Neil F. Comins Discovering the Essential Universe Fifth Edition CHAPTER 1

Size: px
Start display at page:

Download "Neil F. Comins Discovering the Essential Universe Fifth Edition CHAPTER 1"

Transcription

1 Neil F. Comins Discovering the Essential Universe Fifth Edition CHAPTER 1 Discovering the Night Sky WHAT DO YOU THINK? 1. What do astronomers define as constellations? 2. Is the North Star Polaris the brightest star in the night sky? 3. What causes the seasons? 4. How many zodiac constellations are there? 5. Does the Moon have a dark side that we never see from Earth? 6. Is the Moon ever visible during the daytime? 7. What causes lunar and solar eclipses? In this chapter you will discover how astronomers organize the night sky to help them locate objects in it. that Earth s spin on its axis causes day and night. how the tilt of Earth s axis of rotation and Earth s motion around the Sun combine to create the seasons. that the Moon s orbit around Earth creates the phases of the Moon. what causes both lunar and solar eclipses. the scales of the universe. Navigating the Night Sky Constellations Seasonal Asterisms Star Guides In order to more easily locate objects in the sky, we divide the sky into regions named after familiar patterns of stars called constellations. The Night Sky Without and With Light Pollution Ancient constellations were imaginary pictures outlined by familiar patterns of stars. Modern astronomers divide the sky into 88 official constellations or regions of space, many of which contain the ancient star patterns. 1

2 Common Guides to Finding Constellations and Stars Common Guides to Finding Constellations and Stars Using the Big Dipper as a guide The Winter Triangle Common Guides to Finding Constellations and Stars Insight into Science Compare What You Believe with What Nature and Science Show You The Summer Triangle If you think Polaris is the brightest star in the night sky, how did you learn that? There is likely to be a lot of information you learned from a variety of sources that you will have to unlearn while learning astronomy. While this process is often uncomfortable, it is essential if you want to understand how science works and how scientists view the world. Be careful: It is human nature to change new information to fit our current beliefs rather than change what we believe. Fight that urge if science can show you that your beliefs are incorrect! The Celestial Sphere Projection of Earth s equator, poles Earth Latitude = Celestial Declination Earth Longitude = Celestial Right Ascension Astronomers describe the universe as an imaginary sphere surrounding the Earth on which all objects in the sky can be located, called the CELESTIAL SPHERE. As viewed from Earth, the celestial sphere appears to rotate around two axis points, the north and south celestial poles, which are located directly above the Earth s poles. Between these is the celestial equator, which divides the celestial sphere into northern and southern hemispheres. We define the position of an object on the celestial sphere using two coordinates, right ascension and declination. 2

3 Cyclic motions of the Sun and stars in our sky are due to motions of Earth. 1. ROTATION = the spin of Earth on its axis. It takes one day for Earth to complete one rotation. 2. REVOLUTION = the movement of Earth in orbit around the sun. It takes one year for Earth to complete one revolution. 3. PRECESSION = the slow conical (top-like) motion of Earth s axis of rotation. It takes 26,000 years for Earth to complete one cycle of precession. Angles and Arc Angles 90 horizon to top of sky (zenith) 5 angle between Pointer Stars of Big Dipper 1 = 60 arcminutes = 60 1 = 60 arcseconds = 60 The Moon is ½ or 30 or 1800 in diameter The Big Dipper Star Motions Circumpolar Equatorial In Between Rotation of Earth Revolution of Earth around Sun The angular distance between the two pointer stars at the front of the Big Dipper is about 5. Circumpolar Star Trails The apparent westward motion of the Sun, Moon, and stars across our sky each day is caused by Earth s rotation. At middle latitudes, we see the Sun, Moon, and many of the stars first come into view moving upward, rising at some point along the eastern horizon. Then, they appear to arc across the sky. Finally, they disappear beneath the western horizon. We generalize this motion to make statements such as, The Sun rises in the east and sets in the west. The stars near the poles of the celestial sphere (shown here) move in trails that circle the pole and never set. They are called circumpolar. 3

4 Motion of Stars at the Poles Rising and Setting of Stars at the Equator Because Earth rotates around its poles, stars seen from these locations appear to move in huge, horizontal circles. This is the same effect you would get by standing up in a room and spinning around; everything would appear to move in circles around you. At the North Pole, stars move left to right, while at the South Pole, they move right to left. Standing on the equator, you are perpendicular to the axis around which Earth rotates. As seen from there, the stars rise straight up on the eastern horizon and set straight down on the western horizon. Rising and Setting of Stars at Middle Northern Latitudes We can see how different stars appear at different times of day by looking at the position of the Sun against the backdrop of stars. The side of Earth facing the Sun is experiencing day, while the side of Earth turned away from the Sun is experiencing night. Unlike the motion of the stars at the poles, the stars at all other latitudes do change angle above the ground throughout the night. This time-lapse photograph shows stars setting. The latitude determines the angle with respect to the horizon at which the stars rise and set. SEPTEMBER MARCH Earth also revolves around the Sun, which changes our view of the stars. Insight into Science Define Your Terms From our perspective, the Sun appears to move through the stars along a special path called the ecliptic. From an outside view, we see Earth revolve around the Sun. We define the plane of Earth s orbit as the ecliptic plane. As with interpersonal communication, using the correct words is very important in science. Usually, scientific words each have a specific meaning, such as rotation denoting spin and revolution meaning one object orbiting another. Be especially careful to understand the context in which words with more than one meaning, such as ecliptic and constellation, are used. 4

