Worlds in Collision - Four Revolutions in the Earth Sciences - page 173

Moon's mass, density, density distribution, overall shape, albedo (reflectivity), to-
pography, central peaks, and the “rays” that extend outward from the craters.
Daly no doubt hoped that his paper would meet a happier fate than his earlier
writings on continental drift, but it fared no better. Ralph Baldwin and Don Wil-
helmsgaveDalylong-overduecredit ina1992papertitled “Historical Review ofa
Long-Overlooked Paper by R. A. Daly Concerning the Origin and Early History of
the Moon.” 8 They noted how few times the paper had been cited. Today we have
the advantage of Google Scholar, which tells us that in the twenty years following
the publication of Daly's paper, only one peer-reviewed article addressed his hy-
pothesis and then only to dismiss it.
Reginald Daly died in 1957. His long-time Harvard colleague, Francis Birch,
who later held the chair of Sturges Hooper Professor of Geology that Daly had
occupied, wrote a biographical memoir of Daly for the National Academy of
Sciences. 9 In 1958, Marland Billings, another Harvard colleague, eulogized Daly
in the magazine Science . 10 Neither memorial tribute contains the words “Moon”
or “continental drift.” One could perhaps excuse the omission of Daly's theory for
the origin of the Moon, which came after he retired and was a one-off effort. But
his long defense of continental drift was surely one of the most important aspects
of his life, both scientifically and personally.
One can ponder the cost to Birch, Billings, Bucher, and others of finding out late
in life that they had been wrong about the most important discovery in the history
of geology. But one can also contemplate the personal cost to Reginald Daly of
day-to-day life in a department so dead set against continental drift that his me-
morializers would air-brush it from his life. Ursula Marvin tells a story from her
years as a graduate student in geology at Harvard in the 1940s:
Onedayin1945Iwasintheofficeofpetrologyprofessor,EsperS.Larsen,whenDalyentered,
clearly distressed: “Here I am an old man,” he said, “and I may have to give up everything I
have believed in and worked on for half of my life.” I left the room and heard nothing more.
I cannot be certain that Daly was referring to his theory of gravity-sliding, but I find it hard to
imagine what else it might have been. 11
Giant Impact
In 1974, the International Astronomical Union held a colloquium on the origin of
theMoonatCornellUniversity.Atthetime,nineyearsafterhisuncannilyaccurate
prediction of the age of Mare Tranquillitatis, Bill Hartmann was still a scientific
youngster of thirty-five. Staring intently at photographs of lunar craters had made
himawarethattheMoon,andpresumablytheotherterrestrial planets,hadsuffered