Ethernet Is Named After the Luminiferous Ether, an Invisible Medium Einstein Called Superfluous in 1905

The paper, “Ethernet: Distributed Packet Switching for Local Computer Networks,” ran in the July 1976 issue. Its naming line is one sentence, tucked into the section that lays out the system’s parts. You can read it in full in a reprint Cornell posted for a course.

The name fits how the network worked. Every computer hung off one shared coaxial cable, and anything one machine sent, every other machine could hear. The paper calls that cable the Ether: “An Ethernet’s shared communication facility, its Ether, is a passive broadcast medium with no central control.”

It also borrowed from radio. “Like an Aloha radio transmitter, an Ethernet transmitter broadcasts … packets onto the Ether and hopes that they are heard by the intended receivers,” Metcalfe and Boggs wrote. The cable played the part of empty space.

The physics they named it after had a rough 19th century. Light was supposed to travel through the luminiferous ether the way sound travels through air. If so, Earth moving through it should change how fast light seemed to go in different directions.

Albert Michelson and Edward Morley built an instrument to catch that in 1887. Their paper in the American Journal of Science worked out that “the displacement to be expected was 0•4 fringe.” What they saw “was certainly less than the twentieth part of this, and probably less than the fortieth part.”

Eighteen years later, Einstein’s relativity paper made the ether unnecessary. “The introduction of a “luminiferous ether” will prove to be superfluous,“ he wrote in “On the Electrodynamics of Moving Bodies,” dated June 30, 1905.

The ether didn’t survive physics, but the word survived the network. The cable everybody in 1976 shared is long gone from most offices, replaced by switches that send each machine only its own traffic, and the name still says “a medium everyone can hear.” How long a name outlives the thing it describes is the part nobody planned.