# GE 150 Astronomy - PowerPoint PPT Presentation

1 / 48

GE 150 Astronomy. Week #3 January 28 , 2014. Homework. Homework #1 – Due Now Solutions posted on Blackboard Vista after class Grades posted there as well (when finished) Homework #2 – Path of the Sun Download from Blackboard Vista Due beginning of class Jan 30. Path of the Sun.

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.

GE 150 Astronomy

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Week #3

January 28, 2014

### Homework

• Homework #1 – Due Now

• Solutions posted on Blackboard Vista after class

• Grades posted there as well (when finished)

• Homework #2 – Path of the Sun

• Due beginning of class Jan 30

## Path of the Sun

Yearly Changes

### The changing position of the Sun during the year!

March 20th/Sept. 22nd

December 21st

June 20th

Zenith

E

S

N

W

Sun at Noon throughout the year

### Under which of the following circumstances will a vertical flagpole not cast a shadow as seen from the continental United States?

every day at noon

every day at the time when the sun is highest in the sky

when the sun is highest in the sky on the summer solstice

when the sun is highest in the sky on the winter solstice

none of the above

If you are located in the continental U.S. on the first day of October, how will the position of the Sun at noon be different two weeks later?

It will have moved toward the north.

It will have moved to a position higher in the sky.

It will stay in the same position.

It will have moved to a position closer to the horizon.

It will have moved toward the west.

### For an observer in the continental U.S., which of the three shadow plots, shown at right, correctly depicts the Sun’s motion for one day?

All three are possible, on different days of the year.

None of the plots are possible.

## Path of the Sun

Seasons:

Conclusion

### Complete this statement!

When the noontime Sun is ____________________________

it’s summer; and when the noontime Sun is ____________________________

it is winter?

### Which of these are true and which are false statements about the causes of the seasons and what evidence is there to support your answer?

Earth is closer to the Sun in summer than in winter.

During the summer, the Sun is giving off more energy and when it is winter the Sun is giving off less energy.

When it is summer, more sunlight reaches Earth than it does during the winter.

### Seasons Simulator

• Note that the Earth’s rotational axis is tilted relative to the Earth’s orbit and how much directsunlight shines on the northern and southern hemispheresthroughout a year.

• How is this related to the seasons?

Tilted 23.5 degrees from vertical

Not to scale!

67°N

27°N

Equator

27°S

67°S

### The Reasons for the Seasons

• The tilt of the Earth’s axis is the cause for the seasonal changes – it contributes two major effects

### The Reasons for the Seasons: 1

The light from the Sun strikes the ground more directly in the Summer than in the Winter thus concentrating more of the Sun’s energy.

When the Sun is high in the sky during the day, the number of daylight hours is greater and the amount of direct sunlight received is greater. This results in Summer.

Note how little the ‘beam’ of light is spread out in Summer

When the Sun is low in the sky during the day, the number of daylight hours is less and the amount of direct sunlight received is less. This results in Winter.

Note how much more the ‘beam’ of light is spread out in Winter

### The Reasons for the Seasons: 2

The Sun spends more time above the horizon in the Summer than Winter resulting in longer days with more hours for heating

### The tilt of Earth’s axis of rotation produces longer (or shorter) hours of more (or less) direct sunlight

Which positions (A, B, C or D) correspond with which seasons (fall, summer, spring, winter) for the northern hemisphere?

A

D

B

C

### The tilt of Earth’s axis of rotation produces longer (or shorter) hours of more (or less) direct sunlight

What are the possible dates for positions A, B, C and D?

A

D

B

C

### Lecture Tutorial: Seasons p. 93-98

• Read the instructions and questions carefully.

• Come to a consensus answer you agree on.

• If you get really stuck or don’t understand what the Lecture Tutorial is asking, ask one of us for help.

### Homework

• Homework #3 – The Seasons Ranking Task

• Due beginning of class Feb 4

### Looking at the images below, which letter (a-e) best represents winter in the United States?

Sunlight

Sunlight

a

c

2

3

b

e

Sun

Note: this drawing is not to scale.

