class TimeEvolver:
    def __init__(self, sphere, times):
        self.sphere = sphere
        self._tracker = np.zeros_like(shape=(*self.sphere.temperature.shape, 4, len(times)))
        self.times = times
        self.dts = np.gradient(self.times)

    def evolve(self):
        for tID, dt in enumerate(self.dts):
            self.sphere.timestep(dt)