In these six forms of astral activity, observation, if guided by modern spiritual science, recognizes the characteristics of the six planetary spheres, known as 'Moon', 'Mercury', 'Venus', on the one hand, 'Saturn', 'Jupiter', 'Mars', on the other. In the same way the dynamic sphere of the 'Sun' is found to provide the astral activity which mediates between the two groups of planetary spheres.⁵ The following observations may help us to become familiar with the different modes of activity of the force-spheres.