Today's #TuesdaysWithBill question comes from Dan Green (or Dan Green's mouthless gaze, either one). It's a hypothetical, a question many of us have no doubt asked ourselves during times both triumphant and despondent: "What if the Moon really were made out of cheese?"
True to form, the Science Guy tackles this questionable query with aplomb. A cheese moon would affect our tides, likely take a totally different shape, and probably do a number on Earth's gravitational pull. It would also dissuade our most promising lactose intolerant astronauts from Lunar missions, which would be a darn shame. For the rest of us who love cheese though... well, let's not get too invested in this hypothetical. We might not be able to handle the stark disappointment of reality.
Dan Green: Hi. Dan Green here. Bill, I wanted to ask you a hypothetical, if the moon was really made out of green cheese, how much mass would it have? What would its gravity be like? How would it affect our tides differently than the real moon does? And just for fun, how much milk would it take to make that much green cheese? Thanks for your answer.
Bill Nye: Dan. Great question about the moon being made of cheese, specifically as I understand it green cheese. If it were green cheese like really green I would expect it to reflect a little more green light than it does. I mean it would depend, does it have a rind? Does it have that wax that they put on at the cheese shops? I'm not sure. Anyway, I can tell you from experience that -- in general -- cheese floats, in general. So with floating cheese you got to figure its specific gravity, that is to say how much mass it as for how much volume it takes up is somewhat less than rocks. If water is one, rocks are one and a half, they're two, they're twice as dense as water. They're not 50 times as dense, twice as dense. Rocks sink but they don't sink like a bullet. So a moon that was 80 percent the mass of the current moon would have 80 percent of the effect on the tides. But if it were 80 percent of the mass, its orbital distance would probably be different. Would it be set up to libate in the same way, that is to say the moon currently keeps the same face to us with every orbit. That's because it spins almost exactly one time as it goes around the earth. It has a little wobble to it where you actually see somewhat more than just half of the moon if you're really diligent with a telescope paying close attention.
And then the other thing I would wonder about a cheese moon, you know, rocks are pretty solid but cheese often is not. I wonder if it wouldn't have modes or vibrational oscillations within its own shape that are noticeable. I wonder if its spin wouldn't - spinning once with each orbit I wonder if it wouldn't have an equatorial bulge. I wonder what would happen to it when other cheesy objects hit it, you know, meteorites of cheese, cheese-eorites, whatever they're called. And I wonder if it wouldn't out gas or evaporate in the blackness of space. Also cheese freezes. So on the far side of the moon or the near side depending on the time of month, you might have some lunar freezing, which then could potentially affect the shape because it would affect its gravity with one side solid changing density relative to the other side, the geode as it's called, the shape would change with its own gravity. So there would be some issues. You'd notice it right away.
And I think another issue to keep in mind, if the moon turns out to be made of cheese it just really expands our possibilities for a lunar base because there would be limitless food. It does, for those of you who are gluten-free and dairy free, you may not want to be an astronaut on a lunar mission now if it turns out that it's made of green cheese.