ARPANET Day — The Birthday of the Internet

What Is ARPANET Day?

October 29th is celebrated as ARPANET Day — widely regarded as the birthday of the internet. On this day in 1969, the world's first message was transmitted between two computers connected via the ARPANET (Advanced Research Projects Agency Network), the direct predecessor of today's global internet.

The World's First Internet Message: "LO"

At 10:30 p.m. on October 29, 1969, UCLA student programmer Charley Kline attempted to log in to a computer at the Stanford Research Institute (SRI) in Menlo Park — 559 kilometres away. The intended word was "LOGIN," but after successfully transmitting "L" and "O," the receiving system crashed. The world's first internet message was accidentally and poetically: "LO" — as if the network itself was saying hello.

• The team: UCLA's Network Measurement Center, led by Professor Leonard Kleinrock, was the launch site of ARPANET's first node
• The other end: Bill Duvall at SRI confirmed receipt by phone before the system crash
• The retry: About an hour later, the full word "LOGIN" was successfully transmitted — the internet's first complete message

What Was ARPANET?

• Creator: ARPA (Advanced Research Projects Agency), a branch of the U.S. Department of Defense, funded its development
• Purpose: To build a decentralised communications network that could survive a nuclear strike by routing data around damaged nodes
• Packet switching: ARPANET pioneered breaking data into small "packets" sent independently and reassembled at the destination — the foundation of how the internet works today
• Email (1971): Ray Tomlinson sent the first email over ARPANET and invented the @ symbol convention still used today

From ARPANET to the World Wide Web

ARPANET expanded from four nodes in 1969 to thousands by the early 1980s. In 1983, the modern internet's TCP/IP protocol was adopted as the standard. In 1991, British scientist Tim Berners-Lee launched the World Wide Web, making the internet accessible to the general public for the first time.

• Japan's internet: In 1984, Keio University, Tokyo Institute of Technology, and the University of Tokyo launched JUNET — Japan's first network — connecting Japan to the ARPANET world
• Commercial internet in Japan: Commercial internet access became available to the public around 1992
• Today: More than 5.3 billion people — over 65% of humanity — are connected to the internet as of 2023

How to Mark This Day

• Count how many internet-based services you use in a single day — it's likely to be a surprising number
• Share the story of "LO" with a younger person and start a conversation about where the internet came from
• Explore ARPANET history through documentaries or online archives
• Try a brief digital detox and reflect on what life was like before everything was connected

From "LO" to Everything

A single incomplete word — born from a system crash on a quiet October evening in 1969 — grew into the infrastructure that connects billions of human beings. The internet has transformed how we learn, work, love, and understand the world. On October 29th, take a moment to appreciate the extraordinary journey that began with just two letters: LO.