  When a classical system is driven through a continuous phase transition, its
nonequilibrium response is universal and exhibits Kibble-Zurek scaling. We
explore this dynamical scaling in the novel context of a three-dimensional
topological magnet with fractionalized excitations, namely the liquid-gas
transition of the emergent mobile magnetic monopoles in dipolar spin ice. Using
field-mixing and finite-size scaling techniques, we place the critical point of
the liquid-gas line in the three-dimensional Ising universality class. We then
demonstrate Kibble-Zurek scaling for sweeps of the magnetic field through the
critical point. Unusually slow microscopic time scales in spin ice offer a
unique opportunity to detect this universal nonequilibrium physics in current
experimental setups.