5 Seasons The reason for the seasons is the Earth s tilt In different seasons we receive different intensities of sunlight and heat In the summer, sunlight is more direct and less spread out In the winter, sunlight is less direct and more spread out Seasons are caused because Earth s axis is tilted with respect to its orbital plane; as Earth revolves around the Sun, different parts of Earth receive more direct sunlight (summer), whereas other parts of Earth receive sunlight that is more spread out (winter). The seasons we experience are due to the Sun s motion across the celestial sphere. The point of the Sun s path farthest north on the celestial sphere is called the summer solstice (JUN 21), whereas the point of the ecliptic farthest south is called the winter solstice (DEC 21). The two points on the ecliptic where the Sun crosses the celestial equator are called equinoxes. During the vernal equinox (MAR 21), the Sun is moving north, while during the autumnal equinox (SEPT 21), the Sun is moving south. Remember that the seasonal names of the equinoxes and the solstices refer to seasons in the NORTHERN hemisphere. The seasons occurring in the SOUTHERN hemisphere are exactly opposite. The Sun s Daily Path and the Energy It Deposits Here (a) On the winter solstice first day of winter the Sun rises farthest south of east, it is lowest in the noontime sky, stays up the shortest time, and its light and heat are least intense (most spread out) of any day of the year in the northern hemisphere. (b) On the vernal equinox first day of spring the Sun rises precisely in the east and sets precisely in the west. Its light and heat have been growing more intense, as shown by the brighter oval of light than in (a). (c) On the summer solstice first day of summer the Sun rises farthest north of east of any day in the year, is highest in the sky at noontime, stays up the longest time, and its light and heat are most intense of any day in the northern hemisphere. (d) On the autumnal equinox, the same astronomical conditions exist as on the vernal equinox. Insight into Science The Midnight Sun Expect the Unexpected The process of science requires that we question the obvious, that is, what we think we know. Many phenomena in the universe defy commonsense explanations. The fact that the changing distance from Earth to the Sun has a minimal effect on the seasons is an excellent example. This time-lapse photograph was taken on July 19, 1985, at 69 north latitude in northeastern Alaska. At that latitude, the Sun is above the horizon continuously from mid-may until the end of July. 5

6 Precession This precession causes the position of the North Celestial Pole to slowly change over time. Today, the North Celestial Pole is near the star Polaris, which we call the North Star. However, in 3000 BC, Thuban was close to the North Celestial Pole and in 14,000 AD, Vega will be in this location. Gravitational forces of the Sun and the Moon pulling on Earth as it rotates cause Earth to undergo a top-like motion called precession. Over a period of 26,000 years, Earth s rotation axis slowly moves in a circular motion. Phases of the Moon Caused by the changing amount of illumination seen from the Earth as the Moon revolves around it. Another familiar cycle is the lunar cycle. When the Moon orbits Earth, the amount of the side facing Earth that is lit changes, creating the Moon s phases. This phase cycle is called the synodic period and is 29½ days long. 6

7 One common misconception is that the Moon is only visible at night. However, the time of day in which the Moon is in our sky varies depending on its phase. This picture clearly displays the Moon, visible during the day. A synodic month is the time it takes for the Moon to orbit Earth with respect to the Sun and is 29½ days long. A sidereal month is the time it takes for the Moon to orbit Earth with respect to the stars and is 27.3 days long. The two times are different because Earth moves in its orbit around the Sun as the Moon moves in its orbit around Earth. Eclipses Solar Eclipse the Moon shadows the Earth New Moon Lunar Eclipse the Earth shadows the Moon Full Moon During a new or full moon phase, when the Moon, Sun, and Earth are aligned, the Moon may enter the shadow of Earth, or the shadow of the Moon may reach Earth, creating eclipses. However, these eclipses do not occur during every full or new moon because the Moon s orbit is tilted by 5 with respect to the Earth- Sun (ecliptic) plane. PENUMBRAL = the Moon appears dimmed. PARTIAL = part of the Moon enters the umbra of Earth s shadow and is darkened. TOTAL = all of the Moon enters Earth s shadow and becomes a reddish color, only lit from light bending around Earth s atmosphere. During a total lunar eclipse, the Moon moves in and out of the umbra of Earth s shadow. 7

8 Unlike lunar eclipses, solar eclipses occur at specific places on Earth, indicated by the arrow. Eclipse Paths for Total and Annular Eclipses A Total Eclipse of the Sun This map shows the eclipse paths for the 14 total solar and 13 annular eclipses that occur between 2001 and In each eclipse, the Moon s shadow travels along the eclipse path in a generally eastward direction across Earth s surface. Sometimes eclipses occur when the Moon is too far away from Earth to completely cover the Sun in our sky. When this occurs, the Moon appears in the center and a thin ring, or annulus, of light surrounds it. These are called annular eclipses. 8

9 What Have Astronomers Discovered in Our Universe? THE SCALES OF THE UNIVERSE The range of objects we study are from the extremely small subatomic particles, to objects that are gigantic, such as a galaxy or the size of the known universe itself. Each division up the line indicates an increase in size by 100,000. Navigating the Night Sky Summary of Key Ideas The celestial sphere is an imaginary hollow sphere centered on Earth. A map of the sky, analogous to a map of the entire Earth, is impressed on it. The poles and equator of the celestial sphere are determined by extending the axis of rotation and the equatorial plane of Earth out onto the celestial sphere. The surface of the celestial sphere is divided into 88 unequal areas called constellations. Earthly Cycles The stars appear to revolve around Earth once each night. In fact, it is actually Earth s rotation that causes this apparent motion. Earth revolves around the Sun in 365¼ days, defining a year. The Seasons Earth s axis of rotation is tilted at an angle of 23½ from a line perpendicular to the plane of Earth s orbit around the Sun (the plane of the ecliptic). This tilt, combined with Earth s revolution around the Sun, causes the seasons. Equinoxes and solstices are significant points along Earth s orbit that are determined by the relationship between the Sun s path on the celestial sphere (the ecliptic) and the celestial equator. 9

10 The Seasons The length of the day is based upon Earth s rotation rate and the average motion of Earth around the Sun. These effects combine to produce the 24-h day upon which our clocks are based. Earth s axis of rotation slowly changes direction relative to the stars over thousands of years, a phenomenon called precession. The Phases of the Moon The phases of the Moon are caused by the changing relative positions of Earth, the Moon, and the Sun. The Moon completes one cycle of phases in a synodic month, which averages 29½ days. The Moon completes one orbit around Earth with respect to the stars in a sidereal month, which averages 27.3 days. Eclipses The shadow of an object has two parts: the umbra, where direct light from the source is completely blocked; and the penumbra, where the light source is only partially obscured. A lunar eclipse occurs when the Moon moves through Earth s shadow. During a lunar eclipse, the Sun, Earth, and the Moon are in alignment, with Earth between the Sun and the Moon, and the Moon in the plane of the ecliptic. Eclipses A solar eclipse occurs when a strip of Earth passes through the Moon s shadow. During a solar eclipse, the Sun, Earth, and the Moon are in alignment, with the Moon between Earth and the Sun, and the Moon in the plane of the ecliptic. Depending on the relative positions of the Sun, the Moon, and Earth, lunar eclipses may be penumbral, partial, or total; solar eclipses may be annular, partial, or total. Scales of the Universe Astronomy examines objects that range in size from the parts of an atom (~10 15 m) to the size of the observable universe (~10 26 m). Scientific notation is a convenient shorthand for writing very large and very small numbers. What do astronomers define as constellations? Astronomers sometimes use the common definition of a constellation as a pattern of stars. Formally, however, a constellation is an entire area of the celestial sphere and all the stars and other objects in it. Viewed from Earth, the entire sky is covered by 88 different-sized constellations. If there is any room for confusion, astronomers refer to the patterns as asterisms. 10

