LAB ON THE SUN’S PATH (Web Quest)

FUNDAMENTAL QUESTION: How does the path of the sun affect the seasons and day and night at

different latitudes throughout the earth?

Part 1: Open the animation entitled “Seasons—both views animation”

http://www3.eboard.com/boards/16/92/94/Brownstein/att-1573305/SeasonsModule_bothviews_.swf

Click on “orbit view” (bottom left)

Orient the orbit as shown below (click and drag)—to get the animation exactly like this, drag the

date bar to September 22nd, tilt the orbit until the orbit looks like the picture below. Then drag

the Earth until it is aligned like it appears below.

check the box for “subsolar” point (bottom left)

On the right side of the screen check the box for “labels”

Click on “sunlight angle”

Drag the observer until he/she is at approximately 36 °N (the latitude of North Carolina)

Slide the date bar (bottom) until it is December 21st

1. Look at the animation to the left of the screen that shows the orbit of the Earth around the Sun.

a) On Dec 21st, is the northern or southern hemisphere more lit up (and is therefore receiving more

energy)?

b) Note the angle of sunlight for the observer (shown in the bottom right window). Drag the observer

to the southern hemisphere. Which hemisphere is receiving more direct sunlight?

c) Based on your answer to 1b, which hemisphere is experiencing summer? Which is experiencing

winter?

Winter _______________________ Summer _________________________

d) Is the Earth tilted towards or away from the Sun in this position? __________________________

e) In the space to the right

Draw the Earth’s position relative to the Sun.

Draw in the tilt.

Label the North and South Poles.

Draw in the equator.

Shade in the side of the Earth that is in shadow.

2. Look at the animation that has the observer (right side of screen)

a) Change the perspective so the view is “from the Sun.” The dot represents the “vertical ray.” Where

is the vertical ray shining on Dec 21st?

b) Change the perspective back to “view from the side.” Move the observer until he/she is directly on

top of the dot. What latitude is indicated (give the name and number of the line of latitude)?

Name __________________ number _________________

c) What happened to the angle of the Sun’s rays as you moved the observer to that point?

d) Describe the Sun’s rays at this location.

3. Change the date using the red bar at the bottom of the screen. Stop the bar when the vertical ray

(the little dot) is exactly at the equator.

a) On what date does this happen? ___________ the season is?(n. hemis): ___________

b) Which location on Earth is receiving the most direct energy from the Sun? ____________

c) Move the observer to the equator. Describe the angle of the Sun’s rays at the Equator on this date.

4. Move the date bar until the date is June 21st. Look at the animation on the left.

a) On June 21st, is the northern or southern hemisphere more lit up? ____________

b) Move the observer back to 36 °N (North Carolina). Note the angle of sunlight for the observer. Drag

the observer to the southern hemisphere. Which hemisphere is receiving more direct sunlight?

c) Based on your answer to 4b, which hemisphere is experiencing summer? Which is experiencing

winter?

Winter _______________________ Summer _________________________

d) Is the Earth tilted towards or away from the Sun in this position?

e) In the space below

Draw the Earth’s position relative to the Sun.

Draw in the tilt.

Label the North and South Poles.

Draw in the equator.

Shade in the side of the Earth that is in shadow.

5. Leave the observer at 36 °N. Click on “start animation.”

a) Watch the sun’s rays in the bottom right hand corner. When are the rays striking the Earth at this

location most directly (closer to vertical)

b) When are the rays the least direct? ____________________

c) Does the tilt change as the Earth orbits the Sun? __________

d) Explain how the tilt of the Earth influences the amount of energy we receive throughout the year:

6. Move the observer to the North Pole. Click on “start animation” (if it’s not running already)

a) Watch the shadow closely. Note that for half of the year the observer is in shadow and the other

half it is in daylight. This essentially means that sunrise and sunset happen once a year at the North

Pole. Record the dates that the Sun rises and sets, and when there is total darkness at the North Pole.

Repeat this process for the South Pole.

