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Until not long ago, I was working in the drilling and infrastructure business. Some people I was working with used metal rods as a "quick and dirty" method of detecting underground wiring, before bringing in the full power Ditch Witch.

What they did was to take two metal rods (brass or copper, not sure) that are hanged on some pin so they can freely spin horizontally. The person moved it around the surface until the rods aligned with the (supposed) wiring. Surprisingly, this worked.

This is not some magical detection of water with wooden sticks, but rather light weight metals (possibly) interacting with an electromagnetic field generated by underground wires carrying electric current.

Some more info: one of the men also used this to "detect" concrete sewage pipes. I don't see why this would work. He also knew there were underground wires around, just not the exact location.

Can underground wires cause horizontal rotation of metal rods, held above the ground?

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    $\begingroup$ If anyone can come up with a rational explanation then a fortune is waiting to be made... why waste money on expensive CAT scanning machines. $\endgroup$
    – ProfRob
    Jan 17, 2015 at 23:06
  • $\begingroup$ So, see the answer below. Were these wires carrying large dc currents? $\endgroup$
    – ProfRob
    Jan 17, 2015 at 23:15

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Yes. Current running through the underground wires create a circular magnetic field along the axis of the wire. Any moving metal structure in the proximity of the magnetic field will induce a current in the metal and this will create an opposing magnetic field. The opposing magnetic fields create a torque similar to the way torque is generated in a DC motor, and this will cause the metal to rotate towards a point of equilibrium, which for the rod is when it's parallel to the wire - assuming the run of wire is also straight.

Incidentally it was the movement of current carrying wires in close proximity to one another that led to the discovery of electromotive force.

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    $\begingroup$ I probably should have added -that this might only be practical where the underground currents are large - first because of the separation that the buried depth limits, and secondly the electromotive torque has to be sufficiently large to overcome your suspension torque. $\endgroup$
    – docscience
    Jan 17, 2015 at 23:15
  • $\begingroup$ What speed do you have to move the wires at? When I've seen "dowsers" at work, they appear to be moving very slowly. Often, the "signal" they get is when the wires cross - so the example above might be somewhat less mystical. $\endgroup$
    – ProfRob
    Jan 17, 2015 at 23:17
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    $\begingroup$ A rod carrying a current would generate a magnetic field. If the rod was charged it would be a current. That doesn't seem to be the case here. Nobody seems able to demonstrate dowsing in reasonable tests. smithsonianmag.com/science-nature/debunking-dowsing-5028261 $\endgroup$
    – mmesser314
    Jan 18, 2015 at 3:09
  • $\begingroup$ @docscience is it possible to try and calculate the torque and see if it's sufficient to move the rods? $\endgroup$
    – Gimelist
    Jan 19, 2015 at 9:44
  • $\begingroup$ @mmesser314 I don't understand your comment. Can you explain? $\endgroup$
    – Gimelist
    Jan 19, 2015 at 9:45
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The phenomenon is maybe due to small disturbance in the magnetic field of earth. Rods will move the same above any area, where ground is mostly uniform but there's a small touched up patch, like a covered up ditch or a cable or drainage pipe laid down with a plough, etc.

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No, there is no scientific reason under ground wires would not cause "witching rod" to cross. Witching is a "domain" of Dowsing, a type of divination, in which resources underground are discovered.

Wikipedia details some of the experiments that demonstrate the ineffectiveness of witching (and Dowsing) methods. The results of the work typicality find witching, (and Dowsing) to be no better then random change. The Ideomotor phenomenon is likely what causes the rods to cross.

Dowsing is not scientific or effective in controlled test, however there are many anecdotal claims in support of these processes. Take this wild article from Popular Mechanics or this write in to the Guardian . It is possible in the future science will justify the processes of dowsing and witching, but until these processes can be explained they are classified as divination.

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The disturbance of the magnetic field of undisturbed land causes the polarity of the iron in the ground to change. The witching does not find the wires or pipe, but the disturbance of the magnetic field of the natural land

Even engineered compacted full material will display the same results. Polar alignment occurs immediately upon placement if the material. The ditch displaced even this material.

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