If there are seperate planes of existens or universes, the properties thereof are unknown, and it can't be said if they would ever be observable or not untill s

If there are seperate planes of existens or universes, the properties thereof are unknown, and it can't be said if they would ever be observable or not untill someone finds out they are. (finding out they arent isn't possible, which up to now does make this very philosophical question i suppose)