The space where the black hole is is different than the space where we can see clearly, and that difference moves the light we might otherwise see away from our eyes.
For the nerds, the change in density and motion of the spacetime around the black hole refracts the light as it travels.
For example, try and hold a clear glass of water out in front of you and look directly through it to see a light. The light gets moved and causes weird bright spots and such and there’s positions where we don’t even see the light at all – this is refraction.
All black holes emit extremely bright lights too, they’re called jets. Look em up they’re neat, we need special telescopes to even see them
Really, I’d say ‘black hole’ is a misnomer. They behave much more like whirlpools in the media of spacetime
Latest Answers