If a black hole were close enough to Earth to be seen without a telescope, it would appear as a dark spot in the sky. This is because black holes are so dense that not even light can escape their gravitational pull. The only way we would be able to see a black hole is if it were surrounded by matter that was being pulled into it. This matter would heat up and emit radiation, which we would see as a bright ring around the black hole.

The size of the ring would depend on the mass of the black hole. A black hole with the mass of the Sun would have a ring that is about the size of the Earth. A black hole with the mass of a million Suns would have a ring that is about the size of the solar system.

If a black hole were to get close enough to Earth, it would have a devastating effect on our planet. The gravitational pull of the black hole would cause our oceans to boil, the atmosphere to be ripped away, and the Earth to be pulled apart.

Fortunately, there are no known black holes that are close enough to Earth to pose a threat. The closest known black hole is about 1,000 light-years away.