Lyric discussion by Mr_Brightside 

Cover art for Atom Heart 243.5 lyrics by Dark Tranquillity

I hate making guesses as to the meanings of songs, but this one really intrigues me. Great song, by the way. Take note of who wrote the lyrics... Sundin. A bit out of the norm, but definitely not bad.

Anyways, as to my idea about the lyrics... I think it's about nuclear warfare. The name "Atom Heart" gives a bit of a clue. Also worth mentioning is 243.5. That's the atomic weight of Plutonium, which is the material used in atomic weapons. There are also some lines in the lyrics that could really relate to the nuclear theme. "Death rode these silent caravans and steered them to the rim of the world." "The enterprise, academy the crafts held in our hands all devoted to the art of dying" "The enterprise, wolvenlore the cursed seed of man plunged through the tunnels of uncreation"

Just my thoughts... that's what struck me as soon as I listened to the song.