Snow ^{let's rap} 07:25, 22 July 2015 (UTC)[reply]

There are some differences in the biology of bone growth (which is usually what we really mean by "growth"; otherwise we find ourselves all too capable of growing in mass throughout adulthood!). I haven't given this paper a tenth the attention it merits, but see [17] which discusses the differences between Actinopterygii and tetrapods. So in modern fish, "Perichondral bone is deposited on the surface of the cartilages and continues to grow centrifugally as periosteal bone" whereas in tetrapods a rod of cartilage is quickly covered by bone, except for growth at the epiphyseal plate, which ultimately fuses to stop any further bone growth. That said, epiphyseal fusion still does not have to happen; that is a sort of choice made by the developmental plan of the organism.

I would speculate that there may be adaptive reasons for the differences. We have all probably seen pictures of human 'giants' who can't stop growing, hobbling around on crutches. It seems like aquatic organisms are less affected by changes in scale than those on land, since they rarely need to support their own weight. But that's purely a guess. Wnt (talk) 12:50, 22 July 2015 (UTC)[reply]

From a the perspective of evolution and ecology, this is about the trade-offs between allocation of resources to growth vs. reproduction. Lifetime fecundity is one of the main drivers of growth patterns - vertebrate organisms are generally hovering around a local maximum where growth is halted after sexual maturity, unless additional growth will increase lifetime fecundity. A key term is indeterminate growth, though that is used more often for plants. The broad topic would come under Life_history_theory, See e.g. here [18], [19], [20] for (freely accessible) research discussing why indeterminate growth occurs in animals, and how it's tied to resource allocation and impacts of life-history strategies. SemanticMantis (talk) 14:35, 22 July 2015 (UTC)[reply]

Solar system distances vs. gravity

Looking at real-scale models of our solar system, it occurred to me that if the sun was scaled down to a 1 cm wide ball, pluto would be a mere grain of dust at about 40 meters away. Yet the gravitational forces make it rotate around the sun. How can that be, especially with all other planets in between? Gil_mo (talk) 09:55, 22 July 2015 (UTC)[reply]

It goes to show you how strong gravity really is. Bear in mind that in space there is no friction, so your Earthly impressions of gravity don't apply to space. Things clump together in space. If there was no strong force of gravity, there wouldn't be planets.217.158.236.14 (talk) 10:26, 22 July 2015 (UTC)[reply]

Friction exists in outer space. I think what you intend to say is that in a vacuum, there is negligible air resistance... and even though this statement is true, gravity is not in any way reduced by friction. (Perhaps you are conflating the force due to gravity with the total net force on an object, which is computed by summing gravity with any other force that might affect some object). Other forces, including frictional resistance force, may oppose gravity in some cases, reducing the net force; but they don't actually reduce the magnitude of the force of gravity. This is a really important distinction that is usually learned in your first physics courses, and the difference between "net" and "component" forces still matters, even in advanced topics.

In fact, according to our theories that are as accurate as our best we can measurements, force due to gravity is unhindered by anything : there is no way to "shield" the effects of gravity. This means that even our outer planets feel the force of gravity: the effect is not "blocked" by inner planets. In fact, if you apply Gauss's law for gravity, the outer planets actually experience more inward pull, because they are pulled inward by the sun and all the other matter in the solar system! Nimur (talk) 16:16, 22 July 2015 (UTC)[reply]

As for "all the other planets" - the sun makes up an incredible 99.8% of the solar system's mass, and almost all of the rest is Jupiter. Uranus and Neptune do have a small impact on Pluto's orbit - over its history, they've nudged it here and there - but they don't even come close to the sun's effect. The closest Pluto comes to another planet is that it sometimes passes 11 astronomical units (AU) from Uranus, while the furthest it ever comes from the Sun is 49 AU. Even at those extremes, the Sun's pull on Pluto is a thousand times greater than that of Uranus (you can see the sums here and here). Smurrayinchester 10:52, 22 July 2015 (UTC)[reply]

Actually, gravity is the weakest of the fundamental forces, by far. It's astonishingly weak compared to the others. Just think about it: every time you lift anything, you're overcoming the gravitational force of the entire Earth, all 5,972,190,000,000,000,000,000,000 kilograms of it, on that object. The apparent weakness of gravity is a big reason why a lot of physicists like string theory, because it predicts the existence of extra dimensions. If gravity "leaks" into those extra dimensions, that would explain why it appears so weak in the three spatial dimensions that we perceive. The fact that Pluto is still captured by the Sun's gravity despite the great distance between the two is, rather, a testament to how massive the Sun is. Stars are ENORMOUS. The Sun contains over 99% of the entire Solar System's mass. Everything else is a rounding error. An even better illustration of the Sun's massiveness is the Oort Cloud, which is over a thousand times farther from the Sun than Pluto is, yet still bound by the Sun's gravity. But even the Sun is a lightweight compared to some other objects in the universe. Our Sun, along with everything else in the Milky Way, orbits the supermassive black hole at the center of our galaxy. It's 26,000 light-years away from us, yet so massive that it still pulls us along for the ride. And in turn, our galaxy is gravitationally bound up with other galaxies into mindblowingly huge groups and superclusters of galaxies. Just look at something like the Great Attractor, which has a gravitational influence that extends for hundreds of millions of light years, to truly get a sense of the scale of the universe. I'll quickly plug Crash Course Astronomy here for anyone looking for a nicely accessible introduction to space. --108.38.204.15 (talk) 11:36, 22 July 2015 (UTC)[reply]

