Why are CDs round?

Answer:

Current CDs are round, but did you know the first removable storage disks were square? These were the "floppy disks" of the 80s and early 90s. But actually, only the exterior protective cover was square. The flexible plastic jacket was easier to manufacture by folding a plastic rectangle into two and punching a circle in the center and small access windows to access the inside.. Inside the black exterior was in fact a round piece of storage media that was spun around and read, with the same geometry as the CD or DVD.

Now of course, CDs are round so they are easily read as they spin around their central axis. Most people know that.

However, CDs and DVDs are not read by a laser... While an infrared laser diode does shine on the surface of the disk, the reflections from the disk are actually read by a photo-diode (a light detector), tuned to the same color as the laser. Newer DVDs will use a blue laser which will allow to store more data on a smaller area of the new "Blue-Rays" DVDs. ever try spinning a square? they have to spin. To ensure the symmetry of the reading device. so that they can spin without hitting the walls of a cd player/turntable plus the dial that reads the cd would not be able to make a square pattarn fast enough to read a cd yes of corse cd,s are round ask if m3 are niex time. Wheels spin better. Wheels are round. Besides its hard for a laster to read a very fine strip of information on a square CD although there are some CDs that are not round. So that the needle rotates spherically... because they need to spin and it%26#39;s the most efficient way to put information. think about it, rings upon rings of info compared to lines upon lines like a sheet of paper. the circle shape would be more compact. cuz they have to spin so you can hear the music there is a laser that reads the CD, it holds in a nearly steady position and reads "rings" around the cd. It judges what data is on the cd by notches in the cd. As the cd spins, the laser is basically reading a line of information, around the cd. Having a cd that isn%26#39;t round, would one:

Make it not smoothly spin in your cd drive

and two,

make information much less accurate and basically impossible to have readable information on. other than the need for a disc to spin, I think another reason is because a circle have more area to store data as compared to other shapes of the same perimeter. Also no offense to mellifluous...a CD player doesn;%26#39;t use needle. It uses a low intensity laser diode to read the tracks.

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