Unit E Lesson 2: Earth’s Place in the Universe
Completion requirements
Unit E Lesson 2: Earth’s Place in the Universe
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Learning Targets |
Big Question: How has human understanding of the Earth’s place in the universe changed over time?
Our understanding of Earth and its place in the universe has changed dramatically over time.
Our understanding of Earth and its place in the universe has changed dramatically over time.
At the end of this inquiry, you should be able to answer the following questions:
- What is the difference between an equinox and a solstice?
- What is the geocentric theory?
- Who proposed the geocentric theory?
- What is the heliocentric theory, and who proposed it?
- What did Johannes Kepler prove about planetary orbits?
Pages 372 to 375 in your textbook will help you answer these questions.
Introduction
The Sun, the Moon, and the Sky
The sun and moon had prominent positions in the legends and mythologies of many cultures.
This Cree legend about the Origin of the Moon is an example of a legend designed to explain why the sun and the moon appeared at different times.
Why does the sky change throughout the day and throughout the month?
As the largest objects in the sky, the sun and moon held a particular fascination. Many cultures developed a belief system based on gods who controlled the sun, sometimes driving it across the sky as the Greek gods, Apollo and Helios, or the Hindu god, Surya, did. Because people saw the sun only during the day and the moon at night, many stories reflected the belief that the two objects were opposites, sometimes man and wife, or sometimes siblings.
The sun and moon had prominent positions in the legends and mythologies of many cultures.
This Cree legend about the Origin of the Moon is an example of a legend designed to explain why the sun and the moon appeared at different times.
Why does the sky change throughout the day and throughout the month?
As the largest objects in the sky, the sun and moon held a particular fascination. Many cultures developed a belief system based on gods who controlled the sun, sometimes driving it across the sky as the Greek gods, Apollo and Helios, or the Hindu god, Surya, did. Because people saw the sun only during the day and the moon at night, many stories reflected the belief that the two objects were opposites, sometimes man and wife, or sometimes siblings.
Watch
Watch the following video to learn about the phases of the moon.
What Causes the Seasons?
If you live in Canada, you understand the effect that seasonal change can have on life.
Improvements in technology and transportation mean that we can enjoy warmth, light, and fresh food throughout the winter, but in older times, the winter season was especially arduous.
Many cultures developed winter festivals near the time of the winter solstice. For example, the Roman festival Saturnalia is thought to have influenced the modern Christmas celebration. Sometimes the festivities were designed to ask the gods to bring back the light, but always they were a celebration of the return to longer days that would lead to spring and summer.
If you live in Canada, you understand the effect that seasonal change can have on life.
Improvements in technology and transportation mean that we can enjoy warmth, light, and fresh food throughout the winter, but in older times, the winter season was especially arduous.
Many cultures developed winter festivals near the time of the winter solstice. For example, the Roman festival Saturnalia is thought to have influenced the modern Christmas celebration. Sometimes the festivities were designed to ask the gods to bring back the light, but always they were a celebration of the return to longer days that would lead to spring and summer.
Figure 2 – The position of the Earth in orbit around the Sun causes the seasons.
Interactive
Solstice and Equinox
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The BrainPOP video, reviews the concept of Solstice and Equinox.
Click here
to watch "Solstice and Equinox".
You will need a username and password to access the video.
- Username: 0099
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Password: students
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Click here
to complete the quiz on Solstice and Equinox. Remember to check your answers at the end!
Try It!
Practice Worksheet: Models of the Solar System Theories
- DOWNLOAD this practice worksheet (S9_UE_S1_L2_system_theories). If you prefer to use a Google Drive or PDF version of the worksheet, click here.
- Answer the questions on the worksheet as you work through the readings and videos in this lesson.
- When you are satisfied with your responses you can check your work by clicking on the "SUGGESTED ANSWERS" button below.
Wait! Don't view the suggested answers first. This practice work is not for marks, it is meant to help you check your understanding. Check the answers AFTER doing the questions! Keep the practice worksheet for study purposes. If you don't understand something, contact your teacher!
Figure 3 – A solar system illustration.
The Geocentric Model of the Universe
The orbit of the Earth cannot be felt, but the sun’s movement across the sky is evident each day. Therefore, we can understand that many cultures believed the Earth to be the centre of the universe and that the sun revolved around it. This is called the geocentric model. Geo means Earth (as in geography and geology) and centric means at the centre.
