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Lesson 4 The Man in the Moon Precession and Nutation Think About It… How would Earth be different if it did not have a moon? The Moon’s orbit is tilted 5°… http://earthsky.org/astronomy-essentials/what-is-the-ecliptic Precession Precession is… One full cycle of precession takes… the wobble in Earth’s rotational axis. 26,000 years! The force that causes precession is… the sideways pull from the Moon’s gravitational force on Earth. Precession… Our current north star is… Polaris In about 12,000 years, our new north star will be… Vega http://www.wwu.edu/skywise/a101_precession.html A New North Star and Our Seasons… Winters in the N. hemisphere will be… colder (Earth will be farthest from the Sun in July – our new winter!) Summers in the N. hemisphere will be… warmer (Earth will be closest to the Sun in January – our new summer!) Next slide… A New North Star and Our Seasons… http://apollo.lsc.vsc.edu/classes/met130/notes/chapter16/precession.html Nutation Small wobble in the precession of Earth’s axis. It is caused by the 5 degree tilt of the moon’s orbit from the plane of earth’s orbit around the Sun. Tides Lesson 5 Tides… Tides are… High tide… the periodic rise and fall of sea level. Highest level to which the water rises Low tide… lowest level of the water http://www.amusingplanet.com/2012/03/tides-at-bay-of-fundy.html Tides: Bay of Fundy… Low Tide High Tide http://www.srh.noaa.gov/jetstream/ocean/fundy_max.htm The Cause of Tides… Tides are caused by… The Moon and the Earth experience unbalanced gravitational and centrifugal forces due to the fact that they… orbit around their barycenter (Remember that word?!) These forces generate… the gravitational attraction among Earth, the Moon, and the Sun. tidal bulges on opposite sides of Earth. See next slide… Tides… http://mail.colonial.net/~hkaiter/Moon_Phases_Tides.html Tide Simulation: http://astro.unl.edu/classaction/animations/lunarcycles/tidesim.html The Moon and the Earth experience unbalanced gravitational and centrifugal forces due to the fact that they… orbit around their barycenter (Remember that word?!)
