1. Unit 3 Lesson 1 Historical Models of the Solar System
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2. Unit 3 Lesson 1 Historical Models of the Solar System
Florida Benchmarks
SC.8.N.1.4 Explain how hypotheses are valuable if they lead to further investigations, even if they turn out not to be supported by the data.
SC.8.N.1.5 Analyze the methods used to develop a scientific explanation as seen in different fields of science.
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3. Unit 3 Lesson 1 Historical Models of the Solar System
Florida Benchmarks
SC.8.N.1.6 Understand that scientific investigations involve the collection of relevant empirical evidence, the use of logical reasoning, and the application of imagination in devising hypotheses, predictions, explanations and models to make sense of the collected evidence.
SC.8.N.3.2 Explain why theories may be modified but are rarely discarded.
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4. Unit 3 Lesson 1 Historical Models of the Solar System
Florida Benchmarks
SC.8.E.5.8 Compare various historical models of the Solar System, including geocentric and heliocentric.
LA The student will organize information to show understanding (e.g., representing main ideas within text through charting, mapping, paraphrasing, summarizing, or comparing/contrasting).
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5. Remember our Lesson Goal
1. How have people modeled the solar system?

6. What Is the Center of the Solar System?
Unit 3 Lesson 1 Historical Models of the Solar System
What Is the Center of the Solar System?
What is the solar system?
The solar system is the sun and all of the bodies that orbit the sun.
Our current model of the solar system is the sun-centered, or heliocentric, model.
In the heliocentric model, Earth and the other planets orbit the sun.
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7. What is the solar system?
Unit 3 Lesson 1 Historical Models of the Solar System
What is the solar system?
The earliest models of the solar system assumed that Earth was at the center, with the sun, moon, and planets circling it.
These models, which used Earth as the center, are called Earth-centered, or geocentric, models.
The heliocentric model was not generally accepted until the work of Copernicus and Kepler in the late 16th to early 17th centuries.
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8. Who proposed some early models of the solar system?
Unit 3 Lesson 1 Historical Models of the Solar System
Who proposed some early models of the solar system?
Until Galileo improved on the telescope in 1609, people observed the heavens with the unaided eye.
To observers, it appeared that the sun, the moon, the planets, and the stars moved around Earth each day.
This caused them to conclude that Earth was not moving, it was at the center of the solar system, and all other bodies revolved around it.
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9. Who proposed some early models of the solar system?
Unit 3 Lesson 1 Historical Models of the Solar System
Who proposed some early models of the solar system?
The geocentric model of the solar system became part of ancient Greek thought beginning in the sixth century B.C.E.
The Greek philosopher Aristotle (384–322 B.C.E.) was among the first thinkers to propose this model.
His model placed the moon, sun, planets, and stars on a series of circles that surrounded Earth.
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10. Who proposed some early models of the solar system?
Unit 3 Lesson 1 Historical Models of the Solar System
Who proposed some early models of the solar system?
Aristotle thought that if Earth went around the sun, then the relative positions of the stars would change as Earth moves.
This apparent shift in the position of an object when viewed from different locations is known as parallax.
In fact, the stars are so far away that parallax cannot be seen with the unaided eye.
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11. Who proposed some early models of the solar system?
Unit 3 Lesson 1 Historical Models of the Solar System
Who proposed some early models of the solar system?
Aristarchus, a Greek astronomer and mathematician, is reported to have proposed a heliocentric model of the solar system.
His model, however, was not widely accepted at the time.
His attempts to measure the relative distances to the moon and the sun became a major contribution to science.
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12. Who proposed some early models of the solar system?
Unit 3 Lesson 1 Historical Models of the Solar System
Who proposed some early models of the solar system?
Ptolemy was an astronomer, geographer, and mathematician who lived in Alexandria, Egypt.
His book, the Almagest, was based on observations of the planets going back as far as 800 years.
