Context for the level of accuracy. Quoting from the article:
To work together as a single mirror, the telescope’s 18 primary mirror segments need to match each other to a fraction of a wavelength of light – approximately 50 nanometers. To put this in perspective, if the Webb primary mirror were the size of the United States, each segment would be the size of Texas, and the team would need to line the height of those Texas-sized segments up with each other to an accuracy of about 1.5 inches.
Modern hard disks have a track pitch in tens of nanometers, and the read head has to move with matching precision, it also flies 3 nanometers above the surface.
Wow, that's really cool. Thanks for sharing the knowledge. I didn't realize how physically precise modern hard drives were! I suppose if it makes sense if you think about how much information they are storing in a small space.
To work together as a single mirror, the telescope’s 18 primary mirror segments need to match each other to a fraction of a wavelength of light – approximately 50 nanometers. To put this in perspective, if the Webb primary mirror were the size of the United States, each segment would be the size of Texas, and the team would need to line the height of those Texas-sized segments up with each other to an accuracy of about 1.5 inches.