Seasons: The spin cycle

Transcription

1 Earth and Space Sciences Seasons: The spin cycle Have you ever wondered why grapes are harvested in early Autumn or why the winter in Australia happens at the same time as the North American summer? This lesson will help you answer these questions by investigating: How does the Earth move through space? Why do daylight hours change throughout the year? How the North and South Poles differ? Why seasons occur? It s time to put your overcoat away and spring into this lesson! This is a print version of an interactive online lesson. To sign up for the real thing or for curriculum details about the lesson go to

2 Introduction: Seasons (P1) While most of the planet is heating up, there s something strange going on around the South Pole. It s just as cold there as it ever was and it s staying that way! Scientists think they may have just worked out why. Antarctica, the frozen continent that sits on the South Pole, is surrounded by the vast Southern Ocean which only has a few tiny islands dotted here and there. There is no land to stop the wind from blowing or even to slow it down. And so the wind howls along from the west to the east and just keeps on going round and round the continent. In fact, it seems that as a result of other parts of the Earth getting hotter the wind is getting even faster, faster than it has been for 1,000 years. And it is moving further south, closer to Antarctica than it ever was. The faster the wind blows around Antarctica, the more it keeps cold air trapped there, and that s bad news for southern Australia. The wind in the Southern Ocean carries water, which falls as rain in storms over the country, especially in winter. But with the wind moving further south, it often misses Australia altogether and the storms dump their rain back into the ocean where it is no use to farmers. Read or listen to the full Cosmos magazine article here.

3 Left: Scientists analyse ice cores to uncover mysteries about our planet's distant past. Right: Less rain in southern Australia is bad news for grape growers. Credits: Jack Treist and istock. Question 1 List: All across southern Australia winemakers and crop farmers rely on seasonal weather changes. Imagine you are about to set up a crop farm in southern Australia. State three questions you would like scientists to answer before setting up your farm.

4 Gather: Seasons (P1) Loading Credits: Ngflcymru & YouTube. Question 1 Recall: The Earth is tilted at an angle of Question 2 Recall: The planets in the solar system share the same 20 degrees orbital speed tilt angle 23.5 degrees orbital plane 25 degrees

5 Question 3 Describe: What is meant by the terms Autumnal Equinox and Summer Solstice and when does each occur? Credit: istock. Question 4 Describe: Why do we experience seasons? Loading Credits: TED-Ed & YouTube.

6 Question 5 Recall: Antarctic means "of the South". Question 6 Recall: The Arctic is an ocean surrounded by land. True True False False Question 7 Recall: Use the shape drawing tool to label each image as either Arctic or Antarctic. Label Arctic with the cloud graphic and label Antarctic with the star graphic. The first two have been done for you. Question 8 Compare: How are the South and North Poles different from each other? Question 9 Recall: Why is Antarctica colder than the Arctic?

7 Process: Seasons (P1) Loading Credits: TED-Ed & YouTube.

8 Question 1 Sequence: The diagram below shows the Earth in orbit around the Sun at four times of the year. Complete the small boxes with the labels Summer Solstice, Autumnal Equinox and Winter Solstice for the Northern Hemisphere. In addition, add a short description of what is happening to the length of days and nights in between these locations. The Spring Equinox and one description have been completed for you. Days longer than nights Days get longer Spring Equinox Examine the following chart depicting the number of hours of daily sunshine in both Sydney and Perth throughout the year. The amount of sunshine a city receives depends on both the length of day and the amount of cloud cover.

9 Question 2 Calculate: Refer to the chart above for two Australian cities to find the average number of hours of sunshine for each city in summer (November through January), and winter (June through August). Hint: To complete the final column you will have to first calculate the number of days in both summer and winter. Nov Dec Jan Total hours sunshine Total hours sunshine Total hours sunshine Hours sunshine over summer Perth Sydney Jun Jul Aug Total hours sunshine Total hours sunshine Total hours sunshine Hours sunshine over winter Perth Sydney Question 3 Calculate: If the average day length in summer is 15 hours for both Sydney and Perth, use your results in the table above to calculate what percentage of summer days are sunny and what percentage of summer days are overcast for each city. Hint: You will first need to calculate the total number of hours of daylight the cities receive during summer. Question 4 Narrate: Imagine that scientists have found a way to remove the tilt of Earth's axis! Write a short article to be published in Cosmos magazine that outlines why you think this would be a good or bad idea. Try to predict what consequences this might have on weather, culture or even politics around the world.

