Some believe that it must be an external force that guides the instruments, rather than an internal force that emanates from the person dowsing. But this doesn't explain why some dowsers don't need an instrument, they just tune in to physiological changes they feel in their body when they dowse, and let these changes guide them. The most likely explanation is that dowsing is the ability to tune in to some force that science has not yet identified. For instance, water and the items that dowsers find may have a natural magnetic, electromagnetic, or other unknown energy to which dowsers are able to attune their instruments. A fairly simple science experiment shows how moving water can cause electricity to flow.
Water flowing underground also causes some kind of electric current.
Any time electricity flows in any kind of conductor, it creates an electromagnetic field. Back in 1983, a neurophysiologist at the V.A. Medical Center in Loma Linda, California, reported observing effects from electric fields only one-millionth as strong as those formerly considered threshold levels in humans. Dowsers have frequently conducted experiments at dowsing conventions in which they passed electricity through ground, and found they could easily pick up the resulting electromagnetic energies. Scientists have identified three sensors that can pick up this electromagnetic information. Experiments have been performed in muscle testing, in which the subconscious can be programmed to cause involuntary muscles to be strong for a true statement and weak for a false statement.