I learn a new outlandish belief every time I wade into Facebook.

Today’s? The moon is hollow.

It seems to stem from a misunderstood quote from Apollo 12 that the moon “rang like a bell”

NASA intentionally crashed an Apollo 12 stage into the moon to get seismic data. The reverberations lasted longer than expected because of the moon’s structure (not much to absorb kinetic energy, it vibrates well).