The angel is an angle of light entering through the pineal gland from the higher mind, carrying a truth that never changes. It flies in mid-heaven because it moves through the upper reach of consciousness, above the body's noise, before it reaches the lower parts. What it brings down is one message, the everlasting good news, meant for every state and habit in a person at once.
The nations and tongues and peoples of the earth are all the many voices and conditions of the lower, body-bound mind. The light through the pineal reaches every one of them, so the whole inner population hears a single unchanging truth together.
Angel: an angle of light entering through the pineal gland from above, carrying the changeless truth
Heaven: the upper reach of consciousness, the higher mind
Earth: the lower, body-bound mind and its states
Nation, kindred, tongue, people: the many voices and conditions of that lower mind, all hearing the one light