Wikipedia:Reference desk/Archives/Science/2014 April 7

= April 7 =

Induction lamp cooking
As far as I know a powerful enough oscillating magnetic field can light up a lamp. Does it mean that you can make a light bulb glow by putting it on the induction cooking stove? 91.77.167.192 (talk) 08:38, 7 April 2014 (UTC)
 * Those induction cookers need a big thick slab of metal to induce currents in. A light bulb filament is not enough.  If you irradiated it with millimeter wave or other microwaves, perhaps you could light it. Graeme Bartlett (talk) 09:06, 7 April 2014 (UTC)
 * Centimeter wavelengths will certainly light up an incandescent light bulb as generations of schoolboys and numerous You Tube videos can attest. --2A01:E34:EF5E:4640:9D8E:1D42:1F74:5600 (talk) 13:33, 7 April 2014 (UTC)

And what if you attach a light bulb to this “thick slab of metal”, will it light up? I'm just curious if it is possible to get something glowing with a cooker of this type.91.77.167.192 (talk) 13:25, 7 April 2014 (UTC)
 * I don't suggest you do the experiment, but I would think it more likely to melt. What you want is an Induction lamp.--Shantavira|feed me 14:01, 7 April 2014 (UTC)

Could a machine assemble molecules on demand just starting with the atoms?
That would be easier than synthesizing compounds. If you wanted gasoline (C8H18) or cocaine (C17H21NO4), this hypothetical machine would just pick the right atoms and start putting them together. Or maybe, could a machine generate random molecules from a set of atoms? Maybe putting them under pressure, or pass an electrical current through them and see what gets out of the process. — Preceding unsigned comment added by 88.14.192.119 (talk) 17:58, 7 April 2014 (UTC)
 * How do you put them together fast enough? 12 grams of carbon contains 602,000,000,000,000,000,000,000 atoms.  Even if a machine could grab and use a million carbon (and equivalent number of hydrogen) atoms per second, that would still take 602,000,000,000,000,000 seconds to make just 16 grams of methane (CH4).  That's a bit more than 19,000,000,000 years.  The earth has only existed for 4,500,000,000 years.  -- Jayron  32  18:15, 7 April 2014 (UTC)
 * (ec, same idea, other numbers) I think you underestimate the number of molecules that make up a useful amount of gasoline. A molecule of octane weights 114 u. Thus a mol of gasoline weights 114 g. That's 6.022×1023 molecules - in other words, one litre has about 3.6×1024 molecules. If your machine makes a million molecules per second, it would have made about 0.01 litres in the time since the beginning of the universe. A big advantage of chemical reactions is that they happen in a massively parallel manner, thus yielding macroscopic amounts of product in realistic time frames. --Stephan Schulz (talk) 18:21, 7 April 2014 (UTC)


 * Hmmmm, isn't your body made out of such machines? Count Iblis (talk) 18:42, 7 April 2014 (UTC)
 * No, it isn't. You can not program yourself to excrete gasoline or cocaine out of your nose. You (that is, any human) can not even produce all the amino acids the body needs to maintain its structure and function; some of them are essential amino acids, meaning you've got to get them from outside (as food) and can not manufacture them internally (although some other organisms can). There are organisms that can produce hydrocarbons suitable as fuel for internal combustion engines; but there are no "universal" organisms that can produce any chemical compound you want on demand. --Dr Dima (talk) 19:17, 7 April 2014 (UTC)


 * That is the intent of Molecular assemblers - an idea to make very, very tiny robots that are capable of assembling things atom by atom. The way such devices would overcome Jayron's objection is by self-replicating themselves - making enough of them to do the needed work in a reasonable amount of time - then disassembling each other again when the work is done.   It's not entirely clear whether such things are possible, given the laws of physics as we know them...but the idea is not without merit.
 * HOWEVER, this won't get you free gasoline. The amount of energy a machine such as this would require to make gasoline would be many, many times more than the energy you'd get back by burning the gasoline subsequently.   The general problem is that you need to apply significant amounts of force to (for example) dismantle a CO2 molecule into carbon and oxgen atoms - and yet more energy to force them back together into the form you wanted.
 * Anyway - check out the Molecular assembler article - it pretty much explains all of this. SteveBaker (talk) 19:12, 7 April 2014 (UTC)


