  We construct an equilibrium partition function for a non-relativistic fluid
and use it to constrain the dynamics of the system. The construction is based
on light cone reduction, which is known to reduce the Poincare symmetry to
Galilean in one lower dimension. We modify the constitutive relations of a
relativistic fluid, and find that its symmetry broken phase - `null fluid' is
equivalent to the non-relativistic fluid. In particular, their symmetries,
thermodynamics, constitutive relations, and equilibrium partition function
match exactly to all orders in derivative expansion.
