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Comment by rmah | Hacker News Reader

Just a few quick calculations to make it more relatable...

They say the smallest sphere of freshwater lakes and rivers amounts to 93,113 cu km. There are 1 bil cu m per cu km. With a global population of 8.2 bil people, that comes to 11,355 cu m per person. That's a 22.5 meter wide/deep/tall cube (or about 7 or 8 stories tall building).

If we use the sphere that includes groundwater, 10,633,450 cu km. Then we end up with 1,296,762 cu m or a 109m wide cube per person.

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I'm having trouble picturing a 22.5 meter cube. So consider a 200 sq m house; with ceilings of 2.5 m that's 500 cu m. So "your" water fills 22 houses.

Also.. the largest sphere has a radius of about 92 miles. It reaches to the edge of the atmosphere, and about 1/3 of the way to low earth orbit.

> The largest sphere represents all of Earth's water. Its diameter is about 860 miles

Should be a radius of 430 miles, no?

The image is very non-intuitive, IMO, because it's making the water appear so small compared to the entire planet (which, duh, obviously the water is only part of earth), but also drawing the planet that small really hides how friggin big the earth is!

Yes. The fresh-water lakes and rivers sphere definitely does not look like it could fill the Great Lakes next to it. I am not saying it doesn't, I'm just saying it doesn't look like it could.

It does look very small in comparison to say Lake Michigan but most lakes are very thin. Lake Michigan is about 500km by 200km but only .085km(85m) average depth.

Average depth of Lake Michigan is around 300 feet. Longest dimension is about 300 miles. If you drew a map of Lake Michigan on a sheet of letter-sized paper, the paper would be thicker than the average depth of water.

Helped for me to compare to the moon. The water sphere has less than half the radius of the moon (~1080 miles). Think that’s roughly 7-8% of the moon’s volume if it were a perfect sphere.

I thought the border with space is generally (and arbitrarily) said to be the Kármán Line, at 100 km / 62.1 mi. I'm not nitpicking, just curious about other definitions.

Also, I thought LEO typically begins around 180 km / 112 mi.

It's interesting to consider that there's about 26,000,000 km^3 of ice in the Antarctic ice sheet, which would give you a much larger ~150 m^3 cube of ice per person. That's not including the Greenland ice sheet or any sea ice.

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