- Believed the earth was a sphere
because he thought that a sphere
Lesson 1: Ancient represented perfection and
Astronomy symmetry, which were valued in his
philosophical framework
Astronomy
- Study of everything in the universe Anaxagoras (500-428 BC)
beyond Earth’s atmosphere - Understood that the round shadow
- A natural science that studies celestial cast on the moon during a lunar
objects and the phenomena that occur eclipse indicated that the earth was
in the cosmos spherical
- Uses mathematics, physics, and - He also proposed that the moon was
chemistry in order to explain their not a source of light itself but reflected
origin and their overall evolution the light from the sun
Flat earth theories: Aristotle (384-322 BC)
- Supports the idea of a spherical earth
Homer and Hesiod (8th Century BC) in ancient greece
- Played a significant role in - His arguments were based on
establishing the Flat Earth Concept observational evidence and
- Homer is known for his epic Iliad and philosophical reasoning which
Odyssey, it depicts a geocentric view included the position of stars, shape of
of the cosmos, with a Flat Earth the moon, and disappearing of ships
Model - Evidence #1 (Lunar Eclipse)
- Noted that during a lunar eclipse, the
Thales of Miletus (624-546 BC) earth casts a round shadow on the
- Earliest pre-Scoratic greek moon.
philosopher - He argued that this round shadow
- Proposed that the earth was flat and could only be produced by a spherical
disk-shaped, floating on water object
- His ideas were part of his broader - Evidence #2 (Disappearance of Ships)
philosophy that water was the - He observed that as ships sailed away
fundamental substance of all form the shore, they appeared to sink
things below the horizon, disappearing
hull-first
Anaximander (610-546 BC) - This observation suggested that the
- Student of thales and a pre-Socratic surface of the earth is curved
philosopher
- Proposed that the earth was not flat
but shaped like a cylinder - Evidence #3 (Varying Star Visibility)
- The earth floated freely in the center of - He pointed out that travelers going
the universe, unsupported by water or south could see stars that were not
any other substance visible to those in the north
- His was the first concept of earth in - This changing visibility of
space constellations indicated a curved
surface, as different locations on a
sphere would have different celestial
Spherical earth theories: perspectives
- The North Star also known as
Pythagoras (6th Century BC) Polaris, is a prominent star in the
- Often credited with the idea of a northern hemisphere that holds
spherical earth based on philosophical significant importance in navigation
reasoning and observations and astronomy
- Evidence #4 (Shape of the Moon and - Includes stars, planets, comets,
Sun) galaxies, and the universe as a
- He argued that if the Moon and the whole
Sun were both spherical perhaps, the
Earth was also spherical ● Lunar Eclipse/Total Lunar
- Sphere is the most perfect shape, Eclipse/Blood Moon
which aligns with his philosophical - Occurs when the earth passes
views on perfection and symmetry between the sun and the moon
in nature casting a shadow on the moon
● Solar Eclipse
Eratosthenes (276-194 BC) - Occurs when the moon passes
- Was a Greek mathematician, between the earth and the sun
astronomer, and geographer blocking all or part of the
- Known for measuring the most sun’s light
accurate Earth’s circumference - Types of Solar Eclipses
- He used the angles of shadows cast - Partial = beginning of the
by objects in different locations eclipse
(Alexandria and Syene) during the - Annular = can see the sides
summer solstice of the sun
- Total = all black
● Phases of the Moon
- Refers to the varying
appearance of the Moon as
seen from earth resulting from
its position relative to the
earth and the sun.
- - The cycle of phases lasts about
29.5 days and is known as a
lunar month
ASTRONOMICAL PHENOMENA
● Constellations
- Are patterns of stars that form
recognizable shapes or figures
in the night sky
- Been used throughout history
for navigation,storytelling, -
and marking seasons.
MOTION OF THE EARTH
ASTROLOGY VS. ASTRONOMY
● Diurnal Motion (23 0r 24 hours)
Astrology - The apparent daily motion of
- Is a belief system that interprets the the stars and other celestial
influence of celestial bodies on human bodies across the sky caused
life by the Earth’s rotation.
