Arc Second

No, no, no, it's not Jap and Shem's new boat!

Take a look at the Hubble Space Telescope’s mirror: [HST22_lg_web.jpg]

It’s got a certain, fixed diameter (2.4 meters). If you send violet light (400 nm) at it, it takes 6 million wavelengths to get across it, meaning it can resolve angles down to 0.034 arc-seconds! (Remember, there are 60 arc-minutes in one degree, and 60 arc-seconds in one arc-minute.)

Thanks, universe, for Starts With A Bang