There are many evidences of spirit, if not proofs in the modern scientific sense. Spirit is willful and it is not amenable to things like being poured out of a flask or heated over a Bunsen burner. So there is no such thing as a “modern scientific experiment” upon spirit. However spirit DOES get involved in relationships as well as in filling (for good or for evil).
That would depend on what your definition is of spirit or spirits is. Many accept anything abby-normal as good or an experience in the unseen world as good or from God.