Wikipedia:Reference desk/Archives/Science/2017 November 30

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November 30

Packages within large infrastructure projects

On a large infrastructure project, a construction company might split their programme into packages of work and each assigned to a different project manager. These packages would generally be done by physically separating parts of the build. But how are packages of work split out on the client side? Would it be more by which stakeholders are involved rather than physical sections? 90.192.100.85 (talk) 01:41, 30 November 2017 (UTC)

Every big project is different but usually there is a main/head contractor/manager/organisation assigned to be responsible for the complete project. A client is wise to stay out of that because when something goes wrong a client has a very poor legal approach when multiple contractors start to blame each other of being responsible. Project management is a full time expert job that clients are usually not fit to take over themselves. Besides that its also a huge financial and insurance-technical benefit to have someone dedicated to blame in any case of any missed contract fulfillment. --Kharon (talk) 17:25, 30 November 2017 (UTC)

Is mining for agricultural water and drinking water practical?

Is there water deep under the surface other than groundwater that can be mined for or drilled for like a an oil well and be made suitable for use?155.97.8.169 (talk) 05:33, 30 November 2017 (UTC)

Do you mean hydrated minerals like Epsom salt? Sagittarian Milky Way (talk) 05:43, 30 November 2017 (UTC)

See Artesian well. 2601:646:8E01:7E0B:9559:4F0F:AF97:BC2A (talk) 06:01, 30 November 2017 (UTC)

Limits vary but you only get drinkable water relatively near the surface. It is rare to find potable water more than a few hundred meters down. Once water gets really deep and really old, it invariably picks up too many salts and other dissolved materials to be safe to drink without additional treatment. I'm not aware of any efforts to reclaim deep saline water for human or agricultural use. I assume it would be possible in principle but is probably too expensive to warrant much use. Dragons flight (talk) 15:58, 30 November 2017 (UTC)

Yes and this was even already done very successful on a grand scale. Go read our fine Article about the "Great Man-Made River" in Libya. However, like oil fields, such Fossil water sources are not everywhere and not all of the existing ones contain water suited for agriculture. The fossil water may contain to much or to little salt or other substances that would make at least some processing necessary. --Kharon (talk) 16:22, 30 November 2017 (UTC)

Too little salt? Dbfirs 19:00, 30 November 2017 (UTC)

Maybe soft water#health impacts? SemanticMantis (talk) 19:56, 30 November 2017 (UTC)

Most people get sufficient calcium and magnesium from other foodstuffs, but it would be a simple process to add traces to soft water. Sodium deficiency in diet is rare. Dbfirs 12:46, 1 December 2017 (UTC)

The impact of to little salt in irrigation water is disputed, but that is also true for the impact of Herbicides. Agriculture seems to be a strange science. --Kharon (talk) 21:16, 1 December 2017 (UTC)

See Ogallala Aquifer for another example, which has been used extensively for agriculture for many years, and the general concept article at aquifer. Nyttend (talk) 01:28, 3 December 2017 (UTC)

What is the farthest east that the Gulf Stream and its continuations reach?

What is the farthest east that the Gulf Stream and its continuations reach? I know it reaches Murmansk (which is why that harbor never freezes in winter) -- how far beyond it? 2601:646:8E01:7E0B:9559:4F0F:AF97:BC2A (talk) 06:09, 30 November 2017 (UTC)

The Arctic Ocean article includes the line "Inflow from the North Atlantic Current enters through the Fram Strait, cooling and sinking to form the deepest layer of the halocline, where it circles the Arctic Basin counter-clockwise" - which suggests that at least some of it probably goes all the way round the pole (though it obviously cools a lot in the process). Wymspen (talk) 11:01, 30 November 2017 (UTC)

The Gulf Stream is part of a wider system of oceanic currents in the North Atlantic - Arctic basins

It is hard to define hard limits here; the as noted in the articles already cited, the current bleeds out into currents like the North Atlantic Drift, Transpolar Drift, and the Norwegian Current. There's no easily definable point at which the Gulf Stream "stops" and those other currents "start"; there's a broad transitional zone along the north shore of Britain where the temperatures gradually drop, but where we stop identifying the "Gulf Stream" is a bit arbitrary. See the map at right. --Jayron32 14:37, 30 November 2017 (UTC)

Well, I guess when it's no longer any warmer than the surrounding water, we can stop identifying it, right? 2601:646:8E01:7E0B:9559:4F0F:AF97:BC2A (talk) 07:29, 1 December 2017 (UTC)

Even that is not sufficiently well-defined.--Jasper Deng (talk) 09:50, 2 December 2017 (UTC)

It's hard to define where bodies of water begin and end. Like trying to say where the Atlantic ends and the Arctic begins. It's really all just one ocean with many streams and currents within it. We assign regional names for convenience. But there aren't boundaries as there are on land. ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:32, 2 December 2017 (UTC)

Could I ask about Dytrysia taxonomy?

