1. Bell Ringer #2 Directions- Add this to the paper with the first bell ringer. Copy down the entire question and all of the options. Then circle the answer that you choose.
What role did gravity play in the formation of the sun?
A. Gravity caused the protoplanetary disk to become a planetesimal, which became the sun.
B. Gravity caused the protoplanetary disk to rotate and form a solar nebula, which became the sun.
C. Gravity caused the solar nebula to collapse toward the center, causing the center to be dense and hot.
D. Gravity caused small particles to collide to form larger particles called planetesimals, which eventually formed the sun.

2. Vocab Lesson 1
Solar system Heliocenter Geocentric Parallax

3. Homework - Write this in your agenda
Complete page 113 and read lesson 2

4. Lesson 1: Historical Models of the Solar System
Essential Question: How have people modeled the solar system?

5. What is the solar system?
Our solar system is heliocentric meaning the Earth and other planets orbit the sun.
The earliest models were geocentric with the sun, moon, and planets orbiting Earth.
The heliocentric model was generally accepted in the late 16th to early 17th century.

6. Who proposed some early models of the solar system?
It appeared that the sun, moon, planets, and stars moved around the Earth meaning the Earth did not move.
Aristotle proposed the geocentric model and believed if Earth was not the center of all things then the stars would move, but the parallax (shift of position of an object) cannot be seen with the naked eye.
Who proposed some early models of the solar system?
Continued on next slide

7. Who proposed some early models of the solar system?
Aristarchus proposed a heliocentric model which was not widely accepted.
Although it was too small a scale, his attempt to measure the distances to the moon and sun became a major contribution to science.
Who proposed some early models of the solar system?
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8. Who proposed some early models of the solar system?
Ptolemy developed a detailed geocentric model that was used for the next 14 centuries.
His model had planets circling the Earth in large orbits and moving in small circles within their own orbit.
This allowed prediction of motions of planets years into the future.
Who proposed some early models of the solar system?
Continued on next slide

9. Who proposed some early models of the solar system?
Copernicus developed the first detailed heliocentric model.
His model shows the planets orbiting in perfect circles.
This model is generally seen as the first step in the development of modern models of the solar system.
Who proposed some early models of the solar system?
Continued on next slide

10. Who proposed some early models of the solar system?
Kelper discovered that planetary orbits are not circular, but an ellipses.
He has three laws which state that
1. planetary orbits are ellipses with the sun at one focus
2. planets move faster in their orbits when closer to the sun
3. relating the distance of a planet from the sun to the time it takes to go around its orbit once.
Who proposed some early models of the solar system?
Continued on next slide

11. Who proposed some early models of the solar system?
Galileo made improvements to the telescope and used it to observe the moons orbiting Jupiter.
His observations showed that Earth was not the only object that could be orbited.
Who proposed some early models of the solar system?
Write a 2-3 sentence summary on what you learned in this set of notes.

12. The heliocentric model of the solar system
Directions: Working in pairs, you will identify the evidence that led to question the geocentric model of the solar system.
Follow the directions on your paper, write the answers in your composition book.
Work with your partner to come up with the answers to the questions.