Wave a sparkler and a trail hangs in the air that the camera of physics says is never there: a single bright point, remembered. The visual system holds excitation for a fraction of a second after the stimulus goes, roughly a tenth of a second for bright sources, and rapid successive stimuli fuse into continuity. This is why film at 24 frames and displays at 60 read as motion rather than slideshow, with flicker fusion (the rate above which blinking reads as steady light) as the related threshold.
Engineers exploit the effect directly. POV displays spin a strip of LEDs and time their flashes so a floating image draws itself in the air; bicycle wheel lights and holographic-fan advertising signs are the consumer versions. Light painting does it with long camera exposures, and laser shows depend on it completely, since the “shapes” are a single dot redrawn faster than the eye can catch.
Reactive visuals inherit the principle as trails and decay: motion that leaves a fading history reads as more continuous and more musical than motion that does not, because it matches how seeing already works. Every feedback trail in a visualizer is borrowed persistence.