Fun with Hydroplate Math

Over at Dispatches, Ed had a little something about the Hydroplate Creationist hypothesis invented to explain where all the water came from. In short, it asserts that there was a lot of water buried deep underground that somehow got forced up to the surface, causing the torrential flood rains, and for extra silly credit, created the comets and meteorites of the solar system. I had a request I thought would have a fun answer:

For the physics people who love to crunch numbers: Wouldn’t this catastrophe end up superheating the planet or something? I seem to recall a LOT of the flood theories would do that.

Robert B. took on that task and produced this comment:

Okay, so fun with numbers!

As best I can tell, the crust is supposed to have been one solid piece on top of the water. The weight of all that rock on top would indeed have put the water under enormous pressure, about 400 MPa (about 4000 atmospheres). Now, let’s open a one-square-meter crack in the crust of arbitrary shape, ignoring friction at the edges. The top cubic meter of water beneath that suddenly-opened crack is under a net upward force of 400 meganewtons. (Under the circumstances, the downward force of gravity on the water is negligible.)

We’ll guess that the force remained at that average for the whole distance through the crust, which in the mid-Atlantic is about 6 km, for a total work of about 2.5 terajoules on 1000 kg of water. The water is now rising at a hundred thousand meters per second. It will indeed escape Earth’s gravity. If the atmosphere didn’t get in the way, it would escape the sun’s gravity and splash Alpha Centauri. However, the atmospheric drag on an enormous supersonic jet of water that may be either a liquid or a gas or both is seriously complicated fluid dynamics, and I’m the kind of physicist who starts complaining when you put three whole electrons in the same problem, so I’m not really going to think about that much.

However. The total mass ejected into space is claimed to have been 1% of Earth’s mass, about 60 yottagrams. If you are not familiar with the more extreme metric prefixes, suffice it to say, that is quite a lot of grams. To get that much mass out of Earth’s orbit, the pressure has done a rock bottom minimum 5 x 10^31 joules of work. We get some of that energy back from the gravitational potential energy of the Earth’s crust as it drops through the space left suddenly vacant by all that ejected water, a distance averaging somewhere in the tens of kilometers. But that’s only about 10^27 joules, which gets lost in all the flagrant and shameless rounding I’m doing. The net energy loss would cool the entire planet by an average of 10000 K… wait, say what?

*checks my math*

Yyyyyup. A ten thousand degree temperature drop. That number doesn’t even make sense. Even the inner core is only about 5000 K. If we very kindly assume that the temperature change was everywhere proportional to the current temperature, so that most of the heat was lost from the center of the earth, we’re still assuming that the entire planet was three to four times hotter before the flood than afterward. Presently the surface is about 300 K, so before the flood it would have had to be 900-1200 K. Hopefully Noah’s wife didn’t wrap his lunch in aluminum foil, because it would have melted and made his sandwich soggy.

Let’s go back to the part where the entire surface of the earth falls a few tens of kilometers, though. The energy of that falling will eventually end up as heat, the same heat that got lost in the rounding a few paragraphs back. Before it was heat, though, it would have been kinetic energy – motion, in the crust and in the water suddenly flowing on top of it. The wave action would have been inconceivable, in the very literal sense that I can’t think of what the wave action would have been. (See above re: complicated fluid dynamics.)

At a wild guess, at least one percent of the energy would have ended up transferred to the ocean, in exactly the same way that earthquake energy is transferred to tsunamis. That’s ten thousand joules of kinetic energy per kilogram of water, on average, over the entire ocean. (I’m assuming the ocean had the same mass then as now – as far as I can tell, Doc Brown is arguing that it’s not that the water was all that deep, it’s that the continents and mountains as we know them were upthrust late in this same event and so the flood didn’t actually have to cover them.) If all that energy was kinetic at the same time, the water would have been moving at an average speed of about 100 m/s, in nowhere close to all the same direction. If this motion took the form of waves like we’re familiar with (which I doubt it would) they would be hundreds or thousands of meters tall. That’s a pounding that nothing bigger than plankton would have survived.

If the kinetic energy was damping out to thermal almost as fast as it was being converted from potential, then we can save the fish, but (more wild guesswork) we’re still talking about forty days of the kind of sea you get in a hurricane. I doubt any modern ship could have survived that, let alone a wooden hull without so much as an iron nail to its name. And if the crash actually took longer then the flood, as Doc Brown implies, it’s even worse – once you’re on land, that kinetic energy takes the form of a whole series of colossal earthquakes lasting weeks or months. If you’re near the ocean – and for a while there wouldn’t have been anywhere that wasn’t near the ocean – those death waves are now tsunamis.

That’s about all the math I care to do on this, though if anyone wants to see my calculations I can probably reproduce them on request. And by the way, I didn’t use anything but basic mechanics and thermodynamics, plus wikipedia – certainly nothing a mechanical engineer wouldn’t know about. Brown has no excuse.

I just love reading debunks like that. It harkens back to one I enjoyed by Carl Sagan about Velkovski’s Worlds in Collision. One TV Trope that comes to mind is Sci-Fi Writers Have No Sense of Scale. I think that also applies quite well to woos. People can make up just about any story they like and have it sound plausible to our monkey intuition, but physics and math are much stricter and have no sense of literature or style. There has to be enough material to work with and enough energy to do that work. After it’s all done, all the matter and energy you started with has to be accounted for. No addition or subtraction allowed unless you feel like demonstrating a perpetual motion machine or perpetual heat sink. We can let you get away with that stuff in comics, prime time TV, and the movie theater with an affectionate gentle ribbing, but once you’re talking about the real world, you’d better have a physicist doing your audit.

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3 responses to “Fun with Hydroplate Math

  1. yep, Brown is hilarious and pathetic. It’s amazing the outright lies that Christians tell and then hope no one checks.

    I’d believe the “physics” in Sharknado before I’d believe what a Christian apologist tried to tell me.

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