ELI5 Moon Drift - why is the moon moving away from Earth?

Why is the moon slowly moving away from the earth at 4cm per year? How do we even measure it so precisely? Why does the same side of the moon always face the earth? What is the beautiful dimensional coincidence that gives us a a perfect solar eclipse?   ... We explain like i'm five!   Thank you to the r/explainlikeimfive community and in particular the following users whose questions and comments formed the basis of this discussion: deletedscenebrowser, mobius1424, joldz, smlz101, puppypile99 and boymcmoyo To the ELI5 community that has supported us so far, thanks for all your feedback and comments. Send us an e-mail: [email protected]