Have wewe ever assured someone that your friend is reliable kwa saying that he au she "has both feet on the ground"? The fact that such a phrase exists shows how much comfort we take in the idea that the ground beneath our feet is unmoving, unchanging and dependable. Indeed, much of our civilization, from our houses and buildings to our energy, chakula and water sources, depends on unmoving earth.
In truth, however, our planet's seemingly stable surface is made up of enormous pieces of rock that are slowly but constantly moving. Those pieces continually collide with and rub against one another, and...