ASTR 1010 1st Edition Lecture 4Outline of Last Lecture I. Patterns in the Night SkyA. DefinitionsB. DiagramII. The Local SkyA. DefinitionsB. DiagramOutline of Current LectureI. SeasonsA. Solstices and Equinoxes II. Phases of the MoonA. EclipsesB. Diagrams- Lunar Phases- Lunar Eclipse- Solar EclipseCurrent LectureI. SeasonsThe tilt of Earth on its axis causes the seasons to change. The tilt of Earth measures 23.5˚. The axis points in the same direction all year, causing sunlight to hit certain areas of Earth more directly at different times of the year.A. Solstices and Equinoxes- The Summer Solstice occurs around June 21st. Northern Hemisphere is dipped almost directly toward the Sun.- The Winter Solstice occurs around December 21st. Northern Hemisphere is almost pointed directly away from the Sun.- The Spring Equinox occurs around March 21st. Northern Hemisphere goes from being tipped slightly away from the sun to being directly pointing at the sun.- The Fall Equinox occurs around September 22nd. Northern Hemisphere first starts to be tipped away from the sun.II. Phases of the MoonThe phase of the moon depends on its position relative to the sun as it orbits Earth. The half of the moon that is facing the sun is always illuminated, while the other half is in the dark. From earth, we see varying combinations of the illuminated and dark areas. A. Eclipses- A lunar eclipse happens when Earth’s shadow falls onto the moon.- A solar eclipse is when the moon blocks the view of the sunWe do not see an eclipse at every new and full moon because the moon’s orbit is slightlyinclined to the ecliptic plane.B. Diagrams - Lunar Phases- Lunar Eclipse- Solar
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