Technology & Medicine › Digital age
The Internet (TCP/IP)
1974 (Cerf & Kahn design); switched on January 1, 1983· Invention or discovery· Communication & computing
Well documentedSolid records, physical evidence or scientific consensus.
A worldwide 'network of networks' that lets any computer exchange data with any other using shared rules called TCP/IP.
See it on the Technology & Medicine map →How it works
In 1974 Vint Cerf and Bob Kahn published a design for linking separate packet networks, such as ARPANET and radio and satellite networks. By 1978 their rules were split in two: TCP breaks messages into numbered packets and checks they all arrive; IP addresses each packet so 'gateways,' now called routers, can pass it between networks. ARPANET switched to TCP/IP on January 1, 1983. Domain names followed in 1983–85, and commercial traffic was allowed in the early 1990s.
Why it mattered
With no central owner and open rules, anyone could connect or invent new uses: the Web, email, streaming and online shopping. About two-thirds of humanity is now online.
Think of it like
Like the standard shipping container: ships, trains and trucks of any company can carry it, because the box and its label follow one agreed format.
How we know
Cerf and Kahn's May 1974 paper, the formal TCP and IP specifications of 1981 (RFC 791 and 793), network records, and ITU estimates of about 5.5 billion users in 2024.
Still unknown or debated
'Who invented the Internet' has no single answer: credit is shared among packet-switching pioneers, ARPANET's builders, France's Louis Pouzin, whose CYCLADES network shaped TCP/IP, and Cerf and Kahn.
Inside this (2)
Connections (8)
▸Electric telegraph foreshadowed The Internet (TCP/IP)Mostly agreed
The connection
The telegraph was the first network to send messages as electrical signals, faster than any messenger, and it introduced ideas the Internet reuses: coded messages, addresses, and relay offices that stored each message and forwarded it toward its destination. Writer Tom Standage called it 'the Victorian Internet.'
When and how
Telegraph: Britain and the US, 1837–1844. Internet: Cerf and Kahn's 1974 design, building on 1960s packet switching, itself a faster form of telegraph-style 'store and forward' message switching.
How sure are we?
1960s papers by packet-switching pioneers present their designs as improvements on message switching, the method telegraph networks used; the rest of the link is analogy.
Debates and open questions
'Foreshadowed' is a judgment call: some see the telegraph as a true ancestor, others as a loose analogy, since packets and routers were genuinely new inventions.
▸Laser sends data along the fibre of The Internet (TCP/IP)Well documented
The connection
Most Internet traffic travels as pulses of laser light through glass fibres thinner than a hair. Charles Kao showed in 1966 that purified glass could carry light long distances; Corning made such fibre in 1970; and tiny semiconductor lasers switching on and off billions of times a second encode the data. Undersea fibre cables carry nearly all intercontinental traffic.
When and how
Kao at Standard Telecommunication Laboratories in Harlow, England, 1966; Corning in New York State, 1970; the first transatlantic fibre-optic cable, TAT-8, opened in 1988.
How we know
Telecom engineering and cable-industry records document the shift from copper to fibre; Kao's 2009 Nobel Prize recognized his role in it.
Debates and open questions
Little is disputed; the open question is capacity, as engineers debate how close fibre networks are to their theoretical limits and what will carry traffic beyond them.
▸ARPANET grew into The Internet (TCP/IP)Well documented
The connection
ARPANET was a single network. As other packet networks appeared, using radio and satellites, Cerf and Kahn designed TCP/IP so different networks could interconnect. On January 1, 1983, ARPANET switched to TCP/IP and became the first backbone of the Internet; the military split off its own network that year, and ARPANET was retired in 1990.
When and how
Cerf at Stanford and Kahn at ARPA, 1973–74; the switch-over on January 1, 1983, called 'flag day'; the National Science Foundation's network then took over as backbone.
How we know
The RFC memos, especially Jon Postel's 1981 transition plan (RFC 801), and ARPA records chart the change step by step.
Debates and open questions
Whether TCP/IP won on merit is debated: an international standard, OSI, competed into the early 1990s, and TCP/IP may have won simply because it was already running and free.
