On this general topic, guess how distant the horizon (the "vanishing point") is, across open water, assuming clear weather and a six-foot-tall observer standing on a beach? The answer is a mere six miles.

Next curious fact -- the two towers of the Golden Gate Bridge are perfectly vertical, but the top of one tower is 4.6 cm (1.8 inches) farther away from the other, compared to the bottom of the towers -- because there is a small angular tilt between the towers. Guess why ...

Okay, it's because the towers are independently vertical with respect the center of the earth, are horizontally separated by 4,200 feet, and each tower is 746 feet tall. These dimensions assure that the towers have a distinct angle with respect to each other. It's a small difference, but it's not zero.

I thought about these things (and many others) during my four-year solo around-the-world sail (https://arachnoid.com/sailbook/).