Personally, I think it relates to a war. Possibly between the Korean and Vietnam war (One decade later/
And another one must fall down). I think its a child, or teenager living in a city during the time of war, and watches how buildings around him are collapsing.
"The sun in the open sky" could mean that he was living in a city, whose buildings are collapsing, and the horizon is now clear. He escapes the first war (before "decades later"), and while in his new home, another war starts, and he remembers his past.
"The earth isn't humming" could mean that his parents didn't want him to know what was going on, when he was young, and told him that the earth was humming.
Personally, I think it relates to a war. Possibly between the Korean and Vietnam war (One decade later/ And another one must fall down). I think its a child, or teenager living in a city during the time of war, and watches how buildings around him are collapsing.
"The sun in the open sky" could mean that he was living in a city, whose buildings are collapsing, and the horizon is now clear. He escapes the first war (before "decades later"), and while in his new home, another war starts, and he remembers his past.
"The earth isn't humming" could mean that his parents didn't want him to know what was going on, when he was young, and told him that the earth was humming.