NATS 1745: History of Astronomy Exam Review
1. What celestial event is New grange aligned to? Describe what happens at New
Grange on this day.
New grange’s roofbox is aligned to the winter solstice sunrise. On the 21 of December at
sunrise, the hallway fills with a beam of light and is likely to reflect a belief in rebirth or
2. Describe what happens to the Sundagger on the solstices and equinoxes.
At noon on the solstice and equinoxes, the sundagger exhibits 2 beams of sunlight, which
either bisect or frame the spirals depending on the equinox/ solstice
3. What celestial event is Stonehenge aligned to? Describe what happens at
Stonehenge on this day.
Stonehenge’s heel stone is aligned with the summer solstice, the sun rises behind the heel
stone perfectly, (due to the precision of the equinoxes
4. Why do archeoastronomers suspect that Stonehenge's Heel Stone had a missing
When Stonehenge was built the sun rose beside the heel stone, making us believe that
there were originally 2 heel stones to frame the sun
5. What causes the Sun to rise and set every day?
Due to Earth's 24hour eastwardspin around its polar axis, the sun moves westward
across the sky, it rises in the east, reaches its highest point at noon, and then sets in the
6. What is the local time for an observer who is directly facing the opposite side of
the sky from Sun? What is the local time when the Sun is at its highest point in the
sky? What is the local time when the Sun is seen on the Eastern horizon? What is
the local time when the Sun is seen on the Western horizon?
Local noon for sun to be highest point
7. What is the azimuth of the noon Sun in the northern hemisphere? How about the
AZ in Northern = South
AZ in Southern = North
8. What does the word "solstice" mean? How does it describe what happens to the
Sun's rising and setting positions on the solstices?
The word solstice means solar standstill
The sun rising or setting position (the stop of that shift)
Identifies the sun’s rising and setting positions on its northernmost and southernmost
9. What is the azimuth of sunrise and sunset on the Northern winter solstice?
How about the Northern summer solstice? How about the equinoxes?
Azimuth – direction along the horizon,
Winter time sun is mostly south, the winter solstice has to be SE for sunrise and SW
for the set
Summer solstice (longer path), rising NE, setting NW
Equinoxes (equal rise and setting) – rising E, setting W
10. Describe how the Thirteen Towers of Chankillo, Peru were used to track the
time of year. Given that this site is in the southern hemisphere, what is the
approximate azimuth (NE, SE, NW, SW) of the winter solstice marker? How about
the summer solstice marker?
Summer, rise SE, set SW
Winter, rise NE, set NW
13 tower sthe sun shifts through the notches and each interval between the towers mark
If you want to see sunrise you would have to cross to the E side of the hill
11. Which day is the longest day of the year, and why? Which day is the shortest day
of the year, and why? What are the lengths of daytime and nighttime on the
Summer Solstice (June 22): Sun rises and sets at its northernmost position, traversing a
long high arc (longest day, highest noon sun)
Winter solstice (December 22): Sun rises and sets at its southernmost position,
traversing a short, low arc in the sky (shortest day of the year and lowest noon sun).
Fall and Spring Equinox (Sept 23) (fall equinox) and (spring equinox) March 21): Sun
rises due E and sets due W, spending equal time above and below the horizon (equal day
12. What causes the seasons? Describe the orientation of the Earth relative to the
Sun during Northern summer. What season does the Southern hemisphere
experience at this time, and why?
The seasonal changes is in the Sun's daily arc are due to Earth's 23.5 degrees tilt from its
orbit around the sun
Northern Summer the northern hemisphere is tilted towards the sun, the observer sees
the sun directly, it is higher in the sky and feels warmer because the light is more
concentrated Winter –the hemisphere is tilted away from the sun, sunlight hits indirectly (i.e. At an
angle), causing low arcs and less light per area, and less warmth
13. Within what latitudes can an observer see the Sun directly overhead? How did
these latitudes get their names?
Only within the Tropics can the sun be seen directly overhead (Tropic of Cancer) (N)
and Tropic of Capricorn (S) at noon.
The Sun is in the Cancer constellation when the Sun is directly overhead (June
Solstice) in the Northern Hemisphere and the Sun is in the constellation of Capricorn
when the sun is directly overhead in the Southern hemisphere.