Aristotle (384 – 322 BCE), a Greek philosopher and scientist, is most often credited with the proposing the geocentric model, but that isn't quite accurate. Two hundred years earlier Greek philosopher Anaximander proposed a model of the universe where Earth was a cylinder at the centre of everything. Famous Greek philosopher Pythagoras at the same time proposed that the Earth was a sphere, and these two ideas were combined into the first geocentric model. Aristotle formalized and described the model, but he didn't create it. It is with some irony that the geocentric model was based partly on Pythagorean ideas, since Pythagoras did not believe that the Earth was at the centre of the universe.
The orbit of the Earth cannot be felt, but the sun’s movement across the sky is evident each day. Therefore, we can understand that many cultures believed the Earth to be the centre of the universe and that the sun revolved around it. This is called the geocentric model. Geo means Earth (as in geography and geology) and centric means at the centre.
Aristotle (384 – 322 BCE), a Greek philosopher and scientist, is most often credited with the proposing the geocentric model, but that isn't quite accurate. Two hundred years earlier Greek philosopher Anaximander proposed a model of the universe where Earth was a cylinder at the centre of everything. Famous Greek philosopher Pythagoras at the same time proposed that the Earth was a sphere, and these two ideas were combined into the first geocentric model. Aristotle formalized and described the model, but he didn't create it. It is with some irony that the geocentric model was based partly on Pythagorean ideas, since Pythagoras did not believe that the Earth was at the centre of the universe.
Figure 4 – This illustration, "Figure of the heavenly bodies" was created in 1568.
The Heliocentric Model of the Universe
The geocentric model adequately explained the observations of the moon throughout the months of the year, but it was unsatisfactory to some astronomers.
During the European Renaissance, European mathematicians and astronomers began to perform experiments that challenged the geocentric model.
Using observations of the planets and constellations, Polish astronomer Nicholas Copernicus suggested that it was the Sun and not the Earth at the center of the universe. Copernicus suggested that the Earth and the other planets visible to the naked eye (Mercury, Venus, Mars, Jupiter, and Saturn) revolved around the sun in rings. This model is called the heliocentric model. Helio means sun (as in the Greek sun god, Helios) and centric means at the center.
Italian physicist Galileo Galilei used a telescope to track the movement of planets throughout the year to provide evidence that helped confirm Copernicus’ heliocentric model. Meanwhile, German mathematician Johannes Kepler provided evidence that planetary orbits were elliptical and not circular. The orbits of planets are in the shape of an ellipse; they are elliptical. These proven theories are still the basis of current scientific understanding of how the planets in our solar system travel around the sun.
To examine the Geocentric and Heliocentric models further, carefully read pages 373-375 in your Science in Action textbook.
The geocentric model adequately explained the observations of the moon throughout the months of the year, but it was unsatisfactory to some astronomers.
During the European Renaissance, European mathematicians and astronomers began to perform experiments that challenged the geocentric model.
Using observations of the planets and constellations, Polish astronomer Nicholas Copernicus suggested that it was the Sun and not the Earth at the center of the universe. Copernicus suggested that the Earth and the other planets visible to the naked eye (Mercury, Venus, Mars, Jupiter, and Saturn) revolved around the sun in rings. This model is called the heliocentric model. Helio means sun (as in the Greek sun god, Helios) and centric means at the center.
Italian physicist Galileo Galilei used a telescope to track the movement of planets throughout the year to provide evidence that helped confirm Copernicus’ heliocentric model. Meanwhile, German mathematician Johannes Kepler provided evidence that planetary orbits were elliptical and not circular. The orbits of planets are in the shape of an ellipse; they are elliptical. These proven theories are still the basis of current scientific understanding of how the planets in our solar system travel around the sun.
To examine the Geocentric and Heliocentric models further, carefully read pages 373-375 in your Science in Action textbook.
Figure 5 – Johannes Kepler (top left), Galilieo Galilei (top right), and Nicholas Copernicus.
Interactive
Galileo Galilei
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This BrainPOP video reviews the concepts surrounding the heliocentric model of the universe.
Click here
to watch "Galileo Galilei".
You will need a username and password to access the video.
- Username: 0099
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Password: students