HISTORICAL EXPERIMENTATION

Taught in 1999 by Jed Buchwald at the Massachusetts Institute of Technology
 
 
Description
 

Historical Experiments


BULLETIN DESCRIPTION: Replication of selected historic experiments: typical experiments might be early electrometry; Colorimetry using Maxwell color circles; Fresnel, Arago experiments on the interference of polarized light; Faraday and electromagnetic induction; Hertz experiments on resonance between circuits. Reconstruction of instrumentation and experimental apparatus based on close reading of original sources. Emphasizes challenges of historiographic analysis, problems of replication and theory verification as well as principles of transducers, uncertainty analysis, data processing, and technical writing. Contrast and comparison with laboratory practices and techniques of today. 12 units, Institute Laboratory Requirement. J. Buchwald, L. Bucciarelli 


This course has two related purposes. We want students to develop an understanding of modern science's historical roots in a way that will bring out the complex relationships between theory and experiment, and, in particular, that will emphasize the hard work involved in the historical establishment of scientific facts. To that end we will use a combination of lectures with hands-on, laboratory work to bring out the skilled methods, techniques and tacit knowledge involved in the building and conduct of experiments, lessons that apply not only to historical material but also to contemporary scientific work. We will explore the meaning of the distinction between fact and theory in the sciences by linking our laboratory work with the debates and claims made historically by the original discoverers, asking such questions as whether, and in what sense, a fact is tightly bound to a specific theoretical perspective, how anomalies arise and are handled, and what sorts of conditions make historically for good data. These questions, which have their seats in the particular historical experiments that we will discuss and replicate, lead naturally to the second, related purpose of our course. We want students to think through issues concerning the sources of error, both systematic and random, that arise out of experimental situations. Questions concerning the behavior of instruments, such as their resolution, precision and accuracy, as well as the role and establishment of standards will also arise naturally out of our investigations. We will discuss questions of how laboratory reports are produced to persuade other scientists that the investigator's claims are cogent, examining how the character of laboratory reporting has changed over time. The difficult and substantial issues raised by problems of replication will inform much of our work - for example, whether a particular experiment is aimed historically at replicating a novel effect, using substantially different apparatus from that which had been used to produce the effect in the first place, or whether the experiment is intended to be a close reproduction of the original setup.

Course structure:
15 to 18 students 
three historical experiments, with 4 weeks devoted to each. 
Each session will begin with two lectures presenting historical context and relevant background information, for which the students will be given a package of reading material containing original sources as well as relevant histories. 
Laboratory work begins during the second week. We will provide a reading package containing copies of original documents, diagrams from original sources, remarks concerning appropriate materials to use, and questions to be addressed. We may, where appropriate, divide the students into two or three groups, each of which will take a different point of view concerning the issues in question. Laboratory work continues for two weeks. 
In the last week of a given session, the students will bring their results to class for discussion and analysis. 


Historical Experiments:
The list below is not complete, nor developed in particulars, but it does represent historical experiments that we think will be instructive and that can also be accomplished with reasonable facility. We do not intend to provide the students with 'kits', but rather want them to produce the relevant parts of the apparatus in much the same fashion that the original experimenters would have to have done. Naturally this won't always be possible, nor can we in all, or even many, instances use the same materials. We will ourselves construct sample devices ahead of time and do trial runs. 

1. Optics
a. Newton's early prism experiments: pass white light through prism at minimum deviation, measure elongation of spectrum, pass segments of spectrum through a second prism, determine refrangibility, use crossed prisms. 
b. Bartholin and Huygens experiments on double refraction: use calcite and early measurement techniques to explore differences from Snell's law.
c. Build a Wollaston refractometer to measure refractive indexes. Compare measurement results with indexes determined using Brewster angle measurement.
d. Explore Malus' techniques for polarization: build early polarimeter, examine with Biot et al. chromatic polarization. 
e. Fresnel diffraction: reproduce Fresnel's early techniques, explore calculation methods and limitations of early theory, move forward to integral methods and high-accuracy observations (Fresnel reached .01mm, and I think we can do this also). Could also do the "Poisson spot". 
f. Fresnel and Arago experiments on the interference of polarized light.
g. Fraunhofer's "6 lamp" spectrum-mapping technique. 
h. conical refraction: very interesting experimentally and mathematically, crucial in early wave optics. 
i. speed of light using beam-interruption methods (Foucault, later Michelson).
j. reflection of light from metals: not easy, mathematically a bit advanced, but very significant for learning limits of experimental technique. Would use an early polarimeter, 
k. optical rotation in quartz: significant in early optics, highlights phase issues, combines with experiments on phase-shifts in total internal reflection. 
l. speed of light in a moving stream of water (Foucault). 
m. Rayleigh scattering using a dust-filled chamber. 
n. colorimetry using Maxwell color circles 

