Everybody in here knows the answer to that. But it's good to see this kind of article on Yahoo:
Many ghost hunters believe that strong support for the existence of ghosts can be found in modern physics. Specifically, that Albert Einstein, one of the greatest scientific minds of all time, offered a scientific basis for the reality of ghosts...
In fact, the answer is very simple, and not at all mysterious. After a person dies, the energy in his or her body goes where all organisms' energy goes after death: into the environment. When a human dies, the energy stored in his or her body is released in the form of heat, and transferred into the animals that eat us (i.e., wild animals if we are left unburied, or worms and bacteria if we are interred), and the plants that absorb us. If we are cremated, the energy in our bodies is released in the form of heat and light.http://news.yahoo.com/einsteins-laws-prove-ghosts-exist-144407090.html