An interesting concept, vacuum zero-point fields (ZPF), has become, in
some circles, an uncritically accepted idea. Attempts have been made
link it with a nonzero cosmological constant (Lambda), and a number of
cosmology papers now treat Lambda as a free variable to be determined
by observation. Recent work has claimed relevance of ZPF to cosmic vo
ids. The ZPF view is that space is filled with an infinite energy dens
ity of undetectable photons, which, mysteriously, do not gravitate, bu
t which are claimed to lead to all sorts of interesting physical effec
ts. However, the ZPF seem largely to be a computational trick, in whic
h case the vacuum can be considered as simply empty. Even if one adopt
ed ZPF as having some sort of existence, any connection to Lambda is f
raught with difficulties (despite allegations to the contrary, the ZPF
is not Lorentz invariant). If this were not enough, Einstein's choice
of sign for Lambda is noted to be unphysical in the sense that it cor
responds to an imaginary graviton mass.