11 Is the North Star Polaris the brightest star in the night sky? No. Polaris is a star of medium brightness compared other stars visible to the naked eye. with What causes the seasons? The tilt of Earth s rotation axis with respect to the ecliptic causes the seasons. They are not caused by the changing distance from Earth to the Sun that results from the shape of Earth s orbit. How many zodiac constellations are there? There are 13 zodiac constellations, the least-known one being Ophiuchus. Does the Moon have a dark side that we never see from Earth? Half of the Moon is always dark. Whenever we see less than a full Moon, we are seeing part of the Moon s dark side. So, the dark side of the Moon is not the same as the far side of the Moon, which we never see from Earth. Is the Moon ever visible during the daytime? The Moon is visible at some time during daylight hours almost every day of the year. Different phases are visible during different times of the day. What causes lunar and solar eclipses? When the Moon is crossing the ecliptic in the full or new phase, the shadows of Earth or the Moon, respectively, then fall on the Moon or Earth. These shadows on the respective surfaces are eclipses. 11

What does the universe look like from Earth? Chapter 2 Discovering the Universe for Yourself. Constellations

What does the universe look like from Earth? Chapter 2 Discovering the Universe for Yourself. Constellations Chapter 2 Discovering the Universe for Yourself What does the universe look like from Earth? With the naked eye, we can see more than 2,000 stars as well as the Milky Way. A constellation is a region of

More information

Celestial Sphere. Celestial Coordinates. Lecture 3: Motions of the Sun and Moon. ecliptic (path of Sun) ecliptic (path of Sun)

Celestial Sphere. Celestial Coordinates. Lecture 3: Motions of the Sun and Moon. ecliptic (path of Sun) ecliptic (path of Sun) Lecture 3: Motions of the and Moon ecliptic (path of ) ecliptic (path of ) The 23.5 degree tilt of Earth s spin axis relative to its orbital axis around the causes the seasons Celestial Sphere Celestial

More information

1-2. What is the name given to the path of the Sun as seen from Earth? a.) Equinox b.) Celestial equator c.) Solstice d.

1-2. What is the name given to the path of the Sun as seen from Earth? a.) Equinox b.) Celestial equator c.) Solstice d. Chapter 1 1-1. How long does it take the Earth to orbit the Sun? a.) one sidereal day b.) one month c.) one year X d.) one hour 1-2. What is the name given to the path of the Sun as seen from Earth? a.)

More information

Chapter 2 Discovering the Universe for Yourself

Chapter 2 Discovering the Universe for Yourself Chapter 2 Discovering the Universe for Yourself A constellation is a region of the sky. Constellations 88 constellations fill the entire sky. The brightest stars in a 1. all belong to the same star cluster.

More information

Today s Lecture. Getting Started on LaunchPad

Today s Lecture. Getting Started on LaunchPad Today s Lecture! More info about LaunchPad Quizzes and Assignments! Discovering the Night Sky (Chapter 1)! There will be no observing session this evening! the first observing session is scheduled for

More information

Chapter 2 Di D sc s o c ver e i r ng t he e U n U iver e s r e s e f o f r ry o Y urs r e s l e f

Chapter 2 Di D sc s o c ver e i r ng t he e U n U iver e s r e s e f o f r ry o Y urs r e s l e f Chapter 2 Discovering the Universe for Yourself 2.1 Patterns in the Night Sky Our goals for learning: What does the universe look like from Earth? Why do stars rise and set? Why do the constellations we

More information

PHYS ASTRONOMY CHAPTER 2 REVIEW QUESTIONS

PHYS ASTRONOMY CHAPTER 2 REVIEW QUESTIONS MULTIPLE CHOICE PHYS 100 - ASTRONOMY CHAPTER 2 REVIEW QUESTIONS 1. In one way of naming stars, a letter indicates its brightness relative to the other stars in the constellation. a. English b. Arabic c.

More information

Lecture 2: Our Place in Space. Copernican Principle. Multiwavelength Astronomy

Lecture 2: Our Place in Space. Copernican Principle. Multiwavelength Astronomy Lecture 2: Our Place in Space It is now clear that Earth is not central or special in its general properties (mass, distance from central star, etc.) The Sun is an average star The Milky Way is a typical

More information

Today. Appearance of the Sky. Orientation. Motion of sky. Seasons. Precession. Phases of the Moon

Today. Appearance of the Sky. Orientation. Motion of sky. Seasons. Precession. Phases of the Moon Today Appearance of the Sky Orientation Motion of sky Seasons Precession Phases of the Moon The Appearance of the Sky The Local Sky An object s altitude (above horizon) and direction (along horizon) specify

More information

The Celestial Sphere Stars at different distances all appear to lie on the celestial sphere (projection of Earth s positions into space).

The Celestial Sphere Stars at different distances all appear to lie on the celestial sphere (projection of Earth s positions into space). Chapter 2 Discovering the Universe for Yourself 2.1 Patterns in the Night Sky Our goals for learning: What does the universe look like from Earth? Why do stars rise and set? Why do the constellations we

More information

ASTR 1010 Astronomy of the Solar System Professor Caillault Fall 2009 Semester Exam 1 Answers

ASTR 1010 Astronomy of the Solar System Professor Caillault Fall 2009 Semester Exam 1 Answers ASTR 1010 Astronomy of the Solar System Professor Caillault Fall 2009 Semester Exam 1 Answers 1. The number of degrees in a full circle is (c) 360 2. An arcsecond is a measure of (d) angle. 3. How many

More information

The Sky. What do we see? Stars Sun Moon Planets How do we organize what we see? How do they move? Eclipses Time and Calendars

The Sky. What do we see? Stars Sun Moon Planets How do we organize what we see? How do they move? Eclipses Time and Calendars The Sky What do we see? Stars Sun Moon Planets How do we organize what we see? How do they move? Eclipses Time and Calendars Asterisms The Big Dipper The Teapot Constellations In ancient times, constellations

More information

The night sky, and the Earth-Moon-Sun system

The night sky, and the Earth-Moon-Sun system The night sky, and the Earth-Moon-Sun system http://people.physics.tamu.edu/quadri/astr101_fall16/ Homework extension to Thursday Access the homework site ( Pearson Mastering Astronomy ) through ecampus

More information

From our perspective...

