Physical Science
Quarter 4 – Module 2:
Celestial Observations of
Ancient Astronomers
Physical Science – Grade 11/12
Quarter 4 – Module 2: Celestial Observations of Ancient Astronomers
First Edition, 2021
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Physical Science
Quarter 4 – Module 2:
Celestial Observations of
Ancient Astronomers
Introductory Message
For the facilitator:
As a facilitator, you are expected to orient the learners on how to use
this module. You also need to keep track of the learners' progress while
allowing them to manage their own learning at home. Furthermore, you are
expected to encourage and assist the learners as they do the tasks included
in the module.
For the learner:
As a learner, you must learn to become responsible of your own
learning. Take time to read, understand, and perform the different activities
in the module.
As you go through the different activities of this module be reminded of
the following:
1. Use the module with care. Do not put unnecessary mark/s on any part
of the module. Use a separate sheet of paper in answering the exercises.
2. Don’t forget to answer Let Us Try before moving on to the other
activities.
3. Read the instructions carefully before doing each task.
4. Observe honesty and integrity in doing the tasks and checking your
answers.
5. Finish the task at hand before proceeding to the next.
6. Return this module to your teacher/facilitator once you are done.
If you encounter any difficulty in answering the tasks in this module,
do not hesitate to consult your teacher or facilitator. Always bear in mind that
you are not alone. We hope that through this material, you will experience
meaningful learning and gain deep understanding of the relevant
competencies. You can do it!
ii
Let Us Learn
A wonderful day to you little scientist! In this module, you will learn the
concept of Celestial Observations of Ancient Astronomers.
Specifically, you are expected to:
Cite examples of astronomical phenomena known to astronomers
before the advent of telescope.
Let Us Try!
Instruction: Choose the letter of the correct answer. Write the chosen letter
on a separate sheet of paper
1.
How did ancient people make use of their observations in the sky?
A. They used it to plan for war and conquer new lands.
B. They used it to entertain themselves during the night.
C. They used it to predict their future and make stories of heroes.
D. They used it for telling time, navigation, agriculture and religious
practices.
2.
What would you expect to see if the moon passes directly between
Earth and the Sun?
A. Solar eclipse
B. Lunar eclipse
C. Phases of the Moon
D. Motion of planets
3.
Constellations are patterns of stars in the night sky that change from
season to season. Which constellation does NOT belong to the group?
A. Leo
B. Virgo
C. Aries
D. Orion
4.
Which astronomical phenomena was used to mark the onset of
seasons?
A. Motion of planets
B. Appearance of comets
C. Occurrence of eclipses
D. Changing positions of the constellations
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5.
What kind of motion is exhibited by planets that puzzled ancient
astronomers for centuries?
A. eastward motion
B. retrograde motion
C. fixed motion
D. seasonal motion
Let Us Study
Have you ever tried looking up into the night sky away from the city
lights? What did you see? You definitely saw thousands of twinkling stars and
the bright Moon, right? Ancient people had much darker skies and were much
more familiar with the events of heavenly bodies than we are. Do you know
that ancient people were so attentive to many astronomical events in the sky?
Yes, they were so serious about studying the sky for very important reasons.
Early astronomers of ancient civilizations had very important and
practical reasons for studying the sky. They relied so much on the different
astronomical phenomena they observed in the sky to guide them in their daily
lives. Before the invention of the telescope, ancient people regarded the sky
as a big clock, a map, and a calendar for ancient astronomers. Some stars
(such as the North Star or Polaris) served as a navigational guide. Others
served as primitive calendars to predict planting and harvesting seasons and
celebrating their religious feasts. In a real sense, human survival depended
on knowledge of the heavens. That’s why it is not surprising to see ancient
structures built for the observation of astronomical phenomena throughout
the world. Moreover, the ability to predict and explain different astronomical
events was highly prized.
