Rotation&
Revolution
AstronomAstronomyy
The study of the moon, stars and other
objects in space.
AxisAxis
The imaginary line that passes
through the Earth’s center and the North
and South poles.
23.5° angle/tilt
RotationRotationEarth’s rotation, or spin, on its axis (23.5)
causes day or night.
Night & DayNight & Day• The Earth rotates on
it’s axis every 23hrs and 56 mins (almost 24 hrs)
• The sun shines on only ½ of the Earth at a time.– ½ of the Earth is
experiencing night time. While the other ½ is in daylight!
What Is Rotation?
• For every complete rotation one day has passed.
Earth spins counter-clockwise.
Sunset from space
Orbit Orbit
–Earth’s path as it revolves around the sun.
–Earth’s orbit is not circular. It revolves in an oval shape called elliptical
•Revolution or orbit– The time it takes for the earth to
make one complete revolution around the sun is called a year.
One Revolution = One Revolution = 365.25 days or One 365.25 days or One YearYear
- This is why we have a leap year every 4 - This is why we have a leap year every 4 years!years!
Revolution Causes changes of the seasons?
Seasons are caused bySeasons are caused by1. Earth’s revolution
around the Sun2. the unchanging tilt of
the Earth’s axis.
Common Misunderstandings:Common Misunderstandings:Earth’s changing distance to the
Sun does not cause seasons!
The north pole tilts towards the sun
It is Summer time in countries in the Northern Hemisphere.
It is Winter time in countries in the Southern Hemisphere.
Shadows and Seasons
• Summer– Sun is more overhead and “Direct”
which causes more of a direct (strong) path for radiation.
Direct rays on a small area are strong and cause
summer seasons.
Short Shadows
Shadows and Seasons
• Winter– Sun is more slanted and “Indirect”
which causes a less direct (weaker) path for radiation.
Slanting rays focusing on a large area are
weaker and cause winter seasons.
Longer Shadows
One more time…We have seasons because:
1. The tilt of the Earth’s axis
2. The revolution of Earth around the Sun.
As you are annotating…answer the following1. What does the orbit of the Earth
look like? (Perfect circle, “egg shaped” etc.)
2. Where are the ends of the Earth’s axis?
3. Why isn’t Earth’s orbit in a straight line?
4. About what angle is Earth tilted?
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