  One of the most ubiquitous features of quantum theories is the existence of
zero-point fluctuations in their ground states. For massive quantum fields,
these fluctuations decouple from infrared observables in ordinary field
theories. However, there is no "decoupling theorem" in Quantum Gravity, and we
recently showed that the vacuum stress fluctuations of massive quantum fields
source a red spectrum of metric fluctuations given by $\sim$ mass$^5$/frequency
in Planck units. I show that this signal is consistent with the reported
unattributed persistent noise, or "mystery" noise, in the Laser Interferometer
Gravitational-Wave Observatory (LIGO), for the Standard Model of Particle
Physics. If this interpretation is correct, then it implies that: 1) This will
be a fundamental irreducible noise for all gravitational wave interferometers,
and 2) There is no fundamental weakly-coupled massive particle heavier than
those in the Standard Model.