 * They're called refineries, chemical plants, plants, bacteria, yeast, etc. The notion of mechanically assembling molecules, rather than chemically assembling them, strikes me as about as practical as training llamas to become brick-layers. μηδείς (talk) 21:03, 7 April 2014 (UTC)

Are we going out of fertilizer ingredients, in the same way we are going out of oils?
They are the six macronutrients: nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sulfur (S); eight micronutrients: boron (B), chlorine (Cl), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), zinc (Zn) and nickel (Ni). I dont mean locally on the soil of a concrete location, but globally. — Preceding unsigned comment added by 88.14.192.119 (talk) 18:06, 7 April 2014 (UTC)


 * Peak phosphorus, Peak copper -- Finlay McWalterᚠTalk 18:09, 7 April 2014 (UTC)


 * See Peak phosphorus. This is considered, in some circles, to be a greater problem than Peak Oil, and a major looming catastrophe, specifically because of the need of phosphorus in fertilizers. -- Jayron  32  18:11, 7 April 2014 (UTC)


 * Note that only chemical fertilizers are in danger of running out. There's no shortage of manure (especially around elections), and, if night soil is included, we have quite a dollop of that. StuRat (talk) 18:22, 7 April 2014 (UTC)


 * Au contraire, the problem is there isn't enough bullshit in the world, even accounting for politicians, to cover all the fertilizing needs we have. -- Jayron  32  18:24, 7 April 2014 (UTC)


 * If 100% is collected and reused, and no-till farming is employed, along with other methods to prevent soil run-off, then I'd expect very little chemical fertilizer would be needed. StuRat (talk) 18:35, 7 April 2014 (UTC)


 * (if 100% is reused, then we have no harvest! ;) Our yield of e.g. corn is approaching ten times the historical values . Some of the increase is due to pesticides, breeding, and other methods. But without cheap, concentrated chemical fertilizers, corn yields would be back in the ~20 bushels an acre across the USA cornbelt. And that would drive up the cost of the many food products using corn and it's derivatives. Sure, you can compost everything and do low-input agriculture in your backyard, but that doesn't change the fact the the majority of the agricultural industry in the USA is based off of cheap and widely-accessible processed fertilizers. It is true that agronomically, we know how to do better, and grow with less energy and inputs. But what matters is what the large agribusinesses actually do. SemanticMantis (talk) 18:53, 7 April 2014 (UTC)


 * You'd need to set up a system to collect sewage from sewage processing plants and move it to farms. We'd also need to stop flushing old meds, etc.  A dual sewage system could be set up, with things like meds going to a septic tank, instead. StuRat (talk) 19:06, 7 April 2014 (UTC)


 * Um, phosphorus isn't destroyed. If run-off into the oceans is a problem, then the oceans are also the solution--recovery from salt pans and, as the price increases, use of nuclear energy to extract trace elements from the ocean.  It's simply silly to assert we are running out.  It's just becoming more expensive to procure. μηδείς (talk) 20:58, 7 April 2014 (UTC)


 * I would disagree with that. Recycle before it goes into the sea would help prevent algae blooms that cut off light to the sea-floor, which cause the seabed plants to die off, which in-turn removes a vital food source for the local coastal sea-life which in turn means we reduce the amount sustainable seafood that we enjoy. This is a growing problem around the world and some sizeable  lakes too are now dead. The sea is too large a volume for the concentration of Phosphorus  to increase above 13mg/kg to point were it becomes economic to recover it.--Aspro (talk) 21:55, 7 April 2014 (UTC)


 * I didn't say anything about not recycling or preventing run-off, which will also become increasingly economically urgent. The problem is the question as posed is a typical "what if all the farmland gets used for parking lots?!?!" question that ignores market forces.  As phosphorus or farming land or any commodity gets more scarce its value increase, and more money is invested into procuring phosphorus or land values increase, and people sell their sprawling lots and move into efficient high rises high-rises.  You are making the same mistake.  At some point if phosphorus becomes rare its price will increase and people will invest in new ways to concentrate it and it will be economical to recover it at 13mg/liter.