14. What are polar nights and polar days? Within what latitudes do these occur?
Polar nights – 24hrs of nighttime
Polar days – 24hrs of daylight
They happen 23.5 degrees from the N/S poles
15. Where is the zenith? What is its altitude? What is the altitude of the horizon?
What is the altitude of a star that is halfway up the sky?
Where is the Zenith? The point in the sky directly above you (1st question on the exam),
everybody has their own zenith it moves with you.
The altitude of the Zenith 90 degrees
Altitude of horizon 0 degrees
Altitude of star half way up the sky between 45 degrees
16. Does a star's altitude and azimuth depend on the observer's location? How
about right ascension and declination?
Everybody has their own horizon, altitude and azimuth DOES depend on the person's
Right ascension and declination (Longitude and latitude they are coordinates) DOES
NOT depend on your own location
17. If a star has a declination of 10 degrees north, what is the star 10 degrees north
from? If a star has a right ascension of 1h, what is the star 1h from?
The star is 10 degrees North; it is 10 degrees north of the celestial equator
The star is 1 hour away from the line that we call, the line of zero right ascension, which
marks the position at Spring Equinox
18. Where are we on Earth if we see the Northern constellations rotating around our
zenith? What is the name of the point that these stars rotate around? What happens
to this point if we walk south? Where is this point seen when we're at the equator?
Where is this point when we walk south of the equator?
Northern Hemisphere North Celestial Pole
The constellations would get lower
The constellations would disappear into the horizon
19. If an observer sees Polaris at an altitude of 60 degrees, what is the observer's
Latitude is equal to altitude
20. What celestial object did the Polynesians use as the basis of their calendar?
What does this object consist of? How did the Polynesians use this object to identify
the 1st half and 2nd half of their calendar year? In ancient times, how was this
object used in the Andes to determine when to plant?
Pleiades (7 sisters) consist of stars (stars cluster)
Polynesian when Pleiades rose at sun set, that event defined the first half of their
calendar, (December), 6 months later when the Pleiades rose six months later it marked
the second half
If seven sisters were clear and bright they would plant their crops and if it were dim
and hazy they would delay the planting (agricultural marker)
21. What did the Polynesian navigators memorize in order to steer their canoes
while at sea?
Star Compass – Polynesian navigators memorized the rising and setting azimuths of the
bright stars in the sky
1. What motivated the imperial astronomers of Ancient China to monitor the skies?
Why were they more interested in comets and supernovae than in the planets?
The Ancient Chinese monitored the skies because it was the type of astrology they were
interested in, as they feel like something chaotic reflected chaos on earth. The planets are
normal and have predictable cycle to them.
2. What produced the Crab Nebula and Crab Pulsar? How do we know that the
Crab Pulsar is just over 950 years old?
A supernova produces the Crab Nebula/ Crab Pulsar. The pulsar was born when the core
of the supernova collapsed so the Chinese reveal it is 950 yrs. old.
3. In what 2 ways does the construction of the Mayan Pyramid of Kukulkan suggest
a connection to the sky?
365 steps (shows Mayans were aware of the sun's annual cycle)
Annual serpent pattern of light & shade tracks the time of year (ex. On the equinoxes,
full serpent ends at Kukulcan's head; all the triangle shades are on the body of the
serpent. ) 4. What do the remaining openings in the Mayan El Caracol suggest that this
building was used for?
The openings on the observatory are aligned to the N most point and the S most setting
positions of the planet Venus (allowed the Maya to measure the duration of
Venus' full path in the sky.)
5. What two celestial cycles are tracked in the Dresden codex?
Eclipse and Venus cycle.
6. Why did many ancient civilizations believe that eclipses are bad omens as well as
Long complex cycle that makes it hard to identify that eclipse have a long cycle.
7. What causes the Moon's phases? What is a lunation?
The Moon’s phases are caused by the shadow of the Earth onto the moon. A lunation is
number of days between 2 moons, about a month.
8. What are the configurations of the Earth, Moon and Sun during New moon, 1st
quarter moon, Full moon and 3rd quarter moon? What does a "waxing moon"
mean? How about a "waning moon"? Why are crescent moons seen primarily
during the day? Why are gibbous and full moons seen primarily at night?
