Every part of a building is subject to the effects of outside forces—gravity, wind, earthquakes, and temperature changes, to name a few. Throughout history, people have constructed buildings that have withstood these forces over a long period of time, primarily using rules of thumb derived from their own experiences and those of their predecessors. In recent centuries, the scientific and industrial revolutions introduced analytical approaches that allowed designers to go beyond empirical limitations and predict the behavior of building systems and components that existed only in their imaginations. This gave rise to the formalization and specialization of the modern engineering profession, which in turn led to more accurate and cost-effective designs. Today the individual responsible for ensuring that buildings will remain standing while carrying out their intended functions is the structural engineer.