system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are all the windows on planes a specific oval shape, is there a reason?
gpt
Imagine you make a little tear on the edge of a piece of paper. If you then try to pull apart the opposite ends, the tear will easily get bigger, rather than any new tears forming. This is called 'crack propagation', and is similar to what happens when very high stresses -- such as those found within the fuselage of a plane -- are put on the corners of metal windows. In short, all the stress is focused on the single point of the corner of the window, and rounding them out distributes the stress a little more evenly throughout the frame of the window. It actually took a few crashes for people to figure out how important this was, iirc.