New moon: the moon is in between the sun and earth. Full moon: the earth is between the
sun and the moon Waxing means that it is increasing (larger part of its visible surface
illuminated). The waning Moon means that it is decreasing (smaller part of its visible
surface illuminated, so that it appears to decrease in size). The Crescent moon is on same
side of the earth as the Sun (you can see it at night time when the sun goes down). A full
moon is on the opposite side of earth as the sun.
9. What is the Moon's phase during a solar eclipse, and what is causing the Sun to
darken? If an observer sees a total solar eclipse, where is this observer standing? If
an observer standing if he/she sees a partial solar eclipse?
During an eclipse the moon moves in front of the sun (covering the sun) causing it to
become dark. The observer is standing in the umbra where the light from the Sun is
completely blocked by the Earth. An observer standing in the penumbra would see ONLY
part of the sun. (This happen when the light from the sun is partly blocked by the earth,
but NOT completely.)
What does a partial solar eclipse look like?
Partial solar eclipse looks like chunk taken out of the sun
What will the Sun look like if you are standing outside the umbra and penumbra?
Standing outside the umbra and penumbra you will see the sun pecking around the edge
…you would not see the eclipse at all. 10. What is the Moon's phase during a lunar eclipse, and what is causing the
Moon to darken?
When full moon passes through earth’s shadow sunlight is cut off and the moon darkens
in lunar eclipse…. (Moon passing through earth’s entirely)… lunar eclipse last for a few
If a total lunar eclipse is seen, what is the Moon passing through?
When the Moon travels completely into the Earth’s umbra.
How about a partial lunar eclipse?
Happens when only part of the moon passes through the earth’s shadow.
How about a penumbral eclipse?
When the Moon passes through the Earth’s penumbral
What does a total lunar eclipse look like?
It would be copper reddish …the earth has an atmosphere and the sunlight is refracted
around the earth and casts red light on the moon during a total lunar eclipse.
If an observer on the night side of Earth witnesses a total lunar eclipse, will all
observers on the night side of Earth see a total lunar eclipse at the same time?
Observer witness eclipse moon. Yes…they will all see the same eclipse.
11. Why do eclipses not occur every lunation?
Moon orbit have 5degree tilt.
What do we call the time period when eclipses can occur?
On average, how many lunations’ are there between these time periods?
2 times a year
Why are there always at least 1 (or 2) solar eclipses and 1 (or 2) lunar eclipses
during these time periods?
Eclipse season 31381/2full cycle of the moon phases. Longer than 291/2 day than lunar
12. Why are lunar eclipses seen more frequently than solar eclipses?
Solar eclipses are seen less because the observer must be in the moons shadow
13. In the Dresden codex, what does the repeated occurrence of the numbers
'177' and '154' tell us that the Maya understood? What is the significance of the
length of the table?
Because that was the # of days between eclipse seasons The table spans 1 complete eclipse cycle of Mayan dates, so eclipse warnings could be
14. What 2 characteristics of the planet Venus caused the Mayans to identify it as a
special kind of star? Why did they worship this planet?
They associated its movement with the war and considered the most important celestial
body observed by the Mayans
15. What is a "heliacal rise" of Venus? What is it about Venus' appearance at this
time that made it a day of worship for the Maya?
Venus was a morning star…. Mayan could predict its date and direction
Extra info: (Venus appears as a morning star and then 50 days later as an evening star.
Venus was closely watched by the Mayans and was central to their mythologies of death
16. When is Venus seen (morning or evening) during the 236 days after its bright
heliacal rise? Is it getting brighter or dimmer, and why? Why does it disappear after
this period? When it finally reappears, is it a morning or evening star? For the next
250 days, is it getting brighter or dimmer? Why does it disappear again after this
period, before its next heliacal rise?
Venus is seen in the morning during its 236 days after it’s bright helical rise. It is getting
dimmer as time progresses, because it is moving away from the Earth. It disappears after
this period because it’s hidden behind the glare of the Sun. It is now an evening sun, and
it is gradually getting brighter. Venus disappears before its next helical rise because its
dark side faces the Earth.
17. In the Dresden codex, what do the pages containing the rows of 4 Tzolk'in dates
represent? What is the significance of the total number of rows in the table?
The Tzolk’in dates represent the Mayan date of helical rises, 236 days after the helical
rise (Venus’ disappearance), 90 days after the disappearence (the reappearance of Venus),
250 days after reappearence (the disappearance of Venus again). In short, the 4 days
represent one 548 day Venus cycle. The significance of the 65 rows, which is the number
of Venus cycles it takes for it to repeat itself.
