Alexander Graham Bell was certain his greatest invention would change the world. He was almost right. The telephone was indeed revolutionary, letting people talk to each other across great distances as if they were in the same room. Unfortunately, Bell thought his greatest invention was not the telephone, but the photophone. That was a complete flop.
Perhaps it was just ahead of its time. Because the basic idea behind it – using pulses of light to bounce information through free space – is once again set to change the way we communicate. Radio waves have been the medium of choice for sending signals wirelessly for the best part of a century.