  According to the standard model of cosmology, the arrangement of matter in
the cosmos on scales much larger than galaxies is entirely specified by the
initial conditions laid down during inflation. But zooming in by dozens of
orders of magnitude to microscopic (and human?) scales, quantum randomness
reigns, independent of the initial conditions. Where is the boundary of
determinism, and how does that interplay with chaos? Here, we make a first
attempt at answering this question in an astronomical context, including
currently understood processes. The boundary is a function, at least, of length
scale, position, and matter type (dark matter being more simply predictable).
In intergalactic voids, the primordial pattern of density fluctuations is
largely preserved. But we argue that within galaxies, the conditions are at
minimum chaotic, and may even be influenced by non-primordial information, or
randomness independent of the initial conditions. Randomness could be supplied
by events such as supernovae and jets from active galactic nuclei (AGN) and
other accretion disks, which, with the help of chaotic dynamics, could
broadcast any possible microscopic randomness to larger scales, eventually
throughout a galaxy. This may be generated or amplified by a recently
investigated process called spontaneous stochasticity, or effective randomness
in turbulent systems arising from arbitrarily small perturbations.
