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.
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.
- The Hitchhiker's Guide to the Galaxy
- Chapter 3
- The Restaurant at the End of the Universe
- Life, the Universe and Everything
- Chapter 2