Prepare for your quiz First, get out your homework from Friday: Barycenter lab worksheet and your lab write-up. Put your name on these sheets and hand them in the homework bin at the front Review your notes about Earth’s: rotation, revolution, precession, and nutation. First, get out your homework from Friday: Barycenter lab worksheet and your lab write-up. Put your name on these sheets and hand them in the homework bin at the front Review your notes about Earth’s: rotation, revolution, precession, and nutation. 1

Quiz When you are done, place your quiz in the bin Pick up your notes and homework sheet for today When you are done, place your quiz in the bin Pick up your notes and homework sheet for today 2

OBJECTIVE SWBAT evaluate how planetary motion leads to season changes.

AGENDA Quiz Review Earth’s Motions The Sun and the Seasons Video Revolution vs. Rotation? Demo Guided Practice Worksheet The Seasons Foldable Exit Ticket Seasons practice for homework

Review on Earth’s Motions

Barycenter  -A barycenter is the point in space around which two objects orbit.  -The moon does not orbit the exact center of the Earth,  - The moon orbits 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

The moon just doesn’t orbit the Earth. Both the Earth AND the moon orbit around the barycenter.

The sun and planets have a barycenter too! 8

The planet…What do we know? All the planets in our solar system revolve around the sun. But how? Kepler discovered elliptical planetary orbits All the planets in our solar system revolve around the sun. But how? Kepler discovered elliptical planetary orbits B C A

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 (perihelion) and slower when they are farther away from the sun (aphelion) 3. The amount of time needed for a planet to revolve around the sun is proportional to the planet’s distance from the sun B C A

The Seasons Video Clip

The Earth rotates on its axis 1 full rotation = one 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 Comparing Rotations: Earth=24 hrs Mercury=59 days

The Earth orbits (revolves around) the sun How long is one full revolution? 365 days = 1 year Comparing Revolutions: Earth= days Mercury=88 days

So, this is what the Earth looks like right? axis

And it revolves around the sun like this right? This shows orbit

WRONG!

Earth’s axis is not straight –Earth’s axis is tilted 23.5 ° from vertical Earth’s axis is not straight –Earth’s axis is tilted 23.5 ° from vertical ° tilt

The Earth’s orbit actually looks like this This shows orbit

19 Like What? tions/es0408/es0408page01.cfm?chapter_no=visualization

Why does that matter?  The Earth’s tilted axis allows us to have seasons 4 seasons based on Earth’s position to the sun WinterSummerFallSpring

When the Earth is tilted away from the sun, it gets less solar radiation. This means the temperature is colder When the Earth is tilted towards the sun, it gets more intense radiation. This means the temperature is warmer. When the Earth is tilted away from the sun, it gets less solar radiation. This means the temperature is colder When the Earth is tilted towards the sun, it gets more intense radiation. This means the temperature is warmer. 21

So what does this look like for us, in the Northern Hemisphere?? For each part of the demo, fill out your chart based on what is represented by each specific location: 1)tilt (towards/neutral/away) 2)Radiation (high/neutral/low) 3)Temperature (warm/moderate/cold) 4)Season

Tilt (towards/away) Radiation (high/low) Temperature (warm/ moderate/ cool) Season

Winter When the Earth is tilted away from the sun. Coldest temperatures Top tilted away from sun= winter

Spring Moderate (medium) temperatures Starts cold and gets warmer as that part of Earth is tilted toward the sun Beginning to be tilted toward the sun= spring

Summer When the Earth is titled toward the sun. Warmest temperatures Top titled toward the sun= summer

Autumn (fall) Moderate (medium) temperatures Starts warm and gets cooler as that part of Earth is tilted away from the sun Beginning to be tilted away from the sun= spring

The equator divides the earth into top and bottom halves (Northern and Southern hemisphere) Because of the tilt of the earth, the hemispheres have opposite seasons. WHY?

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FOLDABLE 30 FRONT BACK INSIDE WINTERSPRINGAUTUMNSUMMER DRAWING DESCRIPTION DRAWING DESCRIPTION Draw a picture to show the Earth orbiting around the sun. Draw the Earth in the 4 main positions. Use arrows to show the direction the Earth is moving. Describe how much radiation the Earth receives (low/moderate/high) from this tilt. DESCRIPTION DRAWING DESCRIPTION DRAWING DESCRIPTION DRAWING

Why is the Earth’s diameter around the equator larger than around the poles? 31

The diameter around Earth’s equator is larger than that at the poles because of the centrifugal force from Earth’s rotation 32 The equator’s diameter is km more than that measured between the poles Earth is bulgy in the center

EXIT SLIP

POSTCARD Pick a place on the map you will travel to over the summer. Write a postcard telling your friend what season it is there. Explain why it is that season. Describe what the temperature is like. For the picture on your postcard (on the back), draw what the Earth and sun would look like for this season. Pick a place on the map you will travel to over the summer. Write a postcard telling your friend what season it is there. Explain why it is that season. Describe what the temperature is like. For the picture on your postcard (on the back), draw what the Earth and sun would look like for this season Alaska 2.South Africa 3.Brazil 4.England 1.Alaska 2.South Africa 3.Brazil 4.England