Samanth Subramanian on the Undersea Cables That Keep the Internet Alive

Episode Summary

Executive Summary: The episode explores how undersea fiber-optic cables power the modern internet, from their Victorian telegraph roots to today’s AI-driven demand. Guest Samanth Subramanian explains the physical mechanics, financing shifts from state telecom consortia to Big Tech, the geopolitical risks of cable chokepoints and sabotage, and why redundancy—not satellites—remains essential.

Main Topics: Physical infrastructure behind the internet (Priority: 5/5): The hosts emphasize that the internet is not abstract but depends on concrete systems like subsea cables and data centers that require heavy industrial inputs. How subsea cables work (Priority: 5/5): Subramanian explains fiber-optic cables, light pulses, wave division multiplexing, and the ship-based laying/repair process used today and in the telegraph era. Funding and ownership evolution (Priority: 5/5): Cable projects shifted from state-owned telecom consortia to private investors, and now largely to Big Tech firms such as Google, Meta, Amazon, and Microsoft. Redundancy and network resilience (Priority: 4/5): The episode details how multiple overlapping cables, land routes, and route diversity prevent most cuts from causing major outages despite frequent accidental damage. Geopolitics and sabotage risk (Priority: 5/5): Chokepoints like the Red Sea, Strait of Hormuz, and Baltic/Taiwan routes are discussed as potential targets in gray-zone conflict and state rivalry. AI and future demand for capacity (Priority: 4/5): The rise of AI and hyperscale data centers is accelerating demand for more cables and making a fully wireless internet even less plausible.

Key Arguments: The internet depends on fragile but massively scaled physical infrastructure, not just wireless connectivity. Modern fiber-optic cables use glass strands and light pulses, enabling far higher bandwidth than old copper telegraph lines. Cable-laying remains a highly specialized, capital-intensive business dominated by a small number of firms. Big Tech funds many new cables because data traffic is central to their business models and they can afford the large upfront costs. Redundancy is built into the system because every major operator benefits from backup capacity if one cable fails. Most cable cuts are accidental, but governments now treat intentional sabotage as a serious security threat. Geography strongly shapes cable routes, with historic landing points and strategic chokepoints continuing to matter. AI growth is increasing demand for data transport faster than satellites can realistically substitute for subsea cables. Chinese and Western cable ecosystems are increasingly shaped by sanctions and strategic competition, raising fears of a bifurcated internet.

Data Points: Number of subsea cables worldwide: 500 to 550 - Estimate given for the global number of undersea cables Annual cable cuts: Roughly 100 per year - Mostly accidental cuts from anchors or fishing activity Big Tech share of new cable funding: Two out of every three new cables - Subramanian says these are funded and/or owned in part or full by the major tech firms Cost of a transatlantic cable: About $500 million - Approximate cost of a London–New York cable Cable repair duration in Tonga: 16 months - One Tongan island relied on Starlink during the period without cabled internet Short cable example: 41 miles - The Isle of Man to Northern Ireland cable cited as a favorite example Tonga cable loss: Only international subsea data cable severed - A volcanic eruption and landslide disconnected Tonga from global internet access Taiwan landing cables: 15 internet cables - Mentioned as a vulnerability in the event of deliberate disruption

Pivotal Quotes: "the internet is a series of tubes" — Tracy Alloway / Joe Weisenthal reference: Discussion of Ted Stevens’s phrase and why it actually captures the physical nature of internet infrastructure "there's a lot of redundancy built into the system" — Samanth Subramanian: Explaining why most cable cuts do not cause major outages "The internet doesn't function like a highway in the sense that the fastest route between two points is not necessarily the shortest route." — Samanth Subramanian: Describing routing, rerouting, and the complexity of data paths

Implications: Subsea cables will remain critical infrastructure as AI and data demand grow. Their ownership, security, and route planning are becoming strategic issues, with implications for internet access, privacy, geopolitics, and economic resilience.