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APOD: All the Water on Planet Earth (2012 May 15)
Posted: Tue May 15, 2012 4:06 am
by APOD Robot
All the Water on Planet Earth
Explanation: How much of planet Earth is made of water? Very little, actually. Although
oceans of water cover about 70 percent of Earth's surface, these oceans are
shallow compared to the Earth's radius. The
above illustration shows what would happen if all of
the water on or near the surface of the Earth were bunched up into a
ball. The radius of this ball would be only about 700 kilometers, less than half the radius of the
Earth's Moon, but slightly larger than Saturn's moon
Rhea which, like many moons in our outer Solar System, is mostly water ice. How even this much
water came to be on
the Earth and whether any significant amount is
trapped far
beneath Earth's surface remain topics of research.
[/b]
Re: APOD: All the Water on Planet Earth (2012 May 15)
Posted: Tue May 15, 2012 4:27 am
by bystander
Re: APOD: All the Water on Planet Earth (2012 May 15)
Posted: Tue May 15, 2012 5:04 am
by technogeek
According to my back-of-the-envelope calculations, the earth's atmosphere at standard temperature and pressure comes out to roughly 3x the volume of the earth's oceans also at STP ... so put another sphere next to that one with a diameter roughly 1.7x that of the water.
(Yes, scale height means the actual space it takes up is greater than that. And we're ignoring the effects of temperature on water volume. But it's still an interesting visualization. And still a darned thin layer when spread out over the surface of the marble.)
Re: APOD: All the Water on Planet Earth (2012 May 15)
Posted: Tue May 15, 2012 5:51 am
by saturno2
the water of Earth in a ball of 700 km. of radius.
I think this ball is small
It´s a small moon
Re: APOD: All the Water on Planet Earth (2012 May 15)
Posted: Tue May 15, 2012 5:58 am
by saturno2
The water of Earth in a ball of 700 km of radius
I think is a small ball
It´s a small Moon
Re: APOD: All the Water on Planet Earth (2012 May 15)
Posted: Tue May 15, 2012 6:13 am
by alter-ego
technogeek wrote:According to my back-of-the-envelope calculations, the earth's atmosphere at standard temperature and pressure comes out to roughly 3x the volume of the earth's oceans also at STP ... so put another sphere next to that one with a diameter roughly 1.7x that of the water.
(Yes, scale height means the actual space it takes up is greater than that. And we're ignoring the effects of temperature on water volume. But it's still an interesting visualization. And still a darned thin layer when spread out over the surface of the marble.)
Here you go:
http://boingboing.net/2008/03/11/all-th ... nd-ai.html
FYI, a conservative average H
2O content
≈1% within the sphere of air, so its water contribution is minor (as you would think) compared to the surface water.
Re: APOD: All the Water on Planet Earth (2012 May 15)
Posted: Tue May 15, 2012 6:18 am
by Ann
Obviously life on Earth is nothing like mechanical machinery, but I'm going to risk using mechanical machinery as a metaphor for life to explain how I think of the role of water on the Earth.
The way I see it, water works as a lubricant which makes it possible for the "gears of the machine" to move much at all. And then water is a catalyst for chemical processes.
Will the machinery - the biosphere of the Earth - work better if you add huge amounts of lubricants and catalysts? Imagine sinking the cogs and wheel thingy in the picture into a tank of lubricants. Then you make it stay in that tank. You don't necessarily add a lot of power or forces into the tank of lubricant. The machinery is just sitting there, submerged in a tank of quiet liquid. Will there be a lot of things going on with the machinery in the tank of lubricant? I doubt it.
That's how I think of water on the Earth. No, we actually don't have that much of it. So what? Would there be more life on Earth if the Earth had more water? I doubt it. Do we find the greatest amount and variety of life where the oceans of the Earth are deepest? Not to my knowledge.
http://en.wikipedia.org/wiki/Mariana_Trench reports that there is indeed life at the bottom of the Mariana Trench, the deepest part of the world's oceans. But although the Mariana Trench is not a dead place, there is not that much life there.
It's not having huge amounts of water that counts. It's having the right amount of water that counts, and having it in the right phase states - solid, liquid and gaseous - and having it where it can serve as a lubricant for the forces of plate tectonics and volcanism, and having it as a catalyst for life.
