  It is currently unknown whether solid particles larger than dust from
supernova ejecta rain down on Earth at high speeds. We develop a hydrodynamic
and radiative model to explore the detectability of $\gtrsim 1 \mathrm{\; mm}$
sub-relativistic meteors. We find that a large fraction of the meteor energy
during its passage through the Earth's upper atmosphere powers the adiabatic
expansion of a hot plasma cylinder, giving rise to acoustic shocks detectable
by infrasound microphones. Additionally, a global network of several hundred
all-sky optical cameras with a time resolution of $\lesssim 10^{-4}
\mathrm{\;s}$ would be capable of detecting $\gtrsim 1 \mathrm{\; mm}$
sub-relativistic meteors.