 * Hmmm, 160E6 metric tonnes/ yr currently produced = 1.6E11 kg, divided by the 13 mg/kg seawater = 1.2E16 kg of seawater to process. The Nile discharges 2830 m3/s, x365.25x24x60x60x1E6 = 8.9E16 kg/s.  So if you desalinate a substantial river of water to meet the needs of dry surface areas, in theory you should get enough potassium phosphorus left over to do the fertilization.  If you can separate it somehow.  It takes a lot of energy, but so does any solution to the vast deserts predicted to arise from global climate change. Wnt (talk) 23:08, 7 April 2014 (UTC)


 * When did we switch to potassium? There's no shortage of potassium.  I'm assuming you just mistyped. --Trovatore (talk) 23:36, 7 April 2014 (UTC)


 * Burn seaweed in a steam engine (Algae fuel) then process the ashes. Jim.henderson (talk) 23:43, 7 April 2014 (UTC)


 * This brings back the old proposal to build a canal to flood the depression in the African dessert from the Med Sea. You could then let it dry out to get your phosphorus, but you'd also have to remove the salt. StuRat (talk) 23:44, 7 April 2014 (UTC)


 * Ah - Qattara Depression Project. Wnt (talk) 00:30, 8 April 2014 (UTC)


 * Yep, that's the name. Thanks. StuRat (talk) 08:44, 9 April 2014 (UTC)


 * Or process brine left over as water evaporates to a low level behind the proposed Red Sea Dam. Since the Red Sea is of fairly recent origin, it's hard for me to feel too bad about destroying a major ecosystem, if the energy goes a substantial way toward ending global warming and provides irrigation for the entire region.  Besides, I have a crank notion about it as a prophesied solution to the Israel-Palestine conflict. :) Wnt (talk) 00:18, 8 April 2014 (UTC)


 * (Un-indent) What is all this idle talk about extracting phosphorus from seawater, flooding the Sahara, damming the Red Sea, etc., when a much more cost-effective solution has already been devised -- that being to precipitate phosphates out of municipal sewage (at the sewage treatment plant) with, e.g., calcium hydroxide? 24.5.122.13 (talk) 05:13, 8 April 2014 (UTC)


 * I think people are assuming that first we manage to use up all the cheap phosphorus, then we say oh no, what are we going to use, when it's already washed out to sea. Which, given our track record, seems not unrealistic. :(  Besides, I was thinking of this as a byproduct only - the purpose of the Red Sea Dam is electrical power, and if taken to a perhaps unrealistic extreme, creation of new lands irrigated by water desalinated with that abundant power. Wnt (talk) 19:11, 8 April 2014 (UTC)


 * As Wnt correctly stated (I assume it was Wnt, even though the comment appears to be unsigned), the price of phosphorus will begin to rise LONG before all the apatite is mined out, and THAT will make large-scale recovery of phosphorus from sewage the next major source of the stuff even BEFORE the apatite runs out -- and THAT, in turn, will preclude your scenario of all the readily available phosphorus "washing out to sea". 24.5.122.13 (talk) 05:59, 9 April 2014 (UTC)
 * I don't see the unsigned comment, but ... while biology may not know theory, economics is outright hostile to logic. The system that gives us Bitcoins and housing bubbles may or may not react sanely to a shortage of phosphorus. Wnt (talk) 11:42, 9 April 2014 (UTC)
 * 24.5.122.13 (talk) 01:07, 10 April 2014 (UTC)


