1. AIM: The Movement of the Earth
Vocabulary:
Revolution and Rotation

2. Model of Solar System

3. Revolution of the Earth

4. Revolution Animation

5. Revolution Animation
Notice the Tilt of the Earth: It spins along the Red Line

6. Gravity and the solar system
Gravitational forces between the Sun and planets keep the planets moving in orbit around the Sun.
Without these forces, the planets would fly off into deep space.
Their orbits are slightly squashed circles called ellipses.

7. As the planets get further from the Sun:
the speed that the planet moves decreases
the time to complete an orbit increases

8. Distance vs. Speed
For example, Mercury takes just 88 Earth days to complete an orbit, while Pluto takes 248 Earth years to complete an orbit. The planets furthest from the Sun are also the coldest because they receive the least heat energy from the Sun.

9. Graph This! Distance vs. Speed PLANET Mercury 100 45000 Venus 200
Speed (m/s)
Mercury
100
45000
Venus
200
35000
Earth
300
28000
Mars
400
23000
Jupiter
800
12000
Saturn
1500
10000
Uranus
3000
7500
Neptune
4500
4000
Pluto
5900
Graph This!
Distance from the Sun in millions of KM

10. Distance vs. Speed

11. YEARS
A planet's year is the time taken for it to make one complete orbit around the Sun.
The Earth takes 365 Earth days to orbit the Sun.
Remember that different planets take different lengths of time to do this
the further from the Sun, the slower a planet travels and the longer its orbit takes.

12. Rotation on its Axis

15. Days and nights The planets spin as they orbit the Sun.
A day is the time taken for a planet to make one complete turn on its axis
Different planets take different amounts of time to do this.
An Earth day is 24 hours - it takes the Earth 24 hours to make one complete turn on its axis.

16. Days and nights
It is daytime for us when our part of the planet is facing the Sun, and it is night-time for us when our part of the planet is facing away from the Sun.
One way to remember which way the Earth turns is to remember "WE spin", which means the Earth spins from west to east.

17. Days
During the day, the Sun appears to move through the sky.
Remember that this occurs because the Earth is spinning on its axis.
The Sun does not actually move across the sky, it’s the Earth’s Rotation
The Sun appears to move from east to west. It 'rises' in the east and 'sets' in the west.
At midday we face south to see it.

18. Days

19. Night During the night, we cannot see the Sun.
But the Earth is still spinning on its axis.
This means that the stars appear to move from east to west in the sky, just as the Sun does in the day.

20. The Sun in the Sky !
When it is summer in the northern hemisphere, it is winter in the southern hemisphere. The Sun appears to be higher in the sky in the summer than it does in the winter.