From our perspective... 2/9/09 Mastering Astronomy Assignment 3 Why don t we see the same constellations throughout the year? Due Feb 17, 11 am Read Sections 2.1, 2.2 and S1.2 The Earth also revolves around the Sun, which changes

More information

Phases of the Moon. A diagram which demonstrates why the moon goes through phases. Click on image for full size

Phases of the Moon. A diagram which demonstrates why the moon goes through phases. Click on image for full size Phases of the Moon A diagram which demonstrates why the moon goes through phases. Click on image for full size The diagram shows the Moon in different positions along its orbit around the Earth. The Sun

More information

Phys 100 Astronomy (Dr. Ilias Fernini) Review Questions for Chapter 3

Phys 100 Astronomy (Dr. Ilias Fernini) Review Questions for Chapter 3 Phys 100 Astronomy (Dr. Ilias Fernini) Review Questions for Chapter 3 MULTIPLE CHOICE 1. The phases of the moon are caused by its and. a. spherical shape; orbital motion around the sun b. cubical shape;

More information

Today FIRST HOMEWORK DUE NEXT TIME. Seasons/Precession Recap. Phases of the Moon. Eclipses. Lunar, Solar. Ancient Astronomy

Today FIRST HOMEWORK DUE NEXT TIME. Seasons/Precession Recap. Phases of the Moon. Eclipses. Lunar, Solar. Ancient Astronomy Today FIRST HOMEWORK DUE NEXT TIME Seasons/Precession Recap Phases of the Moon Eclipses Lunar, Solar Ancient Astronomy How do we mark the progression of the seasons? We define four special points: summer

More information

Aphelion The point in the orbit of a planet or other celestial body where it is furthest from the Sun.

Aphelion The point in the orbit of a planet or other celestial body where it is furthest from the Sun. SKYTRACK Glossary of Terms Angular distance The angular separation between two objects in the sky as perceived by an observer, measured in angles. The angular separation between two celestial objects in

More information

The Celestial Sphere. Questions for Today. The Celestial Sphere 1/18/10

The Celestial Sphere. Questions for Today. The Celestial Sphere 1/18/10 Lecture 3: Constellations and the Distances to the Stars Astro 2010 Prof. Tom Megeath Questions for Today How do the stars move in the sky? What causes the phases of the moon? What causes the seasons?

More information

Aphelion The point in the orbit of a planet or other celestial body where it is furthest from the Sun.

Aphelion The point in the orbit of a planet or other celestial body where it is furthest from the Sun. SKYTRACK Glossary of Terms Angular distance The angular separation between two objects in the sky as perceived by an observer, measured in angles. The angular separation between two celestial objects in

More information

The Celestial Sphere. Chapter 1 Cycles of the Sky. Models and Science. Constellations 9/26/2013

The Celestial Sphere. Chapter 1 Cycles of the Sky. Models and Science. Constellations 9/26/2013 Chapter 1 Cycles of the Sky The Celestial Sphere A useful, spherical map of the sky, with the Earth in the center of a giant celestial sphere. Stars and planets are plotted on the sphere, at the same distance.

More information

ASTR 105 Intro Astronomy: The Solar System. In-class group projects starting today. Clicker Question. Clicker Question

ASTR 105 Intro Astronomy: The Solar System. In-class group projects starting today. Clicker Question. Clicker Question Apparent Motions of Stars on the Sky REVIEW ASTR 105 Intro Astronomy: The Solar System View from north pole In-class group projects starting today View from generic location View from Equator What would

More information

How we map the Heavens THE CELESTIAL SPHERE

How we map the Heavens THE CELESTIAL SPHERE How we map the Heavens THE CELESTIAL SPHERE Measuring the Sky 180 from one side of the Horizon to the other 1 degree ( ) = 60 arcminutes ( ) 1 arcminute ( ) = 60 arcseconds ( ) To view properly, stand

More information

Eratosthenes Determines the Size of the Earth in about 200 B.C.

Eratosthenes Determines the Size of the Earth in about 200 B.C. Eratosthenes Determines the Size of the Earth in about 200 B.C. Sun's rays Syene Alexandria N S 7.2 o Earth He knows the distance between the two cities is 5000 "stadia". From geometry then, 7.2 o 5000

More information

Astronomy 12 Unit Test Review Charting the Sky

Astronomy 12 Unit Test Review Charting the Sky Astronomy 12 Unit Test Review Charting the Sky Astronomer: Part I- Multiple choice: Answer each question by shading the most appropriate bubble. 01. Astronomy is the study of a. the stars and planets and

More information

Lecture #3: Plan. (Scientific Method) Constellations Celestial Sphere Diurnal Motion Celestial Coordinates Ecliptic Equinoxes & Soltices

Lecture #3: Plan. (Scientific Method) Constellations Celestial Sphere Diurnal Motion Celestial Coordinates Ecliptic Equinoxes & Soltices Lecture #3: Plan (Scientific Method) Constellations Celestial Sphere Diurnal Motion Celestial Coordinates Ecliptic Equinoxes & Soltices v Seasons v Phases of the Moon v Eclipses Scientific Method Propose

More information

The Four Seasons. A Warm Up Exercise. A Warm Up Exercise. A Warm Up Exercise. The Moon s Phases

The Four Seasons. A Warm Up Exercise. A Warm Up Exercise. A Warm Up Exercise. The Moon s Phases The Four Seasons A Warm Up Exercise What fraction of the Moon s surface is illuminated by the Sun (except during a lunar eclipse)? a) Between zero and one-half b) The whole surface c) Always half d) Depends

More information

UCCS PES 1090: Astronomy Lab I Spring/Summer/Fall Celestial Sphere name:

UCCS PES 1090: Astronomy Lab I Spring/Summer/Fall Celestial Sphere name: UCCS PES 1090: Astronomy Lab I Spring/Summer/Fall Celestial Sphere name: 1. What is the celestial sphere? a. An observatory dome. b. The Sun. c. The Earth. d. The imaginary sphere in the sky, on which