Many astronomical events have been observed since the beginning of
early civilizations. These events were diligently recorded which allowed
ancient people to understand them by creating ancient calendars and charts.
Ancient people also attributed these astronomical events to stories of heroism,
myths, and gods in order to understand them and connect with nature. So,
what are those examples of astronomical phenomena they knew by observing
the sky even without a telescope? Well, these are the things we will learn in
this module. The following are examples of astronomical phenomena known
to early astronomers even before the advent of the telescope.
8
Phases of the Moon (Lunar Phases)
Ancient astronomers had observed the phases of the moon for many
centuries. It takes 29.5 days for the Moon to go through its entire phase cycle.
Although half of the Moon is always being illuminated by the Sun, a person
on Earth will see the Moon changing its phases. These phases are the
results of the various angles people see the Moon being illuminated by the
Sun as it orbits the Earth. The picture below shows how the Moon undergoes
different phases as seen on Earth.
The Phases of the Moon
The eight major phases of the Moon are, in order, (1) new Moon, (2)
waxing crescent, (3) first quarter, (4) waxing gibbous, (5) full Moon,
(6) waning gibbous, (7) third quarter, and (8) waning crescent. It must be
remembered that the Moon doesn’t shine but it reflects light from the Sun.
When we see the completely illuminated side of the Moon, the phase is
full Moon (number 5 on the picture). If we can see half the sides of the Moon
are illuminated, the phases are called the first and third quarters (numbers
3 and 7). If the illuminated side of Moon seems to be getting larger, the Moon
is waxing, like in numbers 2 and 4. When it appears to be getting smaller,
the moon is waning, like in numbers 6 and 8. Furthermore, we can see a
crescent if less than half of the illuminated portion of the Moon is visible. It’s
called a gibbous when more than half of the illuminated portion of it is visible.
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The changing phases of the Moon is an important foundation of how
ancient people pursued to understand the heavens. They used the position of
the moon relative to the stars to determine the month, and the lunar phases
to determine the day in the month. Ancient people also used the lunar phases
to guide their planting seasons and determine the perfect time for their
religious ceremonies. Interestingly, the word month is derived from the word
Moon. The phases of the moon are the basis of creating ancient calendars.
Occurrence of Eclipses
Ancient astronomers also recorded the appearance of eclipses. An eclipse
happens when one celestial body like a moon or planet passes into the shadow
of another celestial body. Eclipses do not occur frequently because they need
specific alignment of the Sun, Moon, and Earth. The two types of eclipses that
we can observe on Earth are the lunar and solar eclipses.
A solar eclipse happens when the Moon passes between the Earth and the
Sun. However, a lunar eclipse happens when the Earth passes between the
Moon and the Sun. Both eclipses cause one heavenly body to partially or
totally cover the Sun.
Interesting discoveries in ancient astronomy were possible by studying
eclipses. One example was when Aristotle observed that the Earth’s shadow
10
had a circular shape as it moves across the moon. He suggested that this must
mean the Earth was round. Another Greek astronomer named Aristarchus
was able to estimate the distance of the Moon and Sun from Earth by
observing a lunar eclipse.
In contrast, eclipses had negative interpretations for ancient people. In
ancient Greece, a solar eclipse was seen as a sign that the gods were angry
and was thought to be an omen of bad things to come. For the Assyrians and
Babylonians, lunar eclipses were regarded as evil omens directed against their
kings. In ancient China, eclipses were seen as divine messages that foretell
the future of the Emperor. This made predicting eclipses to be of high
importance for them.
Motion of Planets
Aside from the Sun, Moon, and stars, ancient astronomers noticed five
objects appearing to be points of light that move relative to the other stars.
The Greeks gave this type of objects the name “planetes", meaning
"wanderers”. However, these planets were named after the Roman gods.
Mercury, Venus, Mars, Jupiter, and Saturn are the planets that have been
known and observed since prehistoric times.
