This page is an archive of former "Stamps of the Month" entries from the Homepage of Professor C. M. Lang, University of Wisconsin - Stevens Point.

 
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September, 1998 featured this pair of Danish stamps commemorating the 50th anniversary of Niels Bohr's Atomic Theory which was based on atomic hydrogen. In the theory, Bohr proposed that the electron circled or "orbited" the nucleus which consisted of a single proton. Energy could only be exchanged by having the electron move from one orbit to another; thus, the change in energy could be calculated as …

DE = E2 - E1 = hn

 The latter equality incorporates Planck's Radiation Law into the Bohr Theory. Finally, the rendition of a hydrogen atom with an elliptical orbit suggests the artist's familiarity with Sommerfeld's modification of the Theory. Here he included both a "principal and secondary quantum number" being referenced as the major and minor axes an ellipse.

Si-fra2.jpg (95605 bytes) October, 1998 stamp:  For philatelists, what is being portrayed on this stamp? For scientists, can you identify all the Syst�me International units portrayed thereon? At Paris in 1875, an international treaty on weights and measurements adopted a standard length for the meter. This stamp commemorates the 100th anniversary of that event and the international use of the metric system. Currently, the meter is defined as 1,650,763.73 wavelengths of a particular line in the emission spectrum of the element krypton (86Kr). So, there is both history and modern science presented on this beautiful stamp of France.