Earth In Space

Mr. Ahearn Earth Science

2010

Motions of Celestial Objects

• Celestial Sphere- Imaginary sphere encircling Earth on which all objects in night sky appear.

Motions of Celestial Objects

• Celestial objects appear to move circular or curved paths (east-west 15*/hr)

• Sun, moon, planet, stars

Star Paths• Stars overhead @

equator follow same path as sun.

• Stars in southern hemisphere may only be visible briefly (below celestial equator)

• Northern hemisphere move in circles around Polaris (15*/hr.)

Path of Planets

• Word planet means “wanderer”• Move 15*/hr. plus each has own

characteristic motion.• Retrograde motion

Path of Planets

Constellations

• Apparent patterns people use to mark star positions

Models of the Night Sky

• Geocentric: Earth-centered• Heliocentric: Sun-centered

Evidence for Heliocentric

1. Foucault Pendulum2. Coriolis Effect

Complete Review BookQuestions #1-16

Apparent Motions Of The Sun

• Time is based off of sun’s motion

Seasons

Northern Hemisphere-sun highest in sky June 21 (summer solstice)-sun lowest in sky December 21 (winter solstice)- Sept.22 (vernal equinox) -March 21(vernal equinox)

Latitude and Angle of the Sun

• Path of sun depends on your position• Sun is never directly over head in the

Continental USA• Can be directly overhead in the tropics

(23.5 N to 23.5 S)• Arctic and Antarctic first day of summer

sun never sets, first day of winter sun never rises

Hours of Daylight

• At equinoxes daylight last 12hrs (except @ poles.

• At equator 12 hrs of day and nights yr. round

Answer Questions #17-45 Review Book p.260

The End See you in outer space!