18. What was the primary motivation for studying the sky in Ancient Egypt?
In Ancient Egypt, survival depended on the annual flooding of the Nile river. The sky
was therefore studied for time keeping.
19. Why do we see different stars and constellations at different times of the year?
We see different constellations at different times because Earth is moving through space
in its orbit around the Sun, therefore our visible window changes.
20. Why were the Ancient Egyptians able to use the heliacal rise of Sirius to
determine when the Nile river would flood? What was their mythical explanation
for the cause of the flood? Within the latitudes of Egypt, the heliacal rise of Sirius coincides with the Nile’s annual
flood. Their mythical explanation of why the Nile floods is that Ra (the sun god) needed
help pass through 12 gates during the night and if they helped him by using prayers,
incantations, and sacrifices he would thank them by givig them the flood which allowed
for fertile earth to plant crops.
21. Why did the Ancient Egyptians divide the day into 24 hours?
The Egyptians tracked time at night using a set of constellations which rise at
approximately equal intervals. On average, 12 of these constellations rise each night, so
the Egyptians divided night and day into 12 hours each
22. Why do we add a leap day every 4 years? Who incorporated this rule into our
calendar, and from what civilization did he learn this rule from?
We add a leap year every 4 years in order for the calendar to keep up with the seasons, as
a solar year is 365.242 days, not exactly 365 days. Julius Caesar incorporated this rule
after he learned it from the Egyptians.
23. What is the difference between a year in the Julian calendar and a year in the
Gregorian calendar? Which calender year is equal to the solar year? Which
calendar do we use today?
A year in the Julian calendar incorporates a 4year leapday (a 365 day calendar with 12
months of 2831 days), the Gregorian calendar fixes an 11.5 minute error by removing
leap days from years that are divisible by 100, but not 400. The Gregorian calendar is our
modern calendar and the solar year calendar.
24. What was the primary motivation for studying the sky in Ancient Babylon?
According to the textbook, why did this happen in Babylon but not in Egypt?
The Babylonians tracked the celestial cycles because they believed that the sky foretold
the future. This happened in Babylon but not in Egypt and they did not have a regular
cycle (like Egypt did), and therefore needed to look to the Gods in the sky for answers as
to what is going to happen in the future.
25. Describe (very generally) what we've learned about the Earth's daily spin from
the ancient Babylonian records of solar eclipses.
The Earth’s daily spin is slowing down very gradually and its a cyclical process (we will
eventually speed up)
26. From what civilization did we inherit our units of time and angle? (e.g. 60
minutes in 1 hour, 360 degrees in a circle.) Why are there so many 60s inthese units?
We inherited our units of time and angle from the Babylonians. It is a 60base system
because this number has many factors, therefore it is easily divisible.
27. Where are the zodiac constellations? Why were they significant to the
Babylonian astrologers? Why can we not see our astrological constellation in the
month we were born? The zodiac constellations lie along the ecliptic (path of the sun). They were significant to
the Babylonian astrologers as they were interested in which constellations the Sun, Moon,
and planets appear in each night. The constellations are not visible in the month we are
born, because zodiac is defined as the constellation that the sun is in front of, so therefore
you are facing your constellation during the day, when it is too bright to see it.
28. For each of the 5 visible planets, what aspect of their appearance was used to
choose the Babylonian/Greek god to name them for?
Mercury: (speedy scribe/ messenger God): named for its fast motion across the sky
Venus: (Godess of love/beauty): named for its brightness
Mars: (god of war/bloodshed): named for its red color
Jupiter: (father of the Gods): named for its brightness and “majestic” motion, kinglike
Saturn: (God of old age): named for its faintness and slow motion, much like an old
29. What are 3 starlike phenomena that match the description of the Star of
Bethlehem? Briefly describe each one. Why is it unlikely that the Star of
Bethlehem was one of these phenomena?
Supernova: the explosive death of a massive star (can appear as a temporary star)
Nova: the reignition of a dead star which has yanked fresh gas from a companion star
(can appear as a sudden, temporary star)
Comet: a rocky snowball in orbit around the Sun (can appear as a temporary star).
These are unlikely as no other civilizations recorded a sighting of these around 0 BC.