More information

CELESTIAL MOTIONS. In Charlottesville we see Polaris 38 0 above the Northern horizon. Earth. Starry Vault

CELESTIAL MOTIONS. In Charlottesville we see Polaris 38 0 above the Northern horizon. Earth. Starry Vault CELESTIAL MOTIONS Stars appear to move counterclockwise on the surface of a huge sphere the Starry Vault, in their daily motions about Earth Polaris remains stationary. In Charlottesville we see Polaris

More information

Definition heliocentric: sun is the center of the solar system

Definition heliocentric: sun is the center of the solar system Heliocentric Model Earth, Moon, and Sun Definition heliocentric: sun is the center of the solar system Earth rotates on its axis Moon revolves around earth as the earth revolves around the sun Motion of

More information

Today. Solstices & Equinoxes Precession Phases of the Moon Eclipses. Ancient Astronomy. Lunar, Solar FIRST HOMEWORK DUE NEXT TIME

Today. Solstices & Equinoxes Precession Phases of the Moon Eclipses. Ancient Astronomy. Lunar, Solar FIRST HOMEWORK DUE NEXT TIME Today Solstices & Equinoxes Precession Phases of the Moon Eclipses Lunar, Solar Ancient Astronomy FIRST HOMEWORK DUE NEXT TIME The Reason for Seasons Hypothesis check: How would seasons in the northern

More information

The Night Sky. A view to the north above the new Gemini telescope.

The Night Sky. A view to the north above the new Gemini telescope. Stars fixed positions relative to one another absolute positions move east to west with diurnal rotation of the whole sky which stars are visible depends on the time, season, and position on Earth can

More information

CELESTIAL COORDINATES

CELESTIAL COORDINATES ASTR 1030 Astronomy Lab 27 Celestial Coordinates CELESTIAL COORDINATES GEOGRAPHIC COORDINATES The Earth's geographic coordinate system is familiar to everyone - the north and south poles are defined by

More information

Reasons for Seasons. Question: TRUE OR FALSE. Question: TRUE OR FALSE? What causes the seasons? What causes the seasons?

Reasons for Seasons. Question: TRUE OR FALSE. Question: TRUE OR FALSE? What causes the seasons? What causes the seasons? Reasons for Seasons Question: TRUE OR FALSE? Earth is closer to the Sun in summer and farther from the Sun in winter. Question: TRUE OR FALSE? Earth is closer to the Sun in summer and farther from the

More information

Chapter 7. Mapping the Sky. Earth s Coordinate System

Chapter 7. Mapping the Sky. Earth s Coordinate System BASICS OF RADIO ASTRONOMY Chapter 7 Objectives: When you have completed this chapter, you will be able to describe the terrestrial coordinate system; define and describe the relationship among the terms

More information

8.5: Motions of Earth, the Moon, and Planets pg. 320

8.5: Motions of Earth, the Moon, and Planets pg. 320 8.5: Motions of Earth, the Moon, and Planets pg. 320 Key Concepts: 1. Careful observation of the night sky can offer clues about the motion of celestial objects. 2. Celestial objects in the Solar System

More information

EDMONDS COMMUNITY COLLEGE ASTRONOMY 100 Winter Quarter 2007 Sample Test # 1

EDMONDS COMMUNITY COLLEGE ASTRONOMY 100 Winter Quarter 2007 Sample Test # 1 Instructor: L. M. Khandro EDMONDS COMMUNITY COLLEGE ASTRONOMY 100 Winter Quarter 2007 Sample Test # 1 1. An arc second is a measure of a. time interval between oscillations of a standard clock b. time

More information

I fyou gaze away from the city lights on a clear night, it will seem

I fyou gaze away from the city lights on a clear night, it will seem Section 22.2 22.2 The Earth-Moon-Sun System 1 FOCUS Section Objectives 22.4 Describe the movements of Earth known as rotation, revolution, and precession. 22.5 Explain how the moon goes through phases.

More information

Regents Earth Science Unit 6: Celestial Motions Celestial Sphere

Regents Earth Science Unit 6: Celestial Motions Celestial Sphere Regents arth cience Unit 6: Celestial Motions Celestial phere Celestial Object any object outside arth s atmosphere (in space) ex.: moon, un, planets, stars Celestial phere a model used to represent the

More information

Chapter 2 Discovering the Universe for Yourself 1/22/09 1

Chapter 2 Discovering the Universe for Yourself 1/22/09 1 Chapter 2 Discovering the Universe for Yourself 1 2.1 Patterns in the Night Sky Our goals for learning: What does the universe look like from Earth? Why do stars rise and set? Why do the constellations

More information

Introduction to the sky

Introduction to the sky Introduction to the sky On a clear, moonless night, far from city lights, the night sky is magnificent. Roughly 2000 stars are visible to the unaided eye. If you know where to look, you can see Mercury,

More information

OBJECT: To become familiar with some of the motions of the stars, Sun, Moon and planets as seen from the surface of the Earth.

OBJECT: To become familiar with some of the motions of the stars, Sun, Moon and planets as seen from the surface of the Earth. INSIDE LAB 2: Celestial Motions OBJECT: To become familiar with some of the motions of the stars, Sun, Moon and planets as seen from the surface of the Earth. DISCUSSION: As seen from a point of view centered

More information

AST 105 HW #1 Solution

AST 105 HW #1 Solution AST 105 HW #1 Solution Week of August 24 th, 2015 Note: All Problems are from The Cosmic Perspective (6ed) Chapter 1 2. Briefly describe the major levels of structure (such as planet, star, galaxy) in

More information

Lecture Outlines PowerPoint. Chapter 21 Earth Science 11e Tarbuck/Lutgens

Lecture Outlines PowerPoint. Chapter 21 Earth Science 11e Tarbuck/Lutgens Lecture Outlines PowerPoint Chapter 21 Earth Science 11e Tarbuck/Lutgens 2006 Pearson Prentice Hall This work is protected by United States copyright laws and is provided solely for the use of instructors

More information

Astronomy 1 Fall UCSB Astro 1 - Martin

Astronomy 1 Fall UCSB Astro 1 - Martin Astronomy 1 Fall 2016 Lecture 2; September 27, 2016 Review of Previous Lecture REVIEW OF LECTURE 1 Science is falsifiable and repeatable. Introduced planets, stars, and galaxies. Reviewed some scientific

More information

Astro 101 F15 Test 1. Name: Multiple Choice Identify the choice that best completes the statement or answers the question.

