What hasn't been mentioned yet is that Kubrick was inspired by the short story "The Sentinel" by AC Clarke.
The monoliths in the short story are placed by intelligent beings through space, typically on moons of adjacent planets. The monoliths are sending signals home (wherever that is) once they are broken/destroyed/... This can only happen with nuclear power.
The idea was to have some kind of warning system when intelligence emerges somewhere in space since this new intelligent species needs to be able to leave their own planet AND they need to have discovered nuclear power.
(Disclaimer: I read the short story at least 10 years ago, and I hope I remember it correctly)
The monoliths in the short story are placed by intelligent beings through space, typically on moons of adjacent planets. The monoliths are sending signals home (wherever that is) once they are broken/destroyed/... This can only happen with nuclear power.
The idea was to have some kind of warning system when intelligence emerges somewhere in space since this new intelligent species needs to be able to leave their own planet AND they need to have discovered nuclear power.
(Disclaimer: I read the short story at least 10 years ago, and I hope I remember it correctly)