system
Given the following post, respond as if you're commenting on Reddit:
human
How fast does something have to move from one point to another for a human to no longer see even the slightest blur in-between?
gpt
That depends on how bright the object is, how much contrast it has, how large it is, and so on.

There will always be light from that object hitting the eye from every place along its full path, but how much and how detectable that is depends on many parameters, not just the speed. Once the physics is fixed biologists can look at the response of the eye.