Comments on Vacuum Energy of Harmonic Oscillator

Unlike its classical counterpart, the ground state of a quantum harmonic oscillator yields a non-zero value which has led to a significant problem regarding the cosmological constant. We will show that since observables, including that of energy, serve as a reference frame for an observer, not only is the harmonic oscillator fluctuating at the ground level, so is the reference frame of the observer when the measurement is realized. This may provide an explanation of why vacuum energy calculated from quantum theory is non-zero, yet is not observed, because the observer is also at the same ground level of energy.