Seasons: Why do we have them?

Discover why seasons change! Learn about Earth's tilt and sunlight.

Prior Knowledge (Do these before using the Gizmo) At what time of day is the sunlight the strongest? in the early morning (when the Sun has just risen) at noon (when the Sun reaches its highest point) At what time of year does does the noon Sun rise highest in the sky? early winter late winter early spring late spring early summer late summer early fall late fall Based on your answers, why is it warmer in summer than winter? Accessing Gizmo 1) Go to username: My name + your class period. Example: arbuckle3 (all lower case letters)3) password: clark (all lower case letters)4) Write down the username and password.5) Open the Seasons: Why do we have them? Gizmo. Gizmo Warm-up The reasons for seasons have a lot to do with the angle at which the Sun's rays hit Earth. To see why, select the PLATE tab on the Seasons: Why do we have them? Gizmo. The image shows a solar panel (Plate M) facing the Sun. Check that the Axis angle is set to 0o. 1. Click Fire to release 100 "rays" of sunlight. Look next to "Number of hits" below the plate. How many of these rays hit Plate M? 100 hits 2. Click Reset. Change the Axis angle to 40o, and click Fire. How many rays hit Plate M now? 76 hits 3. Which do you think will warm up the plate more quickly? Direct sunlight (sunlight that hits the plate at a 90o angle) Indirect sunlight (sunlight that hits the plate at an angle of less than 90o) Activity A: Sunlight on a plate Get Gizmo ready: click Reset.Question:How does the angle of sunlight affect the amount of energy that is absorbed? 1. Form hypothesis: How do you think the angle of the plate will affect how much sunlight hits the plate? 2. Collect Data: Set the Axis angle to -80o and click Fire. Record the Number of hits. Repeat for each angle nad fill in the table below. You can use the slider or type the number into the text field directly and click Enter on your keyboard. Axis angle Hits -80o 18 -60o 50 -40o 76 -20o 94 0o 100 20o 94 40o 76 60o 50 80o 18 3.Analyze:What is the relationship between the axis angle and the number of solar rays that hit the plate? 4. Interpret: Select the GRAPH tab. What does the graph show? 5. Apply:At what angle will the plate get the hottest? -80o -60o -40o -20o 0o 20o 40o 60o 80o 6. Extend your thinking: The plate is a model for how sunlight hits Earth's surface. A. Which parts of Earth are most similar to the plate with and axis angle of 0o? Explain.B. Which parts of Earth are most similar to the plate with an axis angle of 80o? Activity B: Sunlight on Earth Get Gizmo ready: Select the EARTH tab on the left and the DESCRIPTION tap on the right.Check that the Axis angle is set to 0 degrees.Question:What causes seasons on Earth? 1. Predict: Look at the image of Earth (not to scale). Plate A is located at the North Pole, and plate G is located at the South Pole. Plates D and J are located at the equator.A. Of the plates that are facing the Sun (plates A through G), which ones will receive the most solar energy?B. Which of plates A through G will receive the least? 2. Check: Click Fire. Select the TABLE tab to see how many rays hit each plate.A. Which plate got the most sunlight? The least?B. Why is it colder at the poles than at the equator? 3. Set up Gizmo: Click Reset, and turn on Show axis. Earth's axis is an imaginary line that connects the North Pole to the South Pole. Earth spins around its axis, which is tilted relative to Earth's orbit. Click Earth axis angle to set the axis angle to a realistic 23o. 4. Collect data: Time A On the DESCRIPTION pane, check that Time A is selected. Click Fire. Select the TABLE pane to see the results, and fill in the table below. Click Reset, and on the DESCRIPTION pane select Time A + 6 months. Click Fire and fill in the table. Plate Angle Hits A -67o 0 B 83o 2 C 53o 16 D 23o 25 E -7o 26 F -37o 22 G -67o 9 4. Collect data: Time A + 6 months Click Reset, on the DESCRIPTION pane and select Time A + 6 months. Click Fire and fill in the table. Plate Angle Hits A -67o 10 B -37o 21 C -7o 26 D 23o 25 E 53o 16 F 83o 2 G -67o 0 5. Analyze: Plates A, B, and C all like in the northern hemisphere, the half of Earth north of the equator. Plates E, F, and G, all lie in the southern hemisphere, south of the equator.A. Which hemisphere gets more direct sunlight at Time A? southern hemisphereB. Which hemisphere gets more sunlight at Time A + 6 months? northern hemisphere 6. Interpret: Plate B is a typical northern hemisphere location, and plate F is a typical souther hemisphere location. Answer each question below.A. On plate B, which season is Time A? start of winterB. On B, which season is Time A + 6 months? start of summerC. On F, which season is Time A? start of summerD. On F, which season is Time A + 6 months? start of winter E. In general, how are seasons in the northern hemisphere related to seasons in the southern hemisphere? 7. Apply: December 21 and June 21 are important dates called solstices. The winter solstice is the shortest day of the year. The summer solstice is the longest day of the year.A. Which date does Time A represent? December 21This date is the winter solstice in the northern hemisphere, and the summer solstice in the southern hemisphere.B. Which date does Time A + 6 monthsrepresent? June 21This date is the summer solstice in the northern hemisphere, and the winter solstice in the southern hemisphere. 8. Summarize: Based on what you have seen, what causes the seasons?