Agree with Dr. Kevorkian above. It's all in relation to where the harmonics are (ex., the harmonic where the Strat neck pickup is), and not where the nut is. Here's a little physics tutorial on guitar string harmonics. Of course, all of this only applies to the open string. When you fret, the harmonic relationships change.
http://www.physicsclassroom.com/class/s ... -Harmonics
http://www.physicsclassroom.com/class/s ... -Harmonics