Ann
Re: APOD: All the Water on Planet Earth (2012 May 15)
Posted: Tue May 15, 2012 6:47 am
by starstruck
Somehow it isn't a very reassuring thought that all the water on Earth can be contained in that relatively small sphere. And considering that the drinkable freshwater element of that sphere is even smaller, it makes the vision of a future water-starved Earth look not at all far-fetched. So, rather like towing an iceberg from the pole to the tropics, perhaps we'd better get to thinking how we can bring Rhea (or how about Jupiter's Europa) a little bit closer in case we need to replenish our supplies at some point!
Incidentally, the article cited in bystander's link (above) makes mention of this sphere being about 4 Sagan teaspoons; a unit of measure I have never come across before. Anybody?
Re: APOD: All the Water on Planet Earth (2012 May 15)
Posted: Tue May 15, 2012 8:14 am
by Sinan İpek
The fresh water would be a sphere of size 1/4 times the big sphere...
Re: APOD: All the Water on Planet Earth (2012 May 15)
Posted: Tue May 15, 2012 9:23 am
by ro_star
this really helps visualizing how little water there is in fact on the earth and how easy it is to pollute it all - most of it is saltwater, and billions of people have no access to fresh drinking water - so if we don't take care of the water we have, to keep it fresh and unpolluted, there is even the risk that a similar civilization with more technical knowledge may one day send an automated probe to remove the water from earth because they happen to need it since they polluted theirs; that's why we should set an example and keep it clean
Re: APOD: All the Water on Planet Earth (2012 May 15)
Posted: Tue May 15, 2012 11:22 am
by mdgarfinkel
I've not seen this exact image before, but a very similar one. The other image, aside from denuding the Earth of its water, shows two additional spheres - one of total water, the other of total freshwater. All three spheres "float" in the darkness of space, with clear separation between them. I wish I knew the primary source of _that_ image, but I came across it as a graphic inside a PowerPoint file somewhere on the Web. I would not be surprised if it were by the same folks at WHOI & USGS.
Re: APOD: All the Water on Planet Earth (2012 May 15)
Posted: Tue May 15, 2012 11:26 am
by neufer
Average H
2O content
≈0.4% within the sphere of air.
Note that both here and in today's APOD no one bothered to remove the snow & ice fields.
(Where's Neil deGrasse Tyson when you need him?)
Re: APOD: All the Water on Planet Earth (2012 May 15)
Posted: Tue May 15, 2012 1:06 pm
by orin stepanek
earth with water removed
SHARE THIS:
112 of 361
April 22, 2009
Happy Earth (?) Day
Earth is an ocean planet. More than 70% of its surface is covered by ocean with an average depth of just over two miles. But how much water is there really? In this illustration, the sphere on the left represents Earth with all of the water removed. The blue sphere to the right shows the approximate volume of all of Earth's water. The tiny blue dot on the far right represents the available fresh water. Another way to think of it is that if we represented the size of Earth with a basketball, all the water on the planet would fit into a ping pong ball and the available fresh water would be smaller than a popcorn kernel. Despite being such a water-rich planet, drinking water is one of our most precious resources.
(Illustration by Jack Cook, Woods Hole Oceanographic Institution)
Re: APOD: All the Water on Planet Earth (2012 May 15)
Posted: Tue May 15, 2012 1:29 pm
by technogeek
saturno2 wrote:It´s a small moon
"That's no moon... I have a bad feeling about this." <grin/>
Re: APOD: All the Water on Planet Earth (2012 May 15)
Posted: Tue May 15, 2012 1:31 pm
by ritwik
During ancient times, Coruscant had vast oceans on its surface, but after thousands of years of overpopulation, these natural bodies of water were drained and the water was stored in the underground, allowing the cities to grow on areas previously covered by seas. Today, Coruscant's only visible large body of water is an artificial sea called the Western Sea. However, the planet still has its large polar caps, from which the citizens get most of the water they need. Due to the scarce natural resources, the planet's huge buildings are mostly self-contained, recycling water, energy and material. Food is largely imported from agricultural worlds.
Re: APOD: All the Water on Planet Earth (2012 May 15)
Posted: Tue May 15, 2012 2:11 pm
by Donald Pelletier
The mean radius of Rhea is greater then 750 km (
http://nssdc.gsfc.nasa.gov/planetary/fa ... tfact.html) . The radius of the water sphere is smaller compare to that moon.
Re: APOD: All the Water on Planet Earth (2012 May 15)
Posted: Tue May 15, 2012 2:15 pm
by neufer
ritwik wrote:
During ancient times, Coruscant had vast oceans on its surface, but after thousands of years of overpopulation, these natural bodies of water were drained and the water was stored in the underground, allowing the cities to grow on areas previously covered by seas.
