1. Theories of Universe Formation

2. Studying Space
Cosmology – the study of the origin, structure, and future of the universe
Astronomers study planets, stars, and galaxies
Cosmologists study the universe as a WHOLE

3. Origin of the Universe
Several models of its origin have been proposed.
Steady State Theory
Oscillating Theory
Big Bang Theory
Parallel Universe Theory

4. Steady State Theory
It suggests that the universe always has been the same as it is now.
The universe always existed and always will.
As the universe expands, new matter is created to keep the overall density of the universe the same or in a steady state.

5. Oscillating Theory
In this model, the universe began with expansion (Big Bang).
Over time, the expansion slowed and the universe contracted (Big Crunch).
Then the process began again, oscillating back and forth (Big Bounce).

6. Big Bang Theory
According to this theory, approximately 14 billion years ago, the universe began with an enormous explosion.
The entire universe began to expand everywhere at the same time and is still expanding today.

7. Parallel Universe Theory
According to this theory, there are an infinite number of universes that exist.
This theory is very new and, therefore, does not have any supporting evidence currently.

8. Think About It…
What does it sound like when a train is blowing its whistle while it travels past you?
The whistle seems to drop in pitch as the train moves away.
This effect is called the Doppler shift.
The Doppler shift occurs with light as well as with sound.

9. The Doppler Shift
The Doppler shift causes changes in the light coming from distant stars and galaxies.

10. The Red Shift
A red shift in the spectrum occurs when objects in space are moving away from Earth.

11. Evidence for the Big Bang Theory
Red Shift – things that are farther from Earth are moving faster than those closer to Earth
Discovered by Edwin Hubble in 1929
Called Hubble’s Law
** Shows universe is still expanding **

12. Evidence for the Big Bang Theory
Cosmic Background Radiation – radiation detected uniformly (the same) from every direction on space
Believed to be left over from the Big Bang
** Shows universe is still expanding **

13. Looking Back in Time
Whether the universe will expand forever or stop expanding is still unknown.
If enough matter exists, gravity might halt the expansion, and the universe will contract until everything comes to a single point.

14. Looking Back in Time
Studies of distant objects in space indicate that an energy, called dark energy, is causing the universe to expand faster.
Scientists are trying to understand how dark energy might affect the fate of the universe.

15. Review

16. Question 1 An explanation based on many investigations
is a __________.
A. law
B. theory
C. hypothesis
D. observation

17. Answer
The answer is B.

18. Question 2
___________ is detected uniformly in space from every direction; it supports the Big Bang Theory.
A. Red Shift
B. Observations
C. Doppler Shift
D. Cosmic Background Radiation

19. Answer
The answer is D.

20. Question 3
______________ states the universe will shift back and forth between expanding and collapsing.
A. Big Bang Theory
B. Oscillating Theory
C. Steady State Theory
D. Theory of Relativity

21. Answer
The answer is B.