How Do We Know the Moon ISN’T Made of Green Cheese?

How Do We Know the Moon ISN’T Made of Green Cheese? July 6, 2013

In a fable going back centuries within various cultures, a simpleton sees the reflection of the full moon in water and imagines that it’s a wheel of green (that is, unaged) cheese. It’s a tale that we often pass on to our children and that we discard with time, like belief in the Easter Bunny.

But how do you know that the moon isn’t made of green cheese?

Physicist Sean M. Carroll addressed this question in a lecture. After a few moments exploring physical issues like the moon’s mass, volume, and density and the (dissimilar) density of cheese, he gave this frank broadside:

The answer is that it’s absurd to think the moon is made of green cheese.

He goes on to say that we understand how the planets were formed and how the solar system works. There simply is no reason to suppose that the moon is made of green cheese and plenty of reasons to suppose that it’s not.

This is not a proof, there is no metaphysical proof, like you can prove a statement in logic or math that the moon is not made of green cheese. But science nevertheless passes judgments on claims based on how well they fit in with the rest of our theoretical understanding.

Let’s apply this thinking to the domain of this blog. To take one supernatural example, how do we know that Jesus wasn’t raised from the dead? The answer is the same: it’s absurd to think that Jesus was raised from the dead.

  • We know how death works. We see it in plants and animals, and we know that when they’re gone, they’re just gone. Rats don’t have souls. Zebras don’t go to heaven. There’s no reason to suppose that it works any differently for our favorite animal, Homo sapiens, and plenty of reasons to suppose that it works the same.
  • We know about ancient manuscripts. Lots of cultures wrote their ancient myths, and many of these are older than the books of the Old Testament: Gilgamesh (Sumerian), Enûma Eliš (Babylonian), Ramayana (Hindu), Iliad (Greek), Beowulf (Anglo-Saxon), Popol Vuh (Mayan), and so on. Bible stories appear to have been lifted from earlier stories from neighboring cultures–the Garden of Eden, global Flood, and Jesus resurrection stories, for example. For whatever reason, people write miracle stories, and we have a large and well-populated bin labeled “Legend” in which to put stories like those in the Bible.
  • We know that stories and legends can grow with time. We may have heard of Charles Darwin’s deathbed conversion to Christianity (false). Or that a decent fraction of Americans thought that President Obama is a Muslim. Or that aliens crash-landed in Roswell, New Mexico. Or that a new star appeared in the night sky with the birth of North Korea’s Kim Jong Il. In our own time, urban legends so neatly fit a standard pattern, that simple rules help identify them. The Principle of Analogy is helpful here: if it looks like yet another legend (for example), that’s a good assumption to start with.
  • We know that humans invent religions. There are 42,000 denominations of Christianity alone, for example, and uncountably many versions of the myriad religions invented through history. There is little reason to imagine that Christianity is the one exception that is actually true.

Natural explanations are sufficient to explain Christianity.

Might the moon actually be made of cheese? Science doesn’t make unconditional statements, but we can assume the contrary with about as much confidence as we have in any scientific statement.

Might Jesus have been raised from the dead? Sure, it’s possible, but that’s not where the facts point. Aside from satisfying a preconception, why imagine that this is the case?

When a religion is good, I conceive it will support itself;
and when it does not support itself, and God does not take care to support it
so that its professors are obliged to call for help of the civil power,
‘tis a sign, I apprehend, of its being a bad one.
— Benjamin Franklin

(This is a modified version of a post originally published 11/7/11.)

Photo credit: TV Tropes

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