NASA defines space as starting at 50 miles (~80 km), FAI defines it as 100 km (~62 miles). Scott Manley gave a nice summary a few days ago: https://youtu.be/0b

NASA defines space as starting at 50 miles (~80 km), FAI defines it as 100 km (~62 miles). Scott Manley gave a nice summary a few days ago: https://youtu.be/0b1VgtyIQN0?t=627 https://youtu.be/0b1VgtyIQN0?t=627 Here's the article he references: https://physicstoday.scitation.org/doi/full/10.1063/PT.3.4599 https://physicstoday.scitation.org/doi/full/10.1063/PT.3.459... EDIT: Added links.