Both of Death's End's "beyond electromagnetic" communication methods now have a Nobel Prize
In Death's End (2010), at the start of deterrence, humanity can detect gravitational waves and neutrinos but can't transmit with either, and both are described as "a whole level above electromagnetic waves." The book even explains why gravitational waves won out for deterrence:
"Theoretically, a modulated beam of neutrinos could transmit information to the other end of the universe... But while neutrinos must be focused in a particular direction, gravitational waves were omnidirectional, thus gravitational waves became the main method of establishing dark forest deterrence."
Real life has caught up on the detection side:
Gravitational waves: LIGO's first detection in 2015, Nobel Prize in Physics 2017.
Neutrinos: the 2026 Nobel Prize in Physics went to Francis Halzen for IceCube and the discovery of high-energy neutrinos from space (first spotted in 2013).
Both prizes are for detecting, not transmitting. We've only managed a toy neutrino message (Fermilab sent the word "neutrino" through 240 m of rock in 2012), and we can't make gravitational waves at all. So we're roughly where the book put humanity: we can listen, but we can barely whisper. Which one do you think we'll learn to send first?