▸Personal computer brought millions of homes onto The Internet (TCP/IP)Well documented
The connection
Through the 1980s the Internet mainly linked universities and labs. Once homes had PCs, a modem could connect them over the phone line, first to services like CompuServe and AOL, then to the Internet itself. Cheap dial-up access and the first popular web browser, Mosaic (1993), brought tens of millions online by the late 1990s.
When and how
The US and Europe, roughly 1989–2000; The World, in Boston, offered the first commercial dial-up Internet access in 1989, and AOL connected members to the Internet in the mid-1990s.
How we know
US Census surveys show household Internet use rising with PC ownership: 18 percent of homes in 1997, about 42 percent in 2000.
Debates and open questions
PCs were not the main on-ramp everywhere: much of Asia and Africa first went online by mobile phone, skipping the PC entirely.
▸The Internet (TCP/IP) carried the World Wide WebWell documented
The connection
The Internet is the network: TCP/IP rules that let any computer send data packets to any other. The web is a service running on top of it: pages linked by URLs and fetched with HTTP. Berners-Lee built on the Internet because it already linked universities and labs; without it, the web would have had no roads to travel.
When and how
The Internet switched to TCP/IP on January 1, 1983; Berners-Lee built the web at CERN, 1989–91, on computers that had just joined the Internet.
How we know
Berners-Lee's 1989 proposal and the HTTP specifications build directly on Internet protocols; he describes this in his 1999 memoir 'Weaving the Web'.
Debates and open questions
People often confuse the two; whether the Internet would have reached the public without the web, perhaps through rivals like Gopher, is speculation.
▸Reusable rockets launch satellites that extend The Internet (TCP/IP)Well documented
The connection
Cheap, frequent launches made it affordable to put thousands of small satellites into low orbit. SpaceX's Starlink, launched mostly on reused Falcon 9 boosters since 2019, provides Internet service to remote areas, ships and aircraft; by 2025 it had thousands of satellites and several million users.
When and how
Starlink launches from Florida and California since May 2019; rivals include OneWeb and Amazon's Project Kuiper, which began launching production satellites in 2025.
How we know
Launch logs and subscriber figures reported by SpaceX and regulators document the link; most Starlink satellites ride boosters that have flown before.
Debates and open questions
Astronomers worry about streaks in telescope images and about space debris; who should regulate huge private satellite fleets, and whether they will stay profitable, is open.
▸Quantum computers may one day break the encryption of The Internet (TCP/IP)Mostly agreed
The connection
Internet security relies on codes such as RSA, which are safe because ordinary computers would take impossibly long to break huge numbers into their factors. In 1994 Peter Shor showed a large quantum computer could do it quickly. Today's machines are far too small and error-prone, but governments are already switching to new 'post-quantum' codes.
When and how
Shor at Bell Labs in New Jersey, 1994; the US standards agency NIST published its first post-quantum encryption standards in August 2024.
How sure are we?
Shor's method is mathematically proven, so the threat is real in principle; no quantum computer has yet factored a number anywhere near the size used in encryption.
Debates and open questions
When, or whether, a large enough quantum computer will be built is fiercely debated, with estimates ranging from about a decade to never; stolen data could be decrypted later.
▸Transatlantic telegraph cable pioneered the undersea cables of The Internet (TCP/IP)Well documented
The connection
The 1866 cable began a worldwide web of undersea cables; by 1900 they linked every inhabited continent. Fiber-optic cable replaced copper from 1988. Today roughly 99% of intercontinental internet traffic travels through several hundred undersea cables, laid by specialist ships much as the Great Eastern did.
When and how
Atlantic, 1866; first transatlantic fiber cable, TAT-8, 1988; today's cables are owned by telecom groups and tech firms such as Google and Meta.
How we know
Industry maps such as TeleGeography's count over 500 active and planned cables; the 99% figure is a widely cited industry estimate.
Debates and open questions
How vulnerable these cables are to accidents and sabotage, after several cuts in the Baltic and Red Sea since 2023, is debated.