  It is shown that if - and only if - ``parallel universes'' exist, an
electroweak vacuum that is expected to have decayed since the big bang with a
high probability might exist. It would neither necessarily render our existence
unlikely nor could it be observed. In this special case the observation of
certain combinations of Higgs-boson and top-quark masses - for which the
standard model predicts such a decay - cannot be interpreted as evidence for
new physics at low energy scales. The question of whether parallel universes
exist is of interest to our understanding of the standard model of particle
physics.
