My volunteering duties at Thomas Edison's labs include a demonstration of Edison's favorite invention, the phonograph. While we have a bunch of disc turntables, the demo is always done on an earlier cylinder machine that's closer to the Old Man's original tinfoil phonograph invention.
I can remember seeing this demonstration in my younger days and being able to make a quick connection between the grooves on the cylinder and the grooves on the 45 rpm records I had at home. I can even recall making a crude record player with a pin and a piece of paper shaped in a cone. The physics behind the whole thing are really so simple that once explained, a child could do it him or herself. You could see the metaphorical light bulbs illuminating their minds as they got the concept.
Today what strikes me is how difficult that connection could be for kids who have spent their whole lives listening to CDs or computer files. The whole concept of a physical transference from a shaped groove, through a diaphragm that moves the air to form soundwaves... is gone. They press a button to start the sound process, but they don't see anything move, except maybe an animated status bar on a screen.
As we move farther and farther away from that actual tactile, physical representation of recorded sound, I wonder if the disc will become as exotic as it was when first introduced. Eventually, will children wonder at the miracle of sound coming off a round black piece of vinyl? Or, God forbid, will they eventually come to believe that the iPod represents the advent of recorded sound?