the square-cube law is the fact that a larger object has a lower ratio of surface area to volume than a similarly-shaped smaller object; i.e. as the scale of an object increases linearly, its surface area increases as a square function, and its volume increases as a cubic function.

thermodynamically, this means an object twice the size has 4 times the heat transfer (which occurs at the outer surface), but 8 times the heat capacity (since heat is stored throughout the volume). so it's heat loss is by raw numbers greater, but lower as a percentage of the total, i.e. the internal temperature is more stable