If all of the people on
Coruscant were bunched up into a ball the diameter of this ball would be about 5 kilometers (or 3 miles).
Re: APOD: All the Water on Planet Earth (2012 May 15)
Posted: Tue May 15, 2012 2:18 pm
by neufer
starstruck wrote:
the article cited in bystander's link (above) makes mention of this sphere being about 4 Sagan teaspoons; a unit of measure I have never come across before. Anybody?
<<Sagan's number is the number of stars in the observable universe. It is named in honor of Carl Sagan. This number is reasonably well defined, since we know what stars are and what the observable universe is, but its value is not known with any certainty(; it is presently estimated to be approximately 70 sextillion).>>
Re: APOD: All the Water on Planet Earth (2012 May 15)
Posted: Tue May 15, 2012 2:41 pm
by Chris Peterson
Sinan İpek wrote:The fresh water would be a sphere of size 1/4 times the big sphere...
A lot smaller than that.
Of all the water on Earth (not considering the hydrates locked up inside), 97% is saline (96.4% in the oceans), 2.9% is fresh (nearly all in snow and ice), and 0.1% is in the atmosphere. Only 0.4% of all the water on the Earth is accessible for drinking and irrigation.
Re: APOD: All the Water on Planet Earth (2012 May 15)
Posted: Tue May 15, 2012 2:50 pm
by Chris Peterson
neufer wrote:Note that both here and in today's APOD no one bothered to remove the snow & ice fields.
That bothered me instantly when I first saw this image a few days ago. Most of the icy areas have been more-or-less fudged out to an acceptable degree, but it hurts to see Greenland represented the way it is. It should look like northern Canada. Granted, the amount of water tied up in the Greenland icepack wouldn't
visibly change the size of the water sphere, but leaving it white really detracts from the image, IMO.
Re: APOD: All the Water on Planet Earth (2012 May 15)
Posted: Tue May 15, 2012 2:55 pm
by dancingbaehr
Does no one think these calculations are a bit odd. Considering the Marinas Trench is 5 miles deep ? What about all the talk of global warming causing the coasts to flood? How possible with such a small amount of water/ ice ? I know it is easy to calculate the volume of the earth but who came up with the formula to calculate surface water ?
Re: APOD: All the Water on Planet Earth (2012 May 15)
Posted: Tue May 15, 2012 3:27 pm
by Chris Peterson
dancingbaehr wrote:Does no one think these calculations are a bit odd. Considering the Marinas Trench is 5 miles deep ? What about all the talk of global warming causing the coasts to flood? How possible with such a small amount of water/ ice ? I know it is easy to calculate the volume of the earth but who came up with the formula to calculate surface water ?
The amount of surface water isn't calculated abstractly, it is measured objectively. The
average depth of the oceans is 2 miles; it doesn't really matter if there are some deeper and some shallower areas. Knowing the average means you can treat the entire ocean as that depth and simply calculate the volume. More rigorously, the shape of the ocean bottom is accurately known, as well as the shape and location of the sea surface.
We get used to seeing maps and globes with exaggerated vertical scales, and don't realize just how shallow the oceans really are in relation to the diameter of the Earth (even in the trenches). For comparison, if the Earth were a chicken egg, the eggshell would need to be 30 times thinner to accurately represent the depth of the oceans.
Re: APOD: All the Water on Planet Earth (2012 May 15)
Posted: Tue May 15, 2012 3:33 pm
by deathfleer
too small a sphere of water. I cant believe it
Re: APOD: All the Water on Planet Earth (2012 May 15)
Posted: Tue May 15, 2012 3:43 pm
by drollere
a sphere 1400 kilometers in diameter of water. ok ... now let's calculate how much trash, garbage, polluted runoff and sewage is dumped into it each year by 7 billion humans. maybe you can tint it brown in proportion. blue is much too optimistic.
Re: APOD: All the Water on Planet Earth (2012 May 15)
Posted: Tue May 15, 2012 3:58 pm
by Chris Peterson
drollere wrote:a sphere 1400 kilometers in diameter of water. ok ... now let's calculate how much trash, garbage, polluted runoff and sewage is dumped into it each year by 7 billion humans. maybe you can tint it brown in proportion. blue is much too optimistic.
That works out to each person on the planet having their own little cube of water about 600 meters on a side.
