The black board

Have you ever thought about the black board ( or white board in a classroom).
Teachers come, write on it, children learn in different proportions and then its erased, sometimes completely and sometimes not quite, and periodically it is cleaned and made as good as new....

Does the blackboard learn or change....or is just part of the lecture and a witness to the whole process.

Its unchanging. Just like the sky does not change whether it is rain or shine??? The clouds come & go , day & night happens...but the sky just remains.