Conversation so far:
What is 39 from A Night at the Opera by the band Queen?
'39 was May's attempt to do sci-fi skiffle. The tale of a group of space explorers who embark on what is, from their perspective, a year-long voyage.
Who sings the song '39' by the band Queen?
Brian May sings the song on the album, with backing vocals by Freddie Mercury and Roger Taylor. During live performances, Mercury sang the lead vocal.

Question: What do the space explorers realize when they come back from their voyage?
Self-contained rewrite: What do the space explorers realize when they come back from their voyage in the song '39' by the band Queen?