Mechanical Feedback: From Stellar Wind Bubbles to Starbursts

The current understanding of mechanical feedback is reviewed by evaluating the standard, adiabatic model for shell formation and evolution. This model is relevant to phenomena ranging from individual stellar-wind bubbles to galactic superwinds, forming the basis for our understanding of the multiphase ISM, IGM, and galactic evolutionary processes. Although significant discrepancies between the model and observation have been identified, to date there are none that require a fundamental revision. A variety of evidence, ranging over three orders of magnitude in spatial scale, is broadly consistent with the standard model. This includes kinematics of individual objects, observations of hot gas, the size distribution of H i shells, and outflow rates from starburst galaxies. However, some of the most pressing issues relating to shell evolution are still outstanding and obstruct efforts to resolve key questions like the fate of the hot gas.