How Close Can a Black Hole Be to Earth?

Did you ever wonder how dangerous being neighbors with a black hole can be? Watch the NASA video with the terrible details of one of them having its lunch! A black hole with six million times the mass of our Sun tore a star to pieces and swallowed it. This happened in the constellation Volans the flying fish at a distance of 375 million light-years from our solar system.

But what if such a monster were hiding near our cosmic border, ready to cross it at any time? how close are black holes to the earth? And at what distance can we feel safe from them?