In fact you could fit more than 11,000 Earths between the Sun and the Earth.

d

Which of the locations, identified with an “x” for each of the situations (A – E), would experience the coolest temperature over the course of one day?

warmest

Cross-Tab Label

0 / 10

Week #3

January 30, 2014

### Homework

• Homework #3 – The Seasons Ranking Task

• Due beginning of class Feb 4

• Homework #4 – Lunar Phases Ranking Task

• Due beginning of class Feb 6

• Exam #1 – Feb 11

• Semi-Anonymous attendance survey

• Eagle ID: 4398

Which of these are true and which are false statements about the causes of the seasons and what evidence is there to support your answer?

Earth is closer to the Sun in summer than in winter.

During the summer, the Sun is giving off more energy and when it is winter the Sun is giving off less energy.

When it is summer, more sunlight reaches Earth than it does during the winter.

Lunar Phases

### How are the motions and positions of Earth and the Sun connected to what happens on Earth?

Earth’s rotation on its axis determines the length of the day.

Earth’s orbit around the Sun determines the length of the year.

The tilt of Earth’s rotational axis with respect to the plane of Earth’s orbit causes the seasons.

### The changing phases of the Moon originally inspired the concept of the month

Some Lunar Facts:

Mean distance: 385,000 km or 30 Earth Diameters

Diameter: 3480 km or 0.273 Earths

Time from New Moon to New Moon: 29.5 days

### Names of Moon Phase

• New Moon

• Waxing Crescent

• First Quarter

• Waxing Gibbous

• Full Moon

• Waning Gibbous

• Third Quarter

• Waning Crescent

### The Causes of Moon Phases

What causes the phases of the Moon?

• Take out a piece of paper and quickly write out a brief answer. Put your name and 1st four digits of Eagle ID # turn in at end of class

### Let’s put it in motion!

Pay attention to where the Moon, Sun and Earth are located and how the Moon appears from Earth at each of these positions.

Look at how much of the Moon is illuminated when at each position.

Look at which side of the Moon is illuminated when at each position.

Phases of the Moon

Although the Moon is always ½ lit by the Sun, we see different amounts of the lit portion from Earth depending on where the Moon is located in its orbit.

Phases of the Moon

Although the Moon is always ½ lit by the Sun, we see different amounts of the lit portion from Earth depending on where the Moon is located in its orbit.

### Lecture Tutorials: Causes of Moon Phases p. 81-83

Read the instructions and questions carefully.

Discuss the concepts and your answers with one another. Take time to understand it now!!!!

Come to a consensus answer you agree on.

If you get really stuck or don’t understand what the Lecture Tutorial is asking, ask one of us for help.

Phases of the Moon

How long does it take the Moon to complete one orbit? How many of the phases will the Moon have gone through in this time?

How long does it take the Earth to complete one rotation? How far will the Moon have moved?

How many phases shown in the picture at the right will the Moon go through in one day?

How much of the Moons total surface is illuminated when it is in the New Phase? Full Phase?

How much of the illuminated surface of the Moon is visible from Earth when it is in the First Quarter Phase, Full Phase?

Lunar Phases II

Rising/Setting/Visibility of Lunar Phases

Are any Moon phases visible during the day?

When does the Moon rise/set?

Does it always rise/set at the same time?

Rising and Setting

### Moonrise and Moonset during Full Moon:

• Full Moon rises as the Sun sets.

• The Full Moon is high in south at Midnight.

• Full Moon sets as the Sun rises.

• Full Moon cannot be seen during the day.

W

W

E

E

E

E

W

W

### Moonrise, Moonset...

• Not all Moon phases are visible at all times of the day

• Never see a Full Moon during the day

• Never see a Crescent Moon at midnight.

• Never see the Last Quarter Moon at sunset.

• Rising/setting times depend on the details of the Earth-Sun-Moon configuration as viewed from the surface of the rotating Earth.