John Wheeler worked on the development of the atom bomb
John Wheeler, the US physicist who coined the term "black hole", has died at the age of 96.
He died at his New Jersey home on 13 April of pneumonia, his daughter said.
Involved in the Manhattan project that developed the world's first atomic bomb, Wheeler was one of Albert Einstein's last collaborators.
Wheeler, who was for many years a professor at Princeton University, also worked with Niels Bohr, the Nobel Prize-winning Danish scientist.
President George W Bush said he was saddened by the death of "one of America's greatest physicists" who had "worked on projects that changed the course of history".
The expression "black hole" became a household term after he used it to describe the phenomenon of a star collapsing into such a dense core that light cannot escape from it.
He made the name stick after someone else had suggested it as a replacement for the cumbersome "gravitationally completely collapsed star" he recalled.
Wheeler also helped nurture the careers of other eminent physcists, including Nobel laureate Richard Feynman, who was known as the "Great Explainer" because of his skill at making complex subjects accessible.
"Johnny Wheeler probed far beyond the frontiers of human knowledge, asking questions that later generations of physicists would take up and solve," said Kip Thorne, a professor of theoretical physics at California Institute of Technology (Caltech) and another of Wheeler's students.
The former Princeton University professor died of pneumonia on Sunday at his home in Hightstown, New Jersey, according to his daughter Alison Wheeler Lahnston. He had been suffering from poor health for the past week.
Born in Jacksonville, Florida, in 1911, Wheeler was 21 when he earned his doctorate in physics from Johns Hopkins University. In the mid-1930s, he travelled to Denmark to study for a year with Bohr, who won his Nobel for work describing the nature of the atom.
During World War II, he joined the Manhattan Project, the effort to create an atomic bomb for the US using nuclear fission.
Unlike some colleagues who regretted their roles after the bombs were dropped on Japan, Wheeler regretted that work on the bomb had not started earlier, feeling it would have saved millions of lives - including that of his brother Joe, who died fighting in Italy.
The physicist remained haunted by a note he received in 1944 from Joe which contained two words: "Hurry up".
During the 1950s and 60s, Professor Wheeler helped transform Albert Einstein's theory of general relativity.
He later helped physicist Edward Teller develop the even more powerful hydrogen bomb.
In 1953, while traveling on a sleeper car to Washington DC, Wheeler misplaced a classified paper on the hydrogen bomb which had been in his briefcase.
He was personally reprimanded by military officials at the behest of President Eisenhower and, as a passionate believer in national defence, was personally embarrassed by the incident.
Professor Wheeler moved to the University of Texas, Austin, in 1976 because he was facing mandatory retirement at Princeton.
During this time, he returned to questions in the field of quantum mechanics that had perplexed Einstein and Bohr. He would refer to these strange laws of physics as a "great smoky dragon".
His wife of more than 70 years, Janette, died in October. He is survived by three children and several grandchildren and great-grandchildren.