3 - Ptolemy proposed the geocentric model, Copernicus proposed the heliocentric model, and Galileo provided evidence supporting Copernicus through telescope observations. 2 - Ptolemy's geocentric model placed Earth at the center, while Copernicus' heliocentric model placed the Sun at the center. 1 - The Big Bang Theory is the widely accepted theory that the universe began in an enormous explosion approximately 13 billion years ago.

1. Formation of
the Universe
and Galaxies
But First! What is a Light Year??

2. THE LIGHT YEAR
 A light year is a way of measuring
distance. That doesn't make
much sense because "light year"
contains the word "year," which is
normally a unit of time. Even so,
light years measure distance.

3.  Light travels at 186,000 miles per second
(300,000 kilometers per second).
 Therefore, a light second is 186,000 miles
(300,000 kilometers).
 A light year is the distance that light can
travel in a year, or:
 186,000 miles/second * 60
seconds/minute * 60 minutes/hour * 24
hours/day * 365 days/year =
5,865,696,000,000 miles/year
 OR…… 1 LIGHT YEAR

4. How have Theories of the
formation and structure of the
universe changed?

5. A Scientific Theory is
an explanation or
model backed by
results obtained from
many tests or
experiments.

6. Why do theories change?
 Scientific theories change when
scientists discover new information
 New technology, new tools, and/or new
observations can provide new
information.
 What new technology and/or tool was
used to came up to a theory?
Greater telescopes and imaging
technology

7. For centuries, there have been
a variety of theories to explain
the formation and structure of
the universe.
We will examine some of these
theories and identify the most
widely accepted theory today.

8. How and when did the universe begin?
No one was around when the universe
began, so who can say what really
happened?
The best that scientists can do is work
out the most foolproof theory, backed
up by observations of the universe.

9. Theory of the
Universe

10. • The universe began
with a hot explosion
called the Big Bang.
The aftermath of the
Big Bang consisted
mostly of radiation,
but as things cooled,
the elements hydrogen
and helium formed.
• http://imgsrc.hubblesite.
org/hu/explore_astronom
y/skywatch/db/307/audi
o/SkyWatch_307-
11252010.mp3

12. The Big Bang Theory
The most commonly accepted theory today
of the formation of the universe is the Big
Bang Theory.
The theory states that the universe
originated sometime between 10 billion and
20 billion years ago from an enormous
explosion of a small volume of matter at
extremely high density and temperature.

14. The Big Bang
Theory
Demonstration

15. Visualizations of
the Big Bang
https://www.youtube.com/watch?v=GYQEWKd92us
video clip of an ice skater spinning
http://www.youtube.com/watch?v=AQLtcEAG9v0

16. In spite of its problems, the Big
Bang is still considered by most
astronomers to be the best theory
we have.
As with any scientific hypothesis,
however, more observation and
experimentation are needed to
determine its credibility.

17. another theory about the universe…
 Big Bang theorists claim that all of the galaxies,
stars, and planets still hold the explosive
motion of the moment of creation and are
moving away from each other at great speed.
 In 1929, astronomer Edwin Hubble announced
that all of the galaxies he had observed were
moving back from us, and from each other, at
speeds of up to several thousand miles per
second.
 Since the Big Bang explosion, they reason, the

18. the Big Bang
video clip[https://www.youtube.com/watch?v=GncYOf29uc4&t=149s]

19. Astronomers use the analogy of
cooking raisin bread to demonstrate
the expanding universe
Expanding the Universe on a Balloon
Demo

20. the Universe After its Big Bang…
 The Universe includes living things,
planets, stars, galaxies, dust clouds,
light, and even time.
 The Universe contains billions of galaxies,
each containing millions or billions of
stars. The space between the stars and
galaxies is largely empty.
 So, if the universe supposedly was formed
by the Big Bang, how did these other
objects form?

21. the Universe After its Big Bang…
As millions of years passed, the dense
areas of the universe pulled in material
because they had more gravity. Finally,
about 100 million years after the Big
Bang, the gas became hot and dense
enough for the first stars to form. Large
clusters of stars soon became the first
galaxies.
Scientists believe that Solar Systems
formed in similar ways. Giant clouds of
dust and gas began to collapse under
the weight of its own gravity. As it did
so, the matter contained within it began
to move in a giant circle, much like the
water in a drain moves around the
center of the drain in a circle.
At the center of this spinning cloud, a
small star began to form. This star
grew larger and larger as it collected
more and more of the dust and gas that
collapsed into it.
Further away from the center of this mass
where the star was forming, there were
smaller clumps of dust and gas that were
also collapsing.
The star in the center eventually ignited
forming our Sun, while the smaller clumps
became the planets, minor planets, moons,
comets, and asteroids.
In short, after the Big Bang,
dense clouds of gas and dust
from the “bang” either
collapsed or stuck together to
form the parts of the universe
we know today.

