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Harold F. Levison
Harold F. (Hal) Levison (born 1959) is an American planetary scientist specializing in planetary dynamics. He currently works at the Southwest Research Institute, Boulder, CO, Boulder, Colorado, and studies planetary orbits and their evolution through Solar System history. Levison is the Principal Investigator of the Lucy (spacecraft), ''Lucy'' mission to tour multiple Jupiter trojans, which was selected as the thirteenth mission in NASA's Discovery Program in January 2017. Among other achievements, Levison is the co-author of SWIFT (scientific software), SWIFT, a commonly used Symplectic geometry, symplectic integrator that solves planetary equations of motion for periods of billions of years. Levison argued for a distinction between what are now called dwarf planets and the other eight planets based on their inability to "Clearing the neighbourhood, clear the neighborhood around their orbits", although his proposal suggested the terms "unterplanet" and "überplanet" and used ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Philadelphia, Pennsylvania
Philadelphia, often called Philly, is the largest city in the Commonwealth of Pennsylvania, the sixth-largest city in the U.S., the second-largest city in both the Northeast megalopolis and Mid-Atlantic regions after New York City. Since 1854, the city has been coextensive with Philadelphia County, the most populous county in Pennsylvania and the urban core of the Delaware Valley, the nation's seventh-largest and one of world's largest metropolitan regions, with 6.245 million residents . The city's population at the 2020 census was 1,603,797, and over 56 million people live within of Philadelphia. Philadelphia was founded in 1682 by William Penn, an English Quaker. The city served as capital of the Pennsylvania Colony during the British colonial era and went on to play a historic and vital role as the central meeting place for the nation's founding fathers whose plans and actions in Philadelphia ultimately inspired the American Revolution and the nation's inde ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
