Starry Night-Phases of the Moon and Misconceptions ...

Starry Night-Phases of the Moon and Misconceptions

Laboratory 6

Objective:

In this laboratory you will take a close look at the lunar phase cycle. We will also explore some

common everyday statements about the moon and its phases, to see if they are correct.

Background:

Moon Phases

As the moon revolves around the earth, its position relative to the earth and sun changes. As a result,

we on earth view the disk of the moon illuminated by different amounts resulting in what we call phases

of the moon. The four main phases of the Moon are New Moon (NM), First Quarter (FQ), Full Moon

(FM), and Last Quarter (LQ). Each of these phases of the Moon will occur at the same position relative

to the Sun, and therefore each of them rises and sets at the same time each month. The approximate times

are as follows:

NM¨C rises around 6am, sets around 6pm

FQ ¨C rises around 12pm (noon), sets around 12am (midnight)

FM ¨C rises around 6pm, sets around 6am

LQ ¨C rises around 12am, sets around 12pm

The moon sets approximately 50 minutes later each night.

Moon Phase Diagram

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Fraction of Illumination

The fraction of the Moon that we see from Earth is called the fraction of illumination, sometimes

noted as a percentage. The fraction of illumination for the phases of the Moon is as follows:

Phase

Fraction of Illumination

New Moon

Waxing Crescent

0%

Between 0% and 50%

First Quarter

Waxing Gibbous

50%

Between 50% and 100%

Full Moon

Waning Gibbous

100%

Between 100% and 50%

Last Quarter

Waning Crescent

50%

Between 50% and 0%

There are 7 to 8 days between the new moon and the first quarter, first quarter and full moon,

full moon and last quarter, and the last quarter and new moon. On the days in between are

crescent and gibbous phases, with the lit potion of the lunar disk getting larger during the

¡°waxing¡± phases, and smaller during the ¡°waning¡± phases. The lunar phase cycle is

approximately 29.5 days.

Instructions:

Statement #1: "The sun comes out during the day and the moon comes out at night."

The first part of this statement concerning the sun must be true, as the Sun being above our

horizon defines ¡°daytime¡±. But the night is not defined by the moon, the night is defined by the

absence of the Sun. So, is the moon always out when the Sun is not? Is the moon ever above

our horizon during the day? Could we actually see the moon during the day if we knew where to

look?

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To explore these questions using Starry Night, we will find out what time the moon rises during

its various phases on its journey around the earth. The dates listed below correspond to one lunar

cycle. For each date, record both the rising time of the moon, and its phase into the table below.

To do this, first we need to be able to locate the Moon. Open the Find tab and type ¡°moon¡± into

the search field. Check the box that appears next to the word Moon. Set the time and date to

those listed and locate the Moon on your screen (it will be labeled ¡°Moon¡± as long as it remains

selected in the ¡°find¡± field). Next open the Info tab and expand the moon data and other data

found within. Record the phase, age of the Moon (in days old), and the rise and set time found

within the listed information. Throughout this procedure notice that the Moon rises at different

times depending on the phase.

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Start by setting the date to Jan 4, 2011. Record the rise time and set time, the phase, and age of

the Moon in the table found in your Answer Sheet at the end of the lab.

Date

Jan 4, 2011 at 11am

Jan 7, 2011 at 2pm

Jan 11, 2011 at 5pm

Jan 14, 2011 at 8pm

Jan 19, 2011 at 11pm

Jan 23, 2011 at 11pm

Jan 26, 2011 at 5am

Jan 29, 2011 at 8am

Feb 2, 2011 at 11am

Rise Time

Set Time

Phase

Age

Statement #2:

"The phase of the moon you see depends on what time of day you look."

If we examine the diagram in the background section shows 8 positions of the various moon

phases, we notice that if we are on earth and we are standing on the side of the earth directly in

the sunlight, when our time would be noon, the new moon phase appears directly over us. If we

are standing where the light and dark sides meet, and at the top of the diagram, it would be

sunset and the first quarter moon would be directly over our heads. If we stand on in the middle

of the dark side of the earth, the time would be midnight and the full moon phase would be

directly over our heads. So it stands to reason that the new moon would appear at noon, the first

quarter at sunset, and the full moon at midnight. However, is that what¡¯s going on here? Does

the phase of the moon depend on what time of day you look at it? Let¡¯s find out.

Follow the moon in our sky on Janurary 23, 2011 from its rise time to when it sets. Notice that

it moves across our sky, but at the end of the day it is still approximately the same size and shape

as it was at the beginning. Determine the rise and set times of the Moon on this date and use

those times to find the age and phase of the Moon at those instances. Use your Answer Sheet.

What is the age and phase of the Moon on this date when it rises?

Age-__________________

Phase-___________________

What is the age and phase of the Moon on this date when it sets?

Age-__________________

Phase-___________________

Is there a noticeable change in what the Moon looks like?

Does the phase of the moon depend on the time of day?

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Statement #3:

"The phase of the moon seen depends on where you are on the Earth."

When looking at the moon phase diagram it is reasonable to think that the moon phases

correspond to different locations on the Earth. But is that how it works? Would a different

location on the Earth have a different viewpoint from another? Would that be enough to change

the appearance of the phases? Let¡¯s find out.

To explore using Starry Night-From L.A., Ca. with time stopped, set the date to 3 hours after

the Full Moon rises in January, 2011 (found in your table) and look at the Moon on your

screen. Now go to New York by changing your viewing location and look at the moon again.

This is accomplished by clicking the triangle located to the right of your current viewing location

toward the top of your screen. Open the menu and select Other and then choose the proper

location from the list. Click on the location and then click on Go To Location. Next go to

Dublin, Ireland and Apatity, Russia and look at the moon again. (Just change locations, the

time and date will change automatically to account for time zones.)

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