Aim: What is evidence of the 2 motions of the Earth?

Do Now: What are 2 motions of the Earth?

Homework: Study for Midterm January 28, 2008

What are the two motions of the earth?

Rotation & Revolution

How long does it take the earth to rotate?

24 hours (one day) to rotate (spin) once on its axis

How long does it take the earth to revolve around the sun?

365 ¼ Days (one year) to complete one revolution around the sun

What does the earth’s rotation cause?

As the earth rotates (counter-clockwise), part of it faces the sun and the rest of it faces away from the sun and is in darkness.

Day & Night

Why does the length of the day change throughout the year?

Due to the tilt of the earth’s axis (23.5° angle)

Example: When the North Pole is tilted toward the sun, the Northern Hemisphere has longer days and shorter nights

= SUMMER

Where does the north pole of the earth always point?

Towards Polaris

(A.K.A. The North Star)

Where does the sun and moon appear to rise and set?

•The sun, moon, & stars all appear to rise in the East and set in the West

•Due to the counter-clockwise rotation of the Earth

How does the rotation of the earth affect the motion of the winds & ocean currents?

Northern Hemisphere:

The Earth rotates Counterclockwise

Causing: winds and ocean currents to be deflected to the Right.

Southern Hemisphere:

The Earth rotates Clockwise.

Causing: winds and ocean currents to be deflected to the Left.

What is the deflection (of winds & water) at Earth’s surface called? Observe an animation of the Coriolis effect over Earth's surface.

The Coriolis Effect.

Yahoo! Video Detail for coriolis.avi

What evidence shows that the earth rotates?

1) Coriolis Effect

2) Satellite Pictures

3) Pictures from the earth of the night sky would show arcs of light, or star trails, from the motions of the earth.

What evidence shows that the earth revolves around the sun?

1) Constellations (patterns of stars) appear to move Observing the Sky: Motion of the Sun and Stars - The Night Sky

2) The Sun appears to be larger during the winter months and smaller as summer approaches.

• Perihelion – earth closest to the sun

•Aphelion – earth furthest away from the sun

LET’S REVIEW…• Why do we have day and night on earth?

• If the earth’s axis was not tilted every where on earth would have how many hours of daylight and darkness?

• Why does the sun appear to rise in the east and set in the west?

• What would happen if the earth did not rotate?

Summary…• What is the Coriolis Effect?• How do we know that the Earth

rotates?• Which motion of the earth causes day

and night?• How do we know the earth revolves

around the sun?

Aim: Why do we have seasons?

Do Now: How does the rotation of the earth affect winds in the Northern Hemisphere?

Homework: Big 8 Review Book

pgs 57-64 & Review Sheet (Study for next Friday’s Midterm) 2/2

The hemisphere that is tilted toward the sun gets:

1. more hours of sunlight

&

2. more direct sun

What causes summer?

The combination of more direct sunlight & longer days causes the Earth’s surface and atmosphere to receive more heat from the sun.

Summer and winter are not affected by the Earth’s distance from the sun.

Which day of the year gives us the most sunlight?

Summer: a) Begins in the Northern

Hemisphere on June 21

b) Called the Summer Solstice “Sun Stop”

c) The most sunlight is received on this day

d) Length of daylight varies depending on your distance from the equator

Which day of the year is the shortest?

Winter:

a) Begins in the Northern Hemisphere on Dec 21st

b) Called the Winter Solstice

c) The day of the year when the Northern Hemisphere gets the least amount of sunlight

What is an equinox?

a) 2 days of the year the sun shines directly overhead on the equator: Spring equinox is March, 21st

& Fall equinox is September, 23rd

b) During this time all places on earth have 12 hours of daylight and 12 hours of darkness.

If it is summer in the northern hemisphere, what season is it in the southern hemisphere?

The Northern and Southern hemispheres have opposite seasons.

Earth: What causes the Seasons?

SUMMARY

• During the year when is the earth closer to the sun?

• Why do we have seasons on earth?

• If the North Pole is having summer, what season is the South Pole having?

Aim: How can we explain time zones on

Earth?Do Now: What causes the seasons on earth?

Homework: Handout (17-4)

What are the time zones?

The earth is divided into 24 time zones (called standard time) WHY 24?

USA has 4 time zones:

1. EASTERN STANDARD TIME

2. CENTRAL STANDARD TIME

3. MOUNTAIN STANDARD TIME

4. PACIFIC STANDARD TIME

As you move west the time in each zone is one hour earlier than in the previous zone.

What is the international date line?

The boundary formed where the 1st and 24th time zones meet

What happens when you cross the International Date Line?

How could you travel back in time?

10 pm

9 pm8 pm

7 pm

EasternCentralMountainPacific

Practice Problem

You board a 6 PM flight from New York’s JFK Airport headed to Los Angeles’ LAX in California. The expected flight time is 5 hours. Predict the time your plane will land and explain why you chose that time.

Why are some time zones crooked?

Time Zones

NASA Math News

Summary

• Why do we have 24 time zones?• What happens when you cross the

International Date Line?• How could you travel back in time?• Why are some time zones crooked?• In your own words, explain what time

zones are.