Oh wait, I just realized what I said was probably very stupid: I was thinking of some computational complexity theorem that links memory and runtime complexity classes in the same way that the "speed of light" sets an ultimate bound on the relation between actual space and actual time.

But the speed of light is the maximum space in the smallest time, which computationally would correspond to filling the largest amount of memory in the shortest time :facepalm: (and thanks for the links!)