Your brain tells huge lies

Every human is technically blind in a small circle in the middle of their vision. This blind spot exists because of a design flaw: the optic nerve passes directly through the retina, leaving a spot with no light-detecting cells.

You don't see a black hole in front of you because your brain is a master at faking data. It looks at the colors and patterns surrounding the hole and calculates a "best guess" to fill it in. You aren't seeing the world; you are seeing your brain's most likely prediction of the world.

This isn't just a passive fill-in. If you look at a wall of red stripes with your blind spot, your brain will manually draw those red stripes across the gap. It is an active, real-time hallucination.

The brain also ignores the blood vessels that sit right in front of your retina. They cast shadows on your photoreceptors all day long, but your brain filters them out as "static" so you can see through them.

If you tilt your head or move your eyes, the blind spot stays in the same relative position, yet the brain updates the lie instantly to match the new background.