Catalyst

1.What are the main results of Earth’s rotation?

2.Why does the Earth’s distance from the sun vary?

3.Explain what causes the seasons.

How does the Earth move?Objectives

Explain precession and its effect on the seasons

Explain nutation and its effect on the seasons.

Agenda

IN: Drawing Earth’s MotionTHROUGH: Precession/Nutation NotesOUT: Lesson ReflectionPRACTICE: Making Models

Notebook

P. Title: How does the Earth move?P. Title: Precession and Nutation

Question of the DayWhy are places near the equator hotter?

On earth, the equator receives more sunshine than do the poles. This is due to simple geometry of the earth's curvature, a given amount of sunshine in a beam falling on the equator, which points directly at the sun, has a much more intense effect than the glancing rays spread over a much larger area of the curving surface near the poles. In addition, extensive ice and snow at the poles reflects back to space some of the sun's energy that reaches the earth.

Much more sunshine is absorbed to heat the earth at the equator. This means the land at the equator becomes hotter than the poles. If we had no atmosphere or oceans, the equator would become too hot for life as we know it, and the poles too cold. However, the atmosphere and oceans take some of the excess heat from the equator to the poles, making both habitable to humans. An interesting connection to make is that if the earth were heated evenly at all latitudes there would be no winds or ocean currents.

Partner Focus

Positivity

Input: Left Top: Create the following chart on the top of your page. Sketch a picture to show rotation and revolution.

Rotation Revolution Precession Nutation

What’s your sign?

Astronomy vs. Astrology

• Astronomy is the study of the universe.• Astrology is a system of horoscopes that claim

to explain aspects of a person's personality and predict future events in their life based on the positions of the sun, moon, and other planetary objects at the time of their birth.

Why Astrology is not Science

• Your zodiac sign corresponds to the position of the sun relative to constellations as they appeared more 2,200 years ago!

• Zodiac signs were originally determined by which constellation the Sun was "in" on the day you were born.

Astronomy

• Early astronomers observed the Sun traveling through the signs of the Zodiac in the course of one year, spending about a month in each.

• However, a phenomenon called precession has altered the position of the constellations we see today.

Astronomy

• Ancient astrologers, the Earth continually wobbles around its axis in a 26,000-year cycle.

• Over the last 2,500 years, this wobble means the signs have slipped one-tenth—or almost one whole month—of the way around the sky

• Most horoscope signs are different after considering the changes caused by precession

So what does precession look like?

• http://www.youtube.com/watch?v=0qHjtp4cdCA

Precession • The Earth’s axis is tilted at a 23.5º angle

• Precession: the change in direction of the Earth’s axis, but without any change in tilt-Like the wobbling motion of a spinning tophttp://vimeo.com/3110658

• 1 precessional cycle: approximately 26,000 years

• Minor effect on the seasons

The North Star

• Our North Star is currently Polaris• Because of precession, in 13,000

years our North Star will be Vega

MSL Prep

In 13,000 years, precession will causeA. no change to the Earth’s seasonsB. the seasons on Earth to be reversedC. the Earth’s axis to be pointing toward a “new”

North Star D. the Earth’s axis to be pointing toward the same

North Star

MSL Prep

In 13,000 years, precession will causeA. no change to the Earth’s seasonsB. the seasons on Earth to be reversedC. the Earth’s axis to be pointing toward a “new”

North Star D. the Earth’s axis to be pointing toward the same

North Star

So the earth moves in 3 ways:

1. Rotation (spinning)

2. Revolution (taking a lap around the sun)

3.Precession (changing direction of the axis)

And let’s add one more…

The Earth is CRAZY!

• 1. Rotation• 2. Revolution• 3. Precession• 4. Nutation

Nutation• 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.• No effect on the seasons

MSL Prep

Nutation causesA. no change to the Earth’s seasonsB. significant changes to the Earth’s seasonsC. no change in the Earth’s tilt D. significant changes to the Earth’s tilt

MSL Prep

Nutation causesA. no change to the Earth’s seasonsB. significant changes to the Earth’s seasonsC. no change in the Earth’s tilt D. significant changes to the Earth’s tilt

Output (Left Bottom)

• Reflect on what we’ve learned today by finishing the following sentences.

– Today, I learned …– I was surprised to find …– I wonder what would happen if…– The important thing about …

Make your own model!

Your job is to create and explain a scientific model that describes:• the daily changes on Earth due to its rotation• the seasonal changes due its the tilt• revolution of the Earth around the sun. • Precession and nutation of Earth’s axis

You can use any of the supplies that I have supplied to create your model.

Working Norms

• Volume: 6 inch voice • All group members must contribute to making

the model. • Use supplies SUSTAINABLY – take only what

you need, and leave some for other groups!• Return all supplies when the timer runs up.