  We present a new theoretical framework for using entropy to understand how
outflows driven by supernovae are launched from disc galaxies: via continuous,
buoyant acceleration through the circumgalactic medium (CGM). When young star
clusters detonate supernovae in the interstellar medium (ISM) of a galaxy, they
generate hot, diffuse bubbles that push on the surrounding ISM and evaporate
that ISM into their interiors. As these bubbles reach the scale height of the
ISM, they break out of the disc, rising into the CGM. Once these bubbles break
out, if they have sufficiently high entropy, they will feel an upward
acceleration, owing to a local buoyant force. This upward force will accelerate
these bubbles, driving them to high galactocentric radii, keeping them in the
CGM for $>\Gyr$, even if their initial velocity is much lower than the local
escape velocity. We derive an equation of motion for these entropy-driven winds
that connects the ISM properties, halo mass, and CGM profile of galaxies to the
ultimate evolution of feedback-driven winds. We explore the parameter space of
these equations, and show how this novel framework can explain both
self-consistent simulations of star formation and galactic outflows as well as
the new wealth of observations of CGM kinematics. We show that these
entropy-driven winds can produce long wind recycling times, while still
carrying a significant amount of mass. Comparisons to simulations and
observations show entropy-driven winds convincingly explain the kinematics of
galactic outflows.
