First internet message across Atlantic

1. The ARPANET moment that people mean by “internet”

On 25 July 1973 a computer at University College London participated in a packet exchange that linked European networks to ARPANET in the United States, marking the first transatlantic computer‑to‑computer connection and the practical beginning of a transatlantic Internet link as understood in networking terms ^[1]. This experiment combined a London‑to‑Norway cable leg with a satellite hop to Virginia and onward across the U.S. network, demonstrating packet switching across mixed physical media and proving the feasibility of intercontinental internetworking ^[1].

2. Why the ARPANET event is different from telegraph and radio firsts

The 1858 transatlantic telegraph cable enabled near‑instantaneous human‑operated telegraph messages between Europe and North America and produced symbolic inaugural exchanges—such as official messages between Queen Victoria and U.S. President James Buchanan—but it relied on Morse operators and single‑channel electrical signaling rather than automated packetized computer traffic ^{[2] [3] [5]}. Guglielmo Marconi’s wireless demonstration in December 1901 proved that radio signals could traverse the Atlantic (the received Morse “S”), but that was wireless telegraphy, not digital packet networking that allows modern Internet services ^{[4] [6] [7]}.

3. The technical leap: packet switching and international routing

What sets the 1973 ARPANET transatlantic connection apart is its use of packet switching: data were broken into packets, routed across heterogeneous links, and reassembled—foundational techniques of the Internet—rather than continuous circuit telegraphy or one‑way wireless pulses ^[1]. The London experiment routed packets via a combination of undersea cable, terrestrial networks and satellite links to reach ARPANET hosts in the United States, a composite proof‑of‑concept for global internetworking ^[1].

4. Continuity: undersea cables, telegraphy and the modern Internet

The telegraph cable projects of the 19th century laid the physical and institutional groundwork for later global communications: the first 1858 cable established the concept of undersea links (despite early failures and short operational life), and by 1866 a more reliable transatlantic submarine cable created a permanent electrical link between continents, a lineage that culminates in today’s fiber‑optic transoceanic cables that physically carry Internet traffic ^{[3] [8] [9]}. Contemporary undersea cables remain the backbone of global Internet connectivity even as technologies and bandwidth have evolved dramatically from those early iron‑wound telegraph lines ^{[10] [11]}.

5. Competing claims and how historians frame “firsts”

Celebrations of “firsts” often collapse distinct technologies under a single narrative; telegraphers rightly claim the first transatlantic messages in 1858, radio historians point to Marconi’s 1901 wireless reception, and Internet historians mark ARPANET’s 1973 transatlantic packet link as the first true cross‑Atlantic computer network event ^{[2] [4] [1]}. Each milestone is technically accurate within its domain, and the choice of which to call the “first” depends on whether the metric is electrical telegraphy, wireless signaling, or packet‑switched computer networking ^{[3] [6] [1]}.

6. What sources can’t prove here

Primary documentation of the exact packet payloads for the 1973 ARPANET experiment and the content of its first exchanged packets is not detailed in the sourced summaries provided; the Science Museum account and related materials establish the date and nature of the link but do not reproduce original packet logs or application‑level messages ^[1]. Where granular archival traffic records are required, consulting original ARPANET technical reports, UCL archives, or early network logs would be necessary beyond the scope of these secondary summaries ^[1].