10 Apply: Seasons (P2) Experiment: Modelling the seasons In this investigation you will conduct a simple experiment to model the seasons. You will use a torch to represent the Sun, a sheet of squared paper to represent the Earth's surface and a protractor to measure the angle of the torch to the Earth's surface. By varying the angle of the torch you will be able to observe the changes in the shape and size of the light beam on the paper. Question 1 Predict: Make a hypothesis for the investigation taking care to explain what you think will happen to the area and shape of the light beam hitting the paper as the angle is changed. Materials Torch Two large sheets of 1 cm paper Pen or marker Protractor 30 cm ruler 2

11 Method 1. Hold the torch so that the bulb is 20 cm above the piece of squared paper. Use a ruler and protractor to make sure the torch is at 90 degrees to the paper. 2. While one person holds the torch steady the other is to trace the outline of the beam hitting the paper. Clearly label this first trace as "90 ". 3. Using the ruler and protractor, move the torch so that the globe is still 20 cm from the paper but at 80 degrees. Trace the outline of the beam hitting the paper, labelling the trace as "80 ". 4. Keep changing the angle of the torch so that you can trace the beam at 70 degrees, 60 degrees and at 45 degrees. 5. Repeat the whole process a second time using a fresh piece of paper. Question 2 Explain: Why is it important to keep the torch globe 20 cm from the paper? Question 3 Explain: Why do you think the experiment was repeated? Results Question 4 Complete: Count the number of squares in each of the shapes you have drawn and complete the table below. Angle (degree s) Description of trace shape Attempt 1: Area of sha 2 pe (cm ) Attempt 2: Area of 2 shape (cm ) Average area of shape 2 (cm )

12 Question 5 Plot: Transfer the data from your table into the graph plotter below to show the relationship between the angle of the torch and the average area of the surface illuminated. Use the x-axis for the angle of the torch and the y-axis for the average area of the surface illuminated. Title auto Series 1 x y Y-Axis This graph needs some data! auto auto auto X-Axis Question 6 Conclude: Summarise the findings of your investigation. Question 7 Evaluate: Once an investigation is performed it is important to reflect on the method used, describe any improvements that could be made and discuss how reliable you think the findings are. Write a short paragraph addressing these issues. Try to suggest at least two improvements for the experiment.

13 Question 8 Predict: How would you expect your results and conclusion to change if you conducted the investigation with the torch 10 cm above the paper? Question 9 Imply: What can you deduce about why we have seasons from this experiment?

14 Career: Seasons (P2) In a vast, icy landscape, thousands of kilometres from home, Australian scientist Dr Nerilie Abram drills down through ancient layers of snow to extract long, cylindrical cores of ice. Using these cores, Nerilie reveals the chilly details of Antarctica s past climate and how it s changing today. Nerilie grew up in a small town called Wangi Wangi in New South Wales. It was during her Year 10 work experience, when she saw satellite images of a massive iceberg drifting off the coast of Antarctica, that she decided she wanted to go there one day. Many years later, after finishing her university studies in Geology, Nerilie started working in Antarctica. She collects ice cores, which involves drilling a hole through the ice to bring up sections piece by piece, sometimes creating a core hundreds of metres long. The deeper the drill goes, the older the ice gets, and the bottom layers can be tens of thousands of years old. By studying the chemical and physical properties of the ice core s layers, Nerilie can see how the climate has changed over time. When she s working in Antarctica, Nerilie lives in an ice core camp and says that it is an amazing experience. In the smaller camps, everyone helps to keep things running taking turns to cook and shovel snow. Because it s difficult to grow fresh food in Antarctica, most meals are made from dried ingredients, and Nerilie says that little things like fresh bread from a bread maker become a big luxury! Having a job that takes her travelling around the world means that Nerilie really appreciates time with her family, and says that having a long shower, sleeping in a proper bed and eating a crunchy fresh salad are all pretty special after a month or two of fieldwork. Question 1 Propose: Imagine that your employer asked you to live and work in Antarctica for a year (scientists, doctors, chefs, mechanics and engineers might have this opportunity), what do you think you would enjoy most about the opportunity and what would you be most concerned about?

15 Cosmos Lessons team Cosmos Education Director: Daniel Pikler Education Editor: Bill Condie Art Director: Robyn Adderly Profile author: Edwina Berry Lesson authors: Paula Mills and Hayley Bridgwood