How Things Look on Instagram: "Inside a compact disc (CD), information is encoded as microscopic “pits” and “lands” (flat areas) arranged along a spiral track. When a CD player reads it, a laser beam shines through the transparent plastic layer onto that spiral. The pit versus land difference causes changes in the reflection of the laser light, which the player interprets as binary 0s and 1s. The laser used to read these pits is extremely fine—smaller than a human hair. Because the pits are very