Over dinner my daughter asked me how the music is stored on a CD, so I got to have a good yak about optics, sampling, error correction and such.

She apparently couldn’t give a stuff about how it lives on her phone, but she seems to find the compact disc fascinating

What I find remarkable is how the CD is still the gold standard of audio quality: 16 bits per channel @ 44.1kHz. Audiophiles can buy equipment capable of 24-bit 192kHz, and maybe 2-3 of them have even used it once, but CD quality is where it ended up.

You probably knew CDs were read by a laser, but did you know the data itself is under the label, not on the shiny side of the disc? The laser focuses on the underside of the label, putting scratches on the shiny side out of focus, helping it 'see through' them

The data is written in a spiral, kinda like an LP. Manufacturers sometimes cheated the 80 minute time limit by decreasing the spacing between the 'grooves' (naughty naughty)