How fast do you have to move to not be seen by the human eye?

To be effectively "invisible" to the human eye, an object would need to move at incredibly high speeds, far beyond the capabilities of typical human perception. The average human reaction time is about 0.25 seconds, which means an object would need to move more than a few meters in that time to blur into invisibility. This translates to speeds exceeding 12-15 meters per second (around 27-34 miles per hour), depending on various factors such as lighting and background. However, true invisibility in a practical sense is more about visual perception limits than just speed.