You see, people recognized that having a ruler be straight would be beneficial to a succession consensus by the creation of an biological heir and thus aid the stability of the realm.
As for the tool: Probably some craftsmen eyeballed it until they managed to create one that was approximately straight.
You make an object (classically, a block of granite) with a perfectly flat side, then make another perfectly flat side that overlaps with it. The edge between them will be perfectly straight.
Okay, but how to you make perfectly flat faces on a block of stone? How do you know if you’ve succeeded? Well, the trick is to make three of them at the same time: you grind blocks A and B together, B and C together, and C and A together, back and forth, with finer and finer grit between them, until all three pairs fit perfectly. (With some mathematical caveats that don’t really apply in practice,) the only way all three can fit like that is if they’re all perfectly flat.
Comments
Probably started with a piece of string tied between two points.
Take a piece of string and pull the ends apart.
You now have a straight line.
Taut string between two points. The straight edge is not that hard.
Three flat surfaces rubbed against each other long enough become really-really flat. Using them we can do a lot of tools
You see, people recognized that having a ruler be straight would be beneficial to a succession consensus by the creation of an biological heir and thus aid the stability of the realm.
As for the tool: Probably some craftsmen eyeballed it until they managed to create one that was approximately straight.
You make an object (classically, a block of granite) with a perfectly flat side, then make another perfectly flat side that overlaps with it. The edge between them will be perfectly straight.
Okay, but how to you make perfectly flat faces on a block of stone? How do you know if you’ve succeeded? Well, the trick is to make three of them at the same time: you grind blocks A and B together, B and C together, and C and A together, back and forth, with finer and finer grit between them, until all three pairs fit perfectly. (With some mathematical caveats that don’t really apply in practice,) the only way all three can fit like that is if they’re all perfectly flat.