Last week, we discovered the reason why window shades on a plane are required to remain open during takeoff and landing. This week, we looked into why aeroplane windows are always round. Is it because they look better round? Or cheaper to install? Or is there a more scientific reason behind it?

In a video posted to YouTube, Real Engineering found the answer to why airplane windows are round, which wasn’t always the case, reports Science Alert. In the early days of aviation, planes had rectangular windows, which worked fine with the first basic aircraft models. However, as planes became more advanced, they had the capacity to fly higher, which required cabins to be pressurized.

Pressurized cabins require a cylindrical shape in order to work properly; this would create a pressure difference between the air inside and the air outside, which increases as the plane gets higher. This causes the plane body to expand ever so slightly, putting stress and strain on the material.

This is where round windows come into effect: on a perfectly rounded cylinder, the stress flows smoothly through the material, a flow that’s interrupted by a window. If the window is rectangular, the interruption in stress flow is more significant, causing pressure to build up on sharp corners. This would be catastrophic since the pressure can eventually smash the glass and crack the body of the plane. But with a round/oval window, the stress levels are evenly balanced out and perfect harmony remains.

Round windows = less stress on the plane = safe flight. A winning solution, in our opinion.

To read the full article on Science Alert, visit sciencealert.com/watch-there-s-a-scientific-reason-for-why-aeroplane-windows-are-always-round.