Landau's Mechanics and also a cranky book on waves & oscillation I read some time ago talks about space and time being homogeneous and isotropic. I assume that the homogeneous property of space means that it does not matter where the motion of a closed dynamical system unfolds, the result will be the same. Homogeneity of time means that given a certain state of a mechanical system, it does not matter what time your clock shows, the unfolding will be the same. As for isotropic, I know it means "same in all direction" but what does that means specifically in terms of space and times? Also, feel free to correct or put in more formal terms my definition of homogeneity of space and time. thx!