Topic 4- Motions of Earth, Moon, and Sun



Topic 4- Motions of Earth, Moon, and Sun

Remember: Heliocentric Model of the Universe

-Sun at the center

I. Rotation

-the spinning of a celestial body on an imaginary axis

A. Earth’s Rotation

1. Direction of Rotation:

West to East

2. Rate of Rotation:

360 degrees in 24 hours

360o in 24 hrs = 15o in 1 hr

B. Effects of Earth’s Rotation

1. Day and Night

[pic]

C. Apparent Motion

-the motion that an object appears to make

|Real Motion |Apparent Motion |

|Sitting at a stoplight, car next to you slowly moves backward |Your car appears to be moving forward |

|Earth rotates (spins on it’s axis) |Sun (and other stars appear to move in a circular path in the sky) |

1. Evidence of Earth’s Rotation

a. Foucault Pendulum

- when a Foucault pendulum is allowed to swing freely, it’s path will appear to change in a predictable way. (It appears that the pendulum is moving, but in fact it’s the Earth below it that is moving.)

[pic]

b. Coriolis Effect

- the tendency of all particles of matter moving at Earth’s surface to be curved away from a straight-line path.

(Curved to the right in the Northern Hemisphere, curved to the left in the Southern Hemisphere)

2. Apparent Daily Motion of the Sun

a. Earth Rotates from West to East

b. Sun appears to move in an arc from

East to West

[pic]

3. Apparent Daily Motion of Stars (at different latitudes)

a. North Pole 90o North

b. New York State 42o North

c. Equator 0o

II. Revolution

- the orbiting of a celestial body around another celestial body

A. Earth’s Revolution

1. Rate of Revolution

360o in 1 year (365 days)

360o in 365 days = ~1o in 1 day

2. Effects of Earth’s Revolution

a. Constellations change throughout the year

b. Seasons!

III. Seasons of the Year

A. Causes:

1. Earth Revolves around the Sun

2. Earth is tilted 23.5o from perpendicular to it’s orbit

3. As Earth revolves, it’s axis always points in the same direction.

B. The apparent path of the Sun changes with the seasons and with latitude (as viewed from Earth)

1. New York State 42o North Latitude

2. Equator Oo Latitude

C. Sun is directly overhead at noon changes with the Seasons (as viewed from space)

D. Length of Daylight changes with the seasons and with latitude

IV. The Moon

-a natural satellite of Earth

A. The Moon’s Revolution

Rate of Revolution

~ 1 month or 27½ days

B. The Phases of the Moon

1. Caused by the moon’s revolution around the Earth

2. The moon phases - the view that we get on Earth (the moon is always lit on 1/2 of surface but we don’t always see that half.)

3. The moon orbiting Earth (as viewed from space)

4. The moon phases (as viewed from Earth)

a. Waning – The decreasing of the moon’s visible illuminated surface.

(From Full Moon to New Moon)

b. Waxing – the increasing of the moon’s visible illuminated surface.

(From New Moon to Full Moon)

C. Eclipses

-Eclipses are named according to what looks darkened from Earth

1. Lunar Eclipse

-the moon looks darkened from Earth

(the moon is in Earth’s Shadow)

2. Solar Eclipse

- the sun looks darkened from Earth(the moon makes a shadow on an area of earth so people in that shadow can’t see the Sun)

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(like throwing a

ball off of a

merry-go-round)

Plane of Earth’s orbit

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