Your data's journey is surprisingly physical. Out on the seabed, the cable — fiber plus all its protective sheathing — is only about the diameter of a garden hose, yet each high-capacity cable can carry up to 200 terabits per second.

These cables face real threats, but not usually the movie-villain version. Fish and shark bites have happened historically, yet cable-protection groups describe them as rare and declining. Today the bigger dangers are fishing gear, anchor drags, earthquakes, and undersea landslides. In 2008, a ship's anchor near Egypt severed cables and disrupted a large share of traffic between Europe and the Middle East. Repairs took weeks.

On land, data hits Internet Exchange Points — massive buildings where hundreds of networks physically connect.