 * Economics is exceedingly and brutally logical. It's people that aren't.  The market makes very logical and unemotional corrections.  People don't like it and try to manipulate it to "soften" the reality.  Left on it's own, the market will correct for overpopulation.  It's people that object to the outcome.  (people manipulate the other way, too, like subsidizing fuel from corn/food).  --DHeyward (talk) 02:46, 10 April 2014 (UTC)


 * Considering that the "market correction" for overpopulation involves millions of people dying, by starvation, war, disease, etc., I can understand why some might object. (It's even possible that it could lead to the extinction of the human race, via nuclear or biological warfare.) StuRat (talk) 03:03, 10 April 2014 (UTC)

LCD TVs that are not black?
My father had a question for me last week. One of his customers had told him that LCD TVs would fit much more nicely to their home design if they were white when powered off instead of black. My father asked me if this is possible. I didn't have any idea, as electronics design is not my profession, it's computer software. I know at least that some monochrome LCDs are light gray when powered off, and the lit crystals are black, but is this kind of thing at all possible on a full-colour LCD? J I P &#124; Talk 18:17, 7 April 2014 (UTC)


 * I suggest the TV be placed in a cabinet and the doors closed when not in use. (Eventually, I hope the cost of displays will come down and reliability will go up to the point where we can use them as lights, always on, displaying an all-while panel or whichever background we prefer.) StuRat (talk) 18:29, 7 April 2014 (UTC)


 * One problem I foresee is that if the error correction is not spot on for every frame, one will notice lots of bright speckles on the picture.   Whereas now, when  a few pixels at a time are randomly going dark here and there for each and every frame,  they are  not  perceived by the eye. I seem to remember the luminous signal on analogue TV is negative going, for the  reason  that the radio static  is less noticeable when there is a good signal to noise ratio. When the S/N ratio diminishes towards no broadcast signal at all, even the cosmic background radiation can be seen as a mass of speckles often referred to as snow.--Aspro (talk) 22:57, 7 April 2014 (UTC)
 * Permit a sceptic to doubt that Aspro's TV is capable of displaying cosmic background radiation. 84.209.89.214 (talk) 12:12, 8 April 2014 (UTC)
 * Oh. It is always wise to be a sceptic (especially if the inland revenue says you owe more tax than the 1% pay in ten years) - so count yourself permited. Here is a link (obviously, if the Big Bang theory gets proved wrong – you can demise it) : The CMB is so bright at millimetre-wavelengths that if you de-tune an old analogue TV to show the snow-like static, a few percent of the signal your TV is picking up will have come from the start of the Universe..  Not a lot of people know that.--Aspro (talk) 23:40, 8 April 2014 (UTC)
 * And Wikipedia turns out to have  a section on the disadvantage of positive modulation (luminance) that I was referring to. 405-line_television_system.--Aspro (talk) 00:02, 9 April 2014 (UTC)
 * Analogue TV's receive at metre and decimetre (VHF and UHF) but not millimetre wavelengths and their no-signal display of electrical noise is dominated by front-end Johnson–Nyquist noise i.e. thermal noise in the input stage transistor. The quoted claim that Cosmic noise forms "a few percent of the signal your TV is picking up" lacks any quantitative values of power or criteria for why CMB is purportedly visible. Does the random speckle display on Aspro's TV look noticeably different when it is moved from a tent to a metal shielded room? Is Aspro in the habit of lecturing to awed visitors that his TV is a viewport to the start of the Universe? And there's no argument about the visibility of impulse interference. 405-line monochrome TV receivers often had an "Interference limiter" control, actually a peak video level clipper or inverter, that had to be carefully adjusted somewhere between white crushing or having white spots bloom on the screen when cars drove by. 84.209.89.214 (talk) 14:17, 9 April 2014 (UTC)
 * The CBM 'peaks' at millimetre wave lengths. The gaussian function means there is a few percent of the electromagnetic spectrum in meter wavelength  noise still to be received on one's old  TV, both visually and backed-up by scientific deduction. As to awe: Here on Ref Desk, we endeavorer to answer the questioners queries. Whether they  experience awe or wonderment at our replies is out of our control. Please don't try to colour my motivations with whatever is going on inside you.--Aspro (talk) 23:01, 11 April 2014 (UTC)


