Brian Woodahl (2022)
Brian Woodahl (2021)
Brian Woodahl (2019)
Brian Woodahl (2007)
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Office: LD 156-S, 278-9244
Class: LE 101 on Tues and Thur 10:30 - 11:45
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Syllabus (PDF). Please print and keep with your notes.
Master Schedule (PDF). Please print and keep with your notes.
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The TOTAL SOLAR ECLIPSE of 2017 (Monday, August 21st)
A solar eclipse only occurs if the New Moon is about within half a degree of the ecliptic plane (defined by the orbit path of Earth as it travels around the Sun). The Moon's orbital path, around the Earth, is (unfortunately) inclined by about 5 degrees to the ecliptic. Thus, there are only two opportunities each moonth (punning) when the Moon passes through the ecliptic. These points are called the nodes (ascending, descending). The Moon passing through a node is not sufficient, it must pass through the node during the New Moon lunar phase.
About twice a year, during an approximately 45 day window (based upon the orbital speeds of the Earth and Moon), the New Moon is close enough to a node that a solar eclipse can occur. Further complicating the motion, the Moon's orbital plane precesses relative to the ecliptic. Hence, the nodes precess around the ecliptic, completing one rotation about every 18.6 years. In addition, because the Moon's path around Earth is elliptical, during many solar eclipses the angular diameter of the Moon is not large enough to fully cover the Sun. Only when the New Moon is near a node and near perigee (i.e. closest to the Earth), does totality occur. On average, it takes about 400 years for totality to occur again at the same geographical location.
Many thanks to Ryan Bertram, who introduced me to this YouTube video (courtesy of Rob Bryanton, Canadian author) that discusses the ten possible dimensions of our universe.
Many thanks to Tim McCormick, who introduced me to this webpage that models early solar system formation.
Department of Physics, IUPUI - Updated on August 1, 2022 at 8:05 AM EDT