Finally, we have Nikola Tesla. While he did not invent alternating current (AC), he did refine it, endlessly championing it over direct current (DC), much to the chagrin of his nemesis, Thomas Edison (for whom he worked for several years, and upon whose designs he greatly improved). His contributions to the development of electrical power supply cannot be overstated, but his most ambitious project—had it been realized—would have put to shame not only those fantastic contributions, but those of pretty much every other inventor to ever exist.
Wardenclyffe Tower, shown above, was built in 1901, and it was meant to be exactly what it looks like: the world’s first wireless transmission tower. The long-term plan was to build a global network of these towers (just like the one that exists today) to transmit information around the globe. The tower stood almost 60 meters (200 ft) high and reached 36 meters (120 ft) underground. Due to financial and tax troubles (and the fact that Tesla, while a genius, was probably kind of insane), the project was never finished, and the tower was demolished in 1917.
But had he somehow been allowed to see the project through to completion, it would not just have beaten our current global wireless network to existence by decades and decades. Tesla intended for this network to transmit not just wireless electric signals, but also wireless electric power, to the whole world.