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h1.
{excerpt}{*}Experiments* \- carefulCareful observations of constructed situations that have the ability to falsify Laws, measure parameters of the laws, or properties of physical objects.
{excerpt}Physics is an experimental science.   That means that the theory must correctly predict the result of every well-done experiment, and that many experiments are specifically done to test the theory. Null experiments are especially sensitive tests of the basic assumptions of the theory because they give no measurable effect if the theory is correct.

h3. Important Experiments in Mechanics


h5. Cavendish Experiment (give ref):

The first measurement of the universal gravitational constant, G, was made using a torsion balance.  A dumbbell was suspended by a thin fiber so that it oscillated with a period which was many minutes.  A precise measurement was made of the angular deflection of the dumbbell due to the presence of larger lead balls placed a known distance from the balls at the end of the dumbbell.

h5. Eotvos Experiment

Eotvos' experiment consisted of a torsion balance in which the  two balls constituting the dumbbell were different types of material.  If the ratio of the sun's gravitational force to the inertial mass of the two balls were not equal, the end of the balance with the higher ratio would accelerate  towards the sun.   Precision of UWash EOT_WASH group exceeds part in 10^12.  Since about 10^-4 of the mass of atoms is binding energy of the nuclei, this means that the mass resulting from E_{binding}/c^2 has equal gravitational and inertial mass to better than one part in 10^8.


h5. Tycho Brae's Measurements of Planetary Positions

These measurements of planetary angular positions, accurate to a few minutes of arc (they were made by eye, which has a resolution of severl minutes of arc), were interpreted by Kepler to give Kepler's Laws of planetary motion.  The biggest triumph of Newton's theory was proving that an inverse square gravitatioinal force directed at the sun gave elliptical orbits with one focus at the sun whose period varied as the 3/2 power of the semi-major axis of its ellipse: three ovserved facts were explained quantitatively by one assumption.

h5.  


h4.

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