Earth formed like a snowball collecting material over about 100 million years, said Professor Claude Allegre of the University of Paris, before the first of his two lectures on Thursday.
Allegre spoke about the scientific perspective on the age of the earth in the Tate Lab of Physics. The lecture drew a crowd of nearly 150 students and faculty, some of whom sat in the aisles.
The presentation, titled, “The Age of the Earth,” began and ended with a tribute to Al Nier, a world-renowned scientist in physics and geology. Nier made the University his academic home until his death in 1994, with the exception of two years at Harvard and three years working on the Manhattan Project.
“[Allegre] gave a heartfelt appreciation for our debt to Al Nier and provided a sweeping summary of our current knowledge of the significance of the age of the earth,” said geology Professor Paul Weiblen, who worked with Nier.
Allegre’s work, and the work of many other faculty members at the lecture, would not have been possible without Nier’s invention, the modern mass spectrometer. Many faculty members and graduate students shared anecdotes about Nier and Allegre after the speech. Nier’s wife, Ardis, who attended the lecture and is a benefactor of it, said her husband always described himself as a “gadgeteer,” though his gadgets were very high-powered.
“I would say that Al Nier is often referred to as the University’s most distinguished scientist,” Weiblen said. “Today the University community had an opportunity to see how his fundamental work in mass spectrometry set the stage for the exciting advances that are being made in understanding the chronology of the formation of the earth and the solar system in the universe.”
With the same enthusiasm that he used to describe Nier, Allegre gave an overview of the current scientific view of the formation of the earth and the universe.
The earth began to form around 4.55 billion years ago, but at that time the earth was no more than an embryo, said Allegre. Many scientists accept the age of the earth as around 4.5 billion years, Allegre said.
“That number will stand as one of the crowning intellectual achievements of the twentieth century,” said E. Calvin Alexander, a professor of geology and geophysics specializing in isotope geochemistry.
Also around that time, the moon split off from the earth, Allegre said.
“This is the only case I know of where the daughter is older than the mother, because the moon was extracted from the earth before the earth was finished,” said Allegre.