Sub-Etha is a form of superluminal communication, or faster-than-light communication network. It was used throughout the Universe as a way for hitchhikers to communicate with passing spacecraft and to ask to be let on board. Ford Prefect was known to use it to aid his interstellar hitchhiking.


Sub-Etha is known to be used with two items of technology. The first is the Sub-Etha Sens-O-Matic, which is used to monitor the Sub-Etha signals of passing ships. The second is the Electronic Thumb which is a small device used to contact spaceships and connect with the crew on board.

Sub-Etha is also used throughout the Milky Way as a way of transmitting data, including news bulletins or updates to The Hitchhiker's Guide to the Galaxy.


The name Sub-Etha is likely a reference to the aether (or ether), which what was once believed to be a kind of medium filling the Universe.



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