Astro 101 F15 Test 1. Name: Multiple Choice Identify the choice that best completes the statement or answers the question. Name: Astro 101 Test 1 Multiple Choice Identify the choice that best completes the statement or answers the question. 1. Which of following BEST describes the science of astronomy? a. Measuring the movements

More information

The Night Sky II. Lecture 26. Finding objects using coordinates

The Night Sky II. Lecture 26. Finding objects using coordinates The Night Sky II Lecture 26 Lec. 26: The Night Sky II 1 Lecture Topics Astronomical coordinates The changing sky Using RA and Dec Finding objects using coordinates What s up tonight? If time: Planetarium

More information

7th Grade Astronomy. Read and answer each question carefully. 1) When viewing a solar eclipse, what is the phase of the moon?

7th Grade Astronomy. Read and answer each question carefully. 1) When viewing a solar eclipse, what is the phase of the moon? Read and answer each question carefully. 1) When viewing a solar eclipse, what is the phase of the moon? A) Waning gibbous B) Waxing gibbous C) New moon D) Full moon 2) In the picture shown, what is the

More information

Page 1. Name: Questions 1 through 4 refer to the following: Questions 5 and 6 refer to the following:

Page 1. Name: Questions 1 through 4 refer to the following: Questions 5 and 6 refer to the following: Name: 3211-1 - Page 1 Questions 1 through 4 refer to the following: Questions 5 and 6 refer to the following: The diagram below represents a plastic hemisphere upon which lines have been drawn to show

More information

Physics 130 Astronomy Exam #1 July 19, 2004

Physics 130 Astronomy Exam #1 July 19, 2004 Physics 130 Astronomy Exam #1 July 19, 2004 Name Multiple Choice: 1. A scientist observes a new phenomenon that disagrees with his explanation or hypothesis. Following the scientific methods, he should

More information

Chapter 2 Review Clickers. The Cosmic Perspective Seventh Edition. Discovering the Universe for Yourself Pearson Education, Inc.

Chapter 2 Review Clickers. The Cosmic Perspective Seventh Edition. Discovering the Universe for Yourself Pearson Education, Inc. Review Clickers The Cosmic Perspective Seventh Edition Discovering the Universe for Yourself The sky is divided into 88 zones called a) degrees. b) tropics. c) constellations. d) signs. The sky is divided

More information

Glossary. Altitude: The distance a heavenly body appears above the horizon as measured in degrees. Asteroid Belt :

Glossary. Altitude: The distance a heavenly body appears above the horizon as measured in degrees. Asteroid Belt : Glossary Altitude: Annual Motion : Aphelion : Asteroid Belt : Asteroids : Asterism: Astronomy: Atmosphere: Axis: Binary Stars : Black Hole: Blue Moon : Calibrate: Celestial Equator: Celestial Hemisphere:

More information

Guide to Using Starry Night Enthusiast With Questions

Guide to Using Starry Night Enthusiast With Questions Guide to Using Starry Night Enthusiast With Questions Initial View When you first start Starry Night Enthusiast you will see a view of the sky, looking South. You may find that you are looking at the starry

More information

Motions of the Earth and Moon

Motions of the Earth and Moon Motions of the Earth and Moon Motions of the Moon The Moon revolves around Earth once in 27.32 days. This is called its sidereal period of revolution because it is measured relative to the stars. The Moon

More information

Celestial Observations

Celestial Observations Celestial Observations Earth experiences two basic motions: Rotation West-to-East spinning of Earth on its axis (v rot = 1770 km/hr) (v rot Revolution orbit of Earth around the Sun (v orb = 108,000 km/hr)

More information

ASTR 693A Coordinate systems

ASTR 693A Coordinate systems ASTR 693A Coordinate systems The following notes contain the essential information you ll need to understand where astronomical sources are in the sky. Further details can be found in Textbook on Spherical

More information

COORDINATE SYSTEMS. What will you learn in this Lab?

COORDINATE SYSTEMS. What will you learn in this Lab? COORDINATE SYSTEMS What will you learn in this Lab? This lab is designed to introduce you to some of the coordinate systems used by astronomers. The coordinate systems to be introduced are Longitude and

More information

The diagram shows the apparent paths of the Sun in relation to a house in the northeastern United States on June 21 and December 21.

The diagram shows the apparent paths of the Sun in relation to a house in the northeastern United States on June 21 and December 21. Teacher: Mr. gerraputa Print Close Name: 1. Approximately how many hours of daylight are received at the North Pole on June 21? 1. 0 3. 18 2. 12 4. 24 2. The diagram shows the apparent paths of the Sun

More information

Moon, Sun, and eclipses

Moon, Sun, and eclipses Moon, Sun, and eclipses The Moon orbits the Earth and returns to the same right ascension every 27.32 days. (It moves eastward against the background of stars.) This is the sidereal (si-der-e-al) period

More information

Reason for the Seasons Notes

Reason for the Seasons Notes Reason for the Seasons Notes Seasons Vocabulary Seasons - Due to the tilt of earth as it travels around the Sun, we have spring, summer, fall, and winter. Source: http://www.srh.noaa.gov/abq/features/whatcausestheseasons/summersolstice2008.php

More information

MEASURING THE SKY. A Quick Guide to the Celestial Sphere. By Jim Kaler. Return to STARS or SKYLIGHTS

MEASURING THE SKY. A Quick Guide to the Celestial Sphere. By Jim Kaler. Return to STARS or SKYLIGHTS MEASURING THE SKY A Quick Guide to the Celestial Sphere By Jim Kaler Return to STARS or SKYLIGHTS THE CELESTIAL SPHERE We observe the sky as it looks, not as it is. You feel like you are on top of the

More information

Phys Lab #1:! The Sun and the Constellations!

