Hot answers tagged

39

Water has lowest EM absorption in the blue part of light spectrum and increases rapidly towards both UV and red parts of spectrum. As a result in visible light water is blue. Same goes for the ice as it has very similar absorption spectrum. While there is a lot of white in the picture, all of it is a thin snow cover on top of blue ice. Once the snow ...


35

When dissolved in water, salt breaks up into sodium and chlorine ions, which combine with water molecules so they cannot easily sink. However, there is a tendency for streams of fresh water to float on salt water and rise to the top. This caused problems for British submarines in the Dardanelles Straits during WW1. Moving from almost fresh water to the ...


26

Why does the salt in the oceans not sink to the bottom? Because there isn't any "salt", per se, in the ocean. Salt, as the compound sodium chloride (NaCl) does not exist as a solid in the ocean. It is dissolved into sodium and chloride ions (charged atoms) that exist within the ocean as a homogenous phase (that is, a "thing"). That said, water with sodium ...


15

"Transparent" is not the same as "white" : white bodies reflect most of the light while transparent bodies let the light though. Once the light enters into water, it may need to travel a long way before it has a chance to go out, and that long travel path provides more opportunities for absorption. Water absorbs light by itself much more than snow, but ...


11

I'm a regular from the Physics Stack Exchange reporting for duty. Why this is a serious question This is a bigger question than you might be giving it credit for. The question is ultimately similar to asking why all the air molecules in the atmosphere do not fall to the floor. Your question comes from a very solid principle in physics which could be called ...


10

We pump it out. Open and closed pit mines usually have pumping installations to get the water out. Look up Mine dewatering on Wikipedia. There have also been numerous accidents in the past where mines were flooded (YouTube: Turkey mining accident: 18 workers trapped after underground water floods mine), and when left alone many abandoned mines will fill up ...


7

Turbulence, because seawater is, almost, always on the move saltier water is mixed with fresher by wave action and, to a lesser extent in surface waters, by Brownian motion. In Fjordland the annual rainfall is so high (up to 8000mm) that there is a permanent freshwater layer several metres thick that you can drink from sitting over the salt water from the ...


6

Saltier water has higher mass density, so the gravitational energy can be lowered that way. The concentration differences go up until the free-energy of creating that big a concentration difference balances the gravitational energy change. Department of Physics, University of Illinois at Urbana-Champaign Making some simplifying assumptions, they find: ...


4

Starting with question 2): you can use heat to evaporate the water but you need some sort of energy or thermal exchange to cool and condense it back to liquid. My understanding is that reverse osmosis (RO) is more energy efficient overall. Question 1) Brine is only put into the oceans from system that are near the sea, which usually use seawater as a water ...


2

October 1st is mostly used, but it varies from country to country. In Norway, the hydrological year start on September 1st, mostly because groundwater levels are at their lowest. At that time of the year, all snow in the mountains has melted, and it is before temperatures fall and the autumn rain settles in. It is probably better to use October 1st than ...


2

One factor that makes distillation expensive is the alloys necessary for equipment to handle hot brine are very expensive. For ambient temperature osmosis fairly common stainless like 316 is satisfactory although care must be taken in design to avoid crevices and other considerations.


2

But it does, but according to each salt's solubility and density. Soluble salts tend to mix into the water and keep suspended. Insoluble salts separate from the solution and creates deposits in the oceanic floor. One famous example was the "de-ironing" of the seas, when iron salts were deposited in the bottom due to the oxigenation of the oceanic water, by ...


1

Ultimately, it comes from precipitation. Ordinarily we think of rain as coming from low-level clouds, but Putkonen[1] has compiled rainfall data in the Himalayas showing significant rains up to several thousand meters altitude, covering the range where practically everyone lives. It is this precipitation that fills the underground tables mentioned by Jean-...


1

Water (solid or liquid) has some absorbtion. It is rather low for pure water for visible or near-visible light and that's why water it is considered transparent. But only to an extent - few meters of water look blue and few hundred meters look black, esp. if you are UNDER those few hundred meters. Then we have snow. Snow has an abundance of optical ...


1

Dumping the brine in a desert would probably be a viable solution in a few places, but many towns don't have a handy desert nearby. It would need to be a really barren desert,almost devoid of life, which few deserts are. Environmentalists would be aghast if you flooded the Sonoran Desert with brine. Bonneville Salt Flats might be better, but they are used ...


1

No, the rate of flow would usually be unaffected. The same volume of water has to get to the sea, so unless the ice was so thick and so well anchored to the riverbank as to exert pressure on the flow of water beneath, which is very unlikely, the rate of flow would remain the same. If, in the unlikely event that the ice exerted pressure on the water, the rate ...


1

This is no an answer per se, just a back-of-the-envelope calculation for fun. Lifting 1 kg (one litre) of water up a height of 1 meter uses 9.8 (let's say 10) joules of energy. Let's say you want to lower the sea level by 1 meter. You need to pump 3.6e17 litres (3.6e14 m2 of ocean area = 3.6e14 m3 to pump * 1000 for litre conversion). Let's say you want ...


1

It all depends where you are and how carefully you choose your water sources. In the Malaysian jungle (peninsular Malaya and Sarawak), I used natural water sources all the time for years on end without ill consequences. There are numerous springs and small streams where the water is always good, but we never used a main river where there was habitation ...


1

Salt does not sink to the bottom in the seas and oceans, because it dissolves in water! If you want to get salt from the seas and oceans, try to vaporize them :-)...


1

Salt does sink to the bottom in the oceans. Why? Your question referring to salt. Salt is a solid chemical compound. Take a lump of rock salt of sodium chloride, throw it into the water: it will sink to the bottom. The reason is that the density of sodium chloride with more than 2 g/cm3 is higher than the density of seawater less than 1.1 g/cm3. Of ...


1

And then there is the saturation issue. Salt can be dissolved in water to a certain degree only. Once that degree is exceeded the salt begins to fall out and sink to the ground. If I remember well the limit for water is something like 35g per litre (depending on the temperature)


Only top voted, non community-wiki answers of a minimum length are eligible