Why is there a border between light and dark on the moon

because the sun illuminates the half of the moon that's facing it leaving the other half dark

id.k ask the border

Explanation:

atomic mass = 39

number of neutrons = 20

number of protons= 19

electronic configuration = 1s2 2s2 2p6 3s2 3p6 4s1

the number of electron in first shell = 2

number of electrons in n=3 shell = 8

it should have an internal chamber and two thermometers sticking out of the top. the internal chamber will also be closed off from the outside.