February 6, 2013 Q2-Pg.Daily Goal: We will be able differentiate between revolution and rotation, and we will be able to explain how they affect days, seasons and years. Homework: Complete your daily Moon Log

Science Starter:1. How many hours are in a day?2. What is a time zone? 3. Make a hypothesis about why we have days

and nights.

http://www.youtube.com/watch?v=79M2lSVZiY4

I am from Oregon. I have a lot of friends in California, Oregon and Colorado. • When I call my friends in Oregon and

California, they are 3 hours behind the time in Charlotte.

• My friends in Colorado are 2 hours behind the time in Charlotte.

• My friend in Tanzania, Africa is 8 hours ahead of the time in Charlotte.

• Make a hypothesis. How can it be different times in different places?

Bonus table group points!

• What time zone are we in right now?• Eastern Standard Time• What time zone are Oregon and California in?• Pacific Standard Time• Two extra points for this one: What time zone

is Colorado in?• Rocky Mountain Time

Draw this diagram in your notes – Don’t label anything yet!

First, some vocabulary…• AXIS – an imaginary line that passes from the

North Pole to the South Pole of a planet, moon or star

• ROTATION – the spinning of a planet, moon, sun, or other object around its axis; the

Earth spins from East to West (If you are standing on the North Pole, it would spin counter clockwise.)

The earth rotates on its axis.• Rotates = spins.• The earth makes 1 full rotation

every 24 hours.

Earth always rotates from west to east.

If I stand here, which way will I turn?

What about here?

An easy way to remember this:

• Give your neighbor a thumbs up, using your right hand.

• Imagine your thumb is the axis.

• Your fist is the Earth.• Your fingers point in

the direction of Earth’s rotation (west to east).

How can you demonstrate rotation?

Who will be my lovely volunteer?Let’s all try!

Draw the Earth’s axis and the direction that it ROTATES

Draw the Earth’s axis and the direction that it ROTATES

Earth’s axis Earth’s rotation

More vocabulary…• ORBIT – the path an object follows as it revolves

around another object. (Think of the electrons orbiting around the nucleus.)

• REVOLUTION – one orbit of an object in space around another object in space; making a full circle to get back to the beginning point

• The Earth orbits counterclockwise around the Sun.

• It takes 365 days (one year) for the Earth to complete one revolution around the Sun.

• How long does it take for the Earth to complete one rotation, again?

• Think Critically! How many rotations does the Earth complete in the time it takes to complete one revolution?

• It takes 365 days (one year) for the Earth to complete one revolution around the Sun.

• How long does it take for the Earth to complete one rotation, again? 24 hours!

• Think Critically! How many rotations does the Earth complete in the time it takes to complete one revolution?

24 hours = 1 day, 1 revolution = 365 days 1 revolution = 365 rotations

Is this an example of revolution or rotation?

What about this?

What about this?

Label Earth’s ORBIT around the Sun.

Earth’s axis Earth’s rotation

Label Earth’s ORBIT around the Sun.

Earth’s orbit

Earth’s axis Earth’s rotation

Label the direction Earth REVOLVES around the Sun.

Earth’s axis

Earth’s orbit

Earth’s rotation

Label the direction Earth REVOLVES around the Sun.

Earth’s axis

Earth’s orbit

Earth’s rotation

Earth’s revolution

Make a hypothesis!

• Which action is responsible for day and night on Earth? Revolution or rotation?

Good… so let’s get back to Earth’s axis. This is what the earth’s axis looks like,

right?

And the Earth revolves around the sun like this, right?

WRONG!

Earth’s Axis: Not So Straight!• The earth’s axis is tilted about 23.5 degrees

from vertical.23.5˚ Axis

So, the earth’s revolution around the sun looks like this.

Who cares about a tilted axis?

He does.

So does he.This kid definitely does.

Why? Those guys like seasons.

What causes seasons anyway?

Hmmm…hypothesize!

You might say…

“I think the Earth has seasons, because the Earth is closer to the Sun in the summer than in the winter.”

You might say…

“The Earth is closer to the Sun in the summer than in the winter.”

But that’s not it.

You might say…

“I think the Earth has seasons, because the Earth is tilted away from the Sun in the winter, so it gets less sun.”

You might say…

“Earth is tilted away from the Sun in the winter, so it gets less sun.”

WINTER

But that’s not quite it.

Big Questions

1. What is responsible for seasons?

2. How and why are seasons different in other parts of the world?

If the earth’s axis was straight up and down…

• We would still have different weather conditions across the face of the Earth, but we wouldn’t have seasons.

If the earth’s axis was straight up and down…

ColdCoolWarmHotWarmCoolCold

Notes: Seasons

The Northern Hemisphere (the top half) of the Earth tilts away from the Sun in the winter and towards the Sun in the summer

BUT this does not mean we “get less sun” in the winter!

What is DOES mean is that the Sun gives off the same amount of energy, but the tilt of the Earth means that the energy we receive is “spread out” over a larger area.

        Summer light                   Winter light

SUMMER(direct rays)

WINTER(indirect rays)

Think/Pair/Share

Based on what you just learned about how seasons work in the Northern Hemisphere, what do you think the weather is like in July in Australia? Explain why in terms of Earth’s tilt.

Australia in July

Australia in December

In the Southern Hemisphere, seasons are opposite of ours (winter in July)

• When the Northern Hemisphere is tilted TOWARD the Sun, the Southern Hemisphere is tilted AWAY)

PracticeDetermine whether it is colder in January or July in each of the following

places. Circle your answer.Canada:January JulyArgentina: January JulySouth Africa: January JulyRussia: January JulyNew Zealand:January JulyIreland: January JulyGreenland: January JulyNamibia: January JulyChile: January JulyEcuador: January July (tricky!)

PracticeDetermine whether it is colder in January or July in each of the following

places. Circle your answer.Canada:January JulyArgentina: January JulySouth Africa: January JulyRussia: January JulyNew Zealand:January JulyIreland: January JulyGreenland: January JulyNamibia: January JulyChile: January JulyEcuador: January July (tricky!) NEITHER!

Near the Equator, there are practically no seasons (same temp. year round) because the Equator is never really tilted away from the Sun.Example: In Ecuador, it is the same temperature (fairly hot) all year round

At the Poles, about half the year is totally dark and half the year is light all the time AND it is always cold because sunlight only hits these places at an extreme angle

Half the year each Pole is pointed directly away from the SunExample: In Antarctica, it is dark from March – August every year and rarely gets above freezing

January

July

Where is this place?

Which picture shows it tilted away from the Sun?

How do you know?

January

July

Where is this place?

Southern Hemisphere

Which picture shows it tilted away from the Sun?

The July picture

How do you know?

It’s clearly much colder in July, so this place must be in the Southern Hemisphere, where Earth is pointed away from the Sun in July

January

July

Where is this place?

Which picture shows it tilted away from the Sun?

How do you know?

January

July

Where is this place?

Near the Equator

Which picture shows it tilted away from the Sun?

Neither!

How do you know?

The climate looks the same in both of the pictures, so the seasons don’t change much. This means that the pictures were taken someplace that doesn’t really experience the tilting of the Earth.

If I am standing here, which gravity is pulling me down. Which way is down?

Easy!

What about now? Which way is gravity pulling me if I am here?

Gravity

• No matter where you are on Earth, the direction “down” will always be toward the Earth’s center.

Which way is down?