30. What is the only plausible celestial event to explain the Star of Bethlehem?
Describe what this event looks like and why it occurs. Why would such an event be
ignored by the court astronomers in Ancient China?
A planetary conjunction is when multiple planets line up in the same region of the sky
appearing as a bright star. A planetary conjunction is plausible because we can see that
Jupiter and Saturn lined up around that time. This may have been ignored by the Ancient
Chinese because they were only interested in unpredictable events.
1. According to the textbook, what was it about Ancient Greece that enabled its
philosophers to theorize about why the sky moves the way it does, as opposed to just
using it for tracking time and astrology?
The fragmented geography and decentralized rule of Ancient Greece allowed for an
intellectual freedom that led to a revolution in scientific thought.
2. Why is Thales called the "Father of Science"? According to legend, what celestial
event did he successfully predict in order to prove his philosophy? Thales is considered the “Father of Science” for attempting to find explanations for
natural phenomena that didn’t involve the gods. His philosophy gained support when he
demonstrated that eclipses are predictable.
3. What did Anaximander believe about the Earth?
Anaximander believed the Earth was “afloat” in air
4. What was Pythagoras proposing when he called the Universe a "cosmos"?
What did he propose about the shape of planetary orbits?
Pythagoras discovered that musical pitch is determined by the length of the instrument;
he then realized the Universe is a “cosmos” – a harmonious system that obeys knowable
laws). He proposed that all celestial motion is perfectly circular and that Earth is a sphere.
5. Who proposed that the Earth is round? Describe 3 observations that suggest
Pythagoras proposed that the Earth is a sphere. His evidence to prove the Earth is a
i. Ships gradually disappear on the horizon, bottomfirst
ii. Earth’s shadow on the eclipsed moon is always round
iii. When you travel north or south, the constellations rise and set more rapidly than they
would if Earth was flat
6. What did Philolaus believe about the Earth? What did this belief explain about
Philolaus believed that the Earth moved. By allowing the Earth to rotate once per day
around a “central fire”, the daily motion of the celestial bodies was explained.
7. What did Herakleides believe about the Earth?
He believed the Earth is spinning daily around its own axis.
8. What did Herakleides believe about the motion of Mercury and Venus, and
He believed Mercury and Venus orbit the Sun to explain the Suncentred appearance of
their motion and their changes in brightness.
9. What observation allowed Aristarchus to estimate the size of the Moon? What
measurement in the sky allowed him to estimate the distance of the Sun compared to
the Moon's distance? Combining these results, what did he correctly conclude about
the relative sizes of the Sun, Moon and Earth (i.e., which is biggest, smallest, etc.)?
What did this conclusion lead Aristarchus to propose about the known Universe?
He used the Earth’s shadow on the eclipsed moon to measure the Moon’s size relative to
Earth’s. He used the angle in the sky between the Sun and quarter moon to measure the
Sun’s distance and size relative to the moon’s. He correctly deduced that the Sun is much larger than Earth, and Earth is larger than the Moon. This led him to propose a
heliocentric model of the Universe, with only the Moon in orbit around Earth.
10. What direction do planets normally move across the sky from night to night? In
what direction is a planet moving when it exhibits retrograde motion?
Planets display both direct (forward) motion (West to East) and retrograde (backward)
motion (East to West)
11. Does a planet's apparent motion appear constant or nonconstant in speed, as
seen from Earth? What about a planet's brightness?
A planet’s apparent speed is not constant – planets appear to slow down and speed up
across the sky. A planet appears to brighten and dim as it moves across the sky.
12. What belief of Plato's directed the objectives of the next generations of Ancient
He believed and taught that all celestial bodies are perfect spheres with constant circular
motion (CCM). The goal of the philosophers after Plato was to explain how the planet’s
paths in the sky could be explained by CCM.
13. According to Eudoxus, what do the planets reside on in space?
He attempted to explain planetary motion by placing the planets on systems of invisible
nested spheres (“crystal orbs”), each spinning with CCM around Earth.
14. Why did Eudoxus propose that each planet is carried around Earth by two
He proposed this in order to place the planets moving around the sky and ensure that
Earth isn’t moving at all.
15. In Aristotle's cosmology, what body is at the centre, and what is everything on
this body composed of? What is everything outside of this body composed of? What
are the qualities of this material?
Aristotle’s cosmology teaches t