Phys Lab #1:! The Sun and the Constellations! Phys 10293 Lab #1: The Sun and the Constellations Introduction Astronomers use a coordinate system that is fixed to Earth s latitude and longitude. This way, the coordinates of a star or planet are the

More information

Motions of the Moon and Eclipses

Motions of the Moon and Eclipses Motions of the Moon and Eclipses The Moon revolves around the Earth and rotates on its axis with the same period. The combined effect of these two motions means that one side of the Moon always faces the

More information

Celestial Coordinates I

Celestial Coordinates I Equipment: Star Charts, Planisphere. Celestial Coordinates I Objective: To become acquainted with basic navigation of the night sky. Discussion: From our vantage point on Earth, the night sky has the appearance

More information

Meridian Circle through Zenith, North Celestial Pole, South Celestial Pole

Meridian Circle through Zenith, North Celestial Pole, South Celestial Pole Chapter 3 How Earth and Sky Work- Effects of Latitude In chapters 3 and 4 we will learn why our view of the heavens depends on our position on the Earth, the time of day, and the day of the year. We will

More information

Where is the Moon in the orbit? The full moon rises at approximately:

Where is the Moon in the orbit? The full moon rises at approximately: East Where is the Moon in the orbit? The full moon rises at approximately: Sunlight Sunlight Sunlight A. Midnight B. Sunset C. Sunrise D. 9 PM E. It rises at different times during the year Third Which

More information

Eclipses and the Motion of the Moon. Chapter Three

Eclipses and the Motion of the Moon. Chapter Three Eclipses and the Motion of the Moon Chapter Three ASTR 111 003 Fall 2007 Lecture 03 Sep. 17, 2007 Introduction To Modern Astronomy I: Solar System Introducing Astronomy (chap. 1-6) Planets and Moons (chap.

More information

Motions of the Earth and Moon

Motions of the Earth and Moon Motions of the Earth and Moon Motions of the Moon The moon revolves around Earth once in 27.32 days. This is called its sidereal period of revolution because it is measured relative to the stars. The moon

More information

Time and the Sky. The Basics

Time and the Sky. The Basics Time and the Sky How do we know when and where can we find a celestial object in our sky? A knowledge and use of the concepts of time and our Celestial Coordinate System offers the best, systematic approach

More information

CELESTIAL CLOCK - THE SUN, THE MOON, AND THE STARS

CELESTIAL CLOCK - THE SUN, THE MOON, AND THE STARS INTRODUCTION CELESTIAL CLOCK - THE SUN, THE MOON, AND THE STARS This is a scientific presentation to provide you with knowledge you can use to understand the sky above in relation to the earth. Before

More information

Name. 1. Most of the stars found in our galaxy are in multiple star systems. a) True b) False

Name. 1. Most of the stars found in our galaxy are in multiple star systems. a) True b) False Name Physical Science 113 - Astronomy Exam I Indicate the most correct answer on your scantron sheet. This is only one correct answer for each question. 1. Most of the stars found in our galaxy are in

More information

(Part I) 1. Practice Quiz 2. Introduction 3. Earth Spins Around Its Axis 4. Earth Revolves Around the Sun 5. Summary

(Part I) 1. Practice Quiz 2. Introduction 3. Earth Spins Around Its Axis 4. Earth Revolves Around the Sun 5. Summary (Part I) 1. Practice Quiz 2. Introduction 3. Earth Spins Around Its Axis 4. Earth Revolves Around the Sun 5. Summary Review Astronomy is the study of objects outside of the Earth s atmosphere This is a

More information

The following words and their definitions should be addressed before completion of the reading:

The following words and their definitions should be addressed before completion of the reading: Seasons Vocabulary: The following words and their definitions should be addressed before completion of the reading: sphere any round object that has a surface that is the same distance from its center

More information

ClassAction: Lunar Cycles Module Instructor s Manual

ClassAction: Lunar Cycles Module Instructor s Manual ClassAction: Lunar Cycles Module Instructor s Manual Table of Contents Section 1: Warm-up Questions... 3 Full Moon and Sun... 4 Limb of the Moon..5 Section 2: General Questions.. 6 Phases of the Moon I...

More information

ASTR 1030 Astronomy Lab 65 Celestial Motions CELESTIAL MOTIONS

ASTR 1030 Astronomy Lab 65 Celestial Motions CELESTIAL MOTIONS ASTR 1030 Astronomy Lab 65 Celestial Motions CELESTIAL MOTIONS SYNOPSIS: The objective of this lab is to become familiar with the apparent motions of the Sun, Moon, and stars in the Boulder sky. EQUIPMENT:

More information

Astronomy AST-1002 Section 0425 Discover the Universe Spring 2017

Astronomy AST-1002 Section 0425 Discover the Universe Spring 2017 Astronomy AST-1002 Section 0425 Discover the Universe Spring 2017 Instructor: Dr. Francisco Reyes Web Page: http://www.astro.ufl.edu/~freyes/classes/ast1002/index.htm Textbook: Astronomy: A Beginners Guide

More information

The Motion of the Sun, Earth, and Stars. Day 1: How to Describe the Sky The Motions of the Stars

The Motion of the Sun, Earth, and Stars. Day 1: How to Describe the Sky The Motions of the Stars The Motion of the Sun, Earth, and Stars Day 1: How to Describe the Sky The Motions of the Stars We know...... that the Earth rotates once every day (in what direction?)... that the Earth orbits around

More information

Astron 100 Sample Exam 1 1. Solar eclipses occur only at (A) New moon (B) 1 st quarter moon (C) Full moon (D) 3 rd quarter moon (E) The equinoxes 2.

Astron 100 Sample Exam 1 1. Solar eclipses occur only at (A) New moon (B) 1 st quarter moon (C) Full moon (D) 3 rd quarter moon (E) The equinoxes 2. Astron 100 Sample Exam 1 1. Solar eclipses occur only at (A) New moon (B) 1 st quarter moon (C) Full moon (D) 3 rd quarter moon (E) The equinoxes 2. If the Moon is at first quarter tonight in Amherst,

More information

Lab 2: The Earth-Moon System and the Sun and Seasons

Lab 2: The Earth-Moon System and the Sun and Seasons Lab 2: The Earth-Moon System and the Sun and Seasons Moon Phases We heard lectures about the moon yesterday, so here we will go through some interactive questions for lunar phases. Go to http://astro.unl.edu/naap/lps/lps.html.

