Straight lines and circles are man’s inventions. They don’t exist in nature. The difference doesn’t matter because we can create close approximations.
Level surfaces are a given in industrialized nations in many situations. Like floors. Doesn’t bother me that the floor at this guesthouse is not level because it’s fun to watch a hot poached egg riding on a layer of steam slowly slide down the plate.
Just to be clear, the yolk is not running away from a stationary egg. The egg is sliding toward the top of the photo.