Download Gravitation and Tides and more Lecture notes Geometry in PDF only on Docsity! SIO15: Lecture 2 Supplement: Tides attraction of bodies due to their mass Gravitation and Tides • Moon pulls on Earth with force, Fg • Earth pulls on Moon with opposite force, -Fg • as Moon orbits, Earth’s surface is deformed -> tidal bulge • Moon orbits at 27.3 days (sidereal month) !! Example is shown for equator. Fig. 2.15 SIO15: Lecture 2 Supplement: Tides Gravitation and Tides * Earth’s surface feels the pull of the Moon on the near side more than on the far side. * On the near side, Earth bulges because forces add. * On the far side, Earth bulges because centrifugal force is greater than attraction of Moon. * At the same time, each point on Earth circles the center of mass of the Moon-Earth system (barycenter, B) once for each lunar orbit. Circular motion causes fictitious (apparent, inertial) centrifugal force, Fc, which is the same for each point. * Forces add up like vectors and deform Earth’s surface. Fig. 2.15 SIO15: Lecture 2 Supplement: Tides Change of Tides at a Specific Location geographic location of semi-diurnal, diurnal tides and mixed tides (depends on many factors, e.g. water body dimensions, coastlines, geometry of continental shelf) Fig. 2.16 SIO15: Lecture 2 Supplement: Tides The Moon, Sun and Tides at a Specific Location during a synodic month, La Jolla experiences two spring tides and two neap tides. http://tidesandcurrents.noaa.gov neap tide spring tide high tide low tide The period between Full Moons is about 29.5 days (synodic month). SIO15: Lecture 2 Supplement: Tides The Moon, Sun and Tides the Sun also pulls on Earth though the lunar (Moon) tides are stronger Spring tide: when Sun, Earth and Moon are aligned (syzygy), then Sun and Moon pull together. The different between high and low tide is then largest. This happens during Full Moon - when the Moon is on the other side of Earth - and during New Moon - when the Moon is on the same side of Earth as the Sun is. The period between Full Moons is about 29.5 days (synodic month). Fig. 2.20
