  A long standing mystery of fundamental importance in correlated electron
physics is to understand strange non-Fermi liquid metals that are seen in
diverse quantum materials. A striking experimental feature of these metals is a
resistivity that is linear in temperature ($T$). In this paper we ask what it
takes to obtain such non-Fermi liquid physics down to zero temperature in a
translation invariant metal. If in addition the full frequency ($\omega$)
dependent conductivity satisfies $\omega/T$ scaling, we argue that the
$T$-linear resistivity must come from the intrinsic physics of the low energy
fixed point. Combining with earlier arguments that compressible translation
invariant metals are `ersatz Fermi liquids' with an infinite number of emergent
conserved quantities, we obtain powerful and practical conclusions. We show
that there is necessarily a diverging susceptibility for an operator that is
odd under inversion/time reversal symmetries, and has zero crystal momentum. We
discuss a few other experimental consequences of our arguments, as well as
potential loopholes which necessarily imply other exotic phenomena.
