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AIM:
The Movement of the Earth
Vocabulary:
Revolution and Rotation
Model of Solar System
Revolution of the Earth
Revolution Animation
Revolution Animation
Notice the Tilt of the Earth: It spins along the Red Line
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.
As the planets get further from the
Sun:
• the speed that the planet moves
decreases
• the time to complete an orbit increases
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.
Distance vs. Speed
PLANET
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
Pluto
Distance *
Speed (m/s)
100
200
300
400
800
1500
3000
4500
5900
45000
35000
28000
23000
12000
10000
7500
4000
3000
Distance from the Sun in millions of KM
Distance vs. Speed
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.
Rotation on its Axis
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.
Days and nights
• It is daytime for us when our part of the
planet is facing the Sun, and it is nighttime 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.
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.
Days
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.
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.