John A. Wheeler, one of America’s greatest physicists, died on Sunday at his New Jersey home from pneumonia.

Wheeler was involved in the Manhattan project that developed the world’s first atomic bomb and was one of Albert Einstein’s last collaborators.

The physicist, who was for many years a professor at Princeton University, also worked with Niels Bohr, the Nobel Prize-winning Danish scientist.

Wheeler, who gave “black holes” their name, describe the phenomenon of a star collapsing into such a dense core that light cannot escape from it.

“Laura and I are saddened by the death of John Archibald Wheeler, one of America’s greatest physicists,” President George W. Bush said Monday in a statement. “His early work with Bohr on how nuclei split apart, his vision of the possibilities of Einstein’s curved space, and his work on quantum theory demonstrated his innovation and brilliance.”

Wheeler also helped nurture the careers of other eminent physicists, including Nobel laureate Richard Feynman, who was known as the “Great Explainer” due to his skill at making complex subjects accessible.

John Wheeler was born in 1911 in Jacksonville, Florida.