Any good scam will have some fact showing behind it:
Why 7.83 Hz? It is the fundamental electromagnetic frequency (EMF) the earth resonates at (AKA the Schumann resonance):
http://en.wikipedia.org/wiki/Schumann_resonances
But then again, this doctor has done a few impromptu experiments involving (re)connecting the human body to the earths EMF:
http://www.spacedoc.net/Earthing_The_Most_Important_Health_Discovery_Ever_5
Understand, I'm not saying anything yea or nay about this, I only wish I was smart enough to
know truth. I just have a penchant for keeping up with the fringes!
I think placebo could reasonably explain the good doctor's test results.
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When I was young, I understood placebo effect to be that a person might
think he felt better, but no change actually occurred (it was just a sugar pill, after all). However, more recent research has proven positive measurable changes in the physiology of those given a placebo.
From Scientific American Mind February, 2009:
Placebo effects can arise not only from a conscious belief in a drug but also from subconscious associations between recovery and the experience of being treated—from the pinch of a shot to a doctor’s white coat. Such subliminal conditioning can control bodily processes of which we are unaware, such as immune responses and the release of hormones.
Researchers have decoded some of the biology of placebo responses, demonstrating that they stem from active processes in the brain.