system
Given the following post, respond as if you're commenting on Reddit:
human
How straightness is achieved in construction?

How did we develop first straight objects? For example to create a ruler we need some straightness reference(I assume). Of course nothing will be 100% straight but when you think all the delicate machinary such as medical devices and the machines used in the space we must be pretty close. Is there a way to geometrically approximate to a straight line without a straight device?
gpt
simplest straight lines are a taut string or a flat water surface.

early surfaces were just created by hand.  our precision has increased over time.  we never hit perfectly straight, just straight enough to suffice.