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?