Ghosts are nothing but energy. Do they have the ability to manipulate solid objects? Some yes, most no. Their energy is real and can be registered with the right equipment. Sometimes you will catch spirit orbs or even full images in a video or photograph. Usually these are harmless specters just passing through. There are times when a spirit will repeat the same action for reasons known only to them. Again this is harmless and people are frightened only because they don’t understand.
In areas where deeply traumatizing events occurred, the spirits involved will stay, possibly so we the living do not forget the sacrifice made by them and many others on that site (Wounded Knee, Trail of Tears, Gettysburg). My feeling is to leave them alone, and acknowledge their presence is keeping the area sacred. Sometimes energy from past events which occurred in a specific place lingers or echos over and over which manifests as ghosts but is only emotional energy that stuck and has changed the electromagnetic field of that area.
Do loved ones who have crossed over ever visit? Mine have. Not often, but yes, I have seen them, heard, them, felt them, or known they were sending a message. If this happens to you, don’t take it as a warning of doom. You are connected to people through energy circuits. Just because they have crossed over doesn’t mean the spiritual connection is broken. And, I believe that we continue to learn, evolve and resolve karma after we cross over, so if you didn’t have the best relationship with a relative, don’t worry about their spirit energy. It is very possible they have come to apologize, make amends or put right some unresolved issue with you. If you had a good relationship with them, why would they not stop by from time to time just to check in and say Hi?