Post on 13-Dec-2015
Review of Time Concepts
Day – the amount of time it takes Earth to rotate once on its axis
Month – the amount of time it takes the moon to revolve around Earth one time
Year – the amount of time it takes for the Earth to revolve around the Sun one time
Earth’s Orbit
Earth’s orbit is elliptical. However, the eccentricity is so low that you might confuse it with a perfect circle!
Seasons in the Northern Hemisphere
Earth’s axis is tilted 23.5 degrees. The axis points to the North Star (Polaris).
Equinoxes and Solstices
Each marks the beginning of a new season:
Summer Solstice – longest day of the yearWinter Solstice – shortest day of the yearAutumnal Equinox – equal day and nightVernal (Spring) Equinox – equal day and night
Axial Tilt & the Seasons
The hemisphere tilted towards the Sun experiences summer (more direct solar angle, more energy absorbed, higher temperatures)
The hemisphere tilted away from the Sun experiences winter (less direct solar angle, lower energy absorption, lower temperatures)