Moreover, square gratings are also finding applications in the field of holography. The ability of gratings to diffract light can be harnessed to create three-dimensional images that are useful in various imaging technologies. Holographic displays and data storage systems, for example, utilize square gratings to manipulate light to reconstruct images that provide depth and realism. This area of research is rapidly advancing, giving rise to new possibilities in visual technologies.

A manhole cover was accidentally launched from its shaft during an underground nuclear test in 1957. During the Operation Plumbbob nuclear tests, a 900-kilogram (1,984 lb) steel plate cap was blasted off the test shaft at an unknown speed and appeared as a blur on a single frame of film of the test. It was never recovered, but it likely burned up in the atmosphere due to friction. If the manhole cover had made it into space, it would have been the first known man-made object in space, as it pre-dated the launch of Sputnik 1 by 38 days. A calculation before the event gave a predicted speed of six times Earth escape velocity. After the event, Dr. Robert R. Brownlee described the best estimate of the cover's speed from the photographic evidence as going like a bat out of hell!^[27][28][29]

Aesthetic Appeal

Manhole cover

Furthermore, in modern cities facing rising sea levels and changing climate conditions, bollards also serve functional roles as barriers against flooding. They stand as sentinels for the future, reminding us of our past while reinforcing our commitment to protecting coastal areas.