I must have forgotten to multiply something. Covid dreams I suppose.
The AI link shows the math.
Actually, I did the calculation myself about ten years ago for a Topix post you might have seen since we're both Topix alumni, and came up with the following result, which is roughly the same as Revoltingest's figure and the AI figure.
I can't vouch for all of the links still being good. I didn't mention or include it in the post with the AI output because it was redundant. I post it now in case you're interested just to show you that it's roughly the same value of water.
I also included some numbers on the total water of the earth and the intensity of rainfall that deposits that much water in 40 days, but the literalists claim that some of the water just burbled up as if from springs and apparently returned there as well by some unknown mechanism and thus the flood was not all due to rainfall, since it's nowhere to be found today:
What volume of water must be added to the earth to flood all of its land. We calculate that by comparing the volume of the unflooded earth to the volume of the earth with ocean levels raised to above the highest mountain, Mt. Everest, which stands about five-and-a-half miles high.
[2] The volume of a sphere is =(4/3)(pi)( r^3)
[3] Thus the volume of the unflooded earth is =(4/3)(3.14)(6370) ^3 = 1.08214805 × 10^12 = 1,082,148,050,000 km3
[5] Volume of flooded earth =(4/3)(3.14)(6378. 85)^3 = 1.08666469 × 10^12 = 1,086,664,690,000 km3 [Notice that the radius has been increased from 6370 to 6378.85]
[6] The difference = about 4,500,000,000 km3 of water that must be added to the earth to cover Everest. Can that much water fall in 40 days?
[7] “About 3,100 mi3 (12,900 km3) of water, mostly in the form of water vapor, is in the atmosphere at any one time. If it all fell as precipitation at once, the Earth would be covered with only about 1 inch of water.”
http://ga.water.usgs.gov/edu/earthhowmuch.html Thus the atmosphere can provide about 12,900 of the 4,500,000,000 cubic kilometers (about 1,100,000,000 cubic miles) of water needed, or about 1 inch of the five miles needed. What would happen to the marine life if you added this much fresh water to the oceans?
So, the water needed to flood the land completely - about four times as much water as the earth presently holds in all forms including oceans, ice, lakes, rivers, ground water, atmospheric water, and the water in living things - could neither appear nor disappear without magic, could not be contained in the atmosphere and fall as rain, would fall like a waterfall (30 ft/hr*) everywhere at once destroying the ark and drowning its inhabitants if it did, and **would kill all non-freshwater living aquatic life to boot.
*[Forty days is 960 hours. For the water to rise 29029 feet in 960 hours, 30.2 feet of water must fall ever hour over every square inch of the earth at once, or twice as much over half of the earth at once. Imagine a shower filling up a three story building in an hour.]
**[If you added another 4,500,000,000 cubic kilometers of fresh water - in excess of a tripling of the total earth water - the salinity of the oceans would fall to about 22.4% of its present level, killing virtually all marine life]
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Edit: apparently, I've posted it here a few times as well: