How It Works: The Physics With Traditional Cooking high heat is being applied to a room temperature steak and a heat gradient forms as the outside heats up faster than the inside. This is due to the laws of thermodynamics that we have not yet covered in Physics 211 but can be generalized as a modification of conservation of energy and the idea of establishing an equilibrium, topics we have heavily covered. Conservation of energy dictates that energy cannot be created or destroyed, but it be altered and change from one form to another. When cooking the form of energy we are generally manipulating is heat and the temperature of our closed system. That being the cooking apparatus and that which is being cooked. The idea of equilibrium is that when you have two different bodies with quite different values of some quantitative element, Thermal energy in the form of heat for example, there will be a net flow of energy from high to low until balance between the two is achieved. Image courtesy of NASA While cooking Sou Vide the heated water is doing work in the form of adding Thermal energy to the Steak, but when the steak reaches the temperature of the water bath the two bodies are in equilibrium, and the the transfer of thermal energy stops. Where with a more typical cooking method this equilibrium will not occur because the cooking apparatus is so much hotter than the desired cooking temperature. At this point the proteins in the food item may continue to denature, or cook, but this happens at a much slower rate at 140°F than 160°F and much much slower than any temperatures above that. This way the stake can remain at lower temps and cook evenly through the entire thing without burning or any other undesirable consequences. Instead of depending on years of experience and training to determine the perfect time stop cooking and serve the dish sou vide uses math and physics to consistently produce near perfect results.