Re:Welsh water use dowsing rods (Score 1)

Alright, I know no one has yet delved into the real physical aspects of what you're talking about to this point, so I'd like to go ahead and give it a shot.

You're likely aware that the machinations of our entire universe are, as far as we are able to tell, based on very certain physical principles. The "laws" of nature we have found using experimentation, for which we assumed reproducibility and consistency, etc: If experiments that produce significant results disagree with a supposed theory of nature, and those experiments are verified not to be flawed in their execution, then the theory is held suspect, and a new theory must be proposed that fits both the previously acquired data as well as data from the new experiments which discredit the old theory. Of course we expect this theory to be able to predict related phenomena, etc:

The usual background. If a person does not believe that the way that science attempts to model the world is an actual reflection of how the world works, then this person believes in magic and the following question has no real meaning to him.

Assuming that this question means something to the dowser proponents:

What is the physical principle by which a dowsing rod works? I don't mean to say that you should know offhand how it works, or that anyone has ever even tested it. The great thing about science is that it has wonderful predictive qualities for phenomena that can be explained using previously constructed (and strongly supported) theories. And we have some pretty ironclad theories, either exact or at least approximate given certain conditions (using regular kinematics when relativistic effects are small despite the fact that they are always present).

Using what we know so far... how does it "detect"? One claims that the dowsing rod points down towards the object you intend to locate. This implies that there is a force that is causing a rotation of the rod in your hands. What provides this force? We know that gravitational forces will cause matter to be attracted to one another. If you had a body with an appreciable mass and connected this dowsing rod to a wall (the wall cannot move), then the body will pull on all atoms in the rod, with the net effect that the center of mass of the rod is being pulled on, assuming it is a rigid body. Depending on the type of support used to anchor the rod to the wall, a torque will be present if the center of mass of the rod is not on the axis of rotation, which it wouldn't be. We know that much.

When the dowsing rod in a real world situation bends down towards the object you wish to find, what causes it? You might say, perhaps, that the object you wish to find is more dense than the surrounding dirt that is present in much of the ground, so there is more mass present the same distance from you, so when you approach the rock the force of the rock on your rod is greater and then some stuff happens. But the difference is incredibly minute. Even if the rock were 10 times as dense as the dirt:

F = Gm1m2/r^2, where m1 and m2 are the masses of the two objects you wish to find the gravitational force for, r is the distance between them, and G is a constant. This works for point particles.

Another concept of physics is the notion that if you have a homogeneously dense object, then the force felt by any other object is equal to having all the mass in the sphere concentrated at the center of volume. This lets us deal with gravitation for objects that are not point particles without using very much math.

So lets say you have a sphere of dirt with a mass of 10kg. In the same volume, a rock that is 10 times as dense would have a mass of 100kg. Let's say your dowsing rod weighs 2kg.

F = 6.673x10^-11 * 2kg*10kg / r^2 = 1.3346 x 10^-9 / r^2 for the dirt.

F = 6.673x10^-11 * 2kg *100kg / r^2 = 1.3346x10^-8 / r^2 for the rock.

Now, we can pick any r we want. If the rod is one meter from the sphere of rock/dirt, then we get forces of 1.3346 x 10^-9 and 1.3346x10^-8.

Not even thinking about torque, that's an awfully small amount of force. Newton's second law states that F = ma. Mass m will accelerate at a rate of a when it feels a force F. Your 2kg rod, if just floating in place, will fall towards the spheres at the following rates:

Dirt-> 6.673x10^-10 m/s^2

Rock-> 6.673x10^-9 m/s^2

To contrast, it falls towards the whole Earth at a rate of 9.81m/s^2. Of course, every little piece of the Earth contributes to that, and in general, being closer to more mass in one direction causes the force in that direction to increase, but for us it is severely swamped just by the size of the Earth. We don't consider that the force on anything is very much bigger when you're near denser parts of the surface, since they're not THAT much denser and underneath the surface it kind of starts to look a lot more uniform anyway. We don't even consider that the force on you is that much less if you're a whole mile off the surface of the Earth, considering its size (that might be useful for something, but not generally for most things).

So, your dowsing rod doesn't work via gravity.

Electromagnetism? Your rod IS made of metal, but it is electrically neutral, that's a given. It can be magnetized, though, but if by SOME mechanism an underground pipe magnetizes the rod, the rod would point a pole towards a pole on the pipe, so the pipe must be magnetic. At least, in a pipe, the water rushing through could be charged, and hence would create a magnetic field. While ions may be in your water, it isn't significant, and it wouldn't cause your pipe to become magnetic and then induce attraction from your rod. And there's nothing special about the pipe in the ground: pipes in random walls should do it to your rod too, causing it go swing wildly. "Wanting to be found" is not a physical property to separate the pipes. Pipes are pipes.

That's just a little bit of musing.

So, how do these rods work? If you accept that they work on a physical principle, do you propose that there is nothing we know from our "vaunted science" that can explain how these rods work? Does the dowsing rod invalidate our notions of physical reality and force us to propose a new theory that incorporates dowsing rods turning towards objects you want to find under the ground?

Do you propose that the "neat trick" of dowsing forces a new paradigm in physics like Einstein's relativity?

Note: I apologize if I said something wrong in the physics. It's a rant for chrissake, I was bound to screw something up.