Networking and the Internet, from First Principles

Have you ever wondered what happens when we text, call, or video chat with a friend or a colleague on another continent, and their reply arrives in a fraction of a second, as though they were in the same room? Behind the scenes, a chain of invisible conversions takes place: your voice, video, or message is translated into radio waves crossing the room to your Wi-Fi router, then electrical pulses in copper (or light, if you have a fiber connection), and then flashes of light inside a glass strand thinner than a hair lying deep on the ocean floor, only for the entire sequence to play in reverse at the other end. I find it mind-boggling that we can communicate instantly with anyone in the world by doing nothing more than creating controlled, patterned disturbances of electricity, light, and radio.