
Perspective: All of Earth's Water in a Single Sphere - bkyan
http://ga.water.usgs.gov/edu/2010/gallery/global-water-volume.html
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_delirium
I'm not sure this actually provides the right perspective, in the sense of a
useful intuition. Taking _anything_ from the part of the Earth we live in
(essentially, the troposphere plus the upper part of the crust) and
visualizing it as a sphere will make it look small, because the troposphere +
upper crust is a fairly thin shell, so doesn't take up a lot of volume when
visualized as a solid sphere next to the earth.

~~~
eevilspock
I disagree. It is a useful perspective because it flies in the face of one's
intuited perspective. How many of us would have estimated that the volume of
water would be so small? We visualize the oceans as really deep gouges on the
Earth's surface because to our puny asses a depth of 1 to 8 miles sounds
amazingly deep. We'd never guess that even with miles deep depressions and
miles high mountains, the Earth is smoother than a billiard ball:

[http://blogs.discovermagazine.com/badastronomy/2008/09/08/te...](http://blogs.discovermagazine.com/badastronomy/2008/09/08/ten-
things-you-dont-know-about-the-earth/)

Combining both of these counter-intuitive perspectives tells us that our
oceans are akin to a very thin film of water on a wet billiard ball. A thin
dirty film is all that billions of bacteria needs to thrive on a billiard
ball, and a thin dirty film is all that billions of animals and plants need to
thrive on Earth.

~~~
_delirium
> How many of us would have estimated that the volume of water would be so
> small?

Well, I did, but that's because it's already been emphasized to me before (in
some kind of geology class) how little volume the crust+troposphere shell
takes up. It's not a water-specific thing, but a crust/troposphere thing, of
which water is a subset. And actually I think the _real_ underlying
counterintuition is just a geometric one, that people don't realize little
volume spherical shells occupy relative to solid spheres.

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DLWormwood
The first thing I thought when I saw is image was that I would love to see an
animation of the sphere collapsing and refilling the oceans, etc. Assuming the
animation simulated actual gravity and water fluid dynamics, I wonder how long
it would take and what it would look like? (That is, the initial reflooding,
reforming of rivers, clouds and ice caps, and so on.)

~~~
kijin
A _realistic_ animation would not be pretty. Actual gravity will not allow the
Earth's solid surface to stay where it is while you dump water on it.

Imagine what would happen if you dropped an 800-mile water balloon in the
middle of Kansas. I'd be surprised if the North American plate didn't break up
into several pieces under the weight of all that water. You'll probably get
supersized volcanoes erupting all over the world due to the sudden stress on
the crust. The volcanoes would then be extinguished by the megatsunami from
the ball of water, causing massive steam explosions. One thing is certain:
There won't be a Mississippi River anymore. Not sure about ice caps, that
could take a few millennia.

Michael Bay and Roland Emmerich are going to love this.

~~~
kaj_sotala
I have to disagree with your assertion that this animation wouldn't be pretty.

