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
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
Figure 2.13
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
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
The Tides
1. Spring Tides
2. Neap Tides
The Tides