The eastward motion of the planets against the background of fixed
stars was observed by ancient astronomers. As the planets move across the
sky, they would brighten and dim at different points in their motion. The
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problem in the observed behavior of planets was that of retrograde motion
which puzzled ancient astronomers for centuries. This is where a planet
seemed to move backwards on its path across the sky through the
constellations before returning to its normal direction. Nevertheless, this was
resolved by Nicolaus Copernicus after he proposed the heliocentric model
which placed the Sun at the center of the solar system instead of the Earth.
It must be noted that planets closer to the Sun revolve faster than the others
further away. Thus, the retrograde motion of a planet is an illusion that an
observer sees when Earth and a planet like Mars having different speeds
overtake each other while orbiting the Sun. The picture below shows the
retrograde motion of Mars.
The Retrograde Motions of Mars
Usually, the planets move along or near the ecliptic. The ecliptic is an
imaginary line in the sky that marks the annual path of the sun. This word is
derived from the fact that it marks the line along which eclipses occur. The
Moon as well as the zodiac constellations also move along or near this path.
To the naked eye, each of the five planets looks like a bright star. Venus
is the brightest planet and even brighter than the stars in the night sky.
Ancient people thought that the Sun and Moon are also planets but this is
not true in our modern astronomy. However, the days of the week were named
after the Sun, the Moon, and the five visible planets.
12
Changing Positions of the Constellations
Early astronomers from different civilizations found their own patterns
of stars in the night sky that change from season to season. These groupings
of stars are called constellations. Many constellations are well-known to be
visible in the night sky such as Orion, Ursa Major, Cassiopeia, and Cygnus.
However, the most familiar are those that comprise the star signs of the
zodiac: Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpius, Sagittarius,
Capricornus, Aquarius, and Pisces. They are also seen along the ecliptic.
Currently, modern astronomers officially recognize 88 constellations covering
the entire sky in the northern and southern hemispheres.
The Earth’s revolution around the Sun is causing the changes in the
positions of constellations over time. As the Earth revolves around the Sun,
different sets of stars appear at different points in the Earth's orbit. This
means that if we view a group of stars this month, they will appear in a
different position and another group of stars will start to appear in the night
sky the following month. The picture below shows how the twelve
constellations of the zodiac change month after month.
The Twelve Constellations of the Zodiac
Historically, the twelve constellations of the zodiac have acquired
special significance for thousands of years. Their changing positions and
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appearance throughout the year marked the onset of seasons. This allowed
the ancient people to create various calendars for them to know when to plant
crops and harvest them. Certain constellations were also utilized to help
seafarers travel across oceans. An example of this is the Ursa Major where
you can spot the Northern Star (Polaris). The height of the Northern Star can
determine your latitude and it will always lead you to a northward direction.
Appearance of Comets
Ancient civilizations also recorded the spectacular appearance of
comets. Comets are smaller celestial bodies that also revolve around the Sun.
They are thought to be leftovers after the formation of our solar system which
happened 4.6 billion years ago. A comet is mainly composed of rock, dust,
and frozen gas. When comets make their way closer to the Sun, they
eventually form tails of dust and ionized gas.
A Comet Appears in the Night Sky over a Mountain
A brilliant comet can be seen from Earth without using a telescope. As
comets move across the fixed background of stars, they first appear as bright,
glowing objects, and they appear to grow larger over time to reveal luminous
tails that can extend more before the comet eventually fades and disappears.
The appearance of a comet in the sky had negative interpretations to the
ancient people. Until the sixteenth century, comets were regarded as
bad omens of the deaths of kings or noblemen, incoming catastrophes, and
possible attacks of heavenly beings against humans.
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Let Us Practice
Activity 1.1: Matching Type
Instruction: Match column A with the correct statements on column B
regarding the examples of astronomical phenomena known to early
astronomers before the advent of the telescope. Write only the letter of the
correct answer on a separate sheet of paper.
