Wikipedia:Reference desk/Archives/Science/2013 May 27

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May 27

Salt and sea salt

There's a lot of advertising and hype about sea salt which, for reasons that remain mysterious to me, is better for you than other salt. I expected that this was a recent craze, but I was watching a not-so-recent film La Regle de Jeu where one of the characters is on a "diet" that she can't have salt but can have sea salt. The chef dismisses it as nonsense, subtitled as "She can eat like everybody else. Diets I can accept, but not obsessions." How far back does this go as a health craze? 71.231.186.92 (talk) 00:20, 27 May 2013 (UTC)

Sea salt contains a little bit of alternative ions to sodium, but it generally doesn't contain enough to really reduce the dose enough to help tremendously with sodium reduction (by comparison to pure or half-potassium formulations on the market). Editorial: I wish I could find good balanced salts for human consumption at supermarkets with better levels of potassium/magnesium/calcium/etc. In terms of nutrition, sea salt is a poor substitute for the more balanced land salt that our ancestors were accustomed to, and which is still favored in some traditional cultures. The notion everybody learns that "table salt" is "sodium chloride" is one of the more dangerous myths in modern culture. Wnt (talk) 01:06, 27 May 2013 (UTC)

Wnt, as you are aware, you can buy the readily available "Lite Salt", which is 50:50 sodium salt and potassium salt, marketed to people who want to reduce sodium intake. However, people usually increase the amount they use as it lacks taste. So you end up with just about as much sodium, and a lot more potassium, which can cause medical issues of its' own. You should be getting calcium from milk. Wickwack 120.145.190.145 (talk) 02:24, 27 May 2013 (UTC)

That's surprising to hear, because in my personal experience it isn't true; if I'm hungry for potassium then I have a hunger for salt but it doesn't fill the need, so I use more and more. Definitely I prefer the flavor of the salt with some potassium in it to the slightly sour taste of pure sodium salt, especially when I'm hungry for it. But I think "Lite Salt" can be formulated with at least a little and maybe a lot of magnesium and calcium with what I think could be an actual improvement in flavor for at least some applications. (I've seen some foods like chick peas actually packed in calcium salt solution) Wnt (talk) 04:02, 27 May 2013 (UTC)

Sea salt is not iodized. Some people think they're getting too much iodine, and those people are usually the types that carry on about eating "natural", so sea salt appeals to them. 202.155.85.18 (talk) 01:50, 27 May 2013 (UTC)

As far as a craze is concerned, it may depend on which country you live in. In Australia, by law, salt packaged for consumers is iodized (salts of iodine added) as it was found that thyriod problems due to iodine deficiency occurred in susceptable people. Australian salt has for decades been sold in very plain packaging, and it has always been sea salt, produced by evaporating sea water in large pans, by Dampier Salt and other companies. It was never labelled as "sea salt" - just "salt" or "table salt". However, in the last few years, shops have been stocking imported sea salt and it (mostly) is not iodised - it gets around the law as it is not packaged in Australia. It is also sold in modern attractive packaging and labelled as "sea salt". The craze is thus driven by three coincident things: a) it avoids the problem of many people who are distrustfull of "population medication" (same as the dubious objection to folate in bread, flouride in water, etc); b) more attractive modern packaging; and c) a hazy notion that as it is different and new, it must be better. For decades, thyroid disease has been very rare, but now to a minor extent it has come back. There is no scientific benefit in the imported sea salt - in fact you are better off with the local iodized salt. However I notice that recently the main Australian retail company has risen to the occaison by marketing "iodized sea salt" (actually exactly what they have always sold) in nice packaging, at a premium price. Wickwack 120.145.190.145 (talk) 02:10, 27 May 2013 (UTC)

Do you have a ref for the Australian law banning the packaging of non-iodized salt? I'm having trouble finding any other source that says that. 202.155.85.18 (talk) 03:14, 27 May 2013 (UTC)

There's no law banning the packaging of non-iodized salt - rather there is a mandatory food standard requiring that salt packaged for retail/domestic use be iodised, and bread for sale be made with iodized salt. Ref Mandatory Iodine Fortification, Food Standards Australia. Wickwack 124.178.154.108 (talk) 04:04, 27 May 2013 (UTC)

Does anybody actually have an answer for the OP: when this fad started? Clarityfiend (talk) 09:32, 27 May 2013 (UTC)

this link suggests that it has been within the last 15 years or so. Since the UK and France tend to be where these things started (Maldon, Fleur de Sel), I would be willing to take that at face value. -- [ UseTheCommandLine ~/talk ] # _ 10:27, 27 May 2013 (UTC)