 * I don't believe that this is easy. Current TVs display white by turning on a backlight, and making the LCD clear so the white backlight can shine through. (roughly speaking)  So, unpowered, they're going to be, if not black, then at least dark.
 * Purely reflective screens can be light-colored when they're powered off. (Think of a digital watch, or a calculator.) But I don't think those would make a very good TV. (Which you want to glow in the dark.) APL (talk) 15:28, 8 April 2014 (UTC)
 * From what I understood from what my father's customer wanted, they wanted the screen to be white without any sort of electricity or light output required. It would be practically the inverse of current full-colour LCD technology - instead of having the pixels dark and grow lighter when powered up, they would be light and grow darker when powered up. I understand that this means that when viewed with no outside light source, such as in a darkened room, the whole TV would be pretty much invisible, regardless of what it was showing. I just want to know that even if we accept this, is this kind of thing at all possible, in full colour? J I P  &#124; Talk 18:10, 8 April 2014 (UTC)


 * I think HP used to make some color graphing calculators with that sort of display, but I'm having trouble finding a reference so it may have been a different brand. Obviously the update time and pixel density were nowhere near what you need for a TV, but the basic principle has been implemented. K ati e R  (talk) 11:52, 9 April 2014 (UTC)
 * Ahh, here it is. Casio's "three-color" display did black red green and blue. It's a looong way from a TV display, but no one has had a reason to develop that technology. K ati e R  (talk) 11:57, 9 April 2014 (UTC)
 * Ah, I had almost forgot about those Casio colour graphics calculators. I used to own a couple of models myself, and I think I still have one. From what I can recall, they accomplished the four-colour reflective LCD with two monochrome LCDs laid on top of each other, with different colours. This leads to a new question: Both Casio and Texas Instruments have now developed graphing calculators with 65536-colour displays. Does anyone know if these LCDs also utilise this reflective technology, or are they backlit the same way as LCD TVs and monitors? J I P  &#124; Talk 18:23, 9 April 2014 (UTC)
 * I have a coworker that just purchased a new TI one. It's a backlit display, and it seems a bit lower quality than the average modern smartphone screen, but incredible compared to the older calculators. Of course, the battery doesn't last for months like the old ones did. K ati e R  (talk) 19:45, 9 April 2014 (UTC)
 * It's certainly possible to make color displays that are reflective instead of backlit. Pixel Qi makes some that will replace the screens on certain laptops, so you could certainly watch a movie on them if you wanted. It'll never get the brilliant colors of a backlit TV on a purely reflective screen though, it's always going to look a bit muted. (But maybe you'd get used to it. Even a glossy magazine cover looks dull and lifeless if you hold it up next to your TV, but they look great on the newsstand next to the other magazines.) APL (talk) 14:15, 9 April 2014 (UTC)


 * Hmmm, how's electronic paper doing? (I think it still has problems, and even in concept might not be well suited for TV use) Wnt (talk) 19:08, 8 April 2014 (UTC)

Is it true that the Pacific Ocean makes the west coast of North America warmer?
My friend told me he wants to move to Vancouver because it's warmer there, and he insists that it's warm because the Pacific Ocean makes the climate warmer there. Is this true? ScienceApe (talk) 19:04, 7 April 2014 (UTC)


 * Yes, similar to how the Gulf Stream in the Atlantic makes Western Europe warmer. The water can be warmer near Vancouver, Seattle, etc, than in Los Angeles.  Of course, that warm water also brings lots of rain, and global warming may eventually change the ocean currents.  StuRat (talk) 19:11, 7 April 2014 (UTC)


 * It is Alaska_Current. Ruslik_ Zero 19:12, 7 April 2014 (UTC)


 * Thanks, StuRat (talk) 08:46, 9 April 2014 (UTC)


