Physicist Inghram, 83, helped to determine age of the Earth

Chicago physicist Mark G. Inghram, who was a member of the research team that determined the age of the Earth at 4.5 billion years, died Monday, Sept. 29, at his home in Holland, Mich. He was 83.

Inghram and his colleagues were the first scientists to use meteorites to determine the age of the Earth. In the early 1950s, astronomers had suspected that the Earth was at least 4 billion years old, but no terrestrial materials had been found that were older than 2.5 billion years. Then, in 1953, Inghram and his colleagues showed that meteorites, which are approximately the same age as the Earth, were 4.5 billion years old. The feat earned him the J. Lawrence Smith Medal of the National Academy of Sciences in 1957.

“Inghram was a master experimentalist and an inventor and developer of mass spectrometers. These were his favorite shovels for excavating new areas,” said Gerald Wasserburg, Crafoord Laureate at the California Institute of Technology.

“His instruments were the vehicles for which whole new fields of science were created and explored. Leaders of the new fields of cosmochemistry and geochemistry were trained in his laboratories under his rigorous guidance and mentorship.”

Mass spectrometry measures the abundances of different elements and different isotopes of elementsÑatoms of the same element with different masses. Using this technique he discovered more than a dozen naturally occurring and radioactive isotopes. His wife recalls him coming home each time he discovered a new isotope and celebrating with a dance. “He was a gifted dancer, graceful and light on his feet,” said his daughter, Cheryl Inghram.

James Cronin, University Professor Emeritus in Physics and the College, first encountered Inghram when Cronin was a student at Chicago in the 1950s. “I remember Mark Inghram as a dedicated teacher stressing the importance of experimental physics,” Cronin said. When Cronin joined the Physics faculty in 1971, he found that Inghram’s enthusiasm for instruction in experimental physics remained undiminished.

“While I was away, Mark had totally rebuilt the 334 advanced laboratory. Many of the experiments built by Mark many years before were still operative and an excellent means of instruction for physics, not just experimental techniques,” Cronin said.

Inghram was born Nov. 13, 1919, in Livingston, Mont. He earned his B.A. from Olivet College in Michigan in 1939, and his Ph.D. from Chicago in 1947.

He was a physicist in the Manhattan Project at Columbia University from 1942 to 1945, and a Senior Physicist at Argonne National Laboratory from 1945 to 1947. He began his long career at the University as a physics instructor in 1947. He was appointed the Samuel Allison Distinguished Service Professor in Physics in 1969 and retired in 1985.

Inghram held several administrative positions at the University: Chairman of the Physics Department (1959-1970); acting Director of the Institute for the Study of Metals (1960-1961); Associate Dean of the Physical Sciences Division (1964-1971); Master of the Physical Sciences Collegiate Division (1981-1985); and Associate Dean of the College (1981-1985). He was a member of the National Academy of Sciences, an honor that five of his former students also attained. Inghram also was a fellow of the American Academy of Arts and Letters, the American Physical Society and the American Association for the Advancement of Science. He received the University’s Llewellyn John and Harriet Manchester Quantrell Award for Excellence in Undergraduate Teaching in 1981.

Inghram is survived by his wife, Evelyn, and two children, Cheryl Inghram, Chicago, and Mark Inghram III, Eagle River, Alaska; two sisters, Martha Truesdell and Rebecca Schultheis; and four grandchildren, Jared Inghram, Jamie Zieba Spenser, Maren Zieba and Joe Revill.