When you send a message to a friend in another country, a video to a relative on the other side of the ocean, or make a video call with someone on another continent, you imagine that everything travels through the air, like a radio signal. Much of what happens on the internet, however, does not fly: it travels along the seabed. Beneath your feet there is a web of cables capable of connecting the world in the blink of an eye.
Believe it or not, more than 95% of all international internet traffic travels through physical cables laid beneath the ocean. Satellites add very little in comparison. It is what experts call the invisible highway: you cannot see it, you do not notice it, but without it the global internet you use every day would not exist.
A cable thinner than a hair
The surprising thing is what is inside. The heart of each cable is a glass fibre almost as thin as a human hair, through which pulses of light travel. That light is what carries your photos, your messages and your emails, at dizzying speeds. A single one of these cables can carry millions of conversations at once.
That delicate fibre does not travel naked. To survive on the seabed, it is wrapped in layers of plastic, steel and other materials until it is as thick as a garden hose. It looks robust, but it needs protection: old cables used tar and wire, and today they are designed with an armour meant to withstand the pressure, the cold and even the teeth of some animals.
Unexpected enemies: anchors, nets and sharks
If you live far from the coast, you may think these cables are safe from everything. Nothing could be further from the truth. Fishing boats with their nets, vessel anchors and even shark bites have caused breakdowns more than once. When a cable breaks, millions of people can lose their connection in a matter of seconds.
To fix this there are repair ships that locate the fault and refloat the cable to weld it back together. Even so, the industry does not stake everything on a single cable. They are spread across redundant routes: if one fails, the traffic is diverted along another path with almost no one noticing. That is the safety net that keeps the world connected.
What about satellites?
With the rise of the satellites populating the sky, you hear more and more about internet from space. But there are some misunderstandings. Satellites are excellent for remote areas, ships or aircraft where a cable cannot be laid. However, for daily traffic between big cities, submarine cables remain faster, cheaper and with far more capacity.
In fact, the vast majority of the information you consider “the cloud” lives in huge buildings of servers connected by these cables. Every time you save a photo, change country in an app or buy something online, there are kilometres of fibre working silently under the water.
The future travels under the sea
The big technology companies invest billions in laying new cables so that your videos, games and apps work better and better. The demand for data never stops growing, and with it the need for more ocean highways, each with greater capacity and lower latency.
The next time you blame the wifi for taking a second to load, remember that the real journey of your data may begin on the seabed, thousands of metres down. The internet is, at its core, a story of light, glass and ocean: the most incredible infrastructure that almost no one stops to look at.
