probably shitty worldbuilding idea: fantasy world that keeps going
they keep sending out expeditions to try and map the whole world and figure out if it's round or flat or what but it just keeps going and they keep meeting new people who've met other people coming the other direction and everybody so far has found that it just keeps going
they eventually realize it is in fact curved by measuring how much travel distance it takes for a tower to disappear behind the horizon, and using the distance between objects of known height they can calculate the dimensions of the planet, but when they set out on an expedition to circumnavigate the world, they find themselves having traveled so far along the curve that, mathematically speaking, they should have circled the planet twice, but it just keeps going. no matter which direction they travel, the outcome is the same.
they try sending out two cartographers in different directions, one travels 15 degrees north, the other travels 15 degrees east. then they start walking toward each other in a straight line. they never meet. they try mapping out the region in each direction, but the farther out they travel from the starting point, the more their maps contradict one another.
if you were to draw a circle on the ground, with a radius of 10 feet, the line should be 62.8 feet long, but when you measure the circumference by walking along the line and measuring how far you've traveled, it turns out to be 64.1 feet long. a minor discrepancy, at that size, but the larger the circle, the larger the discrepancy.
if two people holding 100 foot rope walk in different (but not opposite) directions, there should be a certain point where the rope is drawn taut, as the distance between them reaches 100 feet, but when they perform the experiment, they both walk a small distance beyond that point. when they reach the point of tautness, they follow the rope toward each other and meet in the middle, each of them having walked 58 feet, not 50.
on a whim, or perhaps it's more of a hunch, one cartographer suggests a different approach. they repeat the rope experiment but this time they walk at a very deliberate, measured pace, both at the exact same speed. they find that the amount of time it takes to reach one another from the point of tautness increases the longer the rope, but with one exception: if they walk toward each other at the same pace with their eyes closed, they bump into each other faster than when their eyes are open.
this leads to a theory: perhaps space expands when observed
