In standard H-J theory, only one such trajectory is held to exist, but the equation, taken seriously , asserts the existence of all the trajectories. Taking the equation seriously means that a relative number density R 2 of trajectories can be defined, squared to ensure number density is non-negative, and "relative" because uncountability means if we label a countable number, we can change the number labeled by any factor a without changing the physics. Labeling a countable number al-low measurements of relative density change, which is what the experiments proposed here will do. It is wellknown in fluid mechanics that such relative density comparisons are possible only if the trajectories are conserved. Also, if trajectories were to disappear, it would mean that evolution past the disappearance point would not be defined, a breakdown in determinism. For both reasons, the density of trajectories must be conserved :