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REVIEW The Electromagnetic Spectrum. Figure 2.5. Figure 2.6. II. Solar Energy: From Earth to Sun. Solar and Terrestrial Energy. Sun emits: 8% UV, x-ray, gamma radiation 47% visible radiation 45% infrared wavelengths. Figure 2.7. REVIEW. Distribution of Insolation.
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REVIEW The Electromagnetic Spectrum Figure 2.5 Figure 2.6
II. Solar Energy: From Earth to Sun Solar and Terrestrial Energy • Sun emits: • 8% UV, x-ray, gamma radiation • 47% visible radiation • 45% infrared wavelengths Figure 2.7
REVIEW Distribution of Insolation • Tropics receive more concentrated insolation due to the Earth’s curvature • Tropics receive 2.5X more than poles • Subsolar point
Lecture 3: The Seasons • Seasonality • Reasons for Seasons • Annual March of the Seasons • The Tides
Seasonality • Seasonal changes • Sun’s altitude – angle above horizon • Declination – location of the subsolar point • Daylength
0 The Suns Position
Reasons for Seasons • Revolution • Rotation • Tilt of Earth’s axis • Axial parallelism • Sphericity
Reasons for Seasons • Revolution • Earth revolves around the Sun • Voyage takes ? • Earth’s speed is 107,280 kmph (66,660 mph) • Rotation • Earth rotates on its axis once every ? hours • Rotational velocity at equator is 1674 kmph (1041 mph)
Revolution and Rotation Figure2.13
Reasons for Seasons • Tilt of Earth’s axis • Axis is tilted 23.5° from plane of ecliptic • Axial parallelism • Axis maintains alignment during orbit around the Sun • North pole points toward the North Star (Polaris) • Sphericity
Axial Tilt and Parallelism Figure 2.14
0 Earth-Sun Relations
Annual March of the Seasons • Winter solstice – December 21 or 22 • Subsolar point Tropic of Capricorn • Spring equinox – March 20 or 21 • Subsolar point Equator • Summer solstice – June 20 or 21 • Subsolar point Tropic of Cancer • Fall equinox – September 22 or 23 • Subsolar point Equator
The Egg and the Equinox Bad Astronomy: Only on the day of the Vernal (spring) Equinox, can you stand a raw egg on its end. Good astronomy: If you can stand a raw egg on end, it has nothing to do with the Equinox.
The Tides What are tides? Tides are periodic rises and falls of large bodies of water. What causes tides? Gravitational pull of the moon and the sun.
The Tides 1. Spring Tides 2. Neap Tides