No need say ghost la, can say soul or mind, separated with body, human eyes very limited power, uv ray also cannot see. Don't be limited by ur earth body, meditation a bit follow sifu, when u old age u can start see very interesting thing. If u cannot accept it, it's ok u are muggle. High level sifus can go to magical place while they meditate. Muggle just accept ur fate to continue stay in this dimension. Only u can enlighten urself.