How the World Got Wired · Ships and Sharks

Sharks, Anchors, Fishing Boats, Earthquakes

Now I want to tell you about how cables die.

A cable on the seafloor is a long, lonely thing. It cannot defend itself. It just lies there, at depths where almost nothing visits — in the deepest places, the bottom of the Pacific, it sits four kilometers below the surface, in cold, black water that the sun has never reached. Most of the time, nothing happens to it. It can lie undisturbed for decades.

But sometimes, things happen.

In shallow water — closer to shore, where the cables come up out of the sea and onto land — the biggest danger is fishing. A fishing trawler, dragging nets along the seabed, can catch a cable and tear it. Anchors from anchored ships can crash down on cables and crush them. These are the two leading causes of cable damage in the world. Most cable breaks happen within a few kilometers of shore, in busy coastal waters where boats are dense.

In deeper water, earthquakes and underwater landslides are the main threat. An earthquake at the bottom of the ocean can shake loose huge amounts of sediment, which slides down underwater slopes in a kind of slow-motion avalanche, snapping cables in its path.

And then there are sharks.

This sounds like a joke, but it isn’t. Sharks really do bite undersea cables. Nobody is exactly sure why — possibly because the cables give off faint electrical fields, and sharks can sense electrical fields, and the cables confuse them. Whatever the reason, it has happened often enough that some cables, especially in shark-heavy waters, are now wrapped in extra layers of armor specifically to defend against shark bites. There is footage you can find online of a shark gnawing on an undersea cable. The shark looks small. The cable, on a thousand-mile journey across an ocean, is being interrupted by an irritated fish.

When a cable breaks — by trawler, by anchor, by earthquake, by shark, or by simple old age — somebody has to fix it.

This is the job of repair ships, which are specialized cable ships kept on standby at ports around the world, waiting for a phone call. When a break happens, the nearest available repair ship sails to the spot, which is found using the cable’s own signals — the location of the break can be figured out from how long it takes a test pulse to bounce back. The repair ship deploys an underwater robot, called a grapnel, that grabs the broken ends, drags them up to the surface, splices in a new section of cable, and lowers the repaired cable back down.

It can take days. It can take weeks. In bad weather, it can take longer.

In January of 2022, an underwater volcano erupted near the small Pacific island nation of Tonga. The eruption was so powerful that it was heard in Alaska, more than 9,000 kilometers away. The eruption snapped Tonga’s only undersea internet cable.

Tonga has about 100,000 people. Until that cable was repaired, every one of them was almost completely cut off from the rest of the world. They couldn’t email. They couldn’t post to social media. They couldn’t easily phone their families overseas. Banking failed. News stopped flowing in. The country went dark, in an internet sense, for over a month — until a repair ship made the long voyage from Papua New Guinea and patched the cable back together.

I am telling you this because I want you to understand, clearly and at a young age, that the internet is not magic. It is a physical thing. It can be broken. A volcano can break it. A fishing trawler can break it. A confused shark can chew on it. Whole countries can lose the internet because one ten-centimeter-thick cable, lying in the dark four kilometers below the sea, has been damaged.

The “cloud” is many things, but mostly it is a network of glass threads on the floor of the ocean. Anyone who tells you otherwise has forgotten where they live.

A Note Before We Go On

In the next chapter, we are coming back up to dry land, to talk about the other part of the internet’s physical infrastructure: the boxes, big and small, that decide where every packet goes. The routers. The cables on the seafloor only handle the journey between continents. Inside each continent, inside each country, inside each city, inside your home, packets are being routed by other equipment, built mostly by a single company, founded by two people who fell in love at Stanford and built a billion-dollar business out of the simple problem of getting their two university computers to talk to each other.

The company is called Cisco.

That’s Chapter 8.

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