Energy is a fundamental quantity in characterizing the dynamic evolution of quantum systems, while energy evolution in a nonequilibrium system remains elusive. The realization of a long-lived nonequilibrium state is a favorite method for probing the energy dynamics in the system. Here, we systematically explore the nonequilibrium energy dynamics on the basis of a spherical unitary Fermi gas. The long-lived breathing oscillation, protected by SO(2,1) symmetry, acts as a sensitive probe for precisely measuring energy evolution, enabling quantitative comparisons with theoretical calculations. Unlike in equilibrium systems, the energy evolution in a nonequilibrium system depends on collective motions and is characterized by the dynamic virial theorem. The trapping potential and internal energies increase with the energy injection while oscillating nearly ${\text{180}}^{\circ }$ out of phase. We further theoretically develop and experimentally demonstrate the dynamic virial theorem beyond the harmonic trap. Our work achieves time-resolved observations of energy evolution, providing deep insights into energy injection and redistribution in a nonequilibrium quantum system.

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• Fermi gases
• Ultracold gases
• Feshbach resonance