1) The ancient Greek philosopher Ptolemy devised the geocentric model which placed Earth at the center of the solar system. This view was supported by the Catholic Church. 2) The document outlines four arguments used to support the geocentric model and explains why each is flawed. It also discusses Ptolemy's model remaining unchallenged for 14 centuries. 3) Nicolaus Copernicus later proposed the heliocentric model which correctly placed the Sun at the center. This was initially opposed by the Catholic Church but gained support through evidence from seasons, Galileo's telescope observations, Kepler's laws of planetary motion, and Newton's theory of gravity.

2. ANCIENT CONCEPT OF HEAVENS

5. Ptolemy
and
the
Geocentric Model

6. • Geocentric Model (Geo means Earth and Centric
means Center)
• The model that says the earth in the center of the
Solar System (earth-centered)
• Greek philosopher Ptolemy thought that the Earth is
at the center of the Solar System
• The Catholic Church believed this model because
God placed Earth at the center.

8. Claudius PtolemyClaudius Ptolemy
Devised the Geocentric Model of the Universe.

9. 4 Arguments for the Geocentric Model
• The first argument given,to support the Geocentric Model
was that if the Earth revolved the Sun, then we would feel the
Earth’s motion. But since the Earth’s motion could not be
detected then the Earth, they thought,
could not possibly be moving.
But there are actually (5) ways in which the Earth does
in fact move:

10. 1) The Earth is rotating
on its imaginary axis.

11. 2) The Earth is revolving
around the Sun.

12. 3) The Earth is “precessing”,
or wobbling, on its axis.

13. 4) The Sun is
revolvingaround the center of the Milky Way.

14. separating
5) The galaxies are moving apart,
as a result of the Big Bang.

15. June December
2) We Don’t Observe Stellar Parallax2) We Don’t Observe Stellar Parallax
parallactic shift

16. Heliocentric Model
3) The Moon Could Not Keep Up3) The Moon Could Not Keep Up
The third argument given in support of the Geocentric Model was that if
the Earth orbited the Sun,that the Moon would lag behind.

17. 4) Objects Would Fly Off Earth4) Objects Would Fly Off Earth
The fourth argument given in support of the Geocentric Model, had to do with the
Earth’s rotation on its axis. If the Earth were to rotate on its axis, the ancients
believed, then anything not nailed down would fly off into space. Since the
ancients failed to observe objects flying off into space, then they incorrectly
concluded that the Earth must not be rotating.

18. The Geocentric ModelThe Geocentric Model
Since none of these questions could be
answered, then Ptolemy and the Geocentric
Model remained unchallenged for 14 centuries.

19. HELIOCENTRIC MODEL
AND COPERNICUS

20. Heliocentric Model
• Heliocentric Model -Helio means Sun and
Centric means Center)
• The model that says that the Sun is at the
center of the Solar System (Sun-centered)
• Nicolaus Copernicus proposed that the Sun
was the center of the universe, not the earth.

22. Heliocentric Evidence
• The Catholic Church opposed this model
because it went against the church’s beliefs
and imprisoned, tortured and killed people
who believed this model
• Evidence
–Seasons
–Telescope (Galileo)
–Ellipses (Kepler’s Law’s)
–Gravity (Newton)

23. The Origin of the Solar System

24. The Nebular Hypothesis in its original form was
proposed by Kant and Laplace in, 18th century.
•

25. Collapsing Clouds of Gas and Dust
• A great cloud of gas and dust
(called a nebula) begins to
collapse because the gravitational
forces that would like to collapse
it overcome the forces associated
with gas pressure that would like
to expand it (the initial collapse
might be triggered by a variety of
perturbations---a supernova blast
wave, density waves in spiral
galaxies, etc.).
In the Nebular Hypothesis, a cloud
of gas and dust collapsed by
gravity begins to spin faster
because of angular momentum
conservation.

26. • The law of conservation of angular
momentum states that when no external
torque acts on an object or a closed system of
objects, no change of angular momentum can
occur.

27. The Spinning Nebula
Flattens
• Because of the
competing forces
associated with gravity,
gas pressure, and
rotation, the
contracting nebula
begins to flatten into a
spinning pancake shape
with a bulge at the
center.
The collapsing, spinning nebula begins
to flatten into a rotating pancake

28. Condensation of Protosun and
Protoplanets
• As the nebula collapses
further, instabilities in the
collapsing, rotating cloud
cause local regions to begin
to contract gravitationally.
These local regions of
condensation will become
the Sun and the planets, as
well as their moons and
other debris in the Solar
System.
As the nebula collapses further, local
regions begin to contract gravitationally
on their own because of instabilities in
the collapsing, rotating cloud.

29. END !!!
•