  Where, and how, does energy dissipation of electrical energy take place in a
ballistic wire? Fully two decades after the advent of the transmissive
phenomenology of electrical conductance, this deceptively simple query remains
unanswered. We revisit the quantum kinetic basis of dissipation and show its
power to give a definitive answer to our query. Dissipation leaves a clear,
quantitative trace in the non-equilibrium current noise of a quantum point
contact; this signature has already been observed in the laboratory. We then
highlight the current state of accepted understandings in the light of
well-known yet seemingly contradictory measurements. The physics of mesoscopic
transport rests not in coherent carrier transmission through a perfect and
dissipationless metallic channel, but explicitly in their dissipative inelastic
scattering at the wire's interfaces and adjacent macroscopic leads.
