If it's imperceptible, it's impossible to perceive with any of the senses. The world might be spinning, but it's imperceptible from your couch.
Within the word imperceptible you see the word percept, which means "the object of your perception." Like impossible, the im in imperceptible means it cannot be perceived. Imperceptible is rarely used in the absolute sense of the word — it is usually paired with almost. Horton hears the Who but the tiny sounds of the Whos were almost imperceptible to everyone else.