Chapter Pearson Education, Inc. Chapter Pearson Education, Inc. Chapter 19-22

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1 Suppose you tried to determine where we are in the galaxy by looking in different directions to see how many stars you could see. If you did this, you would pinpoint our location Suppose you tried to determine where we are in the galaxy by looking in different directions to see how many stars you could see. If you did this, you would pinpoint our location Why does a simple survey, such as described in the previous slide, give a FALSE answer? Why does a simple survey, such as described in the previous slide, give a FALSE answer? a) in the center of the galaxy. b) in an arm of the galaxy. c) near the edge of the galaxy. a) in the center of the galaxy. b) in an arm of the galaxy. c) near the edge of the galaxy. a) We can't count enough stars to get a good result. b) Interstellar dust blocks our view. c) Black holes distort the light from distant regions, giving a false result. d) Light from far-away stars that have died block our view, giving a false result. a) We can't count enough stars to get a good result. b) Interstellar dust blocks our view. c) Black holes distort the light from distant regions, giving a false result. d) Light from far-away stars that have died block our view, giving a false result. Since dust scatters blue light more than red, stars seen through a lot of interstellar dust would look Since dust scatters blue light more than red, stars seen through a lot of interstellar dust would look Why is it difficult to get a good picture of what the Milky Way Galaxy looks like? Why is it difficult to get a good picture of what the Milky Way Galaxy looks like? a) bluer than expected for their spectral type. b) redder than expected for their spectral type. c) the same as when seen without dust. a) bluer than expected for their spectral type. b) redder than expected for their spectral type. c) the same as when seen without dust. a) We're in the middle of one of its arms and thus have no perspective. b) It is very large and the edges are far away and faint. c) Dust blocks our view when we look toward the center or in the disk. d) We cannot see it from the outside. a) We're in the middle of one of its arms and thus have no perspective. b) It is very large and the edges are far away and faint. c) Dust blocks our view when we look toward the center or in the disk. d) We cannot see it from the outside. How do we get a good picture of what our Milky Way galaxy looks like? How do we get a good picture of what our Milky Way galaxy looks like? About how long does light take to reach us from the nearest star besides the Sun? (The Sun takes 8 minutes.) About how long does light take to reach us from the nearest star besides the Sun? (The Sun takes 8 minutes.) a) by using infrared or microwaves to penetrate the dust b) by using radio telescopes to see where clouds of hydrogen gas are c) by taking photos from both the top and side of the galaxy to get a good view a) by using infrared or microwaves to penetrate the dust b) by using radio telescopes to see where clouds of hydrogen gas are c) by taking photos from both the top and side of the galaxy to get a good view a) about an hour b) about a week c) about a month d) about four years e) about 1000 years a) about an hour b) about a week c) about a month d) about four years e) about 1000 years About how long does light take to cross the Milky Way Galaxy? About how long does light take to cross the Milky Way Galaxy? What does our galaxy look like? What does our galaxy look like? a) about a month b) about four years c) about 1000 years d) about 100,000 years e) millions of years a) about a month b) about four years c) about 1000 years d) about 100,000 years e) millions of years a) It has a large disk with spiral arms, and is relatively flat and thin. b) It has clouds of gas and dust in the spiral arms. c) Older yellow stars are found mostly in the central bulge. d) Old stars and globular clusters are located in a spherical halo above and below the disk. a) It has a large disk with spiral arms, and is relatively flat and thin. b) It has clouds of gas and dust in the spiral arms. c) Older yellow stars are found mostly in the central bulge. d) Old stars and globular clusters are located in a spherical halo above and below the disk.

