Wikipedia:Reference desk/Archives/Science/2011 August 26

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August 26

Using bath to remove excess fluids

Is using a bathtub filled with water and saturated with epsom salts (or other bath salts) a recognized method of drawing out excess fluids, by changing the osmotic balance ? StuRat (talk) 03:42, 26 August 2011 (UTC)

I'm not sure such a method could do much more except dry out your skin. Excess internal fluid can't escape via your skin all that easily; a diuretic would do the job more efficiently. --Jayron32 04:01, 26 August 2011 (UTC)

Why wouldn't fluid be drawn from the circulatory system into the skin, and from the rest of the body into the circulatory system ? I would think this would take hours, but can't see what would prevent it. StuRat (talk) 04:07, 26 August 2011 (UTC)

Maybe. It could possibly take many hours (like, in the hundreds). Again, possible, but rediculously inefficient when compared to other methods of removing "excess fluids". Diuretics seem like a much more sensible solution. --Jayron32 04:13, 26 August 2011 (UTC)

Well, hemodialysis takes up to about 4 hours. There they remove fluids from the circulatory system slowly, while fluids in the tissue migrate back into the blood stream. So, do you think the migration of fluids into the skin from the blood stream would be much slower than that ? If so, why ? StuRat (talk) 04:20, 26 August 2011 (UTC)

I'd not risk my precious bodily fluids in Epsom salts. But what makes you think you have too much of them in the first place? AndyTheGrump (talk) 04:24, 26 August 2011 (UTC)

This question is not about me. StuRat (talk) 04:43, 26 August 2011 (UTC)

I'd think blood has a higher concentration of water than the outer layers of skin (I think plasma is around 90% while cells are around 70%?--so only need to be more ionic than 10% ionic vs 30%), and that skin is designed to prevent water from escaping easily whereas a dialysis tube is designed to be especially permeable for water. DMacks (talk) 04:28, 26 August 2011 (UTC)

Skin prunes up rapidly when bathing in just water, so water can move into the skin rapidly. Are you saying it's only prevented from moving out rapidly ? How so ? StuRat (talk) 04:43, 26 August 2011 (UTC)

I don't know how skin works, except that skin says it's rather waterproof. But the fact that the skin does prune to such a great degree and speed in 100% water suggests by a simple salt-concentration analysis that the outer layers of skin act as if they have a fairly high salt concentration (rapid and large amount of osmosis in). That means it would be hard to get "more ionic" enough to pull water out effectively. Also, isn't the effect fairly constrained to the skin (otherwise that absorbed water would just as rapidly diffuse into the body and dilute the rest of you), which goes against your idea of water being replaced from inside during the soak in salt-water. Is there a correlation of long baths leading to increased urinary output? DMacks (talk) 04:59, 26 August 2011 (UTC)

That's an excellent question, I wonder if anyone ever studied this ? (It sounds like the type of research used as evidence that the government is wasting taxpayer money, though.) StuRat (talk) 05:04, 26 August 2011 (UTC)

I take long showers, and can report that I do NOT have any greater need to piss afterwards than usual. But then again, I'm just one person -- others might have a different experience (though I don't see why). 67.169.177.176 (talk) 06:29, 26 August 2011 (UTC)

Only a small portion of your body is submerged in water at any given time while in the shower, so I'd expect far less effect. Also, if you haven't meticulously documented your bathing and urinating habits, eliminated other factors (like drinking less coffee while in the shower), and plotted the results; an increase in urination following bathing may not be apparent. StuRat (talk) 06:46, 26 August 2011 (UTC)

Also, I don't know the inner workings of modern hemodialysis machines, but countercurrent exchange lets you get well beyond "equilibrium concentration" (average of inside and outside), and even a more rapid same-direction flow system could do that and use large volumes of extraction liquid (which could be themselves cleansed and recycled), whereas soaking in a bath you have limited buffer capacity for the extracted material. DMacks (talk) 04:33, 26 August 2011 (UTC)

