  The claims that the GSI time anomaly is due to the mixing of neutrinos in the
final state of the observed electron-capture decays of hydrogen-like heavy ions
are refuted with the help of an analogy with a double-slit experiment. It is a
consequence of causality. It is shown that the GSI time anomaly may be caused
by quantum beats due to the existence of two coherent energy levels of the
decaying ion with an extremely small energy splitting (about $6\times10^{-16}
\text{eV}$) and relative probabilities having a ratio of about 1/99.
