I believe in ghosts. It makes sense to me – the conservation of energy, electricity of the brain, ashes to ashes. It seems reasonable that sites of great trauma would have more residual humanness. In a tree-falling-in-the-woods sense I think it takes a living person to see a ghost, but I still consider them real.
I was driving up A1A, the beachside highway in Florida, one night when I was a teenager. A friend and I had taken out my mom's champagne-colored Jaguar XJS, we had the top down, our hair blowing in the warm ocean breeze, laughing and singing Ashanti, just enjoying a beautiful starry evening. The road was empty, but I glanced in the rearview and saw a dark figure in the center of the pseudo-backseat that convertibles sometimes have. I looked back and there was nothing, back at the mirror and there was nothing. I didn't say anything because my friend was the skittish type; I knew if I got her scared she'd get me scared, and we'd never sleep, and it was getting late. So I drove home, a little more quiet and cautious. We're soon getting ready for bed, washing up and winding down, and she turns to me and says, "you know, this is so weird and I'm embarrassed to even mention it, but I have been feeling this ... presence ... all night."
Assuming the general consensus is true, and ghosts are electric, it's very easy to detect them. That is to say, it's easy to detect ambient electricity levels – whether or not that electricity corresponds to a ghost is another question. An EMF detector can be made at home by wiring an antenna up as an analog input. Here's a simple Arduino circuit using a stripped piece of wire as the antenna, and an LED as the output.
int EMFpin = A1;
int EMFval, LEDval;
EMFval = analogRead(EMFpin);
Serial.print("EMFval = ");
if(EMFval > 800) Serial.print("BOO");
LEDval = map(EMFval, 0, 1024, 0, 255);
Serial.print(", LEDval = ");