- For example, Zodiac signs explains ● Annual Motion (happens yearly)
personalities - The apparent motion of the
Astronomy sun caused by the Earth’s
- Is the scientific study of celestial revolution around it.
bodies
SOLSTICES
- Occurs when the Sun reaches its
highest or lowest point in the sky
relative to the earth’s equator resulting
in the longest or shortest day of the -
year
- Summer Solstice : around june - They happen at different times of
20-21, sun is at its highest point, the year
marking the longest day of the year
- Winter Solstice: around december
21-22, sun is at its lowest point,
marking the shortest day of the year
Lesson 2: Models of the
Universe
2 Types of Models of the Universe:
● Geocentric (geo=earth,
centric=center)
● Heliocentrix (helios=sun,
- centric=center)
GEOCENTRIC MODELS
PYTHAGOREAN MODEL
- This model introduced some key ideas
about the structure of the universe like
spherical earth, central fire,
counter-earth, celestial harmony
- and geocentric nature
- He believed that at the center of the
universe was a “central fire” (not the
EQUINOX (equi=equal, nox=night) sun). The sun was thought to be a
- Occurs when the sun is directly above reflection of this fire.
the Earth’s equator resulting in nearly - The model also introduced the idea of
equal day and night a “Counter-Earth” (called
- Types: Antichthon)
- Vernal (Spring) Equinox: around - Since the earth and counter-earth
march 21, marking the beginning of were always opposite each other, the
spring Counter-Earth was never visible
- Autumnal (Autumn/Fall) from earth
Equinox: around september
22/23, marking the beginning of fall
- He also believed that the universe was
composed of four fundamental
elements (earth, water, air, and
fire [terrestrial realm])
- The celestial bodies, including stars
and planets, were thought to be made
of a fifth element called aether (also
known as quintessence)
-
- The Pythagoreans believed in the
concept of celestial harmony, also
known as the “Music of the
Spheres”
- They thought that the planets and
celestial bodies moved in perfect circle
producing harmonious sounds that
were inaudible to humans -
EUDOXUS MODEL
- Made by Eudoxus of Cnidus around
the 4th century BCE
- Geocentric model where celestial
bodies move in perfect circles at
constant speeds
- The model consisted of 27
concentric spheres to explain the
motion of all known celestial objects
-
- Pythagorean model is a geocentric
model
ARISTOTELIAN MODEL
- He (Aristotle) believed the earth was
the center of the universe, and all
celestial bodies, revolved around it in
perfect circular orbits
- Prime Mover or Unmoved Mover -
- the motion responsible in the - Nested Spheres - celestial bodies
outermost celestial sphere containing attached to multiple to multiple
the fixed stars concentric spheres that rotate
around the earth
-
- Retrograde Motion - explained by developed the heliocentric model of
multiple rotating spheres, producing the universe
the appearance of backward motion - He explained that the daily rotation
of earth on its axis accounts for the
apparent motion of the sun and
stars across the sky
- He also proposed that the annual
revolution of earth around the sun
causes the apparent movement of
the sun through the constellations
(zodiac)
- The stars were fixed in place and
were much farther away than
previously thought
PTOLEMAIC MODEL TYCHO BRAHE (1546-1601)
- Is a geocentric model that was - Hybrid Model of the Universe: tycho
developed by the greco-egyptian proposed a compromise between the
astronomer claudius ptolemy (200 geocentric and heliocentric models
BCE) of the universe
- Earth is stationary at the center
of the universe, with the sun
revolving around it
- However, all other planets
(mercury, venus, mars, jupiter,
and saturn) revolve around the
sun
-
- Deferent - planet moved in a large
circular orbit around earth
- Epicycle - within the deferent, the
planet moved in a smaller circular
path -
- In 1600, Tycho hired Johannes
HELIOCENTRIC MODELS Kepler as an assistant
- Tycho’s death in 1601 left his trove of
ARISTARCHUS MODEL data to kepler, who used the detailed
- Aristarchus of Samos (310-230 records of mars to derive his three
BCE) was an ancient greek laws of planetary motion
astronomer and mathematician who
proposed the first known KEPLER’S LAWS OF PLANETARY
heliocentric model of the universe MOTION
- This model challenged the geocentric - Johannes Kepler formulated three
models of aristotle and ptolemy key laws that describe the motion of
- Earth rotates on its axis (rotation) planets around the sun
- He concluded that the Sun is much - Three laws was a direct consequence
larger than Earth and significantly of the law of universal gravitation
farther away than the moon that is further explained by Isaac
Newton
COPERNICAN MODEL - 1st: Law of Orbits/law of Ellipses -
- Nicolaus Copernicus (1475-1543) states that planets move in elliptical
a renaissance-era polish astronomer,
orbits with the sun at one foci of the
ellipse
-
- 2nd: Law of Areas/Law of Equal
Areas - states that planets sweep out
equal areas in equal times, moving
faster when closer to the sun and
slower when farther away
-
-
- 3rd: Law of Periods/Law of
Harmonies - the square of a planet’s
orbital period is proportional to the
cube of its average distance from the
sun
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