(edit conflict) x3 @StuRat. If you see Dehydration#Prevention, you'll see that the average person loses only 350 mL of water per day through the skin, compared to 1000 mL per day through the kidneys. I can't imagine that even encasing yourself in salt would lead to significantly increased diffusion through the skin; the Epidermis is avascular meaning that dry skin doesn't have blood circulation to repleanish its water, so your scenario would require water to diffuse across several layers of skin before reaching the epidermis. Plus you haven't defined where the excess fluid is coming from. Are we talking excess blood volume, excess intracellular fluid, etc. I don't think any of those could be significantly affected by dry skin; which is all a hypertonic salt bath would do to you. --Jayron32 04:35, 26 August 2011 (UTC)

Fluid in tissue, such as intracellular fluid. I think encasing yourself in salt would dry you out rapidly. Isn't that how mummies were made ? StuRat (talk) 04:37, 26 August 2011 (UTC)

Yes, but they are dead and cannot maintain homeostasis. --Jayron32 04:46, 26 August 2011 (UTC)

Right, but what does that have to do with the rate of fluid loss through the skin ? Does being alive somehow slow that down ? StuRat (talk) 04:48, 26 August 2011 (UTC)

(undent) Look at it this way Stu: If what you are proposing were true, then the reverse would be true: soaking in a hypotonic solution (like pure water) would cause a massive influx of water into your body. You'd swell up like a balloon after a few hours of soaking in fresh water. Since that doesn't happen, then the water won't signficantly move in the reverse direction either. --Jayron32 04:52, 26 August 2011 (UTC)

Perhaps that would happen, except that your kidneys remove the water and you urinate it out (hopefully after leaving the pool). StuRat (talk) 04:58, 26 August 2011 (UTC)

(picking up on same theme from above)...I think the ball's in your court here to find some evidence of that (quick look on google scholar isn't finding me anything)--would certainly help support some of your ideas on the topic rather than speculation either way. DMacks (talk) 05:05, 26 August 2011 (UTC)

I believe that corpses floating in fresh water do become bloated with water. Isn't that evidence ? StuRat (talk) 05:08, 26 August 2011 (UTC)

If you ignore the fact that this takes several weeks, then yes. But what about corpses floating in seawater? According to your theory, they're supposed to shrivel up like raisins from dehydration, aren't they? But in fact they become just as bloated as the ones in freshwater, right? And the reason for it is, the bloating is not because of water absorption, but because of gases released into the body cavities during decomposition. In fact, even corpses on dry land that are left unburied (combat casualties, etc.) get bloated as they decompose, even though there can be no significant water absorption. 67.169.177.176 (talk) 06:26, 26 August 2011 (UTC)

Drowned corpses from Commons that are not bloated[1][2][3][[4] [5][6], one that is (warning nasty) and one that was and is relevant to the OP. Cuddlyable3 (talk) 10:34, 26 August 2011 (UTC)

The story of the USS Indianapolis (CA-35) shows that human skin is remarkably resistant to the loss of water to the sea. Wnt (talk) 13:11, 26 August 2011 (UTC)

Consider that when your body temperature increases you begin to perspire and the perspiration contains not only water but body salt. As the perspiration evaporates it leaves behind the body salt on your skin. I know this to be true from clothing put on a rack to dry between uses without washing. Salt builds up on the material until it is practically caked. Does this make me sweat more? I don't know but I do know that high body temperature is the way to go if you want to loose body water through dehydration rather than through a diuretic. --DeeperQA (talk) 05:22, 27 August 2011 (UTC)

Noticed this question hasn't been answered yet. What the OP is referring to is full body (up to the neck) hydrotherapy. Whilst some spars contain naturally occurring Epsom salts, it not the mineral content that's a factor. Here is a paper about an experiment carried out at the Royal infirmary in Bristol and reported in the British Medical Journal. [7] Although it clearly explains some of what is happening, it less clear about why. NASA have found the same effect and has explained it more fully alone the lines (from what I remember) that as the blood is pushed out of the limbs and into the trunk by the water pressure, the blood volume receptors (in the trunk) modify a somewhat complex negative-feed-back-system involving the hormonal balance and that causes the kidneys to increase the production of urine. So to for astronauts without gravity to keep the legs and arms full of blood, the natural elasticity of the circulation system over stimulate these same receptors. Result: they pee in zero gravity a lot more than they do on earth. --Aspro (talk) 11:06, 29 August 2011 (UTC)