And as I said in my first post, in Australia at least, within the last few years. Of course the OP is probably not in Australia, but I expect other Western countries to be similar - they usually are. Wickwack 120.145.154.162 (talk) 11:05, 27 May 2013 (UTC)

The OP noted a character on a sea-salt-only diet in a 1939 film. (Yes, I know it was a work of fiction.) Though I haven't seen the film, I get the impression from the OP and from our article that the point of mentioning the sea-salt diet was to mock the French upper classes' willingness to adopt the latest silly trends, much as we make fun of celebrity fad diets today. So the first question I would ask is whether or not the sea-salt-only restriction mentioned in the film was poking fun at a 'real' trend of the era, or just some sort of generic parody of celebrity fascination with fads.

In other words, though the Guardian might trace the current obsession with sea salt to the last 15 years, it's certainly plausible that it has had its ups and downs, or has had at least a small following, going at least back to 1939. Worth noting is that Switzerland introduced the first national iodised salt program in 1922 [1], and iodised salt first became widely available in the United States in 1924; many other countries followed suit over the next decade or so. Based on my experience with quack medicine, I would be frankly shocked if there weren't some sort of paranoid, reactionary pushback from that era's lunatic fringe in response—leading in turn to health gurus of the era preying on the fashionable and gullible. (See also the anti-vaccination and anti-fluoridation movements.) TenOfAllTrades(talk) 13:54, 27 May 2013 (UTC)

ELectrostatic Energy

What do you know by electrostatic energy of discrete and continous distribution of charges? — Preceding unsigned comment added by Titunsam (talk • contribs) 12:42, 27 May 2013 (UTC)

Oh, heaps and heaps. What do you want to know? — Preceding unsigned comment added by 60.231.241.154 (talk) 13:01, 27 May 2013 (UTC)

This is an encyclopedia. Please see our articles on Electrostatics, Static electricity, and Electric charge, and come back here if you have a more specific question.--Shantavira|^{feed me} 13:18, 27 May 2013 (UTC)

For the equations involved, see the article Electrostatic potential energy, and the article section Electrostatics#Electrostatic energy. Red Act (talk) 17:20, 27 May 2013 (UTC)

Purpose of small building connected to upper floor of generating station

Resolved

The now-defunct Richard L. Hearn Generating Station has a small shed-like building on "stilts" connected to one of the main building's upper floors by a short gangway (the building is visible in this photo, slightly down and to the left of the smokestack). I've seen similar buildings in photos of other old industrial buildings as well.

What is the purpose of these buildings? My guess is that they contain hoists for lifting equipment or material from rail cars or vehicles to the upper floors of the building to which they're attached, but this is only speculation. Confirmation of this guess or information about the true function of these buildings would be appreciated! 142.20.133.199 (talk) 13:24, 27 May 2013 (UTC)

A building I used to work at years ago had a similar attachment, used, as you guessed, as a hoist to lift things off of train cars. Dominus Vobisdu (talk) 14:08, 27 May 2013 (UTC)

This structure looks like it has angle braces which would prevent putting a rail car under it, and the extension to the building does not look to be very substantial, so I wonder how heavy items could be lifted. Edison (talk) 14:29, 27 May 2013 (UTC)

This particular power station was originally built to run on coal, and later converted to gas. The shed-like structure on silts may have been the head compartment of a coal conveyor (which would typically look like a long elongated shed ramping up from ground level at a low angle). The actual conveyor structure has, I am assuming, been removed and the head compartment left in situ. Maybe after the station was converted to gas firing, they needed the ground area for something else but had no particular need to spend money removing the header compartment. Wickwack 120.145.148.85 (talk) 14:48, 27 May 2013 (UTC)

Wickwack, I found a photo of the southwest corner of the main building from the 1960s that (unfortunately) doesn't show the shed-like building (which is attached to the east wall of the main building) but does depict a coal conveyor going directly into the building. It's possible that another conveyor went into the shed on stilts, but that seems somewhat unlikely given the existence of the one shown in the photograph.

