So it goes in the fourth dimension
Slaughterhouse five introduces the Tralfamadorian concept of time. It states that time is a fourth dimension just like the three dimensions that humans can see. Aliens on Tralfamador can see through time just like humans can see through space. Just like our three dimensions, everything has a certain observable position in time that cannot be changed, meaning that humanity's concept of the future is just as fixed as the past. While Billy Pilgrim can't freely see though the fourth dimension like the aliens can, he does time travel randomly. He has seen his future and knows the futures of those around him, including when they die. Billy marks every mention of death with "So it goes", showing how the future is inevitable. The Tralfamadorian view of time is problematic. Is the way we all die inevitable? Can we really not change the future? From a physical standpoint, the Tralfamadorian view makes a lot of sense. If we had a sufficiently detailed model of the universe...