Thanks. It looks like this topic just hasn't been studied much. StuRat (talk) 07:37, 30 August 2011 (UTC)

amount of space

If all of the material in a Black hole was converted back into normal matter, ie. elements how much space would be required to contain it and what about all of the Black holes in the universe? --DeeperQA (talk) 05:09, 26 August 2011 (UTC)

Well, a supermassive black hole contains the mass of hundreds of thousands to billions of solar masses, so it would take up the space of hundreds of thousands to billions of Suns. Of course, if you wanted to prevent them from collapsing back into a black hole again, you'd need to space them out quite a bit. StuRat (talk) 05:13, 26 August 2011 (UTC)

If you multiply that by the 170 billion or so galaxies, you can account for the mass of all the supermassive black holes at galaxy centers. Whether smaller black holes would make an appreciable contribution to the total mass, I can not say. StuRat (talk) 05:18, 26 August 2011 (UTC)

I guess this is really about the maximum density of non-degenerate matter (the amount of matter you have is simply the mass of the black hole, so the volume required depends on the density). I'm not really sure what that is (it's not a desperately well defined concept anyway). It will depend on what level of degeneracy you are willing to accept (clearly you don't want neutron-degenerate matter, but is electron-degenerate matter ok?). It also depends on how many pieces you want the matter in. If you want it all in one piece, then it can't be done - it will collapse into a black hole again. If you want it in small enough pieces that it doesn't collapse under its own gravity then you need to choose where the pressure comes from. Is the pressure simply caused by gravity? In which case, the article Chandrasekhar limit will be useful. If the pressure is applied by magic, then you can do a better job (since gravity will only apply high pressure near the centre, the surface will be at fairly low pressure). --Tango (talk) 11:42, 26 August 2011 (UTC)

The matter I have in mind would be protons or possibly hydrogen atoms separated by enough space to prevent immediate collapse back into a Black hole. Lets say then minimum space to contain all of the hydrogen atoms all of the Black Holes in the Universe could make or lets jump right on up the periodic table and use the densest element separated by enough space to prevent immediate collapse at least long enough to measure how much space would be required. --DeeperQA (talk) 06:07, 27 August 2011 (UTC)

However, what I am really after is only the space that makes up an atom multiplied by the number of atoms all of the Black Holes would make rather than including the space of separation to prevent re collapse into a (many) Black Holes. --DeeperQA (talk) 06:48, 27 August 2011 (UTC)

That would depend on the configuration of the atoms. The "volume" of an atom depends on the surrounding atoms. What element or compound would you prefer? Simply divide the mass of the black hole by the density of your chosen material to obtain your answer. As pointed out above, this configuration would revert to a black hole under its own gravity. Dbfirs 07:58, 27 August 2011 (UTC)

I realize that but the point is to see if there is that much space in existance. --DeeperQA (talk) 08:23, 27 August 2011 (UTC)

If you have the necessary magic to stop it collapsing again, then you only need to make it marginally bigger than the event horizon and it won't be a black hole anymore. There is definitely enough space. The overall density of our galaxy is about one atom per cubic centimeter and the includes the black holes. If you spread that out evenly it would be a very thin gas. The density of the whole universe is even lower because of all the empty space between galaxies. --Tango (talk) 10:26, 27 August 2011 (UTC)

First human to die in space?

I know some animals have died in space, like the dogs the Soviets sent up, but has any human being ever died in space? It seems both the Challenger disaster and the Columbia disaster happened within Earth's atmosphere, so I guess those deaths can't be said to have happened in space. Is the sad record "First human to die in space" still unachieved? Pais (talk) 09:41, 26 August 2011 (UTC)

The Soyuz 11 mission resulted in the deaths of Vladislav Volkov, Georgi Dobrovolski and Viktor Patsayev during preparations for re-entry to the atmosphere, in June 1971. See also List of spaceflight-related accidents and incidents. Ghmyrtle (talk) 09:49, 26 August 2011 (UTC)

