I received my Ph.D. in elementary particle physics, but have since moved into astrophysics (anisotropy of the cosmic microwave background; supernovae for cosmology) and geophysics (origin of the earth’s magnetic flips, impact catastrophes, glacial cycles, red sprites). Some of the most fascinating questions of science lie not on the extremes of our ability to probe, but in the cracks between well-studied disciplines. I prefer experimental work, but will do theory when it is needed.
Lunar impacts. We have been granted several grams of lunar soil; from these we have extracted microtektites (glassy melt droplets) from distant lunar impacts. We are using Ar/Ar dating techniques to date the impacts. Our initial results showed that the cratering rate on the moon (and presumably on the Earth) gradually decreased over the past 3 billion years – but then suddenly increased just 0.4 billion years ago. This result is sufficiently surprising that we are now planning to repeat the measurement at a different lunar site.
Glacial cycles. We have been studying the cycles of the ice ages using data collected from sea-floor cores, Greenland ice, and other terrestrial sources. We have published a careful spectral analysis that shows that the “standard” Milankovitch theory for the glacial cycles is wrong, and we have proposed an alternative explanation: that the cycles are driven by extraterrestrial accretion. We are conducting several experimental programs that should elucidate the cause of the glacial cycles. We are making iridium measurements in both Greenland ice and in Pacific Ocean sea-floor cores, in order to measure variations in extraterrestrial accretion.
I recently completed a book titled “The Ice Ages and their Astronomical Origins,” coauthored by Gordon MacDonald. This book is intended to be a complete introduction for any student (or faculty member) interested in pursuing research in ancient climate.
Permian/Triassic extinctions. I am working with Walter Alvarez to try to understand what happened 250 million years ago, in the catastrophe that exceeded the more familiar Cretaceous/Tertiary event. Among other things, we are investigating the extent to which buckyballs (Carbon-60 molecules) are reliable tracers of impacts.
Nemesis search. We continue to search for the hypothesized solar companion star, using an automated telescope built by our group.
My book “Nemesis” (available in the Physics Library) describes what it was like arriving as a new graduate student at Berkeley. I also wrote a historical novel; for more details, see my web site http://muller.lbl.gov.
R. Muller, “The cosmic background radiation and the new aether drift,” Scientific American 238, 64 (1978).
R. Muller, “Radioisotope dating with accelerators,” Physics Today 32, 23 (1979).
M. Davis, P. Hut, and R. Muller, “Extinction of species by periodic comet showers,” Nature 308, 715 (1984).
R. Muller and D. Morris, “Geomagnetic reversals from impacts on the earth,” Geophysical Research Letters 13, 1177 (1986); summarized in Physics Today, 17 (February 1987).
Richard Muller, Nemesis The Death Star, Wiedenfeld and Nicholson, New York, 194 pp. (1988). Book available in the Physics Library.)
S. Perlmutter, et al., “A supernova at z = 0.458 and implications for measuring the cosmological deceleration,” Ap. J. 440, L41 (1995).
R. A. Muller and G. J. MacDonald, “Glacial cycles and orbital inclination,” Nature 377, 107 (1995).
R. A. Muller and G. J. MacDonald, “Glacial cycles and astronomical forcing,” Science 277, 215 (1997).
T. S. Culler, et al., “Lunar impact history from 40 Ar/39 Ar dating of glass spherules,” Science 287, 1785 (2000). Available online at muller.lbl.gov/papers/lunarAbstract.htm.
R. Muller and G. MacDonald, Ice Ages and Astronomical Causes: Data, Spectral Analysis, and Mechanisms, Springer-Praxis, London, 318 pp. (2000).