Gravity and the Solar System Essential Question: What is gravity’s role in the formation of Solar Systems and in determining the motion of objects as they revolve around the Sun? Objectives: Describe how the Law of Universal Gravitation applies to planetary motion. Defend the claim that gravity created our current Solar system.

Gravity What is gravity? Unit 3 Lesson 2 Gravity and the Solar System Gravity What is gravity? Gravity is a force of attraction between objects that is due to their masses and the distances between them. Every object in the universe pulls on every other object. Copyright © Houghton Mifflin Harcourt Publishing Company 2

Unit 3 Lesson 2 Gravity and the Solar System What is gravity? Gravity accounts for the formation of planets, stars, and galaxies. Gravity also keeps smaller bodies in orbit around larger bodies. (This is why planets orbit the sun.) An orbit is the path that a body follows as it travels around another body in space. Copyright © Houghton Mifflin Harcourt Publishing Company 3

What is the law of universal gravitation? Unit 3 Lesson 2 Gravity and the Solar System What is the law of universal gravitation? Using Kepler’s laws, Sir Isaac Newton became the first scientist to mathematically describe how the force of gravity behaves. Copyright © Houghton Mifflin Harcourt Publishing Company 4

What is the law of universal gravitation? Unit 3 Lesson 2 Gravity and the Solar System What is the law of universal gravitation? The strength of this force depends on the product of the masses and distances between objects. Objects with greater masses have a greater force of attraction than objects with lesser masses have. Objects that are close together have a greater force of attraction than objects that are far apart have. Copyright © Houghton Mifflin Harcourt Publishing Company 5

Knowledge Check What happens to gravitational attraction if the mass or distance changes? Same Less Greater

Knowledge Check What happens to gravitational attraction if the mass or distance changes? Same Less Greater

Knowledge Check What happens to gravitational attraction if the mass or distance changes? Same Less Greater

Knowledge Check What happens to gravitational attraction if the mass or distance changes? Attraction is the same between objects Attraction is greater because of Mass. Attraction is lesser because of Distance. Increasing mass increases strength of attraction, while increasing distance reduces strength of attraction. Decreasing mass reduces the strength while decreasing distance increases strength.

What is Kepler’s First Law? Each planet orbits the Sun in an elliptical orbit with the Sun at one focus or center point.

Kepler’s Second Law A planet will move along the aphelion slower than the perihelion. The area along the aphelion is narrow while the area along the aphelion is wide. So time around both areas would be the same.

Why would a planet travel distance A and B in the same amount of time? Knowledge Check Why would a planet travel distance A and B in the same amount of time? A B

Kepler’s third law The farther a planet is to the Sun, the longer it will take to orbit the Sun.

How does this data table help explain Kepler’s third law? Knowledge Check How does this data table help explain Kepler’s third law?

Unit 3 Lesson 2 Gravity and the Solar System What is gravity’s role in the formation of the Solar System? https://www.youtube.com/watch?v=Uhy1fucSRQI Copyright © Houghton Mifflin Harcourt Publishing Company 15

Unit 3 Lesson 2 Gravity and the Solar System How did the solar system form? 1. Long ago an ancient star exploded littering space with swirling clouds of the materials it had made while it lived and the heavier metals it created while it died. They are called nebulae. 2. Every nebula is different and in our case, the clouds contain nitrogen, oxygen, and other materials needed to build a world like ours. Copyright © Houghton Mifflin Harcourt Publishing Company 16

Unit 3 Lesson 2 Gravity and the Solar System How did the solar system form? Then the tireless force of gravity started to pull it all back together and the formation of our planets begin. 3. Vast spirals of dust begin to form and at the center of one of these a rocky planet called earth started to take shape; built of stardust and a symbol of gravity. Copyright © Houghton Mifflin Harcourt Publishing Company 17

How did the solar system form? Unit 3 Lesson 2 Gravity and the Solar System How did the solar system form? Fast forward 100 million years and it had grown into a giant ball sweeping up tons of celestial debris. 93 millions miles away, at the heart of the giant nebula the pressure and temperature of a ball of hydrogen gas had become so great that the atoms were beginning to fuse. 5. The new star, our sun, was coming to life. As the sun ignited, it gave off a huge ball of solar wind. As the sun ignited, it gave off a huge blast of solar wind or a radioactive gust of energy. Copyright © Houghton Mifflin Harcourt Publishing Company 18

6. This blew all remaining gas and dust out to the edge of the solar system. In the outer reaches of the solar system, we have the huge gas planets. Further in are the denser rockier planets.

D. Pressure from hot expanding gases Which force is important during the formation and creation of the solar system? Knowledge Check A. Planetesimals B. Solar Wind C. Gravity D. Pressure from hot expanding gases