Without the rays, the red lines are plainly straight.
Straight, bent or tilted?
Hering illusion
Are the two red lines straight?
Yes, though they seem to bulge outward in the middle.
Why? One idea: the rays look like the view when you move forward fast, and your brain, trying to see where things will be a split second later, bends the lines.
Picture: Fibonacci, CC BY-SA 3.0 · Wikipedia(opens in a new tab)