COLUMN A
COLUMN B
1. Phases of the Moon
A. This explains the movement of five
visible
starlike
objects
moving
eastwards along the ecliptic relative
from the background stars and
exhibiting retrograde motion.
2. Occurrence of Eclipses
B. This represents the different shapes of
the Moon's portion illuminated by the
Sun as viewed from Earth.
3. Motion of Planets
C. It happens when different groups of
stars can be viewed in the night sky
as the Earth revolves around the Sun.
4. Changing Positions of
Constellations
D. This happens when an icy celestial
object moves closer to the Sun
revealing a luminous tail of dust and
gases.
5. Appearance of Comets
E. It happens when a celestial body
partially or totally covers another
celestial object.
Were you able to do it? I hope you find it easy. In the next activities, you
will still use what you have learned to accomplish them. Let’s continue our
learning journey in this module.
15
Let Us Practice More
Activity 1.2: Scrambled Words
Instruction: For this activity, study the scrambled letters and try to
unscramble or rearrange the letters to form a word or phrase that fits the
given clues. Write your answers on a separate sheet of paper.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
EANDRSEWR
IELONCSTLONSTA
ECTNRSEC
ETOCM
AOSLR PELSECI
EIAOSACPIS
EAHSPS FO HTE OMNO
TIASRSGTIUA
CI EPCTIL
TIUPRJE
_________________________________
_________________________________
_________________________________
_________________________________
_________________________________
_________________________________
_________________________________
_________________________________
_________________________________
_________________________________
The English translation of the Greek word “planetes”.
The different groups of stars forming patterns in the night sky.
The appearance of the moon when less than half of its visible part is lit.
The appearance of this celestial object is considered a bad omen of the
death of kings or noblemen by ancient people.
This happens when the Earth is between the Moon and the Sun and
the Moon partially or totally blocks out the Sun.
One of the well-known constellations.
The different ways the Moon looks from Earth over a month.
One of the twelve constellations of the zodiac.
The imaginary line on the sky that marks the annual path of the sun.
One of the five planets visible to the naked eye.
16
Let Us Remember
The study of the heavens especially certain astronomical phenomena
was very essential to the survival of the ancient people. They used it for timekeeping, navigation, agriculture, and religious practices. The examples of
astronomical phenomena that were known to early astronomers even before
the invention of the telescope are the following:
1. The phases of the Moon or lunar phases represent the different shapes
of the Moon's portion illuminated by the Sun as viewed from Earth. The
phases of the moon are the basis of creating ancient calendars.
2. The occurrence of eclipses happens when a celestial body partially or
totally covers another celestial object. The Sun, Moon, and Earth must
be on a specific alignment for this to occur. Ancient scientific
discoveries were possible by observing eclipses. However, eclipses were
regarded as signs that gods were angry and were thought to be an omen
of bad things to come.
3. The motion of planets explains the movement of the five bright starlike
objects visible in the sky that are moving eastwards along or near the
ecliptic relative to the background stars. The planets were also observed
to exhibit retrograde motion. The days of the week were named after the
Sun, the Moon, and the five visible planets (Mercury, Mars, Venus,
Jupiter, Saturn).
4. The changing positions of the constellations is a phenomenon by which
different groups of stars can be viewed in the night sky as the Earth
revolves around the Sun. Their changing positions and appearance
every year marked the onset of seasons and even helped seafarers travel
across oceans.
5. The appearance of comets happens when an icy celestial object moves
closer to the Sun revealing a luminous tail of dust and gases. This is a
natural celestial phenomenon however comets were usually considered
bad omens of the deaths of kings or noblemen, incoming catastrophes,
and possible attacks of heavenly beings against humans.
17
Let Us Assess
Instruction. Choose the letter of the correct answer. Write the chosen letter
on a separate sheet of paper
1.
What causes the change of constellations in the sky?
