1. LECTURE 24, NOVEMBER 30, 2010 ASTR 101, SECTION 3 INSTRUCTOR, JACK BRANDT jcbrandt@unm.edu 1ASTR 101-3, FALL 2010

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5. a) is explained by general relativity. b) results from the presence of dark matter. c) is a statement of Olbers paradox. d) is the cosmological principle. e) occurs if the universe is static and unchanging. Question 6 The darkness of the sky in an infinite universe 5ASTR 101-3, FALL 2010

6. a) is explained by general relativity. b) results from the presence of dark matter. c) is a statement of Olbers paradox. d) is the cosmological principle. e) occurs if the universe is static and unchanging. Question 6 The darkness of the sky in an infinite universe If the universe is homogeneous in composition, and appears the same in all directions, then for the sky to be dark, it must be either finite in age, or evolving in time, or both. 6ASTR 101-3, FALL 2010

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8. a) the size of the universe. b) the age of the universe. c) the shape of the universe. d) the temperature of the universe. e) the distance the universe has expanded. Question 2 Hubbles constant, H 0, can be related to 8ASTR 101-3, FALL 2010

9. a) the size of the universe. b) the age of the universe. c) the shape of the universe. d) the temperature of the universe. e) the distance the universe has expanded. Question 2 Hubbles constant, H 0, can be related to H 0 is currently estimated to be about 70 km/sec/Mpc. This translates to an age for the universe of about 14 billion years. 9ASTR 101-3, FALL 2010

10. a) is infinitely old and getting larger. b) began expanding long ago, and has a finite age. c) will slow down because of dark matter. d) has repeatedly expanded and contracted. e) will eventually stop and recollapse. Question 4 Hubbles law implies that the universe 10ASTR 101-3, FALL 2010

11. a) is infinitely old and getting larger. b) began expanding long ago, and has a finite age. c) will slow down because of dark matter. d) has repeatedly expanded and contracted. e) will eventually stop and recollapse. Question 4 Hubbles law implies that the universe Using the Hubble constant H 0, astronomers can estimate that the universe was born about 14 billion years ago. 11ASTR 101-3, FALL 2010

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13. a) the Milky Way must be located at the edge of the universe. b) the Milky Way is at the center of the universe. c) the universe is expanding. d) the sky is dark at night. e) the universe has not changed significantly. Question 1 Because distant galaxies in every direction are moving away from us, 13ASTR 101-3, FALL 2010

14. a) the Milky Way must be located at the edge of the universe. b) the Milky Way is at the center of the universe. c) the universe is expanding. d) the sky is dark at night. e) the universe has not changed significantly. Question 1 Because distant galaxies in every direction are moving away from us, 14ASTR 101-3, FALL 2010

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16. a) a Doppler shift of the random motions of galaxies. b) an aging of light as the universe ages. c) space itself expanding with time, stretching light. d) the result of the Milky Ways position at the center. e) due to the temperature differences in the early and late universe. Question 3 The redshift of galaxies is explained best as 16ASTR 101-3, FALL 2010

17. a) a Doppler shift of the random motions of galaxies. b) an aging of light as the universe ages. c) space itself expanding with time, stretching light. d) the result of the Milky Ways position at the center. e) due to the temperature differences in the early and late universe. Question 3 The redshift of galaxies is explained best as As the universe expands, photons of radiation are stretched in wavelength as they move through space. 17ASTR 101-3, FALL 2010

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