One of the strangest stories in the bible is Noah’s Ark. Many people have written about the questions raised by the story: where did the water go? How did marine life survive the mixing of fresh and salt water? How could every species be repopulated from a single pair without massive inbreeding? How did the kangaroos get back to Australia? I’m going to address a different question today: what happens when that much water hits the Earth over that kind of time frame?
First off, we need to establish just how much water we’re talking about. The bible says that the flood covered the Earth up to a height fifteen cubits above the tallest mountain. Mount Everest is 8,848 meters tall, and 15 cubits is another 6.858 meters, so we’re looking for something covering the Earth to a height of (approximately) 8,855 meters. The radius of the earth is 6,378,137 meters. Using the formula for volume of a sphere, we get a total of 4π/3*(6,386,992³-6,378,137³)≈4,533,033,450,701,100,000 cubic meters. Since water has a density of 1,000 kg/m³, that comes to 4,533,033,450,701,100,000,000 kilograms of water. (Note: the actual amount would be much larger because the increased pressure would make the water near the surface denser, meaning more would be required to fill the volume.
Having established how much water we need, now we have to figure out how far up it started. Genesis 7:11 mentions that God “opened the floodgates of heaven”, which seems to refer to the creation story’s mention of a canopy of water above the sky. This works out nicely because the humidity required for regular clouds to form containing that much water would make it impossible to breathe without drowning. Assuming that “above the clouds” refers to the stratosphere, that makes a starting height of 20,000 meters. Using the formula for gravitational potential energy, E=mgh, we get a total energy of 888,474,556,337,415,600,000,000,000 joules, which is rather a lot of energy.
At this point, you may be thinking that even though that’s a huge amount of energy, the Earth is a big place and 40 days is a long time, so it probably comes out to something quite mundane. If so, you are wrong. The Earth’s surface area is 510,100,000 square kilometers, and 40 days comes to 3,456,000 seconds. That means each square kilometer recieves about 503,983,058,614.95 joules per second, the equivalent of 120.455 tons of TNT. That comes out to 21.68 kilotons every three minutes. Every square kilometer. For forty days straight.
At this point you may be thinking, “sure, that’s a lot, but it’s spread out over the course of three minutes, instead of all at once”. Truth be told, the nukes everywhere analogy isn’t the best I could have made, just the one that’s most easily illustrated. 503,983,058,614.95 joules per second per square kilometer is the equivalent of coating the entire planet in MOAB bombs going off once per second. That’s not the kind of thing a wooden boat can protect you from.