Hmmmm.... the Soyuz was reentering the atmosphere, and the valve opened at 104 mi altitude, about twice the height of the Space Shuttle Columbia disaster. The boundary of outer space seems to be arbitrary but is less than 76 mi. So if the article is right about how quickly the astronauts died from the depressurization, maybe this indeed was a death in space while the other was not. But like so many such questions, the more closely examined, the less meaningful the distinction seems to become. Wnt (talk) 13:09, 26 August 2011 (UTC)

Our articles don't seem to be entirely consistent regarding where "outer space" begins. The definitions at Outer space all fall within the lower thermosphere, while Exosphere says the exosphere is the last layer of atmosphere before outer space, implying that outer space doesn't start until 100,000 to 190,000 km (approx. 60,000 to 120,000 miles) altitude. Pais (talk) 15:39, 26 August 2011 (UTC)

The traditional boundary is 100km, roughly the height of the Kármán line. This is the altitude at which it is impossible for an aircraft to fly: in order to generate enough aerodynamic lift to stay aloft, it would need to be traveling faster than orbital velocity. --Carnildo (talk) 01:59, 27 August 2011 (UTC)

For some speculation/conspiracy thoughts, see lost cosmonauts. --Mr.98 (talk) 16:16, 26 August 2011 (UTC)

Yeah, I read about them recently on the Straight Dope, that's what got me wondering about the question. Pais (talk) 19:34, 26 August 2011 (UTC)

CRUDE OIL SPILL CLEAN-UP

In my Country, Nigeria, the oil spills are very common amongst oil prospecting companies. It has got so bad that hectares of arable farm land have been polluted, water sources for drinking, fishing and irrigation have also been contaminated.

Is there any way, method and/or technology that can be deployed to clean up the polluted land and water through private/community efforts?41.78.80.68 (talk) 11:28, 26 August 2011 (UTC)

Oil degrades itself. Cleanup efforts are usually performed to protect animals, not land. Sun, wind, rain, etc... break down, disperse, and degrade oil. The University of Delaware has a nice (short) page that explains what to do here -- kainaw™ 12:54, 26 August 2011 (UTC)

It is possible that oil-eating microbes could help to reduce the problem. The effectiveness of such organisms (typically bacteria) isn't always that clear (see Deepwater Horizon oil spill#Oil eating microbes) but it's a technique. In reports they're still often viewed as experimental. [8] Nonetheless, if you live in a country where oil spills on a certain type of terrain are actually common, it raises the possibility of developing particularly effective strains for the local terrain from old spill sites. For that matter, in theory, simply collecting a truckload of soil from an old spill site and spreading it over a large area of spill at the new site should have some positive effect - I just don't know if it's enough to be worth doing. Wnt (talk) 13:00, 26 August 2011 (UTC)

There is a recently started and ongoing project on one of the Channel Islands - I believe Jersey - using precisely this method to consume a quarry pit full of oil that had been collected from the beaches and dumped there some years before after a major oil spill: it was featured in a recent BBC TV documentary. {The poster formerly known as 87.81.230.195} 90.193.78.50 (talk) 16:32, 26 August 2011 (UTC)

This is too complex an issue for any simple answer. A possible approach may be to build dikes to stop the contamination spreading. Then scrape up the worst of the surface oil into heaps for composting. Then see if the natural soil bacteria can be encourage to brake down the oil naturally by ensuring it has enough nutrients containing nitrogen etc., (dung and lime). Frequent tilling of the soil will help the bacteria and atmospheric oxygen to get to the oil. The more it is tilled the greater will be the surface area available for the bacteria to attack it. That might help to prevent more contaminates from seeping into the water supply -or it might not. It will all take a lot of time and effort and so will need to be well organized to ensure that the remedial work being done is actually yielding good results. Here are some of the techniques that are used in land reclamation. [9] . Any project would have to choose the best methods to suit their local needs and available resources. --Aspro (talk) 13:14, 26 August 2011 (UTC)