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eck
Another interesting perspective: Earth's atmosphere is about five miles thick.
Yes, it trails off exponentially and airplanes can fly and people can breathe
(sort of) at 30,000 feet. However, were it uniformly as dense as it is at sea
level (i.e. the atmosphere most of us are familiar with), it would fit in
about five miles.

~~~
codeflo
That's indeed an interesting perspective; I just double-checked in sane units:

Standard pressure 101 325 N/m^2 divided by standard gravity 9.80665 N/kg gives
the mass of the air per area: 10 329 kg/m^2.

Divide that by an air density of 1.225 kg/m^3 to get a height of 8435
meters[1]. The Mount Everest is 8848 meters high. If the atmosphere were
uniformly dense, the highest mountains would rise above it.

([1] Not in fact accurate to four digits because the constants I used aren't
really constant across that height range.)

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eck
Thanks, codeflo. I calculated similar numbers and only gave a very crude
approximation but I will take your word for it. Obviously, with the thermal
distribution according to altitude it's a poorly defined problem.

Most intuitively, this means that when looking at some object on earth ~5
miles away, you are looking through roughly as much air as you are when
looking at any given planet or star above you in the sky.

I think this is an interesting comparison.

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GavinB
If you somehow started from this state, how long would it take the wave to
reach the opposite side of the planet?

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reneherse
I'm very curious to know as well. However, in the illustration, a whole lot of
that water would be in low earth orbit, so the thought experiment gets
complicated ;)

At first I thought perhaps you could use tsunami wave speed data for a very
rough estimate. But that's wrong, because tsunami speed (roughly between 500
and 900 km/hr depending on ocean depth) is a measure of the wave energy
propagating through the ocean, not a measure of the water's speed over ground.

Instead, perhaps one could start by using a model for the flow of water from a
catastrophic dam breach. Hopefully someone more mathematically inclined than I
will give it a go...

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its_so_on
Being high doesn't put you in orbit, it takes velocity relative to Earth to do
that.

(Rockets going into orbit aren't just climbing, they're also building ground-
speed. If there were an imaginary tower from ground to low-earth-orbit height,
climbing it wouldn't put you in orbit - if you let go of something at the top
of that tower, it would just fall.)

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Thrymr
Unless the tower reaches to geosynchronous orbit (~36,000 km altitude). Then
you've got a space elevator.

You do get some relative velocity due to the earth's rotation, it's just not
enough to put you in orbit until you reach geosynchronous altitude (from your
imaginary tower, not necessarily the imaginary sphere of water).

~~~
Karellen
It's still not enough. At the equator, to do one revolution per day, you're
doing ~1000mph. At 36,000km, because the circumference of the orbit is much
longer than the circumference at ground level, to do one revolution per day,
you need to be doing ~6900mph. So even if you get to geosynch, you still need
to pick up ~5900mph sideways in linear velocity. As well as the energy it
takes to get up there.

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GMali
How likely is it that this sphere of water actually collided with our Earth
billions of years ago? What is the possibility of even more such "water
meteoroids" flying around nearby galaxies?

~~~
Sharlin
Water does not stay liquid in a vacuum. It is either solid or gaseous,
depending on the ambient conditions. It is not well established where the
primordial Earth gained its water. The matter in the protoplanetary disc from
which the Earth coalesced probably didn't contain much water or other
volatiles because of the proximity to the Sun. Instead, it is thought that
water arrived afterwards, via numerous collisions - then commonplace - with
icy comets that originated beyond the frost line.

<http://en.wikipedia.org/wiki/Frost_line_%28astrophysics%29>
<http://en.wikipedia.org/wiki/Origin_of_water_on_Earth>

~~~
lordlicorice
Would a sphere of water that size be massive enough to hold a gaseous
atmosphere heavy enough to allow liquid water far enough down?

~~~
kijin
With a diameter less than half of the Moon, and with a mass only 1/50 of the
Moon, I think it's quite unlikely.

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gregable
Another related perspective on earth oceans. Take a thimble of water and pour
it into the ocean. Allow sufficient time for it to evenly mix. Now scoop a new
thimble of water out of that ocean. Your new thimble will have several
molecules from the original thimble of water.

Orders of magnitude and all that. To me though this shows how connected all of
our resources are and how dangerous pollution can be.

~~~
im3w1l
In order to see how connected all of our resources are, I would want to know
what "sufficient time" amounts to.

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stcredzero
Does it include all the water trapped in material of the mantle?

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gliese1337
Based on the statement that "[t]he sphere includes all the water in the
oceans, seas, ice caps, lakes and rivers as well as groundwater, atmospheric
water, and even the water in you, your dog, and your tomato plant", I would
guess not (although it doesn't specifically say that that's a comprehensive
list). That conclusion is further supported by the observations that 1) we
don't actually know exactly how much water there is distributed through the
mantle, but 2) more water gets subducted than is released by volcanoes, so
it's a large volume and getting bigger and 3) the total amount is probably
comparable in size to the amount of surface water, which would make that
sphere significantly bigger if it were included.

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stcredzero
Considering that the surface water came from outgassing volcanoes, it would be
reasonable to think that there might even be 2 or 3 times as much water still
trapped down there.

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JumpCrisscross
The question of the origin of water on Earth is yet un-resolved, with a
contender to the out gassing theory being deposition by asteroids [1]. Even by
that theory I believe it was volatiles (hydrogen, oxygen) that were
"outgassed" and then allowed to form into H20 in the atmosphere.

