What happened to technology in the 20th Century? For hundreds and hundreds of years, humans traveled by horse, relied upon manual labor to complete tasks like planting crop, or washing clothes. Distant Communication only by letter(then telegraph in the 1800's).
Why over a span of hundreds of years did technology advance so little(in comparison), then all in one century we get: radio, T.V. the automobile, the aeroplane, capability to travel to space, electricity, telephone/cellphone, computers, the internet, all the medical advances...I'm sure I'm missing a few things.
TL;DR What happened in the 20th Century, that caused technology to advance more so than any other century?
Telephone dates back to 1876 BTW. The first transcontinental telephone line was built in 1915, when early vacuum tubes permitted transmitting a voice call truly long distance.