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Chapter 23

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Chapter 23. Sun, Earth, Moon System. EARTH. Position? Center of the universe? No, the Sun is the center of our solar system ; Earth travels around the Sun. Shape? Flat? Would you fall off if you went too far? - PowerPoint PPT Presentation
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Chapter 23 Sun, Earth, Moon System
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Page 1: Chapter 23

Chapter 23

Sun, Earth, Moon System

Page 2: Chapter 23

• Position?• Center of the universe?• No, the Sun is the center of our solar system; Earth

travels around the Sun.• Shape?

• Flat? Would you fall off if you went too far?• No, the Earth is a sphere. Spheres are round, 3-D,

and all points on the surface a equidistant (??) from the center.

• EVIDENCE: Aristotle: » Earth casts curved shadow» Appearance of approaching ships» Pictures from space probes and satellites.

Page 3: Chapter 23
Page 4: Chapter 23

Motion

• Earth rotates around an imaginary line called the axis.

• This causes day and night. • One rotation = 24 hours• Rotates 365 times in a

year

• Earth also revolves around the Sun

• Revolution = 1 year

Page 5: Chapter 23
Page 6: Chapter 23

Rotation causes…..• Day and night

– Rotates counterclockwise or East to West

• Changes in position of Sun, stars, planets– Sun rises in the East

sets in the West– Observed position

changes are due to rotation of Earth.

Page 7: Chapter 23

Revolution

One trip around the Sun!!!

** Revolution = length of a year

(Closer planets have shorter years, farther planets have longer years)

** Orbit = path the Earth takes around the Sun

* Ellipse = shape of the Earth’s orbit.

Page 8: Chapter 23

• http://www.mathsisfun.com/earth-orbit.html

Page 9: Chapter 23

Get your partner to say the following!!

• SPHERE• REVOLUTION• ROTATION• YEAR• ARISTOTLE• EAST TO WEST• ELLIPSE• ORBIT

Page 10: Chapter 23

Revolution

• Closest to Sun in January????

• Farthest in July???• Then what causes

seasons???

Page 11: Chapter 23

Tilt

• The Earth is tilted on its axis at about 23.5o

• Daylight hours are longer for the hemisphere tilted toward the SUN!!

• This hemisphere also receives more INTENSE RADIATION from the Sun.

http://astro.unl.edu/naap/motion1/animations/seasons_ecliptic.html

Page 12: Chapter 23

• http://highered.mcgraw-hill.com/sites/007299181x/student_view0/chapter2/seasons_interactive.html

Page 13: Chapter 23

Equinoxes

• Sun is directly over the equator. • Equal hours of day and night. • Neither hemisphere is pointed toward Sun• Happens twice/year

– N. Hemisphere

»Spring = March 21 or 22

(Vernal Equinox)»Autumn = September 21 or 22

(Autumnal Equinox)

Page 14: Chapter 23

Solstice

• Point at which Sun reaches greatest distance north or south of equator.

• Happens twice/year»June 21 or 22 (Summer Solstice)»MOST DAYLIGHT»December 21 or 22 (Winter Solstice)»MOST NIGHT

Page 15: Chapter 23
Page 16: Chapter 23

Get your partner to say the following:

• Sphere

• Axis

• Rotation

• Revolution

• Ellipse

• Equinox

• Solstice

Page 17: Chapter 23

Get your partner to say the following:

• 24 hours

• 365 days

• Autumn

• Orbit

• Tropic of Cancer

• June 21 or 22

• March 21 or 22


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