Step one in Nigeria would be to get a stable, internationally recognized, effective, non-corrupt government in place, that enforces minimum environmental standards for the oil industry. The primary problem is political, not technical. IIRC, companies in Nigeria routinely abandon marginally productive wellheads without any effective cleanup, protection or monitoring. --Stephan Schulz (talk) 15:08, 26 August 2011 (UTC)

I wonder if locals could then take it over, and produce enough oil from it to pay for clean-up efforts. StuRat (talk) 16:55, 26 August 2011 (UTC)

Not unless the locals know how to maintain oil pipeline infrastructure (assuming it was still in good condition when the oil major left). Googlemeister (talk) 18:27, 26 August 2011 (UTC)

I'm thinking of something far less ambitious, like selling unrefined crude to other locals for use as heating oil. StuRat (talk) 18:31, 26 August 2011 (UTC)

I think you vastly overestimate the value of crude oil and vastly underestimate the cost of cleanup. Also, using crude oil directly is very problematic, too. Not to mention the fact that heating is not an urgent problem in most of Nigeria, and in particularly not in those parts close to the oil fields... --Stephan Schulz (talk) 18:43, 26 August 2011 (UTC)

While I agree it's not that useful, I presume StuRat is referring to things like for cooking, boiling water etc otherwise the suggestion doesn't make much sense as you pointed out. Nil Einne (talk) 21:00, 26 August 2011 (UTC)

Right, or for starting fires for slash and burn agriculture, if they use that method there, or for making torches, etc. StuRat (talk) 05:56, 27 August 2011 (UTC)

Can you use crude oil in a low efficiency power plant if pollution controls are non-existant? Googlemeister (talk) 21:22, 29 August 2011 (UTC)

I suppose you could, using an external combustion steam turbine dynamo. StuRat (talk) 07:27, 30 August 2011 (UTC)

hello.

hi. please send me the complete complete details with examples on INTERFERENCE. — Preceding unsigned comment added by Anish225 (talk • contribs) 12:47, 26 August 2011 (UTC)

See interference. -- kainaw™ 12:50, 26 August 2011 (UTC)

Hurricane Irene: hype or real concern?

So, my mother is all in a tizzy over this Hurricane (Jewish mothers tend to do that) because it is destined to hit all three of the places I live in, (DC; Greenwich, CT; New York). I have been hearing about the Metro North cancelling service and King Michael evacuating low-lying areas of Manhattan (we live on one of the hills in Manhattan so no flooding risk anyway). My mum thinks a tree might fall on our Greenwich house and I have postponed returning to DC until Monday morning as my uni is also in a tizzy (and wanted people to come in on Friday so they could get a little closer to the hurricane). Now, here is my question: Is all of this concern actually necessary or is everyone just up in arms over mostly nothing? I mean I know it's going to cause some damage, but people are acting like we'll have a Northeastern Katrina (and, let's face it, people tend to overreact a great deal). Sir William Matthew Flinders Petrie | Say Shalom! 14:10, 26 August 2011 (UTC)

Patience young grasshopper. If it hits bad and starts blowing around your ears, the answer to your question will reveal itself.--Aspro (talk) 14:51, 26 August 2011 (UTC)

Here is the current Public Advisory from the National Hurrican Center. You can also find the current predicted track on the NHC/NOAA site. Barring a severe change in the path, it is almost certain that there will be flooding in many parts of New York City. As noted in the linked advisory, Irene is a very large cyclone, with hurricane force winds extending up to 80 miles from the center, and tropical storm force winds extending nearly 300 miles. With rain saturated ground and high winds, falling trees are a definite possibility. This is a big storm, it's not "mostly nothing." Being prepared for several hours or even days without power or running water is not overkill, it's prudent. While you may not be affected where you live specifically, other areas nearby may experience effects that hinder the day-to-day operations of that region. All that said, Katrina was a different situation altogether. It was a higher category storm when it made landfall over a city that lies mostly below sea level, and New Orleans had been thought to be outside the track. -- LarryMac | Talk 14:55, 26 August 2011 (UTC)

