If Earth were to be replaced by an Earth-mass black hole, almost nothing in the universe would change. It wouldn’t start sucking things up, there would be no major gravitational disturbances, nothing. All that would happen is that anything that passed through a region the size of a peanut would be absorbed into the black hole, and anything that passed nearby would be distorted. All objects have an event horizon (the surface of a black hole), but most objects are far larger than their event horizon (a black hole with Earth’s mass is about the size of a peanut). Black holes also have something called a photon sphere, where photons (light waves/particles) orbit the black hole. Finally, if you were to try and fall into a black hole (for science of course) you would experience a process known as spaghettification. Since, as you approach the black hole, the parts of your body closest to the black hole are being pulled harder by gravity than those far away, you will be stretched, slowly are first but then more quickly, until all of your body is within the event horizon. What happens then? Nobody knows. The current mathematical models used in physics cannot describe what happens within the event horizon of the black hole.