The spin dynamics of a classical very dilute totally disordered Heisenberg spin glass is investigated at low temperatures. At 0 K, it is supposed that the spins are in metastable equilibrium in one of a great number of possible configurations, different configurations being separated by finite energy barriers. It is found that at 0 K, there are spin waves at very long wavelengths k-1⪢R0 (R0, mean spacing between spins). At finite temperatures, there may be excitations involving a few number of spins whose thermal activation would damp the spin waves. Possible domain structure would reduce the existence of spin waves to LM>k-1⪢R0 (LM, mean dimension of domain). The persistence of a residual (very low) mean magnetization has been neglected.
