By Larry Hecht

Just as Cusa's principle of {weighing}, the balance, was the basis for progress in chemistry, leading to the 1869 discovery of the Periodic Table, Gauss's 1832 development of the magnetometer is the basis of all later discoveries in physics. This is so in a twofold sense. First, because the determination of the absolute intensity of the Earth's magnetic force, was the prerequisite for Weber's experimental proof and advancement of Ampere's nuclear-atomic hypothesis. Second, because the magnetometer embodies the principle of measurement-hypothesis.

Contrary to the claims of ignorant empiricists and positivists, no fundamental experimental truth is ever arrived at by simple observation. Hypothesis itself is the subject of all measurement in science. Building a magnetometer to measure the Earth's magnetic strength, will establish this truth for us.

Everywhere we go on the surface of the earth, a compass needle, or suspended magnet, will oscillate to the east and west of true north, at a frequency which will vary from place to place, and over time, and will also depend on the magnetic strength of the needle. If we could take the same magnetic needle simultaneously to all places on Earth, and if we could be sure its magnetic strength never weakened over time, we could have an absolute standard, against which we could measure the variations in the Earth's magnetic force. As this is not possible, a means must be devised by which a measurement with different apparatus, anywhere on the Earth's surface, at any time, can be reduced to an absolute standard. The apparatus and method for doing this, was invented by Carl Friedrich Gauss in 1832. A brief description of its construction and operation, is found on pp. 35-37 of the Fall, 1996, issue of {21st Century Science}.

It is first to be noted, that the "object" to be measured, the horizontal intensity of the Earth's magnetic strength, which Gauss designates as T, has no tangible substance. It is a "mere" idea, and, furthermore, one whose cause is, to this day, not fully understood. There is no way to walk up to it and throw a tape-measure around its waist, or to place it on a scale, or next to a measuring stick.

It is an hypothesis. But, none the less, it is measured. How? How else, but by other hypotheses! A rich lattice-work of them must be employed, and each examimed carefully for its soundness and accuracy. Once this is done, it is possible to use them, even when we know them to be flawed in some ways, for we take this into consideration, too. These include assumptions about what magnetism is, its distribution in an iron bar, the motion of a pendulum, and also, even more fundamental assumptions about seemingly obvious things, such as measurement of length, time, and mass.

When we have thought all this through, we are ready to carry out our experiment to measure hypothesis with hypothesis. First, we assess the mechanical properties of our iron bar, by suspending it, and counting its frequency of oscillation, when tapped. It is suspended by a silk thread, which has a certain resistance to twisting, which must also be measured. Then, we magnetize the bar, by stroking it with an already-magnetized object. We don't know the magnetic strength to which we bring the bar by this process, so we shall designate this magnetic strength by the unknown M. Now, we suspend the magnetized bar by the silk thread again, and count the oscillations caused by its interaction with the Earth's magnetic force. Our theorem-lattice tells us, that the frequency of these oscillations is proportional to the product of the two unknowns, M x T. By another sequence of measurement-hypothesis (described in the {21st Century}), we can determine the proportion M / T. And, by dividing one measurement by the other, the value of T is found.

The apparatus for making this determination is remarkably simple, by today's standards of machining tolerances, and could certainly be built in a home workshop, or perhaps found in the discard-pile of a university laboratory.

From 1836 to 1843, the {Magnetische Verein} (Magnetic Union), founded and run by Gauss and Weber, promoted the construction and installation of such instruments at magnetic observatories around the world. By 1840, on the basis of data so obtained, Gauss was able to calculate the probable location of the North and South magnetic Poles of the Earth. The former had been found a few years earlier by the Englishman, Captain Ross. The latter was unknown. It was a great triumph for Gauss's theory, and for the U.S.-German republican collaboration, when, in 1841, Captain Charles Wilkes, USN, located the magnetic South Pole at a point in the Antarctic Ocean, within a few degrees of the latitude and longitude Gauss had predicted. The six-ship Wilkes Expedition (1838-42), funded by the U.S. Congress, and directed by the American Philosophical Society under Alexander Dallas Bache, outdid the rival British and French expeditions in other ways as well, and the whole affair surprised and stunned the imperial powers, probably in somewhat the same way as the Soviet Sputnik achievement of the late 1950's, shocked the U.S.A.

So let us have a new Magnetic Union, this time dedicated to the establishment of a pedagogical principle: that measurement is hypothesis. A point which, once established firmly in the mind of the experimenter, is of truly revolutionary power.