Transcript The Moon
The Earth-Moon System Moon Mass 7.3483 x 1022 kg Equatorial Radius 1737.4 km Earth Mass 5.97219 x 1024 kg Mean Radius 6371.00 km Orbital Parameters Average distance from Earth 384,400 km (0.00257 A.U.) Perigee 363,300 km Eccentricity 0.05490 Orbital Inclination to Ecliptic 5.145 degrees Sidereal Orbit Period 27.321661 Earth days Sidereal Rotation Period 27.321661 Earth days Equatorial Inclination to Orbit 6.68 degrees Origin of the Moon • Likely formed after a Mars-sized body collided with Earth • Moon formed out of the debris Phases of the Moon Phases • • • • • • Synodic month 29.53 days Sidereal Lunar Orbit 27.32 days Actual period variable – perturbations Moon and Sun both subtend ~0.5 degrees Eclipses – Lunar, Solar Occur when moon curs ecliptic, twice a year • Approximately 4 to 7 eclipses per year Total Solar Eclipse 1999 Tides in Fundy Bay Different Types of Tides Semidiurnal Mixed Tide Diurnal Tidal Forces What causes tides • Main constituent Principal Lunar Semidiurnal • 12 hr 25 min period • Slightly longer than 12 hrs due to Lunar orbit – same direction as Earth’s spin • Other effects – Sun’s gravity, inclination of Earth’s spin, moon’s orbit, variation in distances • Coastline Spring and Neap Tides