2 We can estimate the mass of our galaxy by We can estimate the mass of our galaxy by When you calculate the Milky Way's mass using the two methods of the previous slide, what do you find? When you calculate the Milky Way's mass using the two methods of the previous slide, what do you find? a) counting all the stars and multiplying by the average mass of a star. b) making an estimate of the number of stars and multiplying by the average mass of a star, then accounting for gas and dust. c) observing the speed of rotation using the Doppler shift, knowing the orbital size and speed to calculate mass with Kepler's law. d) A and C a) counting all the stars and multiplying by the average mass of a star. b) making an estimate of the number of stars and multiplying by the average mass of a star, then accounting for gas and dust. c) observing the speed of rotation using the Doppler shift, knowing the orbital size and speed to calculate mass with Kepler's law. d) A and C a) They agree pretty well. b) The mass you estimate for all the visible stars is only about 1/10 the mass you get from observing motions. c) The mass you estimate for all the visible stars is about 10 times the mass you get from observing motions. a) They agree pretty well. b) The mass you estimate for all the visible stars is only about 1/10 the mass you get from observing motions. c) The mass you estimate for all the visible stars is about 10 times the mass you get from observing motions. How do astronomers interpret the results of the previous slide? How do astronomers interpret the results of the previous slide? Gas is added to the interstellar medium by supernovae and planetary nebulae. What kind of gas would you expect that to be? Gas is added to the interstellar medium by supernovae and planetary nebulae. What kind of gas would you expect that to be? a) Astronomers are bad estimators. b) We don't know the masses of stars well. c) 90% of the galaxy is hidden from view. d) There must be some other kind of matter in the galaxy that we cannot see. e) C and D a) Astronomers are bad estimators. b) We don't know the masses of stars well. c) 90% of the galaxy is hidden from view. d) There must be some other kind of matter in the galaxy that we cannot see. e) C and D a) hydrogen gas b) helium gas c) gas that has a mix of heavier elements in it, such as carbon, oxygen, silicon, iron, etc a) hydrogen gas b) helium gas c) gas that has a mix of heavier elements in it, such as carbon, oxygen, silicon, iron, etc Stars we see in the halo of our galaxy formed even before the Milky Way collapsed into a disk. Since we see them today, they must be Stars we see in the halo of our galaxy formed even before the Milky Way collapsed into a disk. Since we see them today, they must be Why do stars in the halo of the galaxy have almost no heavy elements such as carbon, nitrogen, and oxygen? Why do stars in the halo of the galaxy have almost no heavy elements such as carbon, nitrogen, and oxygen? a) young. b) old. c) low mass. d) high mass. a) young. b) old. c) low mass. d) high mass. a) Those elements have been used up in halo stars. b) Heavy elements are biological, and there is no life out there to make them. c) Halo stars formed before those elements were made. d) Making C, N, and O requires massive stars, and there are no massive stars in the halo. a) Those elements have been used up in halo stars. b) Heavy elements are biological, and there is no life out there to make them. c) Halo stars formed before those elements were made. d) Making C, N, and O requires massive stars, and there are no massive stars in the halo. Halo stars Halo stars Where do stars form in the galaxy today? Where do stars form in the galaxy today? a) are deficient in common elements such as carbon, nitrogen, oxygen, and iron. b) have orbits that plunge through the plane of the galaxy. c) are all more massive than the Sun. a) are deficient in common elements such as carbon, nitrogen, oxygen, and iron. b) have orbits that plunge through the plane of the galaxy. c) are all more massive than the Sun. a) No stars are forming in the galaxy today. b) molecular clouds c) dark dust clouds d) glowing ionization nebulae e) B, C, and D a) No stars are forming in the galaxy today. b) molecular clouds c) dark dust clouds d) glowing ionization nebulae e) B, C, and D

3 How do the elements produced in massive stars get into other stars? How do the elements produced in massive stars get into other stars? Infrared telescopes penetrate dust and show us that stars at the center of the Milky Way are orbiting very fast. Why? Infrared telescopes penetrate dust and show us that stars at the center of the Milky Way are orbiting very fast. Why? a) Supernovae blow them out into space. b) Red giant winds blow them into space. c) The star-gas-star cycle circulates them. a) Supernovae blow them out into space. b) Red giant winds blow them into space. c) The star-gas-star cycle circulates them. a) They are in the process of forming. b) They are being accelerated by a supernova explosion. c) There is probably a massive black hole at our galaxy's center. a) They are in the process of forming. b) They are being accelerated by a supernova explosion. c) There is probably a massive black hole at our galaxy's center. Based on the idea of chemical enrichment, which types of stars contain a higher proportion of heavy elements: stars in globular clusters or stars in open clusters? a) Stars in globular clusters, because they are younger and b) Stars in globular clusters, because they are older and c) Stars in open clusters, because they are younger and d) Stars in open clusters, because they are older and Based on the idea of chemical enrichment, which types of stars contain a higher proportion of heavy elements: stars in globular clusters or stars in open clusters? a) Stars in globular clusters, because they are younger and b) Stars in globular clusters, because they are older and c) Stars in open clusters, because they are younger and d) Stars in open clusters, because they are older and What causes the blue and red colors in a photograph of a typical nebula? a) The ionizing photons from a hot star cause hydrogen gas to glow red and helium to glow blue. b) Dust grains scatter blue light and let red light pass through, similar to the blue sky and red sunsets in our atmosphere. c) The blue color is due to the scattering of light by interstellar