In the beginning it was all voice.
Pictures were drawn in pre-history, but it was one on one with a cave wall.
Text in one form or another entered at least just after the last ice age by individuals writing or chiseling their thought.
Gutenberg's press (15,000 years after the first writing) suddenly sounded the demise of masses of scribes by allowing EASY small runs of publications by having reusable movable type (not specifically the press).
Roll fed paper in high speed presses in the late 1800s (300 yrs after Gutenberg) allowed "the daily newspaper".
Audio (about 50 years after newspapers) starting with Edison allowed a new dimension of interest in the human senses to be tweaked to inform and teach from replayable multiple copy media.
Video (about 20 years after audio) started to make its appearance as movies to the masses for an even greater audience and shortly thereafter "talkies".
Television about 30 years later than movies allowed home viewing and listening to important and educational and entertainment adding more people into the informed class of citizens, however arguable.
The progress above led to massive increases in the ability of people to transmit knowledge and learn.
Unexpected Results: iPad's first exciting result to me was the transformation with some students with impaired communication problems being able to start communicating and learning more with an iPad...this was astounding. It really means that an interactive tablet inspires the mind.
The iPad with interactive apps gets to the smallest and most personal form factor allowing entertainment and education in the most accessible form factor known that can in turn access information that is not currently on the device by downloading it.
It is easy to see that interactivity can explain things more easily and completely than anything including a classroom for detailed examination of a subject because you can "rewind" which you can't do in a classroom.
For those who think iPads are not good for students, I feel sorry. I suspect in short order we will confirm the advantage of iPads in learning improvement across a range of fields and the lowered cost of "books" and support materials. Ultimately, that leaves the teacher free to help with the most troubling issues in the study of each field, as opposed to the rote basics.
Long live the iPad. It can't get a smaller screen and still be easily usable, though it can get thinner and probably will.
That's my long 2 bucks worth. We are in a new era.