The interesting feature of this form of the metric is that one can clearly see that the Schwarzschild radius, which dictates at which distance from the center of the massive body the event horizon is formed, shrinks as the Universe expands. For a comoving observer, which accompanies the Hubble flow this effect is not perceptible, as its radial coordinate is given by r ( comov ) ′ = a ( t ) r ′ , such that, for the comoving observer, r S = 2 M / r ( comov ) ′ is constant, and the Event Horizon will remain static.