TweakTown came across a nice video that shows off how a hard disk drive operates. Taken with a 1000fps video camera, the clip illustrates how the actuator arm moves back and forth 22 times in a quarter of a second.
That works out to just over 0.01 seconds per movement. Incredible. It's not recommended that you try this at home as opening the case of an HDD will allow dust in and will kill the drive extremely quickly. Additionally, most people don't have cameras capable of 1000fps just laying around in their homes.
That said, the video shows just how incredibly nimble and beautiful the inner workings of a disk drive are. That said, a solid state drive is faster and still one of the best upgrades you can do for a computer.