Edison, I think the shed's supporting braces might be large enough that a rail car (or truck) could fit between them; admittedly, however, the shed and gangway do look rather delicate. Dominus, was the hoist building where you once worked supported by angle braces and of a similarly (perhaps deceptively) flimsy appearance as this one? 142.20.133.199 (talk) 15:26, 27 May 2013 (UTC)

It turns out that the shed was connected to a coal chute (very close to Wickwack's hypothesis). This photo from 2004 shows the chute; evidently it was removed before the photo of the building on Wikipedia was taken. There's another photo by the same person that shows the chute in more detail; perhaps it was torn down to prevent people from using it to get to the roof of the plant. Thanks for your assistance, everyone! 142.20.133.199 (talk) 16:49, 27 May 2013 (UTC)

Yep, that's a coal conveyor (a means to take coal from ground level up to the header), not a chute (a chute would guide material travelling downwards). Wickwack 121.215.149.216 (talk) 01:12, 28 May 2013 (UTC)

I need to know the names of 4 things

The following discussion is closed. Please do not modify it. Subsequent comments should be made on the appropriate discussion page. No further edits should be made to this discussion.

---

I need to know the names of these 4 things:

What is the name of the paper-packed plastic tool sold in pharmacies used to hook out the thing punctured into the gums by a dentist? There's the jewelry, gold or silver version of the tool for the same purpose.

What is the name of the flying machine which looks like a jet-ski machine? It has 2 controls, one to move forward and the other to rise up the air.

What is the name of the device used to draw or suck the soul out of a living body? It has a switch with 3 switch positions, the first being the off position and there are the switch position to draw the soul out and the switch position to suck the soul into the device.

What is the name of the white-coloured machine which is capable of teleportation? — Preceding unsigned comment added by Pnf1 (talk • contribs) 14:32, 27 May 2013 (UTC)

Please give us some background here: Are you asking about machines in movies, books, comics? Or conspiracy theories? Anyway, your 3rd question has been asked here [2], maybe you get some tips there.

Your first question is asked here [3]. Aaadddaaammm (talk) 14:48, 27 May 2013 (UTC)

Looks like we're getting another round of those god-damn online quizzes. Looie496 (talk) 19:06, 27 May 2013 (UTC)

I suggest someone close this thread as very obvious soul-sucking trolling. I also suggest we change the quidelines to say, "Do not ask unrelated questions in the same posting". μηδείς (talk) 20:57, 27 May 2013 (UTC)

The discussion above is closed. Please do not modify it. Subsequent comments should be made on the appropriate discussion page. No further edits should be made to this discussion.

How is water pumped to the treetop?

I have been told that capillarity did the job of transporting water through the tree from the root to the top, but that cannot be true because work has to be done all the time. There must be some kind of biochemical pump working in trees and other plants. Do we have an article about the phenomenon? Bo Jacoby (talk) 14:58, 27 May 2013 (UTC).

Evapotranspiration. The process relies on active and passive techniques to cause a pressure-gradient from the root to the leaf, and water flows upward against gravity, e.g. in the xylem. You are correct that it is a tremendous amount of work. Trees, and plants in general, are incredibly thermodynamically efficient; they extract solar energy through photosynthesis and use it to perform chemical and mechanical work. Nimur (talk) 15:04, 27 May 2013 (UTC)

Yes, I believe the majority of the work is passive, and controlled by vapor pressure deficit, among other factors. SemanticMantis (talk) 16:36, 27 May 2013 (UTC)

Get a piece of toilet paper end touch some water with one end to see the water rise to the the other end by capillarity alone. No need for active transport. As water evaporates from the top, more water will rise from the bottom to replace it. Dauto (talk) 18:01, 27 May 2013 (UTC)

The problem here is that you are just performing a thought experiment, but not a real one. If you performed a real one, and tried to pump water up to 100 m, which is what some trees do, you'll see that your physical reasoning is wrong. OsmanRF34 (talk) 22:50, 27 May 2013 (UTC)

In the reference to "Evapotranspiration" I do not quite see the answer. Neither does capillarity alone convince me. A vacuum will support only a column of about 10 meters. When evaporation causes a partial vacuum it might cause the water to rise, but not indefinitely. Some trees are 100 meters or more high. I am still curious about the "mechanism" behind it. --VanBuren (talk) 18:37, 27 May 2013 (UTC)

You have presented one example where purely passive action is insufficient to raise the water. That's why the plant, as a living organism, expends energy to control its osmotic pressure. In combination, the plant's active transport and the physical processes of passive transport work to move the water throughout the organism.

If you click on the link I provided, xylem (upward water transport), you'll see a lot more information.

