1. Topic IV: Motions of the Earth, Moon and Sun

2. Learning Objectives EARTH’S MOTIONS:
Explain and demonstrate the difference between rotation and revolution.
Be able to calculate the rate of rotation and the movement of celestial objects through the sky.
Be able to explain the motion of Polaris in the sky as well as the motion of constellations.
Provide evidence for the Earth’s rotation---Focault Pendulum and Coriolis Effect specifically.
Provide evidence for Earth’s revolution---different constellations through the year, specifically

3. Learning Objectives Draw the eight phases of the moon.
Explain that the phases of the moon are caused by the moon’s revolution around the Earth.
Explain that the tides are caused the by the gravitational attraction of the moon and the sun.
Explain the difference between neap and spring tides and during which phases of the moon each occurs.
Explain the difference between lunar and solar eclipses and during which phases of the moon each can occur.
Explain why the moon rises 50 minutes later each day.

4. Apparent Motions of Celestial Objects
Motions that an object appears to make
Apparent motion of the sun:
Rises in the east and sets in the west
Apparent Motions of The Stars
Looking East:
Stars rise out of the east
Looking West:
Stars set in the west
Looking North:
Circle the north star
Looking South:
Rise in the SE and set in the SW
Star Trails

5. Apparent Motion of the Planets
Retrograde Motion:
Apparent backward motion of planets
Why does it happen:
Earth passes outer planets in orbit
Simulation

6. Apparent Motion of Earth’s Moon
Rises:
In the east
Sets:
In the west
Daily difference:
50min
Apparent Motions of the Sun
Rises:
In the east
Sets:
In the west
What are some changes that occur throughout the year?

7. Apparent Motions of the Sun Contd.
Season Date Sun Rise Sun Set Daylight hrs.
Due West
Fall
9/23
Due East
12hrs.
Winter
12/21
South of East
South of West
<12hrs.
Spring
3/21
12hrs.
Due East
Due West
Summer
>12hrs.
6/21
North of East
North of West
Solstice:
(Sun stop) sun stops increasing or decreasing in altitude. 12/21 and 6/21
Equinox:
(Equal night) 12hrs. Of light and dark all over earth. 3/21 and 9/23
What causes the seasons

8. Changes in the Altitude of the Sun at Noon
Solar noon:
Time of day when sun is highest
Where is the sun directly overhead on the following dates?
Sept. 23:
Equator
Dec. 21:
Tropic of Capricorn
Mar. 21:
Equator
Jun. 21:
Tropic of Cancer

9. Models That Help to Explain Celestial Movement
Geocentric Models:
Earth centered, planets revolve around a stationary earth.
What is good about the geocentric?
1) Explains motions of the sun and other stars
2) The church endorsed it
What was bad?
1) Didn’t explain retrograde motion
2) Didn’t explain Coriolis or Foucault
3) Models should be simple (epicycles)

10. Heliocentric Models Heliocentric Models:
Sun centered, planets rotate and revolve around a stationary sun
What is good about the heliocentric?
1) Explained retrograde motion
2) Explained Coriolis and Foucault
What was bad?
1) Said orbits were perfect circles
2) Church was against it

11. Actual Earth Movements
Rotation:
Spin of earth on its axis
Axis:
Imaginary line that goes through the poles
Does our axis tilt?
Yes at a 23.5o angle
What is the rate of rotation?
15 degrees per hour
What direction does earth rotate?
From west to east or counterclockwise from N. pole

12. Actual Earth Movements
Evidence of rotation:
Foucault pendulum
Coriolis effect

13. Actual Earth Movements
Revolution:
Going around the sun in an orbit
What is the true shape of planet orbits?
Ellipse
Formula:
Distance Between Foci
Length of Major Axis
Evidence of Revolution
1) Constellations changes
2) Diameter of the sun changes
When are we farthest from the sun?
Summer

14. Earth and Moon Motions and Time
Local time:
Time based on earth’s rotation
What can be said about local time of places on the same meridian?
They have the same local time
Local solar time:
Time based on the position of the sun
What instrument is used to measure solar time?
Sundial

15. Time Zone or Standard Time
How far apart are time zones?
15o
As you move east what happens to local time?
Gets later
Where is standard time based from?
Greenwich England
Time Zones

16. Actual Motions of Earth’s Moon
Revolution:
Period of revolution is 27 1/3 days
Moon’s orbit:
Tilted at a 5o angle
Moon Phases
How much of the moon is lit everyday?
1/2
What is the relationship between phases and time?
Cyclic
Waxing:
Bright on right and getting bigger
Phases
Waning:
Bright on left and getting smaller
Period of Revolution:
27 1/3 days
From full to full:
29 1/2
Why is the cycle time different from the period of revolution?
Moon has to catch up to earth
Cool Trick

17. Tides What causes tides? The gravitational pull of the moon High tide:
Higher than normal shoreline
Low tide:
Lower than normal shoreline
Role of the sun:
Strengthens or weakens the tides
Spring tides:
Higher tide range
Neap tides:
Lower tide range

18. Eclipses Explanation Lunar Eclipse: Earth casts a shadow on the moon
How many a year?
2-4 times per year
Why aren’t all full moons eclipses?
Tilt of moon orbit

19. Solar Eclipse Solar Eclipse: The moon blocks the light from the sun
How often:
Once every 200 years or so
Explanation
Real Life