  It has been recently claimed that dark energy can be (and has been) observed
in laboratory experiments by measuring the power spectrum $S_I(\omega)$ of the
noise current in a resistively shunted Josephson junction and that in new
dedicated experiments, which will soon test a higher frequency range,
$S_I(\omega)$ should show a deviation from the linear rising observed in the
lower frequency region because higher frequencies should not contribute to dark
energy. Based on previous work on theoretical aspects of the
fluctuation-dissipation theorem, we carefully investigate these issues and show
that these claims are based on a misunderstanding of the physical origin of the
spectral function $S_I(\omega)$. According to our analysis, dark energy has
never been (and will never be) observed in Josephson junctions experiments. We
also predict that no deviation from the linear rising behavior of $S_I(\omega)$
will be observed in forthcoming experiments. Our findings provide new (we
believe definite) arguments which strongly support previous criticisms.
