In short
In short: a subsea cable is a fiber-optic cable laid on the seabed between two shores. By Meta's figures, about 99% of intercontinental data traffic runs through such cables. The signal weakens along the way, so a 7,000-kilometer cable typically needs about a hundred repeaters to boost it.
When you watch a video from an American site, it doesn't fly through the air. It travels as light in glass strands laid on the ocean floor. Those strands are a physical thing: someone ordered them, someone laid them, and someone has to maintain them for years.
Why AI makes them news
Models are trained and run in huge data centers, and the data between continents has to reach them. On September 21, 2026 Meta announced the Petal cable between France and the US: about 7,000 kilometers and a capacity of 1 petabit per second, which the company says is double the most advanced cables over that distance. It's expected in service in 2029. The detail worth remembering: this cable is ordered by Meta, the company behind Facebook and Instagram.
The cloud has an anchor, and it lies on the ocean floor.
What follows from this
When a tech company orders a cable across the ocean, that's infrastructure news, even if it sounds like social media news.
Primary sources
Meta Engineering: PetalThe visual is generated code-art, no third-party images.