Unit 4: Earth-Sun Relationships Flashcards
Describe the motions of Earth in its revolution around the Sun and its rotation on its axis.
Earth revolves around the sun in an elliptical path. Earth’s orbital path has a radius of about 150 mil km. The distance to the sun varies along the orbit.
Earth rotates west-to-east on its axis. This creates night and day.
What is perihelion and aphelion?
Perihelion: the point of orbit where it is NEAREST to the sun (147.5 mil km) Occurs Jan 3.
Aphelion: point of orbit where it is FARTHEST from the sun (152.5 mil km). Occurs Jul 4.
So, perihelion happens during Northern Hemisphere winter and aphelion during summer.
What is the difference between the spring and autumnal equinoxes?
Twice a year there are 2 positions where the vertical rays of the Sun are found on the equator. These occur March 21 / Sep 23. Every parallel of latitude is half in light and half in darkness; thus, every latitude receives 12 hrs of sunlight and 12 of darkness.
What is the difference between the summer and winter solstices?
June 22 is the summer solstice. Dec 22 is the winter solstice. These are dates where the Sun stands still.
Summer: The Sun is farthest north and the length of time between Sunrise and Sunset is the longest of the year.
Winter: The Sun is farthest south and the length of time between Sunrise and Sunset is the shortest of the year.
What is the international date line and why is it necessary?
The international date line is an imaginary line along the 180th meridian. It is necessary to avoid confusion when traveling.
What is the Plane of the Ecliptic?
The Plane of the Ecliptic is a geometric plane where Earth’s orbit around the Sun lies. Seasons occur because Earth is tilted with respect to plane of the ecliptic.
What is the tilt of Earth’s axis?
23.5 degrees from perpendicular to the Plane of the Ecliptic.
What is the Tropic of Cancer and the Tropic of Capricorn?
Cancer: Northerly latitude (23.5 degrees N) where the Sun’s noontime rays strike the Earth’s surface vertically (on June 22).
Capricorn: Southerly latitude (23.5 degrees S) where the Sun’s noontime rays strike the Earth’s surface vertically (Dec 22).
Why is insolation at the South Pole, on the day of the winter solstice, greater than that received on the equator on an equinox?
The South Pole receives 24 hours of daylight on the winter solstice.
What describes the range of latitude for the vertical noon sun?
Tropic of Cancer to the Tropic of Capricorn
On which day are the vertical rays of the sun directly overhead at 23.5 North Latitude?
June Solstice
