Linear perspective has some fun implications that I think about a lot. Apply a linear operator to a line and you get another line. This is obvious but the inve

Linear perspective has some fun implications that I think about a lot. Apply a linear operator to a line and you get another line. This is obvious but the inverse is also true: if a line is a result of a linear operator the input was also a line. This is fun to think about when looking at jet contrails and bridges, the milkyway and pretty much any curve you have looked at your whole life. If it isn't straight as you see it then it's not straight in reality.