Suppose a person sitting on the object falling into black hole were to emit signal at regular interval in his own reference frame.
These signals would reach us at infinity at progressively increasing interval of time..
As the object approaches event horizon , the timing between arrival of two signals would become infinite.
Hence we would never see an object crossing event horizon.
Now the object would fall into the black hole(and reach singularity) in finite proper time in it`s frame.
This would result into increase in the mass of the black hole. Which would change the gravity. So with respect to us although we would never see object crossing even horizon we would see an increase in the gravity.
Does it not in some sense violate causality.
We see object that has not yet fallen into blackhole abut yet there is an increase in the gravity of the black hole ?????????