Seasons
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Transcript of Seasons
Seasons
The Zodiac throughout the Year
Example: In Winter sun in Sagittarius, Gemini at night sky; in summer sun in Gemini, Sagittarius at night sky
The Seasons• Change of seasons
is a result of the tilt of the Earth’s rotation axis with respect to the plane of the ecliptic
• Sun, moon, planets run along the ecliptic
Ecliptic horizontal, Celestial equator and Earth axis tilted
Demos
• TeacherTube video• Season apparatus• Wikipedia Icecover
What changes?
• Sun is closer to the celestial north pole in the northern summer– Therefore it is higher in the sky
• Therefore the sunlight hits us more directly– Therefore the energy deposit per unit area is higher
» Therefore the temperature goes up
– Therefore the sun is above the horizon longer• Therefore there is more sunlight per day
– Therefore the temperature goes up
Illumination Angle and Energy density
From Wikipedia
What does not change
• The direction of the Earth’s axis (still points to the CNP)
• The distance to the sun (there is a 1.7% change of the distance to the Sun, but we get closest to the Sun in early January!)
• The fact that we are about an Earth radius closer to the Sun at noon in the summer is negligible (6300km compared to 150 mill.km is 0.004%)