More information

Kinesthetic Astronomy: Longer Days, Shorter Nights

Kinesthetic Astronomy: Longer Days, Shorter Nights GRADE LEVEL 3 rd -8 th ; California Content Standards for 3 rd, 5 th, 6 th 8 th SUBJECTS Earth & Space Science, Using Models DURATION Preparation: 20 minutes Activity: 60 minutes SETTING Classroom Objectives

More information

Earth s Motions Big Questions:

Earth s Motions Big Questions: Earth s Motions Earth s Motions Big Questions: How can we make a model to help us understand our universe? What are the motions of the Earth? How do we know? How do the motions of the Earth affect our

More information

ESCI 110: Earth-Sun Relationships Page 4-1. Exercise 4. Earth-Sun Relationships and Determining Latitude

ESCI 110: Earth-Sun Relationships Page 4-1. Exercise 4. Earth-Sun Relationships and Determining Latitude ESCI 110: Earth-Sun Relationships Page 4-1 Introduction Exercise 4 Earth-Sun Relationships and Determining Latitude As the earth revolves around the sun, the relation of the earth to the sun affects the

More information

Earth and Space. How Earth Moves. Earth Spins. Day and Night

Earth and Space. How Earth Moves. Earth Spins. Day and Night Earth and Space How Earth Moves Earth is always moving. You cannot feel Earth move because you move with it. But things you see can help you know that Earth moves. For example, you can see the sun and

More information

1 Astronomical Coordinate Systems... Continued

1 Astronomical Coordinate Systems... Continued General Astronomy (29:61) Fall 2012 Lecture 4 Notes, August 27, 2012 1 Astronomical Coordinate Systems... Continued 1.1 The Equatorial Coordinate System The most basic astronomical observation is that

More information

THE NIGHT SKY- Finding Your Way

THE NIGHT SKY- Finding Your Way ASTRONOMY 101 Laboratory NAME SECTION THE NIGHT SKY- Finding Your Way WEEK 1 USING The Edmund Scientific Star and Planet Locator The instructor will present a brief over view. See image below and your

More information

Rotation of the Earth

Rotation of the Earth Earth rotates from West to East Axis of Rotation Why does the Sun appear to rise in the east and set in the west? link to animation by Barth Van Bossuyt 2011 Rotation of the Earth Rotation is the spin

More information

Motions of Earth, Moon, and Sun

Motions of Earth, Moon, and Sun Motions of Earth, Moon, and Sun Apparent Motions of Celestial Objects An apparent motion is a motion that an object appears to make. Apparent motions can be real or illusions. When you see a person spinning

More information

Note S1: Eclipses & Predictions

Note S1: Eclipses & Predictions The Moon's Orbit The first part of this note gives reference information and definitions about eclipses [14], much of which would have been familiar to ancient Greek astronomers, though not necessarily

More information

CHAPTER 17 EARTH S CYCLES

CHAPTER 17 EARTH S CYCLES CHAPTER 17 EARTH S CYCLES Lesson 1 How does Earth move? Earth spins like a top as it circles around and around the Sun. Earth is tipped to one side as it moves. This tilt causes the changing seasons. Why

More information

ì<(sk$m)=bdifce< +^-Ä-U-Ä-U

ì<(sk$m)=bdifce< +^-Ä-U-Ä-U Genre Comprehension Skill Text Features Science Content Nonfiction Sequence Captions Call Outs Diagrams Glossary Day and Night Sky Scott Foresman Science 3.15 ì

More information

I. Introduction: II. Maps of the Earth: NAME: COORDINATE SYSTEMS. What will you learn in this Lab?

I. Introduction: II. Maps of the Earth: NAME: COORDINATE SYSTEMS. What will you learn in this Lab? NAME: COORDINATE SYSTEMS What will you learn in this Lab? This lab is designed to introduce you to some of the coordinate systems used by astronomers. The coordinate systems to be introduced are Longitude

More information

3 - Celestial Sphere

3 - Celestial Sphere 3 - Celestial Sphere Purpose: To construct and use a Celestial Sphere to show the motion of the Sun and stars in the sky. Materials: 2 plastic hemispheres wood base star chart sheets - north and south

More information

Unit 5 Test

Unit 5 Test 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. Unit 5 Test 1. How many days does it take to complete a single Lunar Cycle? A. About 365 B. About 1 C. About 28

More information

Partners(s) NAVIGATING THE STARS USING THE CELESTIAL SPHERE

Partners(s) NAVIGATING THE STARS USING THE CELESTIAL SPHERE Name Partners(s) Section Date NAVIGATING THE STARS USING THE CELESTIAL SPHERE After your instructor has shown you how to set your position on the celestial sphere, answer the following questions. 1. Set

More information

A Warm Up Exercise. The Motion of the Sun. A Warm Up Exercise. A Warm Up Exercise. A Warm Up Exercise

A Warm Up Exercise. The Motion of the Sun. A Warm Up Exercise. A Warm Up Exercise. A Warm Up Exercise A Warm Up Exercise The Motion of the Sun Which of the following is NOT true of a circumpolar star? a) It rises and sets from my latitude b) Its direction can be far North c) Its direction can be far South

More information

Chapter 1 Charting the Heavens The Foundations of Astronomy. Astronomy: The Oldest Science. Questions to ponder. Scale.

Chapter 1 Charting the Heavens The Foundations of Astronomy. Astronomy: The Oldest Science. Questions to ponder. Scale. Chapter 1 Charting the Heavens The Foundations of Astronomy Chapter 1: Charting the Heavens Scale: relative size and distance units speed of light, distance, and time Measuring distance and size triangulation

More information

ASTRONOMY 161. Introduction to Solar System Astronomy

ASTRONOMY 161. Introduction to Solar System Astronomy ASTRONOMY 161 Introduction to Solar System Astronomy Seasons & Calendars Monday, January 8 Season & Calendars: Key Concepts (1) The cause of the seasons is the tilt of the Earth s rotation axis relative

More information

PHYS-1000 Chapter 2 Homework Solutions Due: September 9, 2012

PHYS-1000 Chapter 2 Homework Solutions Due: September 9, 2012 1. Two stars that are in the same constellation A. must both be part of the same cluster of stars in space. B. must both have been discovered at about the same time. C. may actually be very far away from

More information

Prelab for Coordinate Systems. 1. Define the 3 major coordinate systems used in astronomy (Complete sentences):

Prelab for Coordinate Systems. 1. Define the 3 major coordinate systems used in astronomy (Complete sentences): AST 113 Spring 2008 Prelab for 1. Define the 3 major coordinate systems used in astronomy (Complete sentences): Horizon: Equatorial: Ecliptic: 2. What defines the origins (zero points) for these coordinate

More information

MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.

MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 1) Which of the following statements about the celestial equator is true at all latitudes? A) It extends

More information