 * More moderate; both less cold and less hot; see Oceanic climate Jim.henderson (talk) 19:13, 7 April 2014 (UTC)


 * See http://cliffmass.blogspot.com/2012/06/why-are-coastal-water-temperatures.html for a pic showing unusual cooler water temps hugging the coast. StuRat (talk) 19:16, 7 April 2014 (UTC)


 * (ec)Warmer than where? Large bodies of water have, in general, a mediating influence on peak temperatures, both high and low. So Seattle is warmer in January than e.g. Bismarck, North Dakota. On the other hand, Bismarck is warmer than Seattle in Juli. Also see continental climate vs. oceanic climate. --Stephan Schulz (talk) 19:17, 7 April 2014 (UTC)


 * Note that water behaves like land if it freezes solid, but remains mostly liquid near Vancouver year-round. And where the currents go the other way, as in Maine or Korea, it's not particularly warm in winter. StuRat (talk) 19:19, 7 April 2014 (UTC)


 * Even in Maine, costal areas are a lot warmer in winter than North Dakota. Similarly, South Korea is warmer in winter than North Dakota. North Korea has a continental climate, with winter temperatures influenced by weather systems coming out of Siberia. But still, its winter is not colder than North Dakota's. --Stephan Schulz (talk) 21:46, 7 April 2014 (UTC)


 * Still, if one wants a Canadian city with a mild climate, with little snow, then Vancouver is a better choice than Newfoundland: . StuRat (talk) 00:28, 8 April 2014 (UTC)


 * Well, St. John's, Newfoundland and Labrador is about 150 miles further north than Vancouver, so that may have a bit to do with it as well. -- Jayron  32  01:49, 8 April 2014 (UTC)


 * "The Pacific Ocean makes the west coast of North America warmer" is only true down to the latitude of Seattle or so. Farther south the ocean has a cooling effect.  In San Diego, for example, it is usually very pleasant if you are within a couple of miles of the ocean, but rapidly gets blazing hot if you go a little farther inland. Looie496 (talk) 01:57, 8 April 2014 (UTC)

If all you care about is the annual average temperature, then the Pacific ocean doesn't have a large effect. Along the Pacific coast, annual average temperatures run from about 1 C below to 2 C above what you would expect based solely on latitude and elevation. That said, the ocean has a very strongly moderating effect on seasonal and weather variation. The difference between winter and summer along the Pacific coast is only 10 C or less, while 20-30 C ranges are typical for most of the US. Similarly, there is much less variation is weather. The Pacific Coast isn't much warmer on average, but it is more predictable, and one can avoid both extreme heat and cold. Dragons flight (talk) 19:42, 8 April 2014 (UTC)


 * Like others here, I too suspect Science Ape's friend is referring to the low temperatures (winters) being warmer on the Pacific Coast. This map of the US, for example, shows the average annual extreme minimum temperatures 1976 - 2005. I found it in our article on hardiness zone. ---Sluzzelin talk  09:07, 9 April 2014 (UTC)


 * Interesting. I wonder why the Pacific coast has such a wide band which is warmed by the sea, while in Maine it's such a narrow band.  Is this due to the prevailing wind direction ? StuRat (talk) 09:55, 9 April 2014 (UTC)


 * Yes - see Westerlies. Wnt (talk) 18:24, 9 April 2014 (UTC)


 * Thanks. StuRat (talk) 16:16, 10 April 2014 (UTC)

Inflatable hot tub mystery.
We have an inflatable hot-tub. It's construction is more or less identical to a kiddies paddling pool - three stacked inflatable rings with an inflatable "floor", each with it's own air valve. The "floor" valve is underwater, the other three are on the outside of the tub. The thing is made of some kind of very heavy duty vinyl and is about 5' in diameter and two feet deep and contains around 250 gallons of water at around 38 degC (100F). There is a separate heater/water pump and a gizmo to blow air into the water via a channel around the inside of the bottommost ring..but I don't think that's relevant here. We've been using it off and on for about 6 months - and it's never been completely emptied or deflated in all that time.

