A software developer explaining his job to an engineer:
Imagine that you are hired to build a bridge over a river. The width of the river increases slightly every day, except when it shrinks. Your budget does not allow for you to use concrete or steel - you can only afford timber and cut stone. Gravity changes from hour to hour, as does the viscosity of air. Your only tools are a hacksaw, a chainsaw, a rubber mallet, and a length of rope.
Welcome to my world.