Nature does not do anything in straight lines. No natural feature of the landscape, or living thing on Earth has straight lines. Only we humans make straight lines. A Rabbi friend of mine says that human beings are like pebbles, and not like bricks. Pebbles have rounded outlines, and protuberances everywhere. You cannot categorize pebbles-each one is different from every other. Bricks are all alike, by design, but humans should not be treated like bricks, but like pebbles.
So, when you see an aerial photograph, you know without thinking about it that straight lines across the terrain are roads, built by people, and not natural features. If you happen to see a pond with straight sides, you can be sure that some farmer or landscaper, and not Nature, built it. When archaeologists look for signs of human habitation in a jungle, they specifically look for straight lines, that could be the remains of buildings or roads built by ancient civilizations. Ground-penetrating radar, called LIDAR, is great for finding those hidden signs.
This photo of the girl doing her studying under the fire-escape staircase, shows the contrast. The building and its brick cladding show all the straight lines needed to make a structure. Bricks, doors, windows, and the staircase itself, all straight lines. The girl’s laptop computer, all straight lines. But look at the girl, and the grass, and the rocks-no straight lines there.
This old house in Tennessee has lots of straight lines, both horizontal and vertical.
The multi-story building is all made up of straight lines, exactly in alignment so the stresses on the floors don’t make the building less sturdy.
I see these straight lines from my desk every day. The metal pole has many faces, all of which are straight lines, and the power lines are also straight. However, the devices holding the power lines to the pole are curved, as are the insulators, to distribute the stresses more evenly.
In our neighborhood, there are three storm-water overflow ponds, bounded by chain-link fences with vertical slats through them. The fence itself is made up of somewhat curved links, but they look pretty straight at a distance. I took this picture, to show the natural feature, doing its best to poke through those straight slats. That is a cane of Himalayan Blackberry, our local invasive species. It is nearly impossible to eradicate, and the thorny canes need to be cut back all summer so they don’t take over. Someone obviously cut this one off at some point, but it’s already growing back. They are tenacious plants, with no straight lines!
This airport moving sidewalk is all straight lines. This photo is also an excellent demonstration of the “vanishing point” perspective.
Finally, I thought this wooden flooring is the perfect demonstration of the difference between human-made features, and natural ones. Each plank of flooring is perfectly rectangular, indication human manufacture, but the wood-grain is persistently curved. The planks are cut in straight lines, but the curving wood grain almost makes the boundaries of each plank invisible!