I used to host a paranormal radio show at university, which was fun (most nights) and there was a lot of talk from both sides of the argument as to why ghosts only seemed to start in the sort of late 1400s. As a man of science, I'm happy to hear both sides of the argument and while I'm open minded, I also have the common sense to realise when there's an explanation for something that many suggestible people would try and irrationalise.
Anyway, this is one of my theories on it.
As we all know, we are all made up of energy. It exists in different states across the spectrum within us, mostly as stored up potential energy that we release as kinetic energy, through both voluntary (such as walking, smiling, chewing etc) and involuntary (heartbeat, diaphragm, digestion) movement. However, our brain signals and patterns exist through electromagnetic energy, which dances through our neurons and axons as we think and recall memory. Now, nobody knows what happens when we die, the exact moment of death cannot be catalogued for obvious reasons, but after death, that energy has to go somewhere. Energy cannot be destroyed (as part of the law of conservation of energy, one of the key principles of the First Law of Thermodynamics), so it must be transferred somewhere else. It doesn't necessarily have to change it's state, although I suppose it's possible that it could.
Electromagnetic energy has some very strange properties, it has been known to create 'ghost' proteins and DNA strands in the human body, which causes enzymes to behave oddly. Therefore, it is not totally unbelievelable that it could happen on a larger scale, that the electromagnetic energy that constitutes our conciousness could leave some sort of imprint on an environment for a period of time. Obviously certain factors would stipulate how long the energy lingered for, such as temperature, air pressure and other various stimuli.
Now, something energy is not is sentient, which is why I've always doubted so called psychic mediums and some self proclaimed ghost hunters. But an echo or imprint of a person's energy could linger behind after death, almost like a photograph or a recording. Perhaps this thought energy could manifest itself as a sound at a certain frequency; certainly we know that it can in other walks of life, but it's highly doubtful anybody could have an intelligent conversation with said energy. Even if it sounded as such, it would purely be coincidence.
So yes, I think it's feasible that you could get some sort of remnant after death, but not a concious, sentient one, more a recording of that persons thought processes.