A. This is due to the rotation of Earth on its axis.
B. This is due to the motion of stars in the universe.
C. This is due to the motion of the Earth in its orbit around the Sun.
D. This is due to the motion of the Sun along the line of the ecliptic.
2.
How did ancient people make use of their observations in the sky?
A. They used it to plan for war and conquer new lands.
B. They used it to entertain themselves during the night.
C. They used it to predict their future and make stories of heroes.
D. They used it for telling time, navigation, agriculture, and religious
practices.
3.
Which of the following planets cannot be seen through the naked eye?
A. Venus
C. Neptune
B. Jupiter
D. Mercury
4.
What would you expect to see if the Moon passes directly between the
Sun and Earth?
A. Solar eclipse
C. Phases of the Moon
B. Lunar eclipse
D. Motion of planets
5.
How many days does the Moon complete its phases?
A. 26.5 days
C. 28.5 days
B. 27.5 days
D. 29.5 days
6.
Which constellation does NOT belong to the group?
A. Leo
C. Aries
B. Virgo
D. Orion
7.
Which astronomical phenomena was used as the basis of creating
ancient calendars?
A. Phases of the Moon
B. Occurrence of comets
C. Appearance of eclipses
D. Changing positions of the constellations
18
8.
Which astronomical phenomena was used to mark the onset of
seasons?
A. Motion of planets
C. Occurrence of eclipses
Changing positions of the
B. Appearance of comets
D.
constellations
9.
What would you expect to see when the Earth passes directly between
the Sun and the Moon?
A. Solar eclipse
C. Phases of the Moon
B. Lunar eclipse
D. Motion of planets
10.
Which astronomical phenomena is considered to foretell the future of
the Emperor in ancient China?
A. Motion of planets
C. Occurrence of eclipses
B. Phases of the Moon
D. Appearance of comets
11. Which astronomical phenomena signifies incoming catastrophes for
ancient people?
A. Motion of planets
C. Occurrence of eclipses
B. Appearance of comets
D. Phases of the Moon
12. What celestial bodies are moving along or near the ecliptic aside from
the five visible planets?
A. Sun, Moon, and Earth
B. Sun, Moon, and comets
C. Sun, Moon, and meteors
D. Sun, Moon, and zodiac constellations
13. What is the direction of the motion of planets along the ecliptic against
the background of fixed stars?
A. northward
C. eastward
B. southward
D. westward
14. Which planet is the brightest among the others that can be seen in the
night sky?
A. Venus
C. Neptune
B. Jupiter
D. Mercury
15. What kind of motion is exhibited by planets that puzzled ancient
astronomers for centuries?
A. eastward motion
B. retrograde motion
C. fixed motion
D. seasonal motion
19
Let Us Enhance
Instruction: Answer the following questions based on what you have learned
from the contents and activities of this module. Please refer to the rubric for
essay on how you will be scored on this part.
1.) How did ancient people use their knowledge of some astronomical
phenomena?
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
2.) Why does the Moon change phase?
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
3.) Why do constellations appear to change positions in the sky month
after month?
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
4.) How do you differentiate solar eclipse from lunar eclipse?
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
5.) How did the ancient people interpret the appearance of a comet?
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
20
RUBRIC FOR ESSAY
Excellent
Good
5 points
3 points
Poor
1 point
Content
The student showed an
excellent
understanding of the
topic and the content is
very informative.
The student showed a
good understanding of
the topic and the
content is quite
informative.
The student showed
no understanding of
the topic and the
content has no new
information.
Explanation
The student gave 3 or
more excellent
suggestions with very
good supporting
arguments.
The student gave 2 or
3 suggestions but the
supporting arguments
are somewhat weak.
The student gave 1 or
2 suggestions with
support but the
arguments are weak
or missing.
Grammar
and
Organization
The student’s
sentences were
grammatically correct
and the paragraphs are
well-written and
complete. There are
also no spelling and
punctuation errors.
