Eight powers of ten: similarities in black hole accretion on all mass scales

In this paper we discuss the recent advances in the quantitative comparison of accretion, and the accretion:jet coupling, in accreting black holes in both X-ray binaries (where MBH ∼ 10M⊙) and Active Galactic Nuclei (105 ≤ MBH ≤ 109). These similarities include the radiative efficiency and jet power as a function of accretion rate, which are themselves probably the origin of the ‘fundamental plane of black hole activity’. A second ‘fundamental plane’ which connects mass, accretion rate and timing properties provides us with a further physical diagnostic. Patterns of radio loudness (i.e. jet production) as a function of luminosity and accretion state are shown to be similar for X-ray binaries and AGN. Finally we discuss how neutron stars are a useful control sample, and what the future may hold for this field.