2004
History of Geology Award

Stephen G. Brush
University of Maryland

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Division Awards

Presented to Stephen G. Brush

 Citation by Sally Newcomb

Professor Brush has come into the history of geology from a process of inquiry that ranged from acclaimed work in physics research, through a growing interest in the origin of the major ideas of physics, to realization of the importance of geology in investigation of earth cooling and age determination in 19th and 20th century science. He earned an A.B. in physics at Harvard, and a Ph.D. in theoretical physics at Oxford University, where he was a Rhodes Scholar. His computer calculation done as a post doc at the Lawrence Radiation Laboratory showing that idealized classical plasma would exhibit a phase transition to an ordered solid state is now employed in studies of stellar and planetary structure. He is currently Distinguished University Professor of the History of Science at the University of Maryland. His publication list runs to 48 pages, so we will concentrate on the geology.

That publications list clearly shows that he had an early interest in the history of the major ideas in physics and how they progressed through time. An incomplete list of the ideas that he investigated in depth includes those about kinetic theory, thermodynamics, the equation of state, statistical mechanics, and random processes. For our interests, among other things, Dr. Brush has written a three volume history of planetary physics, published in 1996, that in many ways is a statement of his ruminations about geology, and how its ideas were advanced and received over the 19th and 20th centuries. In the second volume, Transmuted past: The age of the Earth and the evolution of the elements from Lyell to Patterson, he contrasted the methods and assumptions of humanist history and scientific geology in their common goal of studying the past. He was concerned with how the age of the earth and geological time were determined, the methods of geochronology, and cosmic evolution. He contrasted the methods of the humanities and the sciences in comparing the geologist Charles Lyell to the historian of his time, Leopold von Ranke, and the geologist Archibald Geikie to his contemporary historian, G.M. Trevelyan. This, and his further thoughts about history and geology should be required reading for all of us here. Due to his knowledge of the history of mathematical methods, Professor Brush also brings rare insight to his comments about the progression of ideas about central and volcanic heat. The third volume, Fruitful encounters: The origin of the solar system and of the moon from Chamberlin to Apollo, also contains much of interest to geologists.

It would be remiss to omit several other facets of Prof. Brush's contributions. He has been a constant and effective voice for the participation of women in science, both currently and in recognition of their historical contributions. A number of publications written over at least 35 years attest to this. In articles about the discovery and chemical history of the earth's core, he called attention to the generally little known work of the Danish seismologist, Inge Lehmann, in the discovery of the solid core within the liquid core (Am.J.Phys. 1980,48(9), 705-24; EOS 1982,63(47), 1185-88). In 1985 he published "Women in physical science: from drudges to discoverers" (The Physics Teacher, Jan. 1985, 11-19) which discussed the work of ten women, four of whom were Nobel prize winners, and six of whom made discoveries that arguably were of equal value. Prof. Brush also has been, and is, a voice for university faculty, and has served as the chairperson of the University Senate at the University of Maryland.

His concern for the proper practice of science has for many years extended to writing and testifying about the challenges of the non-science of creationism, a great concern for many of us who teach in the earth sciences, as well as those who work in evolutionary biology. In an article in The Science Teacher (1981,48(4), 29-33), "Creationism/evolution: the case against equal time" he pointed out how creationism differed from science, despite efforts to make it seem like a scientific theory. In 1982, in the Journal of Geological Education, he examined the criticisms by creationists about radiometric dating as applied to the age of the earth ("Finding the age of the earth by physics or by faith?" 30(1), 34-58). In that article, he reviewed the history of scientific work that led to our current understanding of the age of the earth. Those arguments were refined in his later books. This literature bears re-reading in our present climate of opinion about the nature of science.

Prof. Brush continues as an exemplar for the history of science including geology, and as a voice for science in general. The award from the Division of the History of Geology to him is most fitting.

  2004 History of Geology Award - Response by Stephen G. Brush

I am greatly pleased and honored by the History of Geology Division Award, and regret that I cannot be here to receive it in person.

Many of you probably started your careers with a strong interest in geology and later developed an interest in the history of that science. My own path was different: I began in physics and chemistry, then pursued a side interest in the history of those subjects, which led me to 19th century kinetic theory and thermodynamics. Here I found a fascinating problem: how can one explain the irreversible flow of heat from hot to cold, if matter is composed of atoms that obey Newton's time-reversible laws of mechanics? Newton's laws recognize no fundamental difference between past and future, yet there is obviously a difference in the natural world. Is there some mysterious "arrow of time" that points in only one direction?

The efforts of Ludwig Boltzmann and other physicists to solve this problem in the late 19th century are well known to historians of science and have become part of the collective memory of the physics profession. But something is missing from the standard account: the role of geology. The connection is revealed in Lord Kelvin's 1852 paper in which he asserted a general principle of Dissipation of Energy. Energy is always conserved but tends to be converted into less useful forms, as time marches on. As a result, he wrote, the Earth, whose surface was once too hot for life to exist, will in the future be too cold. The cooling of the Earth from its initial state as a hot fluid ball was for Kelvin the most important example of an irreversible process.

But the cooling of the Earth was not merely an application of a fundamental principle of physics. It was also an important part of the reason for proclaiming that principle. In the same year, 1852, the British geophysicist William Hopkins announced a similar (though less general) principle: terrestrial refrigeration is part of the inevitable "progressive development" of inorganic matter "towards an ultimate limit." It is hardly a coincidence that Hopkins was a mathematics tutor at Cambridge University who prepared the young Kelvin for the crucial Tripos examination.

Kelvin was convinced that the physical history of the Earth was one of the most fundamental problems in all of science. Hence his effort to estimate the age of the Earth, which led him into conflict with uniformitarian geologists, since his own estimates of 100 million years or less seemed to exclude their assumption that much longer periods were available for slow processes to form the Earth's surface.

The significant point here is not that a physicist disagreed with geologists, but that a geological problem was considered important by a physicist. More generally, I found several examples of problems in planetary science that stimulated contributions to physics, chemistry, and astronomy.

My personal hero in the history of geology is Thomas Chrowder Chamberlin. In his 50s, with an established reputation as a leader of American geology, he moved into theoretical astronomy and overturned Laplace's nebular hypothesis, because he found it incompatible with evidence from glacial formations in North America. His planetesimal hypothesis for the origin of the Earth made Kelvin's calculations irrelevant (as did the introduction of radiometric dating) and remained a significant approach in planetary cosmogony throughout most of the 20th century, although his hypothesis about the encounter of the Sun with another star has been discarded.

To sum up: the focus of my work in the history of geology has been the interactions between geology and other sciences. Today these interactions continue to be important, for example in the study of the planet Mars. Geologists are the experts who can figure out whether Martian rocks were formed by water and hence suggest the existence of life on that planet. Here is the beginning of a new story to be told by future historians of geology.