  While the basic laws of physics seem time-reversal invariant, our
understanding of the apparent irreversibility of the macroscopic world is well
grounded in the notion of entropy. Because astrophysics deals with the largest
structures in the Universe, one expects evidence there for the most pronounced
entropic arrow of time. However, in recent theoretical astrophysics work it
appears possible to identify constructs with time-reversal symmetry, which is
puzzling in the large-scale realm especially because it involves the engines of
powerful outflows in active galactic nuclei which deal with macroscopic
constituents such as accretion disks, magnetic fields, and black holes.
Nonetheless, the underlying theoretical structure from which this accreting
black hole framework emerges displays a time-symmetric harmonic behavior, a
feature reminiscent of basic and simple laws of physics. While we may expect
such behavior for classical black holes due to their simplicity, manifestations
of such symmetry on the scale of galaxies, instead, surprise. In fact, we
identify a parallel between the astrophysical tug-of-war between accretion
disks and jets in this model and the time symmetry-breaking of a simple
overdamped harmonic oscillator. The validity of these theoretical ideas in
combination with this unexpected parallel suggests that black holes are more
influential in astrophysics than currently recognized and that black hole
astrophysics is a more fundamental discipline.
