I’m spending the day trying to get some work done on the book-in-progress, so I’m avoiding both work- and blog-related stuff. I don’t want to leave the site completely quiet, though, so here’s a question to ponder, relating to SteelyKid’s continuing fascination with Goodnight Moon:
How does a cow jump over the moon?
The father of one of SteelyKid’s classmates, who is not originally from the US, asked why there’s a cow jumping over the moon in that (or, as SteelyKid puts it: “Cow jumping MOON!!”), and I don’t have a good answer. I’m aware of the nursery rhyme and the Tolkien joke, but why anybody would posit a cow jumping over the moon in the first place, I don’t know.
If you run the numbers (and yes, I’m dorky enough to do this), it’s awfully improbable.
The Moon orbits at a distance of around 400,000 km from Earth, meaning that an 800-kg cow would require something like 800,000,000 J of energy to just barely clear the Moon’s orbit. So, where would a cow get that kind of energy?
Well, I grew up in a dairy farming area in New York, so I know that one of the things cows regularly eat is corn. The Internet helpfully tells me that there are 262 kJ in an ear of corn, so a cow would need to eat a bit more than 3,000 ears of corn to get enough energy to be able to jump over the moon. That works out to about a tenth of a cow’s annual corn consumption. Of course, you’d probably need to include at least some of the mass of the corn in the calculation, which would inflate the total a bit. That, or include the propulsive effect of ejecting that much waste corn in the effect of the “jump,” but that’s not really an image I want to pursue.
So, clearly, the cow must be making use of some higher-efficiency method of generating energy. If we were to assume a nuclear-powered cow, running off uranium fission reactions that release 200 MeV per fission, the energy required works out to about 2.5×1019 uranium atoms fissioning. Which sounds like a lot, but the mass of an atom is pretty tiny, so that’s only about 9.8 micrograms of total material. Even if you account for a relatively low conversion efficiency, you’re not looking at a huge amount of fissionable material.
Clearly, then, the cow jumping MOON!! must come from some Western state with lots of uranium in the ground and water, and has evolved sophisticated energy-extraction abilities through the many years of ranching out west. If we can track this sucker down, and harness this power for more productive activities than the frivolous leaping of orbiting satellites, the whole climate change problem will be licked in no time.
(What? It’s not any less plausible than anything else that will come out of Congress in the next few years…)