Per Aspro, the decision whether the pre-storm coverage was hype or reasonable precaution can only be made in hindsight. If the storm fizzles or makes an unexpected turn out to sea, most people will claim the hype was unwarrented. If the storm does major damage, mostr people will claim that the coverage was warrented, and will likely go further and claim that there was not enough preparation. --Jayron32 14:59, 26 August 2011 (UTC)

Since the eyewall collapse yesterday, the storm has become less likely to strengthen over the ocean before landfall, but you can see how that widened the area of hurricane force winds here: http://www.wunderground.com/tropical/tracking/at201109_cumwind.html but NYC is likely to get about 10 inches of rain over a very short time period -- as shown at http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=1902 where Masters estimates a 20% chance of NYC floodwall overtopping and inundation of the subways. If the eyewall reforms before it hits the coast, that would be bad. 76.254.20.205 (talk) 18:27, 26 August 2011 (UTC)

Look to 1954 etc. Flooding in lower Fairfield County near the shore and along rivers. Staten Island and Long Island will likely get flooding. Lots of trees will fall. Manhattan above the old city is on a pretty good rocky spine. Jersey shore will flood (it is quite flat). Philadelphia would worry me more as the tidal surge (depending on exactly when anything hits) could cause significant flooding. DC is actually relatively inland from Hatteras (quite a bit west in fact) - I doubt it will get much more than flooding of the swampy parts (um -- which is a lot of DC). All IMHO of course. Collect (talk) 14:59, 26 August 2011 (UTC)

DC is more accurately described as NNW of Hatteras (even NNNW, if such a designation existed). --LarryMac | Talk 20:17, 26 August 2011 (UTC)

Lesser hurricanes like this typically cause less damage from wind and storm surge, but can actually produce more rain. This is because a major hurricane must move fast or exhaust it's fuel supply (warm ocean water which it rapidly cools). So, it passes quickly. A lesser hurricane, on the other hand, only slowly cools the water, so can "park" on a spot (particularly over a small island) and deliver rain for days. I don't believe this hurricane is predicted to do so, however. StuRat (talk) 18:39, 26 August 2011 (UTC)

What this hurricane is predicted to do is make landfall in a heavily-populated area that has very saturated soils due to prolonged rains. That alone increases the risk for flooding tremendously. Another risk that Irene poses is its large wind field. Large storms are able to produce stronger storm surges than their sustained winds would suggest. In fact, the latest analyses for Irene from the Atlantic Oceanographic and Meteorological Laboratory (08/27/2011 0130Z as of the time I checked) indicate that Irene has the potential to produce a "5.0 storm surge" in the Integrated Kinetic Energy scale—this is equivalent to a Category 4 hurricane. While it is impossible to know at this time whether this threat will materialize, the storm needs to be taken very seriously. Titoxd^{(?!? - cool stuff)} 03:10, 27 August 2011 (UTC)

Looks like a lot of it was hype, at least for New York, but it is interfering with transportation now (for instance I cannot attend my first class in DC as the Amtrak NE Corridor is closed down). In Connecticut though, much of the state is without power and quite a few trees are down. Don't know about DC though. Sir William Matthew Flinders Petrie | Say Shalom! 15:57, 29 August 2011 (UTC)

Asian guinea pig?

According to Traditional Burmese calendar, also [10] and [11], the "planetary vehicle" or zodiac sign associated with Friday is the guinea pig. Since Cavia porcellus is native to South America, it seems unlikely to be an animal in any traditional Asian zodiac. Is there some other animal, native to Southeast Asia, that also gets called the Guinea pig? I found nothing at Guinea pig (disambiguation). 85.178.84.35 (talk) 22:53, 26 August 2011 (UTC)

According to this book (page 93), the traditional Friday animal is the ox. Perhaps the "tradition" has changed -- such things have been known to happen. Looie496 (talk) 00:30, 27 August 2011 (UTC)

This is probably just coincidence, but ... apparently the guinea pig, like the capybara, is not regarded as "meat" by Roman Catholics in South American regions where it is commonly consumed, and thus can be eaten by them on Fridays when meat is abstained from. [12] But I don't have any evidence this was a factor here, and apparently Roman Catholicism in Burma is quite uncommon. Wnt (talk) 22:29, 28 August 2011 (UTC)