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This interesting and surprising device, sometimes called the homopolar generator, is one of the more forgotten of the significant experiments in the history of physics. It is perhaps the only table-top demonstration of special relativity.

A cylindrical alnico magnet, one inch in diameter and six inches long, having its poles at the ends, with a residual magnetic induction of about one Tesla, is rotated around its axis at 1725 RPM. Brushes are positioned on the axis of rotation at one end and on the "equator" of the cylinder. While the magnet is being rotated a potential between the brushes of about 13 mV is observed. This potential reverses in sign when the direction of magnetic rotation is reversed or when the poles of the magnet are interchanged.

The description of gravitation by curved spacetime is a grand concept due to Albert Einstein. The form of his field equations for the determination of the metric coefficients for a given distribution of matter and field stress-energy is an assumption. The source term (right hand side) of these equations for the Einstein-Hilbert curvature tensor is taken to be the stress-energy tensor [] of all matter and fields except that of the gravitational field itself [].

Although the abstract rules of quantum mechanics and quantum field theory seem to be able to describe the results of quantum optics experiments, it would be highly desirable to comprehend what is actually "going on" in terms of a physical picture of quantum phenomena. Actual experimental realizations in a single manner of correlation of the Einstein-Podolsky-Rosen-Bohm type predicted for entabgled two-photon states can focus attention on this "conceptual incompleteness" of quantum mechanics.