Do Now 1. What is the big bang theory? 2. What is some evidence to support the big bang theory? 3. What is a red shift and what does that tell us about distance of objects in space? 4. Explain in your own words what Hubble’s Law states. Hint: think about your lab from last class

The Earth’s Role in our Solar System atch?v=5c_lL6I3OaA

The Earths role in the Solar System  6I3OaA

Objective  SWBAT explain how the earth moves around the solar system by analyzing Kepler’s Laws, precession, nutation, and barycenter.

Check this Kid Out… 02H0&feature=youtu.be 02H0&feature=youtu.be

Notes on the Universe  The universe is made of galaxies which are made of many stars. Some stars have planetary systems similar to our solar system. Earth is a satellite planet of one particular star (our sun)

The (whole) Earth moves in 3 ways. The Earth: 1.Rotates (Rotation) 2.Orbits 3.Revolves (Revolution)

The earth rotates on its axis. Rotates = spins. The earth makes 1 full rotation every 24 hours.

The axis of the Earth is tilted at an angle of 23.5 degrees. The axis always points towards the North Star.

We have day and night because of the Earth’s rotation.

DRAW A PICTURE OF THE EARTH TILTED ON ITS AXIS…

The Earth also revolves around the sun in an elliptical orbit. The earth makes one full revolution around the sun every days. 365 days = 1 year

Kepler’s First Law  Law of Ellipses  Each planet takes an elliptical path around the sun

1 st Law: Law of Ellipses The path of the planets around the sun are elliptical in shape with the center of the sun being located at one focus The shape of the ellipse is determined by the location of the two focus points!

Kepler’s Second Law  Law of Equal Areas  Planets travel faster when they are close to the sun and slower when they are farther away from the sun

2 nd Law: Law of Equal Areas This law states that an imaginary line from the sun to a planet sweeps out equal areas in equal time intervals

Kepler’s 2 nd Law of Planetary Motion

Are they the SAME?  The short wide glass is holding the SAME amount of water as the tall skinny glass!

Planet moves FASTER in orbit when CLOSE to the SUN, and SLOWER in orbit when FAR FROM the SUN WHY? GRAVITATIONAL PULL

Kepler Animation vity-and-orbits

Kepler’s Third Law  The amount of time needed for a planet to revolve around the sun is proportional to the planet’s distance from the sun

Kepler’s 3 rd Law

Kepler’s Three Laws of Planetary Motion (A Summary) 1. Each planet takes an elliptical path around the sun 2. Planets travel faster when they are close to the sun and slower when they are farther away from the sun 3. The amount of time needed for a planet to revolve around the sun is proportional to the the planet’s distance from the sun B C A

Precession  The direction this axis of a planet is pointing in will change, but the tilt will not change.  This will change the stars near the pole but will not change the seasons (as long as the angle of the tilt, 23.5 in the case of Earth, stays the same)

Precession Animation  XczMfMo

Nutation  Nutation happens when the axis of a planet starts to wobble (do the wobble!)  The angle of the axis will change during nutation ½ degree one direction or the other  Nutation happens over the course of 18 years  Nutation is a direct result of the moon (or moons) of a planet

Barycenter  A barycenter is the point between two objects where they balance each other (For example, the middle balancing point on a scale).

Barycenter Example  For example, the moon does not orbit the exact center of the Earth, but a point on a line between the Earth and the Moon approximately 1,710 km below the surface of the Earth, where their respective masses balance.  This is the point at which the Earth and Moon orbit as they travel around the Sun

Do Now 1. Draw a picture of the Earth on it’s axis. At what degree is it tilted? 2. Describe Kepler’s first law. 3. What does the law of equal areas state? 4. Draw a picture depicting his 1 st and 2 nd law. 5. Describe Kepler’s third law.

Barycenter Animation  BANgbRkws BANgbRkws  cles/barycenter.html cles/barycenter.html

Application & Critical Thinking 10 minutes

Exit Ticket: 11 points 1. Draw the shape of Earth’s orbit around the sun. (1 pt) 2. Explain why Earth takes the path you drew in question #1. (1 pt) 3. What is the angle of the Earth’s tilt on its axis? (1 pt) 4. Explain what Kepler’s law tells us. (1 pt) 5. Explain why the sun is always in motion. Use both the sun and Earth in your example. (1 pt) 6. Explain how Earth moves about the solar system (be sure to use rotate, revolve, nutation, precession, and barycenter, in your response). (5 pts)

Today’s Exit Ticket: 11 points 1. Draw the shape of Earth’s orbit around the sun. (1 pt) 2. Explain why Earth takes the path you drew in question #1. (1 pt) 3. What is the angle of the Earth’s tilt on its axis? (1 pt) 4. Explain what Kepler’s law tells us. (1 pt) 5. Explain why the sun is always in motion. Use both the sun and Earth in your example. (1 pt) 6. Explain how Earth moves about the solar system (be sure to use rotate, revolve, nutation, precession, and barycenter, in your response). (5 pts)