A common way to compute density is, of course, to take the ratio of an object's mass to its volume. But other types of densities exist, such as the resistance of somebody's brain to the imparting of common sense.
Neil deGrasse TysonItaly valued cathedrals while Spain valued explorers. So worldwide, five times as many people speak Spanish than Italian.
Neil deGrasse TysonThere's a lot of memorization that goes on in school. You memorize vocabulary words and all these sorts of things.
Neil deGrasse Tyson