The student’s
sentences had many
grammatical errors
and the paragraphs
had no structure.
There are many
spelling and
punctuation errors.
Conclusion
The student
summarized personal
thoughts in a very
convincing and
persuasive concluding
statement.
The student’s
sentences had minor
grammatical errors
and the paragraphs
are correct but with
few inconsistencies.
There are also few
spelling and
punctuation errors.
The student
summarized personal
thoughts but made a
somewhat weak
concluding statement.
The student did not
summarize personal
thoughts in the
concluding
statement.
Let Us Reflect
Astronomical observations were very essential to early astronomers for
the survival and growth of their civilizations. These astronomical events were
also used by ancient people as a source of myths and a guide to predict their
future much like what you hear from a horoscope since they believed that the
positions of stars and planets influence the events here on Earth. In at least
300 words, write an essay answering the question, “Do you think that stars
could predict someone else’s fate or destiny? Why?”. The essay rubric in
the previous activity is still the same guide to score your output. Please write
your answers on a separate sheet of paper.
________________________________________________________________
________________________________________________________________
________________________________________________________________
________________________________________________________________
21
22
Let Us Reflect
Let Us Practice More
Answers may vary.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Let Us Enhance
Answers may vary.
Let Us Assess
WANDERERS
CONSTELLATIONS
CRESCENT
COMET
SOLAR ECLIPSE
CASSIOPEIA
PHASES OF THE MOON
SAGITTARIUS
ECLIPTIC
JUPITER
1. C
2. D
3. C
4. A
Let Us Practice
5. D
6. D
1.
2.
3.
4.
5.
7. A
8. D
9. B
B
E
A
C
D
10.C
11.B
12.D
Let Us Try!
13.C
14.A
1.
2.
3.
4.
5.
15.B
D
A
D
D
B
Answer Key
References
“A brief history of astronomy,” Canadian Space Agency, last modified
March 12, 2020, https://www.asccsa.gc.ca/eng/astronomy/
basics/brief-history-astronomy.asp
“Classical planet,” Wikipedia, last modified February 4, 2021,
https://en.wikipedia.org/wiki/Classical_planet
“Comet,”
Wikipedia,
last
modified
February
12,
2021,
https://en.wikipedia.org/wiki/Comet#Early_observations_and
_thought
“Constellation,” Wikipedia, last modified February
https://en.wikipedia.org/wiki/Constellation
“Eclipse,”
Wikipedia,
last
modified
January
https://en.wikipedia.org/wiki/Eclipse
5,
28,
2021,
2021,
Frank Adam, Astronomy: At Play in the Cosmos, New York: W. W. Norton
& Company, 2016.
“History of Astronomy,” Wikipedia, last modified January 19, 2021,
https://en.wikipedia.org/wiki/History_of_astronomy
“Lunar
phase,” Wikipedia, last modified February
https://en.wikipedia.org/wiki/Lunar_phase
8,
2021,
“Naked Eyes,” Center for History of Physics-A Division of the American
Institute
of
Physics,
accessed
February
1,
2021
https://history.aip.org/exhibits/cosmology/tools/toolsnakedeyes.htm
OpenStax, Astronomy, Houston: Rice University Houston, 2018,
https://d3bxy9euw4e147.cloudfront.net/oscmsprodcms/medi
a/documents/Astronomy-OP_zItt6LJ.pdf
“The Early Origins of Astronomy,” Wikibooks, last modified June
17,2017,https://en.wikibooks.org/wiki/General_Astronomy/T
he_Early_Origins_of_Astronomy
Thomas T. Arny and Stephen E. Schneider. Explorations: An
Introduction to Astronomy, New York: McGraw-Hill, 2010.
“What
Is an Eclipse?,” NASA, last modified Aug
https://www.nasa.gov/audience/forstudents/58/features/nasa-knows/what-is-an-eclipse-58
7,
2017,
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