Contrary to what General Wesc asserts, negative numbers, like imaginary numbers and just about any kind of numbers, are ubiquitous in the real world. We can't live without them. True, there are no negative quantities of everyday items in nature. However, there are negative rates of change, there are negative distances relative to something (negative sea level, for instance), there are negative slopes, negative charges, ad infinitum. To say that negative numbers are not present in the real world, only relevant to mathematics, is incredibly naive, and reminiscent of those who say that algebra, calculus, or whatever math course they are taking or refusing to take at the moment is irrelevent to the real world. I assert that ALL MATH is relevant to the real world, some more so than others, but negative numbers are incredibly fundamental.