dust grains and the red color arises from hydrogen emissions. d) The blue light comes from young, hot stars and the red light from older, cooler stars. e) The blue color comes from gas moving toward us and the red color from gas moving away from us. What causes the blue and red colors in a photograph of a typical nebula? a) The ionizing photons from a hot star cause hydrogen gas to glow red and helium to glow blue. b) Dust grains scatter blue light and let red light pass through, similar to the blue sky and red sunsets in our atmosphere. c) The blue color is due to the scattering of light by interstellar dust grains and the red color arises from hydrogen emissions. d) The blue light comes from young, hot stars and the red light from older, cooler stars. e) The blue color comes from gas moving toward us and the red color from gas moving away from us. True or False?: Many spectacular ionization nebulae are seen throughout the Milky Way's halo. True or False?: Many spectacular ionization nebulae are seen throughout the Milky Way's halo. True or False?: The Sun's velocity around the Milky Way tells us that most of our galaxy's dark matter lies within the Sun's orbit. True or False?: The Sun's velocity around the Milky Way tells us that most of our galaxy's dark matter lies within the Sun's orbit. a) True, they are the sites of new star formation. b) True, but they are concentrated in the spiral arms. c) False, there are no young, hot stars to cause ionization nebulae in the halo. d) False, there are very few stars in the halo. e) False, there is very little mass in the halo. a) True, they are the sites of new star formation. b) True, but they are concentrated in the spiral arms. c) False, there are no young, hot stars to cause ionization nebulae in the halo. d) False, there are very few stars in the halo. e) False, there is very little mass in the halo. a) True, the Sun's motion in the galaxy shows that we are near the edge of the Milky Way disk and therefore exterior to most of the mass of the galaxy. b) True, the Milky Way's rotation curve stops increasing well before the orbit of the Sun, indicating that the majority of the Milky Way's mass lies within the Sun's orbit. c) False, the Milky Way's rotation curve remains flat well beyond the orbit of the Sun, indicating that the majority of the Milky Way's mass lies beyond the Sun's orbit. d) False, the Milky Way's rotation curve looks similar to the rotation curve of planets in our solar system where most of the mass lies near the center. a) True, the Sun's motion in the galaxy shows that we are near the edge of the Milky Way disk and therefore exterior to most of the mass of the galaxy. b) True, the Milky Way's rotation curve stops increasing well before the orbit of the Sun, indicating that the majority of the Milky Way's mass lies within the Sun's orbit. c) False, the Milky Way's rotation curve remains flat well beyond the orbit of the Sun, indicating that the majority of the Milky Way's mass lies beyond the Sun's orbit. d) False, the Milky Way's rotation curve looks similar to the rotation curve of planets in our solar system where most of the mass lies near the center. Which type of galaxies have a disk, bulge, and halo? Which type of galaxies have a disk, bulge, and halo? Which type of galaxies lack a disk? Which type of galaxies lack a disk? e) A and D e) A and D

4 Which type of galaxy contains a high percentage of cool interstellar gas and dust? Which type of galaxy contains a high percentage of cool interstellar gas and dust? Which type of galaxy contains little cool interstellar gas and dust? Which type of galaxy contains little cool interstellar gas and dust? Which type of galaxy is particularly common in clusters of galaxies? Which type of galaxy is particularly common in clusters of galaxies? What is a standard candle? What is a standard candle? a) a candle of known brightness b) a galaxy of known brightness c) any object whose luminosity is known independently from its apparent brightness d) a star made of the same elements as the Sun e) a star with the same composition as a halo star a) a candle of known brightness b) a galaxy of known brightness c) any object whose luminosity is known independently from its apparent brightness d) a star made of the same elements as the Sun e) a star with the same composition as a halo star What standard candle is useful at the greatest distances? What standard candle is useful at the greatest distances? What did astronomers debate about the nature of spiral nebulae until the 1920s? What did astronomers debate about the nature of spiral nebulae until the 1920s? a) main sequence stars b) Cepheid variables c) a star whose distance is known from parallax d) white dwarf supernovae e) None of the above a) main sequence stars b) Cepheid variables c) a star whose distance is known from parallax d) white dwarf supernovae e) None of the above a) whether they were nebulae located in the Milky Way, or spiral galaxies located far outside our galaxy b) whether they were forming planets or stars c) both of the above d) none of the above a) whether they were nebulae located in the Milky Way, or spiral galaxies located far outside our galaxy b) whether they were forming planets or stars c) both of the above d) none of the above How did Edwin Hubble prove that the spiral nebulae were distant galaxies? How did Edwin Hubble prove that the spiral nebulae were distant galaxies? What is Hubble's Law? What is Hubble's Law? a) He measured their parallax. b) He measured their Doppler shifts c) He found Cepheid variables in them that looked pretty bright. d) He found Cepheid variables in them that looked very faint. a) He measured their parallax. b) He measured their Doppler shifts c) He found Cepheid variables in them that looked pretty bright. d) He found Cepheid variables in them that looked very faint. a) The faster a galaxy is moving away, the farther away it is. b) The farther away a galaxy is, the slower it is moving away. c) All galaxies are getting closer together over time. d) Galaxies are expanding over time, with their stars growing farther and farther apart. a) The faster a galaxy is moving away, the farther away it is. b) The farther away a galaxy is, the slower it is moving away. c) All galaxies are getting closer together over time. d) Galaxies are expanding over time, with their stars growing farther and farther apart.

