Cosmology is the branch of astronomy that studies the origin and evolution of the universe. In ancient times, educated people in the eastern Mediterranean region knew the Earth was round based on the teachings of Pythagoras, who believed spheres to be perfect forms. Aristotle also understood that the sun must be farther than the moon from Earth due to solar eclipses. Later, Eratosthenes calculated Earth's circumference to be approximately 250,000 stadia. The document then discusses precession of Earth's axis and how the north star will change over time, as well as differences between the geocentric and heliocentric models of the solar system.

5. What is cosmology?
Cosmology is a branch of
astronomy that involves the
origin and evolution of the
universe (Tillman and Harvey,
2022).

6. Before, educated people in the
eastern Mediterranean region
knew the Earth was round. This
belief may have stemmed from
the time of Pythagoras, a
philosopher and a mathematician
who believed circles and spheres
to be “perfect forms” and
suggested that Earth should
therefore be a sphere.

7. Aristotle also knew that the Sun must be
farther away from Earth than the Moon
because occasionally the Moon passed exactly
between Earth and the Sun, and hid the Sun
temporarily from view. We call this a solar
eclipse.

10. The Sun is so distant from us that all light rays
that strike our planet approach us along
essentially parallel lines.

11. Eratosthenes thus
found that Earth’s
circumference must
be 50 × 5000, or
250,000 stadia.

12. Precession is the direction in which the Earth’s
axis points do indeed change slowly but
regularly.

13. As a result of this motion, the
point where our axis points in
the sky changes as time goes
on. While Polaris is the star
closest to the north celestial
pole today (it will reach its
closest point around the year
2100), the star Vega in the
constellation of Lyra will be
the North Star in 14,000 years.

14. Earth travels around
the Sun in the same
direction as the
other planet and in
nearly the same
plane, but its orbital
speed is faster.

15. Furthermore, because the Greeks believed that
celestial motions had to be circles, Ptolemy had
to construct his model using circles alone.

16. When the planet is at
position x on the epicycle
orbit, it is moving in the
same direction as the center
of the epicycle; from Earth,
the planet appears to be moving eastward.
When the planet is at y, however, its motion is
in the direction opposite to the motion of the
epicycle’s center around Earth.

21. The Elements of the Zodiac Signs:
• Earth: embodies personality—like the physical earth
itself—are grounded, dependable, and hard-working.
• Water: the symbol of emotions, dreams, healing, and
intuition, as well as the cycles of death and birth. They
thrive when they can go with the flow, as they prefer an
emotional or intuitive approach to life.
• Air: known for communication, intelligence, and
versatility. They approach life from a logical standpoint,
though at times can be indecisive or fickle.
• Fire: they are passionate, energetic, creative, known for
their spontaneity and knack for inspiration.

22. The Modalities of the Zodiac Signs:
• Cardinal: are quick and ambitious. They are
the initiators of the zodiac.
• Fixed: are determined and stable. These signs
follow through on a project.
• Mutable: versatile and resourceful. They're
the ones who put the final touches on projects.

24. Rat: quick-witted, resourceful, versatile, kind.
Ox: diligent, dependable, strong, determined.
Tiger: brave, confident, competitive, unpredictable.
Rabbit: quiet, elegant, kind, responsible.
Dragon: confident, intelligent, enthusiastic.
Snake: enigmatic, intelligent, wise.
Horse: animated, active, energetic.
Goat: calm, gentle, sympathetic.
Monkey: sharp, smart, curious.
Rooster: observant, hardworking, courageous.
Dog: lovely, honest, prudent.
Pig: compassionate, generous, diligent.

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infographics & images by Freepik
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