Ever heard a muffled, rumbling thunder-like sound but observed no flashes in the sky? Then you may have borne audible witness to a brontide. This term describes that very familiar sound, but instead of being generated by lightning, these noises are thought to be caused by short instances of seismic activity deep in the earth. Oddly, not too much is known about these effects because of the difficulty involved in studying them. While simple acoustic transmission through the earth has been found to account for some brontides, scientists postulate that eruption of pockets of natural gas beneath the surface might also be responsible for the readings. Additionally, the increased prevalence of artillery, artificial or test explosions and sonic booms from military aircraft makes isolating natural brontides extremely difficult. Brontḗ is the ancient Greek term for thunder, for which the brontosaurus is named, being so large and heavy. There you go, you learned two things today.