Presentation on theme: "Sun’s Path. Part I. Earth’s Rotation Review A.Proof 1.Foucault Pendulum Experiment a.Pendulum continues to swing in the same plane w/o changing direction."— Presentation transcript:
Part I. Earth’s Rotation Review A.Proof 1.Foucault Pendulum Experiment a.Pendulum continues to swing in the same plane w/o changing direction b.Change in direction is caused by the Earth turning beneath it
I. Earth’s Rotation Review B.Direction of Rotation 1.West to East a.Sun rises generally in the east C.Speed of Rotation 1.360 degrees / 24 hours = 15 deg/hr 2.Sun appears to move 15 deg/hr
Part 2. Celestial Objects A.Objects in space that show daily movement as a result of Earth’s rotation 1.Sun = 15 deg/hr 2.Moon = 15 deg/hr 3.Stars A.Star trails
Part 3. Measuring Altitude A.Maximum altitude of sun is at solar noon.
Part 4. Measuring Azimuth http://astro.unl.edu/naap/motion3/animations/sunmotions.html
Part 5. Key Dates A.Equinox (Sept 21, March 21) 1.Equal day, equal night 2.12 hrs daylight EVERYWHERE on Earth 3.Sun rises in EAST and sets in WEST 4.Sun’s direct rays are hitting the equator (sun is directly overhead) 5.Vernal Equinox – Spring, 3/21 6.Autumnal Equinox – Fall, 9/21
5. Key Dates B.Winter Solstice (Dec 21) 1.Shortest period of daylight in Northern Hemisphere, sun lowest in altitude 2.Rises and sets farther south than any other day 3.Sun’s direct rays are at 23.5º South, directly overhead at Tropic of Capricorn 4.1 st day of winter 5.24 hours of darkness North of Arctic Circle
5. Key Dates C.Summer Solstice (June 21) 1.Longest period of daylight in Northern Hemisphere, sun highest in altitude 2.Rises and sets farther north than any other day 3.Sun’s direct rays are at 23.5º North, directly overhead at Tropic of Cancer 4.1 st day of summer 5.24 hours of daylight North of Arctic Circle
Part 6. Pattern of Change Sept 21 – Dec 21 (Fall)Dec 21 – Mar 21 (Winter) Sun’s Altitude Length of Day Sunrise / Sunset Direct Ray’s of Sun Lower Shorter Moving south (SE / SW) Moving to Tropic of Capricorn (23.5 º S) Higher Longer Moving back to East and West Moving to Equator (0º)
Part 6. Pattern of Change Mar 21 – June 21(Spring)June21–Sept21 (Summer) Sun’s Altitude Length of Day Sunrise / Sunset Direct Ray’s of Sun Higher Longer Moving north (NE / NW) Moving to Tropic of Cancer (23.5 º N) Lower Shorter Moving back to East and West Moving to Equator (0º)
VII. Seasons A.Caused by the Sun’s rays striking different areas of Earth’s surface B.Reasons for the Seasons 1.Earth REVOLVES around the Sun 2.Earth’s axis is tilted 23.5º 3.Parallelism of the axis (axis stays parallel while it travels around the sun) http://astro.unl.edu/naap/motion1/animations/seasons_ecliptic.html
VII. Seasons C.Season do NOT depend on the distance from the sun – orbit is an ellipse! 1.Closest to sun (Perihelion) a.On January 4 th b.91.5 million miles 2.Farthest from Sun (Aphelion) a.On July 3 rd b.94.5 million miles
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