Everything has a frequency, right? The earth vibrates at a certain frequency. Our bodies vibrate. Our electrical appliances, buildings, everything. That's what physics is all about. (Right? I never studied much science-wise, but I think this falls under physics.)
I've already heard from a few sources how certain frequencies are best for healing in our bodies (and certain ones are more harmful). The frequency of the earth is supposed to be very healing for bones, for example. Apparently, also falling into that range is the purring of a cat! Yessssss! Cat people win again!
(Thanks Gemma Busquets for making this fantastic graphic.)