An element is a chemical substance made up of a particular kind of atom and hence cannot be broken down or transformed by a chemical reaction into a different element, though it can be transmuted into another element through a nuclear reaction.
Almost 40 years separate Shirley Ann Jackson's achievement, as the first African-American woman to earn a Ph.D. in theoretical high energy physics at Massachusetts Institute of Technology, and Jedidah Isler, the first African-American woman to receive a Ph.D. in Astrophysics from Yale.
Lene Vestergaard Hau Professor of Applied Physics, Harvard University Hau was the first to bring light, which moves at a constant, breakneck pace of 186,282 miles per second in a vacuum, to a screeching halt. She did it within a cloud of sodium atoms cooled to a few billionths of a degree above absolute zero.