2.1 Do Now Take 15 minutes to complete the do now. Make sure to write your name, date, and 2.1 on top of your paper. Read the Article “New Planet Discovered Similar to Earth” and fill in what you know about the Kepler planet in the appropriate circle: Kepler Planet Earth Objective EEn.1.1.1 TSW explain the Earth’s motion through space (nutation, barycenter (sun's moving), and precession) by checkpoints. EQ: How does the Earth move? What is the difference between precession and nutation? Kepler’s Laws Kepler created 3 laws that discussed how our Earth and the planets move. Kepler’s 1st Law of Planetary motion. Today we will learn about st 1 Kepler’s Law: Law of Ellipses Planets move in elliptical orbits with the Sun at one focus. Why does the Earth move in an ellipse? ● An ellipse is an oval-shaped figure whose shape is determined by 2 foci. ● The Sun is at one focus planet’s orbit; the second focus is empty because of the gravitational pull. How does the Earth move? 1.Rotation 2.Revolution 3.Precession 4.Nutation Rotation ● Rotates = spins. ● 1 rotation=24 hours/ 1 day Looking at the picture below, why is the left hemisphere experiencing a warm day and the right hemisphere experiencing a cooler night? DAY warmer NIGHT cooler Revolution •Revolves (orbits around) the sun •1 revolution= 365 days/ 1 year ● http://www.youtube.com/watch?v=vDgUmTq4a2Q Quick Quiz #1 What is the difference between rotation and revolution? A. Rotation is when the Earth orbits around the sun and Revolution is the Earth spinning. B. Rotation gives Earth 1 year (365 days) and Revolution gives Earth 1 day (24 hrs) C. Rotation is when the Earth spins and Revolution is when the Earth orbits around the Sun. D. Rotation moves in an ellipse and Revolution moves in a circle around the sun. Precession ● The change in direction of the axis of the Earth, but without any change in tilt -Like the wobbling motion of a spinning top ● 1 precessional cycle: approximately 26,000 years http://www.youtube.com/watch?v=Dw4Xhw4q4ec Just like a spinning top! http://vimeo.com/3110658 http://www.youtube.com/watch?v=AC5HuGGIX7k Quick Quiz #2 Which is the best explanation for precession? A. Precession is how the Earth revolves around the sun B. Precession is how the Earth spins C. Precession takes 1 day to make a rotation D. Precession is the change in direction of the Earth’s axis as it rotates Nutation What do you notice about the movement of the Earth? Nutation ● The wobbling/swaying motion during the precession of our axis. ● This causes a 1 degree change in the tilt of the Earth’s axis. Quick Quiz #3 What is the best explanation of nutation? A. The spinning of the Earth B. The wobbling of the Earth’s axis C. The change in direction of the Earth’s axis D. The orbiting of the Earth around the sun Kepler’s 2nd law A planet that speeds up when it is closer to the Sun because of the Sun’s gravitational pull. Animation A planet travels the same distance in the same time and but at different speeds (velocities). Identify the following on the picture: which side is faster? Quick Check 1. Therefore, Earth moves ________________________ (faster/slower) in summer than in winter, so summer in the Northern Hemisphere must be ___________________________ (longer/shorter) than winter. 2. Isaac Newton later determined that the force of GRAVITY holds the planets in orbit around the Sun. When a planet is closer to the Sun, the force of the Sun’s gravitational attraction on the planet is _________________________ (stronger/weaker) than when the planet is farther from the Sun. Kepler’s law and Barycenter Barycenter- is the center of mass between two points. All bodies (planets, the sun) in our solar system revolve around a barycenter. Center of Mass Unbalanced Balanced So what does this mean? ● Yes, the sun is the center of the solar system. ● But the sun and planets are BOTH revolving around the barycenter (the center of mass between them). http://en.wikipedia.org/wiki/File:Orbit4.gif Where is the barycenter located? For two objects that are of different masses, the barycenter is CLOSER to the one with MORE mass. Barycenter Lab Barycenter Lab Barycenter Lab Barycenter Lab Barycenter Lab Barycenter Lab Complete the results and conclusion section of your lab writeup. This will be worth a 30 point project grade. Remember to write in complete sentences! Kepler’s 3rd Law of Planetary Motion The time it takes to REVOLVE around the Sun= the distance from the Sun. The farther you are from the sun, the longer it takes to get around the sun. Just like a track! For example: Earth The Earth takes ___________ (longer/shorter) than Mercury to revolve around the sun. The Earth takes _____________ (longer/shorter) than Mars to revolve around the sun. Kepler's third law of planetary motion describes a relationship between the A. Shape of orbit and location of Sun. B. Speed of the Earth and its position in orbit. C. Distance from the sun and length of year. Which of these statements about Kepler's Laws is true? A. A planet moves faster when its orbit is close to the sun. B. The planet travels faster when it is away from the sun. C. Planets travel in circular orbits Exit Ticket Complete the Earth section of the Do Now.