Several years ago, I became very interested in active transport in plant life - specifically, at what point in Earth's history the first plant roots evolved; because, prior to the first root, the Earth soil would have been awfully inhospitable to life as we know it today. So I created the first Wikipedia article on plant evolution and researched as much as I could, hoping that a botanist would fill in some details. In fact, Evolutionary history of plants and several new articles were created, with more information than I ever expected to find on plant water- and nutrient- transport. For obvious reasons, tissue specifically adapted for water transport was among the first special-purpose multicellular items to evolve among any life form.

Nimur (talk) 18:57, 27 May 2013 (UTC)

And if that's not enough, Big Basin State Park has a whole textbook worth of Redwood Ecology and Natural History, including material suitable for students of all levels. There's a whole "science activity" where you calculate and balance water transport in a redwood forest. In places like Santa Cruz, fog drip is important: the forests are so huge that their water cycle is effectively at a dynamic equilibrium with the atmosphere. Sometimes, fog emanates from the trees as transpired water; and sometimes fog condenses from the atmosphere and enters the trees directly through the needles. Nimur (talk) 19:20, 27 May 2013 (UTC)

If people here are interested in the theoretical limits of this, they can consider the following thermodynamics problem. Suppose you have a glass of water at room temperature T and the relative humidity in the room is r. How much work can you extract from the water per unit mass of the water? To what altitude could you lift the water using that work? Count Iblis (talk) 21:47, 27 May 2013 (UTC)

Obviously, you allow life to evolve in the glass of water; preferably in the form of an algae that can convert atmospheric gases into stored hydrocarbons; then permit some of the lifeforms to decay into fossil fuel; and use the rest of the water to evolve intelligent life, who can use the fossil fuel to develop a manned space program and launch a small portion of the remaining water into Earth orbit and beyond. This is, of course, assuming that your thought-experiment has no time-limit and that you allow solar energy as an input to the otherwise-closed system. Nimur (talk) 22:10, 27 May 2013 (UTC)

We don't allow any external energy sources unless they are used in a fully neutral way (e.g. if you add work to the system you have to subtract that amount of work to compute how much net work you have gained from the water). The beauty of thermodynamics is, of course, that you can compute the answer without having to think about the details of how you would actually extract the work. Count Iblis (talk) 22:40, 27 May 2013 (UTC)

But, plants do extract energy from the sun. I don't think it's a good idea to model an individual organism (or an ecosystem of many organisms) as an Isolated system. There is a net input of energy that is available for non-conservative work. Nimur (talk) 22:58, 27 May 2013 (UTC)

Yes, but then the problem is that with solar energy there is no restriction to how high you can pump the water. Thing is that trees operate under the same constraints as one would have if the system were perfectly isolated. Count Iblis (talk) 23:41, 27 May 2013 (UTC)

I politely disagree; trees can use photosynthesis to set off a chain of biochemical reactions that expend energy to pump water. This is accomplished by using active transport at the cellular level to induce an osmotic pressure. So, a living tree with working cells can pump water higher than a dead tree with the same capillary vascular structure, as a result of energy input to the system. Nimur (talk) 23:55, 27 May 2013 (UTC)

I see, so solar energy does play an import role in how trees pump water and that is what the OP's question was about. Still, trees are not able to pump water higher than the thermodynamic limit for an isolated system (which is quite obvious if you compute it), so I'm still wondering if the energy derived form solar power is merely assisting in the thermodynamic processes for which the bulk of the work is derived from evaporation, rather than that energy itself being a large part of the work, because in the latter case you could easily evade the limits form the thermodynamics of the isolated system and there would then be no upper limit to the maximum height of trees. In the latter case, you would expect the height of trees to be limited at least approximately by the thermodynamic limit, which is indeed the case. Count Iblis (talk) 12:02, 28 May 2013 (UTC)

• I think all this boils down to that no one really knows the complete answer. See: Plant Physiology Online: How Water Climbs to the Top of a 112 Meter-Tall Tree. Some of this site's other essays are also interesting.Aspro (talk) 13:09, 28 May 2013 (UTC)

Funny i watched a youtube video about this very topic just a few days ago. Veritasium is a pretty decent "science" channel on youtube. Previously they did an experiment of how high you could "suck" water up a straw. They found that even a vacuum pump couldn't get water higher then 10m becuase after that point, the pressure has to be so low that the water literally boils. So, how does a tree do it? Search for "the most amazing thing about trees" on youtube, (i can't access youtube at work so can't paste the link). Vespine (talk) 03:34, 29 May 2013 (UTC)

See here: [4]. Very well explained. The 10 meter limit applies to gases, not liquids. Because of that the evaporation causes a significant negative pressure sucking up the water column even higher than 100 meters for the tallest trees. --VanBuren (talk) 12:49, 30 May 2013 (UTC)

My cat and formic acid, etc.

