About the Author Mike Seeds was a professor of physics and astronomy at Franklin and Marshall College in Lancaster, Pennsylvania, from 1970 until his retirement in 2001. In 1989 he received F&M College�s Lindback Award for Distinguished Teaching. Mike�s love for the history of astronomy led him to create upper-level courses on archaeoastronomy and on the Copernican Revolution (�Changing Concepts of the Universe�). His research interests focused on variable stars and automation of astronomical telescopes. Mike is coauthor with Dana Backman of Horizons: Exploring the Universe, 12th edition (2012); Universe: Solar Systems, Stars, and Galaxies, 7th edition (2012); Stars and Galaxies, 8th edition (2013); The Solar System, 8th edition (2013); and ASTRO, 2nd edition (2013), all published by Cengage. He was senior consultant for creation of the 20-episode telecourse accompanying his book Horizons: Exploring the Universe. Dana Backman taught in the physics and astronomy department at Franklin and Marshall College in Lancaster, Pennsylvania, from 1991 until 2003. He invented and taught a course titled �Life in the Universe� in F&M�s interdisciplinary Foundations program. Dana now teaches introductory Solar System astronomy at Santa Clara University and introductory astronomy, astrobiology, and cosmology courses in Stanford University�s Continuing Studies Program. His research interests focus on infrared observations of planet formation, models of debris disks around nearby stars, and evolution of the solar system�s Kuiper belt. Dana is employed by the SETI Institute in Mountain View, California, as director of education and public outreach for SOFIA (the Stratospheric Observatory for Infrared Astronomy) at NASA�s Ames Research Center. Dana is coauthor with Mike Seeds of Horizons: Exploring the Universe, 14th edition (2018); Universe: Solar Systems, Stars, and Galaxies, 7th edition (2012); Stars and Galaxies, 8th edition (2013); The Solar System, 8th edition (2013); and ASTRO, 2nd edition (2013), all published by Cengage.