1. Motions of Earth, The Moon and Planets

2. Celestial Motion Earth Centred Model
Celestial bodies move from west to east
Geocentric
Early man believed the earth was the centre of the universe
Aristotle’ s CELESTIAL SPHERES

3. Celestial Motion Sun Centred Model
Early 1500’s Copernicus proposed sun-centered model
Heliocentric
Better explained retrograde motion

4. Earth’s Motion Earth’s Rotation: Earth’s Revolution: Earth’s Tilt:
Earth spins on its axis = ROTATION
it takes Earth 24 hours to rotate
Earth’s Revolution:
Earth moves around the Sun = REVOLUTION
it takes Earth days to revolve
Earth’s Tilt:
Earth is tilted 23.5 from the vertical

5. Seasons
Solstice: when the tilt is either closest or furthest from the Sun – first day of Summer (closest tilt) first day of Winter (furthest tilt)
Equinox: when the hours of daylight = hours of darkness (first day of Spring & first day of Fall)
Seasons Animation

6. Phases of the Moon
The Moon is non-luminous as it reflects the light from the Sun.
We see different amounts of the illuminated surface of the Moon. They follow a predictable pattern called the lunar cycle.

7. Moon Phases New Moon: the Moon is dark, we cannot see
Waxing = getting larger
Waning = getting smaller
Full Moon
Quarter = half Moon
• Crescent – phases where the moon is less
than half illuminated.
• Gibbous - phases where the moon is more

8. Moon Phases Terminology • Waxing - "growing" or expanding in
illumination
• Waning - "shrinking" or decreasing in
illumination.

9. Tides – The Pull of the Moon
Tide – the rising and falling of the ocean
Gravity of moon and sun pull the Earth’s water toward them.
• This causes tides: – The rising and falling of the surface of large bodies of water

10. Tides – The Pull of the Moon
TWO high tides and TWO lows tides on Earth each day.
The time between low and high tide is approximately SIX hours.
Highest = Spring tides
Lowest = Neap Tides

11. Eclipses
Eclipse: the darkening of a celestial object due to the position of another celestial object
Lunar Eclipse: Occurs when the Earth is positioned between the Sun and the Moon.
Solar Eclipse: occurs when the Moon is positioned between the Sun and Earth