How long is the groove on a CD?

It depends on how the cats are blowing, daddy-o. (Oh, sorry—, we momentarily flashed back to our neo-Beatnik days.)

Anyway, the groove on a compact disc isn’t exactly a groove in the same sense as what’s on a phonograph record. It’s more like a path of binary-coded bumps (which some people call “pits,” though that’s a misnomer).

The bumps are so small that only a laser beam could find them.

The laser beam reflects off the bumps differently than it does off the flat parts in between, shining back into a sensor that interprets the flashing reflections as shining either “on” or “off.” The electronics of your CD player interpret this as a series of ones or zeros, 44,000 times a second, and decodes these ones and zeros into music.

Not surprisingly, it takes a lot of bumps to convey all of this information to your CD player and speakers.

That’s why the total distance covered by the laser beam when playing a CD is more than three miles.