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### Author Topic: Trouton-Noble experiment and relativity  (Read 3157 times)

#### sorincosofret

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##### Trouton-Noble experiment and relativity
« on: 14/05/2008 09:03:12 »
Trouton-Noble experiment and relativity

Background and actual explanation
The Trouton-Noble experiment was performed in 1903 in an attempt to measure the velocity of the Earth’s movement through “ether” by observing the rotation of a charged capacitor. The basic consideration was that if a freely suspended parallel plate capacitor is charged at high voltage, it will turn spontaneously to minimize its total energy and will seek a stable position parallel to the direction of the motion of the Earth in the ether (the zero-point field). The idea was based on the Maxwell equations that a purely electric field in one reference frame can be magnetic in another and that the separation of these interactions depends on which reference frame is chosen for description. Specifically, a charged capacitor moving through the ether with its plates parallel to the direction of motion should possess magnetic energy as well as electrostatic energy because a moving charge is equivalent to a current.
Their idea was to look for the turning motion of a charged plate capacitor suspended at rest in the frame of the earth. The energy of a capacitor at rest in the ether, U’, is:
U' = εE'2/2
Energy in motion through ether:
U = εE2/2+μB2/2
Thus, there should be a torque tending to rotate the capacitor until the plates are aligned perpendicular to the velocity through the ether, which is the lowest energy state. Because the orientation of the capacitor with respect to the earth's motion through the ether should presumably be different at different times of the day, one may look for a rotational effect. Trouton and Noble made the prediction of this electromagnetic turning moment using the then available prerelativistic formulas for a moving charged capacitor. When the experiment was performed by Trouton and then by Trouton and Noble, they obtained a null effect. Chase repeated the experiment later, and more recently Hayden, with a more sensitive instrument, but again they reported a null result.
The Trouton–Noble experiment is generally regarded as the electrostatic equivalent of the Michelson–Morley optical experiment.
The negative results of the Trouton–Noble experiments have been explained on the basis of relativistic arguments. If the capacitor is in equilibrium for an inert observer at rest with respect to the capacitor, then it cannot appear to be rotating in a uniformly moving frame, for otherwise this effect could be used to single out the preferred frame that has no rotation.
This Trouton-Noble experiment continues to intrigue theorists and experimentalists, even in actual time (Teukolsky-1996; Hayden-1994; Cornille, Naudin, and Szames 1998, 1999).
Michel Janssen has made a detailed analysis and multitude of interpretations for this simple experiment and interested persons can find entire history and detailed mathematical approach on his webpage.
In all prerelativist and relativistic explanations, it is implicitly supposed the apparition of a magnetic field when a charge is moving relative to a referential.

Proposed explanation

Actual explanations are not able to respond at a simple question: from where the magnetic field B appear when a condenser is moving related to a referential?
Fitzgerald’s answer, more precisely, magnetic field is generated from capacitor’s kinetic energy is hilarious.
Special relativity theory in principle permit a transformation of another form of energy in magnetic energy, but again no mechanism is available.
There is no clear answer for this magnetic field apparition, and in fact, the proposed explanation start form the simple idea already formulated in atomic book, that a moving charge does not represent an electric current. Consequently a moving charge does not produce a macroscopic magnetic field. It is necessary to highlight ,,macroscopic”, because a charge (an electron as example) posses a proper magnetic moment and consequently a moving charge produce a small magnetic effect. But this magnetic effect is some order of magnitude lower then expected magnetic effect calculated with Maxwell equations. In principle, a further extension and increasing precision of this kind of experiment, will lead to a small effects due to the electrons magnetic moments and their arrangements but this does not mean a positive effect as is claimed by recent repetition of experiment made by Cornille.
The up presented experiment has nothing to do with relativity and the entire discussion was made by great theoretician physicist without connection to experimental reality and in fact all these discussion represent at least a consume o inutile papers.
Experimentally, it is a little bit difficult to observe, the existence of a magnetic effect in a short time of condenser discharge.
But there is known from the beginning of electricity a device, called van der Graff, which can produce quite enough amount of charge.
The absurdity of Trouton Noble interpretation can be very easy observed if it’s possible to show in another way that a moving charge does not produce a macroscopic magnetic effect.
A Van de Graff generator is an electrostatic machine which produces ,,electricity” using mechanic friction and permits to accumulate very high voltages on a hollow metal globe. The potential differences achieved in modern Van de Graff generators can reach 6 megavolts.
First part of experiment consists in repeating the already known experiments using Van der Graff generator, more precisely sparks or induction charge effects.
In second part of experiment a verification of capability of Van der Graff generator to produce an electric current is tested. In the absence of an electric current, practically there is no magnetic field around moving charge and Maxwell equations are without sense.
In this purpose between the generators spheres or between the high voltage sphere and an external null point a resistor and an ampermeter are connected. The device is started and the intensity of produced current is followed.
Strange enough, there is no indication of an electric current in the circuit and consequently there is no macroscopic magnetic effect around a conductor traveled by a moving charge; this is a direct proof that a charge flowing does not represent an electric current. It is very strange and inexplicable in actual electrodynamics how a Van der Graff generator can produce a voltage difference of millions of volts but is incapable of producing a microampere electric current. In the same time the generator can produce sparks and this mean there is an appreciable quantity of electric charge on the sphere.
The further extension of this electric experiment to relativity does not need any explanation ….

#### alpha

• First timers
• Posts: 4
##### Trouton-Noble experiment and relativity
« Reply #1 on: 21/08/2008 21:57:41 »
<http://arxiv.org/PS_cache/physics/pdf/0603/0603110v3.pdf>

#### lyner

• Guest
##### Trouton-Noble experiment and relativity
« Reply #2 on: 22/08/2008 15:41:21 »
Quote
It is very strange and inexplicable in actual electrodynamics how a Van der Graff generator can produce a voltage difference of millions of volts but is incapable of producing a microampere electric current.
You do talk rubbish sometimes. It's a well known, repeatable, SCHOOL demonstration to show the microamp current flowing from a VDG generator. Do you have no experience at all of real Science?

#### Bored chemist

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##### Trouton-Noble experiment and relativity
« Reply #3 on: 22/08/2008 16:22:46 »
"The Trouton-Noble experiment was performed in 1903 in an attempt to measure the velocity of the Earth’s movement through “ether” by observing the rotation of a charged capacitor. "

"The negative results of the Trouton–Noble experiments have been explained on the basis of relativistic arguments. "

"The Trouton–Noble experiment is generally regarded as the electrostatic equivalent of the Michelson–Morley optical experiment."

And they both show that the luminiferous ether doesn't exist.
so it's true to say that "The further extension of this electric experiment to relativity does not need any explanation …."

Incidentally, when the sparks happen there is a significant current. It's possible, but not easy to measure. You can calculate a rough value for it if you can find the capacitance of the charged dome of the VderG  and the inductance of the circuit through which the current flows.
The stored energy E of the capacitor is E=1/2 CV^2 and that energy ends up (largely) in the magnetic field where it's E=1/2L I^2.
Solve the equations for I and you get an upper bound to the current.

Another way to calculate the current that flows is to estimate the charge transfered by the spark (Q) and the time that it takes (T). I=Q/T

Yet another way is to calculate it from the average current (measured, as Sophie said, with a reasonably sensitive meter) and the ratio of the duration of the spark and the time interval between sparks.

In general however I think it would be better not to waste time on these measurements because the original post, as is so often the case with Sorin's ideas, makes no real sense.

#### The Naked Scientists Forum

##### Trouton-Noble experiment and relativity
« Reply #3 on: 22/08/2008 16:22:46 »