Why Tactopoda and Arthropoda are not in this taxonomy Template:Taxonomy/Ditrysia. Some taxonomy use Tactopoda and Arthropoda and some didn't. This page Riodinidae, have Arthropoda. This page use Tactopoda Template:Taxonomy/Arthropoda --Hayate891 (talk) 08:52, 30 November 2017 (UTC)

Simply because there is a disagreement within the scientific community about how those groups should be classified. The template you link to includes Panarthropoda, which is proposed to include both Arthropoda and Tardigrada (which is elsewhere within Tactopoda). Clearly different people have contributed to those Wikipedia pages, and they hold differing views on the subject. Wymspen (talk) 10:52, 30 November 2017 (UTC)

Hmm. Thanks. I guess, I'm going to go with Arthropoda instead of Euarthropoda. I have to pick one. And I thought, "watch this page" means I will get notification from any edit in this section.-_- --Hayate891 (talk) 11:52, 1 December 2017 (UTC)

Removing ink from a book

What makes ink on paper so resilient? The methods I hear of: acetate (blurs more than erases), laser (only works on some toners, which is not proper ink), sanding (damages paper, works well for marking on edges), all damage the page somehow. Is it impossible to remove ink from a book without damaging the paper.Hofhof (talk) 18:59, 30 November 2017 (UTC)

Isn't that the point of ink originally? I'd say that the method of removing it depends very much on the type of ink, if it is stuff that dissolves in water for instance (and your paper doesn't), you could gently wash the paper until the ink is gone (and iron it afterwards I suppose). Most books/papers I've left in the washing machine or out in the rain don't handle water that well though... Rmvandijk (talk) 19:13, 30 November 2017 (UTC)

It's also the purpose of pencil. However, one is somehow ingrained with the paper while the other can be applied and removed several times. --Hofhof (talk) 00:01, 1 December 2017 (UTC)

See Check washing for a couple examples on how to remove ink from paper. Basically, you need a solvent that matches the ink polarity. RudolfRed (talk) 20:00, 30 November 2017 (UTC)

Palimpsest may be of interest. In the past it was worth it to remove the ink from manuscripts to avoid having to buy something to write on. Sagittarian Milky Way (talk) 03:02, 1 December 2017 (UTC)

Palimpsests are done on parchment or vellum - a much thicker, and more expensive, material that could be scraped to remove a surface layer. Paper, being much thinner and fairly fragile, doesn't take kindly to such treatment. Wymspen (talk) 16:29, 3 December 2017 (UTC)

Paper is a biomaterial made from cellulose. Cellulose, as found in plants, has a large surface area and is very hydrophilic, so it readily absorbs anything water-based. There isn't anything particularly special about most inks. The "specialness" is in the paper, not the ink. As you mentioned, the real challenge is getting the ink out without damaging the paper. This is a consequence of thermodynamics. Once the ink is absorbed into the paper, the resulting ink-and-paper mixture has a high entropy, with molecules of ink and paper jumbled together. Returning this to a low-entropy state (ink and paper fully separated) requires doing lots of work, the same as for any homogeneous mixture, like salt in water. But that means inputting lots of energy, which makes it difficult to keep the paper intact. By contrast, at least when desalinating water we don't have to worry about destroying the water, meaning we can just dump energy into it until it evaporates away, leaving the salt behind. --47.157.122.192 (talk) 09:57, 1 December 2017 (UTC)

The entropy discussion is true, but pointlessly technical and not really helpful to explaining the situation. Being true is not a synonym for being useful. The answer is "the ink is waterproof". This chemistry discussion forum actual covers the discussion of ink fairly well. The ink does not dissolve readily in water, so attempts to wash it out are unsuccessful. This more general article discusses the chemistry of various inks and their composition. Here is a nice discussion from Ink World Magazine on the history of inks and some of the various compounds used to make them work better. --Jayron32 12:40, 1 December 2017 (UTC)