The chaotic orbits of asteroids and Earth

The chaotic orbits of asteroids and Earth. Ever since Isaac Newton, astronomers and mathematicians have sought to understand the dynamics of the solar system, but even the seemingly simple case of the three-body Sun-Earth-Moon system eludes an analytical solution (see PHYSICS TODAY, January 2010, page 27). Obtaining accurate results for Earth’s motion requires numerical calculations that include not only the Sun, Moon, and other planets but also the larger asteroids such as Ceres (now considered a dwarf planet), whose mass is 1/6000 of Earth’s, and Vesta, less massive still by a factor of 4. Long-term knowledge of Earth’s position is useful for paleoclimate studies, since the changes in incident sunlight allow calibration of geological records (see PHYSICS TODAY, December 2002, page 32 ). In 2004 Jacques Laskar and colleagues at the Paris Observatory calculated Earth’s position back 40 million years, allowing calibration of the Neogene period, which began 23...