Ha ha, I know it's a weak force in comparison to the others, but it is capable of being massively strong nonetheless. It's strong enough to form planets and keep the solar system together.217.158.236.14 (talk) 14:10, 22 July 2015 (UTC)[reply]

You've scaled the distances down by about 1.4E11, but in doing so you've scaled the masses down by around 2.7E33, since the dependence of mass on length is cubic. Therefore the gravitational force (which depends linearly on mass) has been disproportionally scaled in your thought experiment.--Phil Holmes (talk) 11:09, 22 July 2015 (UTC)[reply]

If you scale down all distances in the solar system and scale down masses in proportion to the cube of distances (i.e. keep the average density of each body the same) *and* scale down velocities too then the orbital periods will be unchanged. So your model Earth will still orbit your model Sun with a period of one year - but it will be moving very slowly. Gandalf61 (talk) 11:46, 22 July 2015 (UTC)[reply]

How does pregabalin work

Hi. I'm trying to find out exactly how pregabalin works for neuropathic pain and need some help. What I don't understand is how it could "know" to deal with the pain in the painful part of the body and not elsewhere - unless it sort of numbs all sensations everywhere? Thank you for pointers. 184.147.131.217 (talk) 14:09, 22 July 2015 (UTC)[reply]

The keyword you may want is "mechanism." which leads to many publications available at no cost on PubMed, a service of the National Institutes of Health. Here's one such paper, Pharmacology and mechanism of action of pregabalin, (2007), which rapidly drives into the technical details of the biochemistry. Nimur (talk) 16:37, 22 July 2015 (UTC)[reply]

Thank you very much! Can you help a little with the translation? It says subtly reduces the synaptic release of several neurotransmitters and a mechanism that may entail reduction of abnormal neuronal excitability through reduced neurotransmitter release. Is this saying that it does indeed reduce all feeling across all nerves equally, especially those that are reacting to something (eg biting tongue same as the neuropathy)? 184.147.131.217 (talk) 16:50, 22 July 2015 (UTC)[reply]

1) "subtly reduces the synaptic release of several neurotransmitters" sounds like it applies to all nerves.

2) "reduction of abnormal neuronal excitability" sounds like it only applies to nerves which are malfunctioning, such as in neuropathy. StuRat (talk) 16:54, 22 July 2015 (UTC)[reply]

Thanks, but I would like to know what it actually means not just what it sounds like. What I really want to understand is how (or if it actually does) the drug would distinguish between all nerves and malfunctioning nerves. 184.147.131.217 (talk) 17:07, 22 July 2015 (UTC)[reply]

Generic plastic solvent

I have a bunch of rare earth magnets imbedded in plastic in a toy. I would like to dissolve away the plastic to get all the magnets for a different project. Any suggestions on what sort of solvent to start with? The toy in specific is "Geomag" a magnetic stick and ball construction set. Tdjewell (talk) 14:57, 22 July 2015 (UTC)[reply]

Can you get your hands on some dichloromethane? That works on most plastics. 209.149.113.45 (talk) 15:16, 22 July 2015 (UTC)[reply]

There are lots of types of plastic, and at least two very different broad categories - Plastic#Thermoplastics_and_thermosetting_polymers. I looked at the company web page [21], and cannot easily determine what kind of plastic they use. I think knowing the type of plastic will be pretty important. SemanticMantis (talk) 15:19, 22 July 2015 (UTC)[reply]

You might try peppermint oil. It can dissolve some plastics and isn't nearly as toxic as most other solvents (it is toxic in high enough doses, though). Plus it makes everything smell nice. StuRat (talk) 16:49, 22 July 2015 (UTC)[reply]

Transporters

Is it true that the transporters in Star Trek actually kill the person and then build an exact copy at the destination out of different atoms? 117.168.207.243 (talk) 16:53, 22 July 2015 (UTC)[reply]

Since it's a fictional device, there is no "truth" except for how the authors claimed it would work. That device supposedly dissembled them into atoms, physically sent those same atoms to the remote location, then reassembled them there. I would call that killing them and bringing them back to life, although whether the result is a "new person" or not is debatable. Now, as for reality, that bit about sending the actual atoms to the target is plain silly. The way a transporter would really work would be to just send the information (pattern), but reassemble the person from different atoms there. However, according to physics, one atom with the same proton, neutron and electron configuration is identical to another, so it would make no difference. This does mean the same technology could possibly be used to clone an individual as many times as wanted, so perhaps that's why they made it use the same atoms in the Star Trek universe, to avoid people from asking why the various parties don't just clone themselves an army using the transporters. StuRat (talk) 17:01, 22 July 2015 (UTC)[reply]