Details about our solar system and Earth's rotation and revolution through time and space

1. Earth’s
Rotation
& Revolution
Chapter 2 , Section 1:1

2. Section Objectives
Identify what makes up the solar
system.
Describe how Earth moves in space.
Describe how Earth’s tilt, rotation, and
revolution around the sun cause the
four seasons.

3. The Solar System
Our solar system = 8 planets (including Earth) and
many smaller bodies, all orbiting the sun

4. A Tour Through the Rest of the
Solar System
Mercury Venus Earth Mars
The Big Picture - Comparing Planet and Star Sizes (2:34)

5. Disqualified: Poor Little Pluto!
FUN FACTS
 Discovered in 1930
 Since then, many other similar bodies
have been found, including at least one
asteroid - Eris - that is larger than Pluto
 In 2006, astronomers classed Pluto and
Eris as dwarf planets
 Some astronomers believe that Pluto
was once a moon of Neptune but it
somehow escaped into its own orbit.
 Technically, Pluto's name is now
134340 after being declassified as a
planet.
 Because of Pluto's irregular orbit, there
are periods of times when it is closer to
the sun than Neptune.
 What Happened to Pluto? (3:31)

6. Elliptical
Orbits
Orbit: the path a planet or other object travels as it
rotates around the solar system
Orbits have an elliptical shape
Each planet or object takes a different amount of time to
complete its orbit
Earth: 1 orbit = 365 ¼ days (1 year)
Mercury: 1 orbit = 88 days (abt 3 mos.)
Pluto: 1 orbit = 250 years

7. Two Types of
Planets
Like Earth
Mercury, Venus, and Mars (also Pluto)
Solid and small
Few or no moons
Rotate or spin slowly
Like Jupiter
Huge balls of gas
Have many moons and/or rings
Spin rapidly

8. The Sun
About 93 million miles from Earth
Made mostly of intensely hot gases - as
hot as 27 million degrees Fahrenheit!
Light and warmth from the Sun makes
life on earth possible!

9. The Sun, cont.
IInnssiiddee tthhee SSuunn ((66::1133))

10. The Earth

11. The Moon
Earth’s nearest neighbor
Orbits Earth every 30 days
Cold and rocky, no water or
atmosphere
Gives off no light
Light seen when the moon
“shines” is actually a
reflection from the sun!
First Moonwalk, 1969 (1:44)

12. Eclipses
A solar eclipse occurs
when the moon moves
between the sun and the
earth, thus completely
blocking out the sun for a
part of the planet
A lunar eclipse is when the
sun blocks the moon from
sight on earth
Solar Eclipse: Turkey,
2008 (2:22)

13. Earth’s Movement
Every planet rotates, or spins, on its axis
Axis: an imaginary line the runs through Earth’s
center between the North and South Poles
It takes 24 hours to finish a complete spin on Earth’s axis
24 hours = 1 day
As Earth spins, different parts of the planet are in light or
darkness

14. Earth’s Movement (cont.)
Earth orbits the
Sun once every
365 ¼ days.
365 days = 1 year
Every four years,
1 day is added
(¼+¼+¼+¼=1) as
Feb.29!
This is called a
leap year!
What is a Leap
Year? (3:58)

15. The Sun and the
Seasons
Earth is tilted 23 ½° (degrees) on
its axis
Seasons change as the Earth orbits
orbits around the Sun
When the Northern or Southern
Hemispheres receive DIRECT RAYS from the
Sun, they experience summer
When those hemispheres receive INDIRECT
RAYS from the Sun, they experience winter
This is why hemispheres have opposite seasons
Winter in the Northern Hemisphere = summer in the
Southern Hemisphere!
Reasons for the Seasons (2:18)

16. The Sun and Seasons (cont.)

17. Solstices and Equinoxes
Four days mark the beginning of the four
seasons: Solstices and Equinoxes (5:53)
Summer Solstice (June 21)
North Pole is tilted toward the Sun
Sun is directly over Tropic of Cancer (23 1/2˚ N)
Northern Hemisphere - longest day, shortest night
(opposite in Southern Hemisphere)
Winter Solstice (December 22)
North Pole is tilted away from the Sun
Sun is directly over Tropic of Capricorn (23 1/2˚ S)
Northern Hemisphere - shortest day, longest night
(opposite in Southern Hemisphere)
Vernal (Spring) Equinox (around March 21) and
Autumnal (Fall) Equinox (around September 23)
Day and night of equal length
Sun shines directly over the Equator

18. Any questions?