22. What is a “nebula”?
 A cloud in space
 Made of gas and dust
 Can have stars inside
 Most of the ones we see are inside our
Milky Way Galaxy
 Different types
Orion image at

23. The Solar Nebula
Theory
Basis of modern theory
of planet formation.
Planets form at the
same time from the
same cloud as the star.
Sun and our solar system
formed ~ 5 billion years ago.
Planet formation sites
observed today as dust
disks of T Tauri stars.

24.  a), (b) The solar nebula contracts and
flattens into a spinning disk. The large
blob in the center will become the Sun.
Smaller blobs in the outer regions may
become jovian planets.
 (c) Dust grains act as condensation
nuclei, forming clumps of matter that
collide, stick together, and grow into
moon-sized planetesimals.
 (d) Strong winds from the still-forming
Sun expel the nebular gas.
 (e) Planetesimals continue to collide
and grow.
 (f) Over the course of a hundred
million years or so, planetesimals form
a few large planets that travel in
roughly circular orbits.

25. So… Big Bang & Solar Nebular?
How are they related?
 The Big Bang Theory considers the creation of all the
matter and energy that exists in the universe..
Anywhere..
 The Solar Nebula theory uses that matter and energy, to
create galaxies and solar systems.

26. What is a “galaxy”?
 A large group of stars outside of our own Milky
Way
 Made of billions to trillions of stars
 Also may have gas and dust
 Spiral, or elliptical, or irregular shaped
Image at

27. Spiral galaxy--Andromeda
NOAO/AURA/NSF Images at

28. Elliptical Galaxies
Images at
http://hubblesite.org/newscenter/archive/releases/galaxy/elliptical/2007/08/image/

29. Irregular Galaxies
NASA and NOAO/AURA/NSF Images at
http://hubblesite.org/newscenter/archive/releases/galaxy/irregular/2005/09/res

30. Our Galaxy: the Milky Way
 has about 200 billion stars, and lots of gas
and dust
 is a barred-spiral (we think)
 about 100,000 light-years wide
 our Sun is halfway to the edge, revolving at
half a million miles per hour around the
center of the Galaxy
 takes our Solar System about 200 million
years to revolve once around our galaxy

31. The Milky Way
Image at

32. another Theory which has
changed over centuries is the
scientific model of our solar
system

33. The Great Debate! Models of
the solar system activity

34. Ptolemy’s Model of the Solar System
 Ptolemy’s theory is known as
the Geocentric Model because
he thought the Earth was the
center of the universe
 In Greek, “Geo” means earth
 He believed his theory for
several reasons
 Gravity of all objects were
attracted to the earth, which
suggested to him that the
earth must be the center.
 He thought the Earth did not
move because objects fell in
the same place if thrown up in
the air. He thought if the
earth moved, objects would
fall in a different place.

35. Copernicus’ Model of the Solar System
 Copernicus’ theory is called the
Heliocentric Theory because he
thought the sun was the center of
the universe.
 In Greek, “helios” means sun
 Galileo made additional
observations using a telescope
which supported the heliocentric
theory.
 Galileo observed that Venus
went through a full cycle of
phase’s like the Moon. This
could only be explained if
Venus were orbiting the Sun.

36. Why was the geocentric
model of the solar system
replaced by the
heliocentric?

37. Models of the Solar System
 Video Clip of Models: http://www.youtube.com/watch?v=GmwAr54L_pM
 Animation of the Geocentric Model:
https://www.youtube.com/watch?v=UtOEnTiAZlU
 Animation of Heliocentric Model
http://astro.unl.edu/naap/ssm/heliocentric.html

38. Distributed Summarizing:
You are Galileo, write a letter to
Copernicus’ ghost to tell him how Galileo
has saved his name – be sure to include
Galileo’s findings, how he fixed
Copernicus’ reputation, and what the solar
system has been proven to actually look
like (which solar system model). The letter
must be a minimum of 5 sentences.

39. Summarizing strategy
3 – Identify three people who have
contributed
to the models of our solar system
2 - Describe two models that were
debated for
hundreds of years
1 - Name of the theory that explains the
formation of the universe