The Reasons for the Seasons

Rotation Earth spins on axis

(imaginary line through center of Earth from North to South Pole)

Rotation is counter clockwise as seen from North Pole

Earth spins on its axis like a top

Rotation - Axis Earth tilt = 23.5°

Axis currently pointed at Polaris (the North Star)

Polaris

Rotation Earth rotates once

every 24 hrs

The rotation causes day & night

Earth’s rotation causes celestial objects to appear to move from east to west in Northern Hemisphere

Night and Day Map

Just Checking…

THINK…PAIR…SHARE

What does it mean when we say the Earth rotates?

How would you define or explain the concept of Earth’s axis?

Revolution Movement of one object around another Earth revolves around our Sun

counterclockwise Earth’s orbit is almost circular rather than oval

shaped but is still referred to as an elliptical orbit 365 ¼ days to revolve once around the Sun (~ a

year)

CPS Quiz

The imaginary line that runs through the north and south poles of the Earth is called the

A. EquatorB. AxisC. LongitudeD. Latitude

CPS Quiz – Decide weather each example is of

A. Rotation or B. Revolution The Earth spinning on it’s axis. A baseball player running

around the infield. Takes 1 year A top spinning Causes day and night. Takes 24 hours The moon circling the Earth

Location and Distance in Orbit

http://www.uwm.edu/~kahl/CoVis/Seasons/Handout available at

1. angle of Sun in the sky at a given time and latitude

2. number of hours of daylight at a given time and latitude.

Two Primary Reasons for the Seasons (on Earth)

Seasons

Seasons Northern hemisphere tilts towards

Sun = warmer (Summer)

Seasons Northern hemisphere tilts away from

Sun = cooler (winter)

Seasons In the Spring and the Fall, the tilt of

the Earth is such that the spread of sunlight shines on the Earth approximately equally

Seasons

Southern hemisphere seasons are opposite Northern hemisphere seasons

If its Winter here, then Australia is having _?_.

Solstices Occur twice yearly when the Sun is directly over

“Tropics” (23.5°N and 23.5°S Latitude) Summer Solstice is the longest day of the

year in the Northern Hemisphere (Sun directly over Tropic of Cancer-23.5°N-at noon)

Winter solstice = shortest day of the year for Northern Hemisphere (Sun directly over Tropic of Capricorn-23.5°S-at noon)

Equinox equal night & day Occurs twice each

year Half-way between

solstices noon sun directly

over equator Sun will be at its

highest point in our sky at noon but never directly overhead in Texas… why do you think this is true?

CPS Quiz – Your answer should refer to Carrollton

TX. This occurs because the Earth’s axis is tilted as it moves around the sun.

This occurs when the Northern hemisphere is tilted towards the sun.

This is when the length of day and night are equal.

The shortest and longest days of the year when the noon sun is directly overhead at 23.5 degrees.

This occurs when the Northern hemisphere is tilted away from the sun.

A. WinterB. SummerC. SolsticeD. EquinoxE. All of the

above

Based on this Night and Day Map…

• What season do you think it is in Carrollton?

• What time do you think it is in Carrollton?