1. Section 5: The Expanding Universe page 622

2. The Big Bang Theory
According to the Big Bang theory, the universe was formed in an instant, billions of years ago, in an enormous explosion.
Monsignor Georges Henri Joseph Edouard Lemaitre

3. Evidence of the Big Bang Theory 1: Retreating Galaxies
All of the distant galaxies astronomers have observed are moving rapidly away from our galaxy and from each other.
Edwin Hubble

4. Speeding Galaxies
Use the graph to answer the questions about moving clusters of galaxies.

5. Speeding Galaxies Reading Graphs:
How far away is the Bootes cluster? How fast is it moving?
About 2.5 billion light-years; about 39,000 km/sec

6. Speeding Galaxies Reading Graphs:
Which galaxy is moving away the fastest? Which galaxy is closest to Earth?
Hydra; Virgo

7. Speeding Galaxies Drawing Conclusions:
How are the distance and speed of a galaxy related?
The greater the distance from Earth, the greater the speed of the galaxy.

8. Speeding Galaxies Predicting:
Predict the speed of a galaxy that is 5 billion light-years from Earth.
Its speed would be about 80,000 km/s.

9. Moving Galaxies
The galaxies in the universe are like the raisins in rising bread dough, moving away from the center; the ones farthest away are moving the fastest.

10. Evidence for the Big Bang Theory 2: Cosmic Background Radiation
The cosmic background radiation is the leftover thermal energy from the big bang.
Arno Penzias
Robert Wilson

11. Age of the Universe
Present theory places the age of our universe at 13.7 billion years old.

12. Formation of the Solar System
About 5 billion years ago, the solar system formed from a collapsing cloud of gas and dust.

13. The Future of the Universe
New observations lead many scientists to believe that the universe will expand forever.

14. Dark Mysteries Dark Matter ---
Matter that does not give off electromagnetic radiation.
Dark Energy ---
A mysterious new force that is causing the universe to expand more rapidly.