Jules Henri Poincare. b. Apr. 29, 1854, d. July 17, 1912, was one of France's greatest theoretical scientists. His contributions to mathematics, mathematical physics, and celestial mechanics were often basic, profound, and highly original. His interest in the foundations and philosophical issues of the fields in which he worked were also influential and of considerable importance, particularly in France. Poincare entered the Ecole Polytechnique in 1873 and later studied at the Ecole des Mines, from which he received his doctorate in mathematics in 1879. He accepted a professorship of mathematical physics at the Sorbonne (University of Paris) in 1881, remaining there for the rest of his life. In mathematics, Poincare can be said to have been the originator of algebraic topology and of the theory of analytic functions of several complex variables. He also made fundamental advances in the theory of Abelian functions and in algebraic geometry. Moreover, as a student of Charles Hermite, Poincare was interested in number theory; his major contribution was related to a problem in the theory of Diophantine equations.

Poincare was deeply involved in the mathematics relevant to problems of celestial mechanics, the three-body problem, and theories of light and electromagnetic waves. He is credited by many as a codiscoverer (with Albert Einstein and Hendrik Lorentz) of the special theory of relativity. He helped place celestial mechanics on a rigorous basis in two major works: New Methods of Celestial Mechanics (3 vols., 1892-99; Eng. trans., 1967) and Lecons de mecanique celeste (Lessons of Celestial Mechanics, 1905-10).

Of his most popular and philosophical writings, notice must be made of Science and Hypothesis (1901; Eng. trans., 1905), Science and Method (1908; Eng. trans., 1914), and The Value of Science (1904; Eng. trans., 1907). Joseph W. Dauben Bibliography: Bell, Eric T., Men of Mathematics (1937; repr. 1986); Dantzig, Tobias, Henri Poincare, Critic of Crisis (1954; repr. 1968); Hadamard, Jacques S., The Early Scientific Work of Henri Poincare (1922) and The Later Scientific Work of Henri Poincare (1933); Morgan, Bryan, Men and Discoveries in Mathematics (1972); Slosson, Edwin E., Major Prophets of Today (1914; repr. 1968).

Heinrich Ruldoph Hertz.The German physicist, engineer, and mathematician Heinrich Rudolph Hertz, b. Feb. 22, 1857, d. Jan. 1, 1894, was the first person to demonstrate the existence of radio waves. His chief inspiration was Herman von Helmholtz. After studying the work of James Clerk Maxwell, Hertz demonstrated in 1887 that the velocity of radio waves (also called Hertzian waves) was equal to that of light. His work ordered the field of electrodynamics, putting an end to fruitless arguments about action at a distance. The unit of frequency (one cycle per second) is named the hertz in honor of Hertz's work. J. Z. Fullmer Bibliography: Appleyard, Rollo, Pioneers of Electrical Communications (1968).

Oliver Heaviside. English mathematical physicist and electrical engineer Oliver Heaviside, b. May 13, 1850, d. Feb. 3, 1925, made important contributions to electromagnetic theory and measurement and anticipated several advanced developments in mathematics and electrical engineering. Heaviside had a brief career as a telegrapher until growing deafness forced him to retire at age 24. He then conducted private electrical research in a state of near poverty. His views on using inductance coils for improving the performance of long-distance cables, opposed at the time, ultimately proved correct. In 1901 he predicted the existence of the ionosophere, as did American scientist A. E. Kennelly at almost the same time, so that for several years that atmospheric layer was called the Kennelly-Heaviside layer. Heaviside's fame grew, and he was granted a pension and received many honors before his death. Bibliography: Nahin, P. J., Oliver Heaviside, Sage in Solitude (1987).

Edwin Hubble. "Humason assembled spectra of the nebulae and I attempted to estimate distances." So wrote Hubble of his colleague Milton Humason in 1935 by which time spectra had been obtained for over 150 nebulae. Hubble was a stern warner of using the Doppler effect for galaxies and argued against the recessional velocity interpretation of redshift, convincing Robert Millikan, 1923 recipient of the Nobel Prize for Physics and director of physics at the California Insitute of Technology, that the redshift interpretation as an expanison of the universe was probably wrong, the year before both of their deaths in 1953.

Hubble ended his book Observational Approach to Cosmology with the statement:..."if the recession factor is dropped, if redshifts are not primarily velocity-shifts, the picure is simple and plausible. There is no evidence of expansion and no restriction of time-scale, no trace of spatial curvature, and no limitation of spatial dimensions. Moreover, there is no problem of internebular material. The observable region is thoroughly homogeneous; it is too small a sample to indicate the nature of the universe at large. The univers might even be an expanding model, provide the rate of expansion, which pure theory does not specify, in inappreciable. For that matter, the universe might even be contracting."