North Pole:

Sunrise_______________ Sunset_________________ Total darkness ________________

South Pole

Sunrise _______________Sunset_________________ Total darkness ________________

b) Open up the “Length of Day” animation. Advance the date until the “shadow line crosses the North

Pole. Is the date the same as the one you listed above?

c) Set the date to December 21st. Does the sun rise on this date at the North Pole?

d) Set the date to June 21st. Does the sun set on this date at the North Pole?

e) What time of year in North Carolina results in the greatest amount of daylight?

Part 2: Sun’s Path for North Carolina (36°N) Open up the file entitled “Sun’s Motion Animation.”

http://www3.eboard.com/boards/16/92/94/Brownstein/att-1574287/sunmotions%5B1%5D.swf

When the animation is on the screen, do the following:

Maximize the screen (on an Apple, drag the screen from the bottom corner to the side of the

screen)

Set the date for December 21st.

Set the latitude for 36°N

Click the following in the boxes to the right of the screen: “show the sun’s declination angle,”

and “show stick figure and its shadow.”

“Dragging the Sun’s Disc” should be set to “time of day.”

Make sure no other boxes are clicked.

Click and drag the animation with the stick figure so the “dome” is orientated as shown in the

picture below:

Set the time of day to 12:00

December 21st

1. Click and drag the Sun towards the bottom right until it lines up exactly with the horizon—this is

sunrise.

a) What time does sunrise happen on this date? ________________________

b) What direction does the Sun rise on this date? _______________________

2. Slowly drag the Sun back towards noon until you first see a shadow (about 8am) for the observer (the

stick figure).

What direction does the shadow point? _______________

3. Continue dragging the Sun towards the noon position (do not go beyond noon).

a) What happens to the altitude of the Sun as you are doing this? _____________

b) What happens to the direction of the observer’s shadow? ____________________

c) What happens to the length of the shadow? _______________________________

d) What direction does the shadow point directly at noon? _____________________

e) What direction in the sky would the observer look to see the noontime Sun?______

4. Click and drag the globe so that you are now looking at the western horizon

a) Drag the Sun towards sunset. What time does the

Sun set on this date? ________

b) What direction does the Sun set?_____________

c) As you drag the Sun from noon until sunset, what happens to the length of the observer’s shadow?

d) What happens to the length of the shadow from noon until sunset?

March 22nd and Sept 22nd

Answer the questions below for both months (make sure you check both months before you answer the

questions). Set the time to 12:00 and orient the dome as shown in the diagram on page one of this lab:

1. Does the Sun’s path change when you change the date from March 20th to September 20th?

2. Click and drag the Sun towards the bottom right until it lines up exactly with the horizon—this is

sunrise.

a) What time does sunrise happen on this date? ________________________

b) What direction does the Sun rise on this date? _______________________

3. Slowly drag the Sun back towards noon until you first see a shadow (about 6:20am) for the observer

(the stick figure).

What direction does the shadow point? _______________

4. Continue dragging the Sun towards the noon position (do not go beyond noon).

a) What happens to the length of the shadow? __________________________

b) What direction does the shadow point directly at noon? __________________

c) What direction in the sky would the observer look to see the noontime Sun?______

5. Click and drag the globe so that you are now looking at the western horizon (as shown in the diagram

on page two of this lab)

a) Drag the Sun towards sunset. What time does the Sun set on this date? ________

b) What direction does the Sun set?_____________

6. How many hours of daylight occur on these dates? ___________________. Because of

this, these seasons are referred to as _____________________________.

June 21st:

Rotate the dome so that you are looking from the east again. Set the time to 12:00.

1. Click and drag the Sun towards the bottom right until it lines up exactly with the horizon—this is

sunrise.

a) What time does sunrise happen on this date? ________________________

b) What direction does the Sun rise on this date? _______________________

2. Slowly drag the Sun back towards noon until you first see a shadow (about 5:15am) for the observer

(the stick figure).

