While we may use them to take photos of the gorgeous view outside while flying at 30,000 feet in the sky, the plane windows, which once were square, are round for a very scientific reason!
Earlier, planes had rectangular/square windows. So what changed?
Multiple airliners crashed in the early 1950s which were caused by square windows.
"In the 1950s, when jetliners were starting to become mainstream, the de Havilland Comet came into fashion. With a pressurised cabin, it was able to go higher and faster than other aircraft. However, the plane had square windows and in 1953 two planes fell apart in the air, killing 56 people in total. The reason for the crashes? The windows."
Basically, "where there's a corner, there's a weak spot. Windows, having four corners, have four potential weak spots, making them likely to crash under stress – such as air pressure," explains this Independent article.
Learning from the mistake made by using square windows, use of circular or oval shaped windows was initiated, as it avoids the problem by not allowing stress to concentrate at the corners