His tests with patients, later known as the 21 grams experiment, were limited in sample size and poorly designed. The 21 grams experiment reminds us how many of life’s mysteries remain unresolved. Lights, camera, 21 gramsBeyond scientific research, the 21 grams experiment has also found an enduring home in pop culture. The 21 grams experiment’s influence has even reached as far as Japanese manga: In one episode of the One Piece series, a scientist suggests souls weigh 21 grams. It’s just what people want to believe.”The 21 grams experiment makes us wonder, Hood says.