One of Bear's favorite themes is reality as a function of observation. In "Blood Music", reality becomes unstable as the number of observers (trillions of intelligent single-cell organisms) spirals higher and higher. "Anvil of Stars" (sequel to "The Forge of God") and "Moving Mars" postulate a physics based on information exchange between particles, capable of being altered at the "bit level." (Bear has credited the inspiration for the idea to Frederick Kantor's 1967 treatise "Information Mechanics" (see Digital physics)) In "Moving Mars", that knowledge is used to remove Mars from the solar system and transfer it to an orbit around a distant star.