56
votes
Why is the pond in my backyard not frozen when it is -15 °C (5 °F) outside?
Water is a rather strange substance. With most substances, the solid phase is denser than is the liquid phase. This is not the case with water. Ice is less dense than liquid water. A side effect of ...
- 20k
53
votes
Accepted
Why is the pond in my backyard not frozen when it is -15 °C (5 °F) outside?
Water melts at 0 °C (32 °F) but freezing is a more complicated affair. It is safe to say water gains the ability to freeze at 0 °C, but it can get much cooler before it actually does so resulting in ...
- 13.9k
45
votes
Why doesn't the 71% water of the earth dry or evaporate?
There are two ways this problem needs to be looked at. The first is more astronomy than Earth science. The Earth as an entire system is largely contained. Its gravity and magnetic field retains ...
- 5,667
38
votes
Why does the salt in the oceans not sink to the bottom?
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 ...
- 4,453
38
votes
Antarctic and arctic meltwater is "bad" because it's dark, but why is transparent liquid on white stuff so dark?
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 ...
- 669
33
votes
While desalinating ocean water, would it be bad if we didn't pump the brine back into the ocean?
What does it take to reduce the salinity?
The salinity of sea water is around 35 g/kg. There are around 1,350,000,000 km³ of water, so roughly 1.3x1021 kg of seawater (1 kg/l, which is a bit off for ...
- 431
29
votes
Is a complete global flood physically possible on Earth?
Just to add some further discussion to @Pont and @fre0n excellent answers.
The problem of the water needed to submerge the world during the Genesis flood have been discussed for centuries. The ...
- 5,896
29
votes
Why does the salt in the oceans not sink to the bottom?
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 ...
- 22.1k
28
votes
How can we have groundwater depletion when the Earth is 78% covered with oceans?
How can we still lack groundwater?
That 71% of the Earth's surface is covered by oceans is completely irrelevant to the issue of fresh groundwater depletion. Salty groundwater is useless for drinking ...
- 20k
25
votes
Accepted
Is it possible for rivers to freeze completely and stop flowing?
I am interpreting your question as referring to rivers with flowing water freezing as as opposed to glaciers, which are already frozen.
Under current climatic conditions, small rivers can freeze ...
- 20.2k
25
votes
Why doesn't the 71% water of the earth dry or evaporate?
Why doesn't 71% water of the earth dry or evaporate?
The simple answer: Because it rains.
The not so simple answer: By some estimates, the Earth has already lost about a quarter of its water, and it ...
- 20k
23
votes
Accepted
Is a complete global flood physically possible on Earth?
there is not enough existing water inside this geosystem IMO for such a thing to occur. Let's see these figures here:
One estimate of global water distribution
Oceans, Seas, & Bays 1,338,000,000 ...
- 2,623
22
votes
Why is the pond in my backyard not frozen when it is -15 °C (5 °F) outside?
Due to convection (the cold water sinks while the warm water rises), the entire pond needs to be brought to near-freezing temperatures before the surface can freeze. With only the top of the pond in ...
21
votes
Accepted
What does it mean for waves to "feel" the bottom?
In water wave physics, when we say that the wave "feels" the bottom, we mean that the water depth affects the properties of the wave.
The dispersion relationship for water waves is:
$$
\omega^2 = ...
- 4,925
20
votes
Is a complete global flood physically possible on Earth?
The "precipitation rate" part is easy to answer, at least to a first approximation. We have 40 days and nights (960 hours) in which to raise sea level above the peak of Mount Everest (let's round up ...
- 5,370
19
votes
While desalinating ocean water, would it be bad if we didn't pump the brine back into the ocean?
The residue dry powder you refer to is salt.
Salt is toxic to most plants. The United Nations claims the world is already losing 2000 hectares per day of farm land to salt-induced degradation. This is ...
- 20.2k
17
votes
What does it mean for waves to "feel" the bottom?
Feel the bottom refers to the fact that the wave-induced velocity field extends all the way from the top of the water column to the bottom of the water column. When the wave "feels the bottom" it ...
- 3,981
17
votes
Antarctic and arctic meltwater is "bad" because it's dark, but why is transparent liquid on white stuff so dark?
"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 ...
- 277
16
votes
How is it possible to use up the water in a region?
This is a really complex problem and would require a really detailed explanation about atmospheric circulation, meteorology and hydrology.
The short answer to your question is that water is going ...
- 1,248
15
votes
Why is the pond in my backyard not frozen when it is -15 °C (5 °F) outside?
The water in a pond is in contact with the ground and the ground is not even close to freezing even if the air temperature is 27° below freezing.
- 2,137
14
votes
Accepted
Water veins underground causing health problems
In my opinion, there is no such thing as water veins as described in this article, but, it is a fact that there is water circulation underground.
In the natural environment, water can either ...
- 2,623
14
votes
What would be the effect of bringing seawater pipes to the Sahara desert?
This is an interesting question & I've been waiting to see what answers, if any, would be written.
One affect of creating such a lake would be a localized increase in humidity in the vicinity of ...
- 20.2k
14
votes
Accepted
How is it possible to use up the water in a region?
You're making a mistake, at least for the second case:
In the second case, the water ends up as rain, presumably within a few hundred kilometers of the evaporation point.
You cannot model a dry ...
- 11.1k
14
votes
Accepted
Ground water is almost every where, then how do mines and other holes are digged so that ground water doesn't drain into it
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 ...
- 2,625
12
votes
Is this ice cover real - and what circumstances are required to make it?
Yes, it is real. Whoever took the photo, congratulations on a very fine image.
I have never seen this texture on such a scale, but something similar can be achieved in the laboratory by creating a ...
- 14.1k
12
votes
Accepted
Water on Mars and Earth
If water on Earth came from meteorites, why doesn't Mars have substantial water?
First off, that's a conjecture regarding the origin of the Earth's water rather than a known fact. A few times a year ...
- 20k
11
votes
How much land does it take to support New York City?
The average ecological footprint of a US citizen has been estimated as 8.00 global ha.
Multiplying 8.5 million by 8.00 hectare gives 680,000 km², or around 5 times the area of New York state.
Of ...
- 11.1k
11
votes
Is it possible for rivers to freeze completely and stop flowing?
In a way, glaciers are just like frozen rivers. A good start on that topic comes from USGS. Ice (whether in a frozen river or in a glacier) is still a fluid and thus is always moving because of its ...
- 14.7k
11
votes
If water is a renewable resource, why is there water scarcity?
What I miss in the other answers is water quality.
Even is there is sufficient water available it is often of insufficient quality for the purpose you want it for:
We often don't drink straight out ...
- 2,625
11
votes
Accepted
Will the oceans swallow all of the land?
If no new mountains were built, yes. Ultimately the processes of erosion would render the continents flat, and the seas would be left shallow and filled with sediments. The reason that this doesn't ...
- 281
Only top scored, non community-wiki answers of a minimum length are eligible