About dead people

The only book that ive read that the main character talks to the dead is Harry Potter and Sourcers Stone. This happened in the end of the book, and he only talked to them for a breif period of time. I think it was pretty weird being able to see you dead parents in a mirror and being able to talk to them, but its also very unrealistic. It made me think if anyone could actually talk to the dead, not like through meditating, but i think that people have seen ghosts and things like that and i wonder if its possible to actually communicate with them. I highly doubt it, but just reading about talking to the dead just made me think...