National security hawk John Bolton served as President George W. Bush's ambassador to the United Nations from August 2005 to December 2006, and became President Donald Trump's national security adviser on April 9, 2018.
Former Vice President Joe Biden tops Democratic contenders for the 2020 election among 32 percent of Democrats, according to a June poll by Harvard CAPS/Harris. Clinton came in second with 18 percent and Sen. Bernie Sanders third with 16 percent.
In 1996, Dominique Dawes won Olympic gold with the U.S. women's gymnastics team as well as an individual bronze medal—becoming the first African American to win an individual Olympic medal in women's gymnastics.
Astronomer Edwin Hubble revolutionized the field of astrophysics. His research helped prove that the universe is expanding, and he created a classification system for galaxies that has been used for several decades.