What direction does the shadow point? _______________

3. Continue dragging the Sun towards the noon position (do not go beyond noon).

a) What happens to the length of the shadow? __________________________

b) What direction does the shadow point directly at noon? _________________

c) What direction in the sky would the observer look to see the noontime Sun?______

4. Click and drag the globe so that you are now looking at the western horizon (as shown in the diagram

on page two of this lab)

a) Drag the Sun towards sunset. What time does the Sun set on this date? ________

b) What direction does the Sun set?_____________

Follow-up Questions:

1. Set the time to 12:00. Move the black bar to the month of January (on the bar above the clock).

Slowly drag the bar to the right until you reach December.

a) Describe what happens to the altitude of the Sun as you go from January to December:

b) During which month is the Sun:

lowest in the sky at noon? _____________ highest in the sky at noon?______________

c) During which month does the observer have:

the shortest shadow? ________________ the longest shadow? _________________

d) Explain why the shadow length has the pattern you describe above:

e) Is the Sun ever directly overhead in North Carolina?

Part 3: The Sun’s path in other locations worldwide

1. Change the latitude to 23.5 °N. Set the time to 12:00. Set the date to June 21st.

a) Does the observer have a shadow at this location on this date? What does that tell you about the

location of the Sun at noon at 23.5 °N on June 21st?

b) Rotate the dome so that you are looking directly down at the observer.

Now that you are looking directly down on the observer,

where is the noontime Sun relative to the observer?

Were you correct in your answer to 1a? _________

c) What season in the Northern Hemisphere is this?

_____________________________________

d) Why is 23.5° a significant number?

2. Set the latitude to 0°. Rotate the globe so you are looking from the east again. Keep the date at June

21st.

a) Is the Sun directly overhead on June 21st at the equator?__________

b) Go to the “month” bar and drag the black bar until the Sun’s path is directly lined up with the blue

line in the center of the dome (begin at January and drag the bar to towards December). This will

happen twice during the year.

During which months did the Sun’s path line up with the blue line? _______________

Which seasons begin on these dates? ___________________

Where is the Sun located at noon relative to the observer on these dates?__________

3. Set the latitude to 23.5° S (you will need to enter in 23.5 and then click on the box to change it from N

to S). Keep the time at 12:00. Do not change the date from the last question.

a) What direction must the observer look to see the noontime Sun? __________

b) How is this different from the Northern Hemisphere?

c) Change the date to December 21st. Rotate the globe so you are looking down on the

observer (as you did on the previous page).

Where is the noontime Sun relative to the observer on this date?

Does the observer have a shadow?

Follow up questions:

1. The “vertical ray of the Sun” refers to when the Sun is directly overhead. For the dates listed below,

identify where the Sun is directly overhead at noon and the season in the Northern Hemisphere for

those dates:

December 21st: Vertical Ray _____________ Season _____________

March 22nd: Vertical Ray _____________ Season _____________

June 21st: Vertical Ray _____________ Season _____________

September 22nd: Vertical Ray _____________ Season _____________

2. If our tilt changed, predict how our seasons would change.

a) If the tilt increased:

Summers would be _____________ Winters would be _______________

b) If the tilt decreased

Summers would be _____________ Winters would be ________________

3. Open the “seasons interactive” animation.

http://www3.eboard.com/boards/16/92/94/Brownstein/att-1573293/Seasons--interactive.swf

a) Set the “inclination” to Earth (bottom of animation). Click “stop” to prevent the Earth from moving

on its own. Move the Earth to the summer position for the northern hemisphere and watch the

thermometer. Then click on Venus. Finally, click on Uranus.

How does the tilt change for each setting?

Venus setting_____________________ Uranus setting______________________

How did the summer temperatures change for each setting?

Venus setting_____________________ Uranus setting_______________________

b) Move the Earth to the winter position for the northern hemisphere and follow the same directions

from 3a. Make note of the temperature differences for each setting.

c) Now that you have used the animation, clearly explain how a change in tilt will affect our seasons: