Transcript Tideclipse
Tides and Eclipses • Read Your Textbook: – Chapter 3 • Homework Problems – Review Questions: 1, 2, 5, 8 – Review Problems: 1, 2, 6 – Web Inquiries: 3, 4 (1, 2 in 5th ed.) Earth and Moon • The Moon is … – – – – – 1/4 the diameter of the Earth 1/100 the mass of the Earth 1/50 the volume of the Earth 60 Earth radii away Gravitationally locked in a synchronous orbit (the far side is never seen from the earth) • To Scale... Earth Moon Same Side View • The moon’s rotation equals its revolution period. • The same side always faces earth. • 50% is always illuminated by the sun. Observational Apparitions Moon Horizon Illusion http://www.GriffithObs.org/IPSMoonIllus.html Observational Apparitions Man on the Moon? Observational Apparitions Lady on the Moon? Observational Apparitions Lady on the Moon? Observational Apparitions Toad on the Moon? Observational Apparitions Toad on the Moon? Observational Apparitions Tidal Forces • As the Earth Rotates, we are carried into and out 2 High and 2 Low Tides Every Day Tides (Weak and Strong) • Sun’s tidal influence is ~ 1/2 that of the moon Strongest Tides Moon New or Full Weakest Tides Moon 1st or 3rd quarter Other Factors • Winds • Ocean Currents • Coast Line Geometry and Topography • Tides are predictable for any given location! Moon’s Orbit • Sidereal Month – Orbit – Star reference • Synodic Month – Phases – Sun reference Observing From Spaceship Earth horizon Spaceship Earth Spaceship Earth Spaceship Earth Spaceship Earth Earth Rotation Stars overhead Stars rising Stars setting Lunar Phases Lunar location with respect to the sun determines phase seen at the earth. Lunar Phases • The 3rd quarter moon rises when? • The full moon sets when? Lunar Phases • New 0.00 • 1st Quarter 0.25 • Full 0.50 • 3rd Quarter 0.75 horizon Lunar Phases • The 3rd quarter moon rises when? – Rises at Midnight – Sets at Noon • The full moon sets when? – Sets at Sunrise (6 am) – Rises at Sunset (6 pm) Observational Geometry horizon Observational Geometry • Inner Planets – Mercury – Venus • Outer Planets – – – – – – Mars Jupiter Saturn Uranus Neptune Pluto Inner Planet Sun Earth Orbit Outer Planet Conjunctions • Inner Planets – Conjunction (Aligned with the Sun) • Inferior Sun Conjunction • Outer Planets – Conjunction (Aligned with the Sun) • Always Superior, Never Inferior Sun Conjunctions • Inner Planets – Conjunction (Aligned with the Sun) • Inferior • Superior Sun Elongation • Inner Planets – Conjunction (Aligned with the Sun) • Inferior • Superior – Greatest Elongation (Farthest From Sun) • Eastern • Western Sun Elongation • Inner Planets – Conjunction (Aligned with the Sun) • Inferior • Superior – Greatest Elongation (Farthest From Sun) • Eastern • Western Best Time to View Inner Planet Conjunction • Outer Planets – Conjunction • Aligned with the Sun • Always Superior, Never Inferior Sun Opposition • Outer Planets – Conjunction • Aligned with the Sun • Always Superior, Never Inferior – Opposition • Opposite the Sun • Earth Closest Approach Best Time to View Outer Planet Sun Eclipse Conditions New or Full Moon Moon at a “NODE” in its orbit. Lunar Eclipse • Moon in Earth’s Shadow Eclipses Are Shadows • Solar Eclipse Shadow Caught By Weather Satellite Image Solar Eclipse Geometry Total Solar Eclipse Partial Solar Eclipse Annular Solar Eclipse The Saros Cycle The repeating of eclipse geometries known to the ancients: http://sunearth.gsfc.nasa.gov/eclipse/SEsaros/SEsaros.html The Eclipse Home Page: http://sunearth.gsfc.nasa.gov/eclipse/eclipse.html