2. Ch. 4 Sec. 5 The Expanding Universe

3. Discover activity- How Does the Universe Expand pg. 148 1.What happens to the distances between galaxies that are close together? 2.What happens to the distances between galaxies that are far apart? 3.If the universe is expanding, do galaxies that are close together move apart faster or slower than galaxies that are far apart? Explain.

4. Big Bang Theory theory that universe formed in an instant, billions of yrs. ago, in an enormous explosion

5. Video clip-The Big Bang

6. Edwin Hubble discovered : 1.galaxies are moving away from us & each other 2.relationship between distance to a galaxy & its speed

7. Hubble’s law farther away galaxy is  faster it is moving away from us

8. Video clip- Moving Galaxies

9. The galaxies in the universe are like the raisins in rising bread dough. How does rising raisin bread dough resemble the expanding universe?

10. cosmic background radiation faint radiation glow that comes from all directions in space leftover thermal radiation from the big bang

11. How old is the universe? 13.7 billion years old

12. Video clip-Cosmic background radiation

13. Formation of the solar system

14. 1. 5 billion yrs. ago, solar nebula (giant cloud of gas & dust) collapsed to form our solar system

15. 2. Gravity pulled solar nebula together

16. 3. Solar nebula shrank & began spinning very fast

17. 4. Solar nebula flattened- formed a rotating disk

18. 5. Gravity pulled gas into center- nuclear fusion began- sun born

19. 6. Remaining gas & dust formed planetesimals- formed planets

21. dark matter matter that does not give off electromagnetic radiation 23% of universe’s mass

22. dark matter cannot be seen directly- presence can be inferred by effects of its gravity on visible objects

24. Video clip-Dark Matter

25. dark energy force causing expansion of universe to accelerate

27. What was the big bang? Giant explosion after which all of the matter in the universe began moving apart

28. When did the big bang occur? About 13.7 billion years ago

29. Describe two pieces of evidence that support the big bang theory? 1.Hubble’s law- the observation that the farther away a galaxy is, the faster it is moving away from Earth 2.cosmic background radiation- radiation left over from the big bang

30. How old is the solar system? About 5 billion years old

31. What force caused the solar system to form? Gravity pulled the solar nebula together and them pulled most of the gas into the center of the disk, where the gas eventually became hot and dense enough for nuclear fusion to begin and form the sun

32. Place the following events in the proper order: planets form planetesimals form solar nebula shrinks nuclear fusion begins in the sun

33. What is dark matter? Matter that does not give off electromagnetic radiation

34. How do scientists know that dark matter exists? Its presence can be inferred by observing the effect of its gravity on visible objects, such as stars, or on light

35. What evidence has led scientists to predict that the universe will continue to expand forever? The expansion rate of the universe appears to be increasing.