The energy value remained elusive until 2003, when the nuclear clock proposal triggered a multitude of experimental efforts to pin down the excited state's parameters like energy and half-life. The detection of light emitted in the direct decay of Th would significantly help to determine its energy to higher precision, but all efforts to observe the light emitted in the decay of Th were failing. The energy level was corrected to 7.6 ± 0.5 eV in 2007 (slightly revised to 7.8 ± 0.5 eV in 2009). Subsequent experiments continued to fail to observe any signal of light emitted in the direct decay, leading people to suspect the existence of a strong non-radiative decay channel. The detection of light emitted by the decay of Th was reported in 2012, and again in 2018, but the observed signals were the subject of controversy within the community.