He developed a detailed geocentric model that was used by astronomers for the next 14 centuries.
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13. Who proposed some early models of the solar system?
Unit 3 Lesson 1 Historical Models of the Solar System
Who proposed some early models of the solar system?
In Ptolemy’s model, the planets moved on small circles that in turn moved on larger circles.
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14. Who proposed some early models of the solar system?
Unit 3 Lesson 1 Historical Models of the Solar System
Who proposed some early models of the solar system?
Ptolemy’s “wheels-on-wheels” system fit observations better than any model that had come before.
Ptolemy’s model allowed prediction of the motions of planets years into the future.
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15. Who proposed some early models of the solar system?
Unit 3 Lesson 1 Historical Models of the Solar System
Who proposed some early models of the solar system?
The Polish astronomer Nicolaus Copernicus felt that Ptolemy’s model of the solar system was too complicated.
He knew about Aristarchus’s ideas when he developed the first detailed heliocentric model of the solar system.
Copernicus adopted Ptolemy’s idea that planetary paths should be perfect circles.
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16. Who proposed some early models of the solar system?
Unit 3 Lesson 1 Historical Models of the Solar System
Who proposed some early models of the solar system?
Like Ptolemy, Copernicus used a “wheels-on-wheels” model.
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17. Who proposed some early models of the solar system?
Unit 3 Lesson 1 Historical Models of the Solar System
Who proposed some early models of the solar system?
Copernicus’s model fit observations a little better than Ptolemy’s geocentric model.
Copernicus’s model is generally seen as the first step in the development of modern models of the solar system.
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18. Who proposed some early models of the solar system?
Unit 3 Lesson 1 Historical Models of the Solar System
Who proposed some early models of the solar system?
Johannes Kepler was a German mathematician and astronomer.
After careful observation and analysis, he realized that planetary orbits were not circular but were more like ellipses.
He formulated three principles, which are today known as Kepler’s laws.
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19. Who proposed some early models of the solar system?
Unit 3 Lesson 1 Historical Models of the Solar System
Who proposed some early models of the solar system?
Kepler’s first law states that planetary orbits are ellipses with the sun at one focus.
The second law states that planets move faster in their orbits when they are closer to the sun.
The third law relates the distance of a planet from the sun to the time it takes to go once around its orbit.
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20. Who proposed some early models of the solar system?
Unit 3 Lesson 1 Historical Models of the Solar System
Who proposed some early models of the solar system?
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21. Who proposed some early models of the solar system?
Unit 3 Lesson 1 Historical Models of the Solar System
Who proposed some early models of the solar system?
Galileo Galilei was a scientist who approached questions in the fashion that today we call scientific methods.
He significantly improved the newly invented telescope and used it to view celestial objects.
He observed the moons Io, Europa, Callisto, and Ganymede orbiting Jupiter. Today, these moons are known as the Galilean satellites.
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22. Who proposed some early models of the solar system?
Unit 3 Lesson 1 Historical Models of the Solar System
Who proposed some early models of the solar system?
Galileo’s observations showed that Earth was not the only object that could be orbited.
This gave support to the heliocentric model.
Galileo also observed that Venus went through phases similar to the phases of Earth’s moon.
These phases result from changes in the direction that sunlight strikes Venus as Venus orbits the sun.
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23. Unit 3 Lesson 1 Historical Models of the Solar System
Galileo
Galileo was an Italian mathematician, physicist, and astronomer who lived during the 16th and 17th centuries.
He demonstrated that all bodies, regardless of their mass, fall at the same speed.
He also argued that moving objects retain their velocity unless a force acts upon them.
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24. Galileo Galileo made improvements to telescope technology.
Unit 3 Lesson 1 Historical Models of the Solar System
Galileo
Galileo made improvements to telescope technology.
He used his telescopes to observe sunspots, the phases of Venus, Earth’s moon, the four Galilean moons of Jupiter, and a supernova.
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