This lecture covers the S-matrix and its application to fermions, focusing on the dynamics of heat transfer in various convection scenarios. The instructor begins by discussing the convective heat transfer coefficient, emphasizing its variability along surfaces. Examples of natural and forced convection are provided, including a termite mound and an outdoor camping stove. The lecture then delves into the concepts of boundary layers, detailing the differences between thermal and momentum boundary layers and their growth characteristics. The instructor explains the significance of the Prandtl number in determining the relationship between these layers and discusses the implications for heat transfer efficiency. The lecture concludes with a dimensional analysis of mass, momentum, and energy conservation equations in boundary layers, highlighting the simplifications that can be made under certain conditions. The importance of accurately resolving gradients in temperature and velocity for predicting heat transfer and shear stress is also emphasized, providing a comprehensive overview of the principles governing convective heat transfer.