Shouldn't the torus and the latter sphere be partially transparent if they are build from motion blur ? They seems to become opaque again at some point and it feels strange to me.
However the light emitted by the moving object should be lower than the static object. So as the distance increases, the object should become darker and darker.
"Infinitely fast" being a stand-in for "sufficiently fast" and gated by the speed of light, of course.
If you're going to make up nonsense, you're not talking about physical reality you're talking about cartoons or magic and fantasy.
When something moves fast in photography it has motion blur and that spreads its coverage over a larger area. In this demo the motion blurred 'torus' and 'sphere' both get made artificially more opaque to make the animation work. You can see it happen.