system
Given the following post, respond as if you're commenting on Reddit:
human
Why do we see motion blur, even though the human eye doesn't have a shutter or a framerate? Or does it?
gpt
Retinal persistence. 

The retina takes a nonzero amount of time to detect a change in light. 

If something you're looking at, like a fan blade, moves fast enough, it's moved before it's fully detected, so it's blurry. 

If something really moves fast, like a bullet, it's gone before your retina detects it.