ASTR 1110 book summary - ch.2.2

ASTR 1110 book summary - ch.2.2 - Point on the Celestial...

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Astronomy – Book Notes 2.2 The Reason for Seasons - The tilt of the Earth’s axis causes sunlight to fall differently on Earth at different times of year. - Earth’s axis – remains pointed in the same direction in space (towards Polaris) throughout the year. - Earth orbits the sun – the orientation of Earth’s axis relative to the sun changes throughout the year. - Seasons are Earth are caused only by the axis tilt and not by any change in the Earth’s distance from the sun. - Solstices and Equinoxes o Summer Solstice June 21 – First day of Summer North Hemisphere receives its most direct sunlight Has its maximum tilt toward the sun (Southern Hemisphere – receives its least direct sunlight) winter in the southern hemisphere Point on the Celestial Sphere where the ecliptic is farthest north of the celestial equator – moment in time when Sun appears at that point each year Sun directly overhead Tropic of Cancer o Winter Solstice December 21 Northern Hemisphere receives its least direct sunlight
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Unformatted text preview: Point on the Celestial Sphere where the ecliptic is farthest south of the celestial equator moment in time when Sun appears at that point each year o Spring Equinox ( vernal equinox ) March 21 (moment when) Northern Hemisphere goes from being tipped slightly away from the Sun to being tipped slightly toward the Sun. Point in Pisces on the Celestial Sphere where the ecliptic crosses the celestial equator moment in time when Sun appears at that point each year o Fall Equinox ( Autumnal Equinox ) September 22 (moment when) Northern Hemisphere first starts to be tipped away from the Sun. Point in Virgo on the Celestial Sphere where the ecliptic crosses the Celestial equator moment in time when Sun appears at that point each year-Precession gradually changes the orientation of Earths axis in space o North Star Changes: Polaris is North Star right now but a couple centuries form now will no longer be north star...
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