Or mirrors, as it were. And they are smooth!

The figure of each mirror (the technical term for the shape of the surface) is incredibly accurate: the bumps in the surface are on average smaller than 25 nanometers. A nanometer is a billionth of a meter… to give you an idea of how small this is, a typical human hair is 400 times thicker than the deformities in the mirror.

[...]

I’ll add that mirrors like this – the size they are, made of beryllium, figured to this accuracy – has never been accomplished before. And that’s only part of it, since of course all 18 mirrors must act as one once JWST is in orbit.

The James Webb Space Telescope will launch in 2018 if we are lucky. I can’t wait to see what we find!