Question

Do black holes have a direct effect on earth? If so, how?

Answer 1

Black holes are much too far from Earth to have any significant effect.

Explanation:

A black hole's gravity is all-powerful, but only within a limited distance from the center -- the Schwarzschild radius, within which light cannot escape. Beyond that distance a black hole is just like anything else having the same mass.

So a typical black hole formed from the collapse of a massive star might have a mass equal to several times our Sun or maybe several tens of solar masses, but it's many light years away -- too far away to exert much gravity on Earth. The massive black at the center of our galaxy has millions of solar masses but is tens of thousands of light years away -- so it has even less impact on Earth.