That being said, the possibility of large masses of water subducting under the
crust and sitting in the lower mantle has been deemed _plausible_ [2](but not
_probable_ ).

[1] <http://en.m.wikipedia.org/wiki/Origin_of_water_on_Earth#_>

[2]
[http://news.nationalgeographic.com/news/2002/03/0307_0307_wa...](http://news.nationalgeographic.com/news/2002/03/0307_0307_waterworld.html)

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jlcx
Interestingly, there is an estimate of the size of a sphere containing the
water of the world's seas in Twenty Thousand Leagues under the sea:

"THE PART OF THE planet earth that the seas occupy has been assessed at
3,832,558 square myriameters, hence more than 38,000,000,000 hectares. This
liquid mass totals 2,250,000,000 cubic miles and could form a sphere with a
diameter of sixty leagues, whose weight would be three quintillion metric
tons."

According to Google and Frink, 60 leagues is less than 1/4 of the 860 miles
estimated here; I'm not sure how much of that is due to the smaller scope of
the estimate in Verne's book.

~~~
kijin
Those numbers don't make any sense. 2,250,000,000 cubic miles is ~100 times
the volume of a sphere with a diameter of sixty leagues. It's also over 6
times the volume cited in the article, while having only twice the weight.
That can't happen unless water's density varied dramatically.

So Verne both overestimated and underestimated, and didn't bother to check if
his numbers were consistent with one another.

~~~
yew
I can't speak for this estimate in particular, but Verne usually did his
(quite extensive) calculations in metric units. Many older translations of his
work swapped in imperial or US customary units without adjusting the values
for the 'benefit' of English-speaking readers.

~~~
kijin
Aha, that might actually explain the inconsistency between the volume and
weight. Imagine that the volume was originally stated as 3.6 billion cubic
kilometers, which would actually weigh around "three quintillion tons"
(actually close to four, but let's forgive that). A translator might have
turned that into 2.25 billion cubic miles, thinking that one mile = 1.6
kilometers. But of course, non-mathematical types usually don't notice that
one _cubic_ mile = 4.1 _cubic_ kilometers.

~~~
simias
I've looked up the original text and it uses the same units except for the
weight which is expressed in "tonneaux" instead of metric tons: "[...] dont le
poids serait de trois quintillions de tonneaux." So they basically swapped the
units without bothering to calculate the correct value.

Now how much a tonneau weights is left as an exercise to the reader...

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brownbat
This seems geared to make the amount of water on the planet look small, but it
backfired for me.

I still remember the first time I flew over Lake Michigan, and my mind was
blown at the impossible scale of all that water.

In this image, most people compare the water to the Earth. Nice, homey, medium
sized Earth. In comparison, the water looks tiny.

I was drawn to that far tinier lake to its right, which once blew my mind.
Comparing the lake to the big wet globe feels like skipping a few steps in
Powers of Ten (or Gurren Lagann).

All I know for sure is that my poor human brain sucks at scale. "Bigger than I
understand" arrives far too soon.

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JacobIrwin
Nice work. It would be fun to see a comparison of the sphere containing
Earth's water against a sphere of Earth's [relatively-]habitable area (say,
the cumulative mass between the average depth of the sea-floor to the average
height above sea level (of all exposed land massess)). For your intents, it
could be a meaningful comparison in conjunction with you recent works. Thanks
for sharing!

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jakeonthemove
That's really not a lot of water, huh... And even less of it is directly
consumable or even usable. This actually makes me think that mining asteroids
for frozen water might not be such a bad idea (although it would still need to
be purified)...

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lambtron
It would be fascinating to see in separate 'spheres of water' the make up of
all the oceans, all the atmospheric moisture, etc.

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vraid
[http://en.wikipedia.org/wiki/File:Earth_water_distribution.s...](http://en.wikipedia.org/wiki/File:Earth_water_distribution.svg)

Here is an image showing just that, in a cubic format. The sphere of ocean
water would have a radius of 684 kilometers, while the remaining water, most
of which is glaciers and groundwater, would form a sphere of 227 km radius.

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karl_hungus
It is what it is.

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NHQ
Terrific