2. Electricity, Magnetism, Electromagnetism, Electro-optics 
a. mid-18th century Leyden phial experiments -- issues of charge transfer and conservation. 
b. Cavendish null-experiment on the inverse square. Great experiment, nice issues of calculation, experimental limits, etc. 
c. Coulomb torsion-balance electrometer. Vexing problems, good for learning vagaries of devices. Combine with charge-density mapping of two spheres placed near one another (later calculated by Poisson). 
d. Faraday capacitor: measurement and discussion of specific inductive capacity. Requires torsion-balance electrometer. Very significant on route to field theory. 
e. Voltaic pile in original form, including methods of testing for charge production. 
f. Volta and electric quantity/intensity: origin of concept and techniques for dealing with capacitance. 
g. Ampere experiments on forces between wires connected to voltaic piles. Magnificent null-experiments, not too hard to do, much learning potential (including how to handle general bilinear force relations). Build an early "ammeter". 
h. Arago's disk: later attributed to current induction by motion (disk spinning under a suspended magnet drags magnet along). Raises many interesting issues. Good recent literature. 
i. Faraday and electromagnetic induction. Iron horsehoe, wound with wire, use early ammeter. 
j. Faraday and magnetic permeability: motions of diamagnetic and paramagnetic objects in fields, raised important questions of 'polarity' vs. field explanations.
k. Faraday effect: rotation of plane of polarization of light passing through a transparent dielectric (usually carbon disulphide). Lots of historical resonance, not too hard to do. 
l. Kerr effect: rotation of plane of polarization & production of ellipticity in reflection of plane-polarized light from surface of a magnet. Very significant historically, probably very hard to do. Uses a device that Zeeman later used for Zeeman effect. 
m. Hertz experiments on resonance between circuits: invention of resonator and oscillator. Beautiful experiments, not too hard to do. Involves use of induction coil. 
n. Hertz's experiment to show the electrodynamic effect of rapidly-changing dielectric polarization. Very nice experiment, requires rather large block of pitch however. Probably could do it with asphalt, but must be sure the substance used has very low conductivity. 
o. Hertz propagation experiments as originally performed. Easy to set up once resonator and oscillator in hand. 
p. Hertz reflection and polarization of electric wave experiments. 
q. Hall effect as originally performed. Would use different metals to probe effect's character and possible interpretations. 
r. Ohm's law using original devices and meanings. 

3. Heat and Thermodynamics 
a. Specific and latent heats using the Lavoisier-Laplace ice calorimeter. Very instructive. 
b. Experiments on the law governing adiabatic gas expansion. Very instructive since can be used to show among other things that a law now taken as a canonical implication of energy conservation can be obtained on assumption of heat conservation instead. 
c. Joule-Thomson throttling experiment, showing no temperature change without performance of work. 
d. Thomson-Thomson experiment showing lowering of melting point of ice with pressure. Important as an early implication of Carnot's claims. 

4. Dynamics, Kinematics, Pressure 
a. Conjectured Galileo inclined-plane experiment, using frets and a song for timing to determine the law relating times to distances. 
b. Chaldni figures for acoustics. 
c. Bernoulli pressure experiments - variation of pressure in flow. Needs some research since I am not certain that anyone actually did anything like this in the 18th century, at least systematically. 
d. The air-pump: construct one on 17th century 'schematics', examine various situations, including the interesting one of "anaomalous suspension", in which disks pressed hard together apparently do not separate under certain circumstances when the chamber is evacuated. Used at the time as an argument against Boyle's vacuum. 
e. vis viva, vis mortua and the measure of  'force': relation between depth of penetration of a falling object into a substratum like clay in relation to height fallen. 

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