The other day, we had occasion to empty the water and deflate all of the air chambers. I was surprised to find that the "floor" had about two gallons of water sloshing around INSIDE the sealed air bladders.

I'm totally mystified as to how the water got in there! The floor is under considerable pressure (2 feet of water resting on it) - so if there were some kind of a leak, you'd expect it to deflate in short order - and it didn't seem to be deflated to any noticable degree. The air must be at about the same pressure as the water when the tub is full. It's conceivable that the air we put into the floor part at the outset was really humid - but even if all of the water vapor condensed out of that air...there was FAR too much water in there to be accounted for in that way.

It's not exactly important that I know the answer - but it's been bothering the heck out of me for the past week...and I can't explain it!

There is a picture of the hot tub here:

http://www.ebay.com/itm/like/350868160135?lpid=82

...ours has an outer protective cloth cover in bright blue and an inflatable "lid" that covers it when not in use - but that's the thing I'm talking about here.

SteveBaker (talk) 19:31, 7 April 2014 (UTC)


 * I'd say an equal volume of air leaked out as the water that leaked in, so the total volume remains the same. The water likely leaked in at the valve, the air might have also leaked out there, but too slowly to notice the bubbles, or perhaps there's a pinhole leak elsewhere.  The water pressure might go up instantly when you first sit in the tub, just enough for a few drops of water to drip in each time.


 * It might actually make more sense to fill the bottom with water than air, as that should make it more stable in the wind. It would also make it heavier, but if you don't plan to move it until you drain it, then that's OK.  StuRat (talk) 20:06, 7 April 2014 (UTC)


 * My problem with that idea is that when you step into the tub, the weight of your foot on the floor must increase the pressure of the air inside above that of the water on top of it...so I could believe in a bubble being expelled through a tiny hole each time - but the water would have to force it's way in through a positive pressure gradient.  It's not like the floor is a rigid container either - it's flexible/stretchable plastic - and you'd think that the tension it adds would keep the air pressure consistently higher than the water pressure.  SteveBaker (talk) 20:29, 7 April 2014 (UTC)


 * In that case, maybe when you get out, the lowered pressure in the air bladder sucks in some water to replace the gas bubbles which escaped when you got in (escaped from the air bladder, not from you, as those gas bubbles aren't relevant here). StuRat (talk) 00:25, 8 April 2014 (UTC)


 * Get a copy of the owner's manual or contact the manufacturer. They will likely have something to say about the issue. μηδείς (talk) 20:52, 7 April 2014 (UTC)


 * I think a pinhole leak/defect is always possible; it's also conceivable that water could permeate the polymer directly. (Trying to calculate that, based on the exact polymer and plasticizer compositions, would be a decent test of the Refdesk). Wnt (talk) 22:54, 7 April 2014 (UTC)


 * Even if there is just a bit of vapor permeability (whether directly through the polymer layer, or through the valves) there will be tendency for liquid water to accumulate on the bottom of the bladder. The liquid in the hot tub (and the polymer layer in contact with it) is likely to often (or always) be at a temperature higher than the ground under the tub.  Warm vapor that enters through the top side of the bladder cools and condenses when it reaches the bottom, forming a pool of liquid water...that will just keep growing, for however many months the tub remains in use.  TenOfAllTrades(talk) 14:02, 8 April 2014 (UTC)


 * Did you inflate it yourself? Is it possible someone deliberately put water in to anchor it before inflation? -- Q Chris (talk) 14:52, 8 April 2014 (UTC)


 * I'm going to guess that the floor has one of those valves that is in-only unless you squeeze it a certain way.
 * If so, and if the water pressure was higher than the floor's air pressure (or became so thanks to temperature changes, or momentary changes in the weight people put on it.) water could flow into the floor without an actual "leak", but air would not be able to flow back out, per its design.
 * Ok, it's not a perfect theory, and it requires that the cap on the valve is not water-tight, but it could be close. APL (talk) 15:11, 8 April 2014 (UTC)