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All of Earth's water in a single sphere (2019)

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Re: All of Earth's water in a single sphere (2019)

#141

Post by rachofsunshine »

arrowleaf wrote: post #135
nwiswell wrote: post #111

Earlier quoted context omitted.

This didn't sound right, so I did the math. The volume of all water is 1,386,000,000 km^3, which is then 1.386e+21 liters, or right about the same number of kilograms. The mass of Earth is about 5.972e+24 kg. So the percent fraction by mass is 0.0232%. A "drop" is typically estimated at 1/20th of one mL, which is then 0.05 grams. We can estimate the mass of a small-ish bowling ball at 5kg, or 5000 grams. 0.05 / 5000…

You'd have to use the volume of earth, not the mass. Google tells me that lava is ~3x denser than water.

Lava is not really representative of the Earth as a whole, as it turns out. The mantle (which is the vast majority of Earth's volume) isn't a liquid, it's a squishy deformable solid. Magma that comes from the mantle is only liquid because of the removal of pressure or the addition of water; it wasn't liquid down there. And a lot of lava comes from crustal melting, not mantle material.

Earth as a whole has a density about 5.5x that of water.

Re: All of Earth's water in a single sphere (2019)

#142

Post by maxbond »

PaulHoule wrote: post #133
maxbond wrote: post #92

Earlier quoted context omitted.

Is there reason to believe the stars are less of a dead end than Mars? It's easy to imagine us making a huge bet on interstellar travel, and just dying in interstellar space. Surely there's untold abundance in the stars, but if you can't actually reach it, then it may as well be a mirage. Whenever I consider the possibility of interplanetary colonization, I come back to the conclusion that the only way to make it fea…

I did a lot of analysis for the problem of "build a solar sail factory on a carbonaceous chondrite asteroid that makes sunshades to deploy at the L1 point", particularly from a chemical engineering point of view. One interesting thing was that a lot of the chemistry involved was similar to the chemistry of decarbonization and carbon capture, particularly when you get CO2 as a waste product it is too precious to vent…

It's interesting speculation. I just can't accept the existence of a spacecraft that can last 100 years without a catastrophic failure, or Ceres being reforged into a factory, or a nation of people who live entirely independent of Earth until I see it.

Sometimes people talk about these things as if they are inevitable, but I would say there's an extremely good chance we go extinct without ever leaving this solar system (Voyager 1 notwithstanding). I think this is a valuable and grounding perspective in planning for the long term future of humanity, because we have to accept that that future takes place here on Earth and largely with the technology we already have. Space colonization is seductive, but like all silver bullets, impossible to operationalize within the constraints imposed on us by our situation.

But it's probably not a useful one when picking SETI targets or generating other research ideas, and that stands on it's own merit.

Re: All of Earth's water in a single sphere (2019)

#143

Post by MalcolmDwyer »

tamimio wrote: post #137

I would like to have a zoomed-in picture of that 'tiny' freshwater lakes and rivers to see its height. From this perspective, it doesn’t add up. Just above it, the Great Lakes look far bigger, not to mention other lakes and rivers in the world.

The Great Lakes span across hundreds of miles, but the deepest point is less than a quarter mile, and most of it is much shallower than that. I.e., it's a super thin film over that big surface area.

Re: All of Earth's water in a single sphere (2019)

#144

Post by DiggyJohnson »

marcosdumay wrote: post #58
umvi wrote: post #16

> This sphere includes all of the water in the oceans, ice caps, lakes, rivers, groundwater, atmospheric water, and even the water in you, your dog, and your tomato plant. Does it include water in the mantle? ( https://www.bnl.gov/newsroom/news.php?a=111648 ) or other non-liquid water for that matter like hydrates (ebsom salts, etc)

Yep, it's quite misleading since the region where they looked for water at all is an incredibly thin layer on the outside of the planet, but they show it all as if it applied to all of the volume.

There’s nothing wrong with their representation. You’re describing a different comparison.

Re: All of Earth's water in a single sphere (2019)

#145

Post by DiggyJohnson »

FredPret wrote: post #31
moralestapia wrote: post #23

Earlier quoted context omitted.

No, it doesn't. It includes all of the water in the oceans, ice caps, lakes, rivers, groundwater, atmospheric water, and even the water in you, your dog, and your tomato plant.

"Groundwater" is a little ambiguous - H2O in the mantle is also "ground water", no?

No, it’s completely inaccessible. Unless you are just playing word games, then sure.

Re: All of Earth's water in a single sphere (2019)

#147

Post by elfbargpt »

tamimio wrote: post #137

I would like to have a zoomed-in picture of that 'tiny' freshwater lakes and rivers to see its height. From this perspective, it doesn’t add up. Just above it, the Great Lakes look far bigger, not to mention other lakes and rivers in the world.

"Yes, Lake Michigan looks way bigger than this sphere, but you have to try to imagine a bubble almost 35 miles high—whereas the average depth of Lake Michigan is less than 300 feet (91 meters)"

Re: All of Earth's water in a single sphere (2019)

#148

Post by dredmorbius »

ars wrote: post #134
zamadatix wrote: post #116

Earlier quoted context omitted.

I don't buy it. Even allowing counting iron as separate from what rocks can be composed of (and using mass instead of volume) you still have 30.1%+15.1%=45.2% of the Earth as oxygen and silicon (which are most certainly part of what makes a rock) at which point you've already disproved the claim Earth is more a ball of iron than a ball of rock. A ball of iron covered with a ball of rocks is a more fair statement thou…

https://s3-us-west-2.amazonaws.com/courses-images-archive-re... Everything up to and including the mantle is either iron or has a lot of iron. But to your point the mantle also has a lot of silica. So I guess it depends on your definition of "mostly".

Mass is the defining characteristic of a quantity of matter. Given that much of the iron is under far higher compression than the outer layers of silicate rock, this also advantages iron.

By mass, iron (32.1%) is still a minority constituent of the Earth.

https://en.wikipedia.org/wiki/Abundance_of_the_chemical_elem...>

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