I have a lovely wonderful cat. I also have something of an ant infestation. My cat loves it. She stalks, kills AND EATS the ants. I don't know if that's common but she is having a ball. I have two issues. One is that I know ants have formic acid in them. Should I be worried about my cat's ingestion of quite a lot of ants? What I am more worried about is that I want to have an exterminator come in but if they poison the ants and then my cats eats the ants, she will get the poison. That has kept me from making an appointment. Any thoughts?--71.190.242.180 (talk) 15:43, 27 May 2013 (UTC)

From a quick google I see that there are a few mentions of cats going mad for formic acid, but I haven't been able to find any authoritative references. One of the things you could do is tip a kettle of boiling water over the ant nest which should kill most of the little blighters, if you are worried about noxious substances and your cat. --TammyMoet (talk) 19:22, 27 May 2013 (UTC)

I'd suggest you just express your concern to the relevant professional exterminator. There are supposedly "organic" solutions like oleic acid. A professional who can't comment might not be the one to go with. μηδείς (talk) 20:59, 27 May 2013 (UTC)

I wonder if you mean Boric acid which in the US is considered safe for children and pets as long as you keep them away whilst its being applied. [5] Once the little critters stop moving the pussy will no longer be interested in them. Aspro (talk) 12:58, 28 May 2013 (UTC)

Boric acid harms fertility and unborn children, and is a restricted product for the general public in the EU, so I question this casual attitude. 86.163.0.30 (talk) 19:27, 28 May 2013 (UTC)

Does this question violate the no medical advice policy? Count Iblis (talk) 23:17, 27 May 2013 (UTC)

Not if we give the proper advice, which is to see a professional. Or, in this case, two professionals: the vet, and the exterminator. Cats love to attack, kill and eat bugs, so there's certainly cause for concern. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:42, 27 May 2013 (UTC)

There's much better things to do with ants than try to kill them you know. 78.245.228.100 (talk) 06:39, 28 May 2013 (UTC)

One thing worth bearing in mind is that most common ant insecticides contain permethrin - which is pretty toxic for cats. You would definitely need to raise the issue with any exterminator you hire. Yunshui 雲‍水 10:40, 28 May 2013 (UTC)

Formic acid is a weak acid, much like acetic acid, the acid in vinegar. And there is much less acid in ants than there is in vinegar. So I wouldn't worry for your cat in terms of the acidity. — Preceding unsigned comment added by 148.177.1.217 (talk) 14:40, 28 May 2013 (UTC)

There are plenty of humans around the world who eat ants of various species. In Colombia, for example, they sell toasted leaf-cutter ants instead of popcorn in movie theaters. Cats certainly have different digestive systems - but I doubt the cat will suffer from eating them. SteveBaker (talk) 15:17, 29 May 2013 (UTC)

That's it, I can't hold it in any longer. Not with the specific mention, sorry!

Mamie, in a manner placid

Fed the cat boracic acid

Whereupon the cat grew frantic

And executed many an antic

Ah, cried Mamie, overjoyed:

"Pussy is an alkaloid!" [6]

Wnt (talk) 18:48, 31 May 2013 (UTC)

No blossoming

I've noticed that in a matter of weeks, the trees where I live (Colorado) have gone from being bare to being completely green. It looks like the blossoming phase has been completely skipped. We had a few snowstorms at the end of April and the beginning of May, completely freezing all the trees as they were starting to sprout on the branches. Is it possible that the blossoming phase rapidly sped up due to the cold and snow?71.229.194.243 (talk) 23:58, 27 May 2013 (UTC)

It's possible that the blossoms were frozen at a critical point so that they didn't form properly. --TammyMoet (talk) 09:47, 28 May 2013 (UTC)

It sounds like some trees had their bloom cycles aborted by a cold snap. That can have the effect of leaves emerging sooner, since they are not being "blocked" by the flowers. Other trees may have had a different reaction to the cold, e.g. very late emergers. Generally, this is the topic of phenology, and if you want to know more about what happened in CO this season, you can check out the US National Phenology Network, here [7]. SemanticMantis (talk) 12:01, 28 May 2013 (UTC)

Thanks. 71.229.194.243 (talk) 00:42, 30 May 2013 (UTC)