5 If faster galaxies are farther away, and there is a direct proportion between speed and distance, then If faster galaxies are farther away, and there is a direct proportion between speed and distance, then How do scientists estimate the age of the universe? How do scientists estimate the age of the universe? a) all galaxies must be avoiding ours. b) all galaxies must have begun moving apart at the same place and time. c) our galaxy must be in the center of the universe. a) all galaxies must be avoiding ours. b) all galaxies must have begun moving apart at the same place and time. c) our galaxy must be in the center of the universe. a) They take the distance to a nearby galaxy and divide it by its speed of recession (time = distance/velocity). b) They take the distance to a very distant galaxy and divide it by its speed of recession (time = distance/velocity). c) They take the distance to any galaxy and divide it by its speed of recession (time = distance/velocity). a) They take the distance to a nearby galaxy and divide it by its speed of recession (time = distance/velocity). b) They take the distance to a very distant galaxy and divide it by its speed of recession (time = distance/velocity). c) They take the distance to any galaxy and divide it by its speed of recession (time = distance/velocity). Is measuring the speed of a receding galaxy a complex scientific process? Is measuring the speed of a receding galaxy a complex scientific process? What does it mean to say that our universe is expanding? What does it mean to say that our universe is expanding? a) Yes, we're talking about cosmology and the edge of the universe. b) No, it's just the Doppler shift the shifting of spectrum lines. c) No, it's the same principle police use to give you a speeding ticket. d) B and C a) Yes, we're talking about cosmology and the edge of the universe. b) No, it's just the Doppler shift the shifting of spectrum lines. c) No, it's the same principle police use to give you a speeding ticket. d) B and C a) Galaxies are moving apart through space. b) Space itself is expanding. c) Everything is expanding, including galaxies, star clusters, and star systems. a) Galaxies are moving apart through space. b) Space itself is expanding. c) Everything is expanding, including galaxies, star clusters, and star systems. When we look at a very distant galaxy, billions of light years away, we see it When we look at a very distant galaxy, billions of light years away, we see it What do we see when we look beyond the cosmological horizon? What do we see when we look beyond the cosmological horizon? a) when it was younger. b) when it was older. c) when the whole universe was younger. d) when the whole universe was older. e) A and C a) when it was younger. b) when it was older. c) when the whole universe was younger. d) when the whole universe was older. e) A and C a) Galaxies that are just about to form. b) Galaxies that are about to enter the universe. c) White dwarfs that are about to go supernova. d) The beginning of the universe. e) We cannot look beyond the cosmological horizon because we cannot look back to a time before the universe began. a) Galaxies that are just about to form. b) Galaxies that are about to enter the universe. c) White dwarfs that are about to go supernova. d) The beginning of the universe. e) We cannot look beyond the cosmological horizon because we cannot look back to a time before the universe began. True or False? If you want to find elliptical galaxies, you'll have better luck looking in clusters of galaxies than elsewhere in the universe. True or False? If you want to find elliptical galaxies, you'll have better luck looking in clusters of galaxies than elsewhere in the universe. True or False?: If the standard candles you are using are less luminous than you think they are, then the distances you determine from them will be too small. True or False?: If the standard candles you are using are less luminous than you think they are, then the distances you determine from them will be too small. a) True, galaxy clusters have a much higher percentage of elliptical galaxies than do other parts of the universe. b) True, elliptical galaxies are found exclusively in galaxy clusters. c) False, elliptical galaxies are more commonly found away from galaxy clusters. d) False, elliptical galaxies are never found in galaxy clusters. e) False, you would have an equal chance of finding an elliptical galaxy in any environment in the universe. a) True, galaxy clusters have a much higher percentage of elliptical galaxies than do other parts of the universe. b) True, elliptical galaxies are found exclusively in galaxy clusters. c) False, elliptical galaxies are more commonly found away from galaxy clusters. d) False, elliptical galaxies are never found in galaxy clusters. e) False, you would have an equal chance of finding an elliptical galaxy in any environment in the universe. a) True, because they are less luminous, they are further away. b) False, because they are less luminous, they are closer than you think and your distance determination is too large. c) False, standard candles produce the same measurement at the telescope no matter what distance they are. d) It depends on the standard candle: if they are Cepheid variables, they will still pulsate at the same rate no matter what distance they are from you. a) True, because they are less luminous, they are further away. b) False, because they are less luminous, they are closer than you think and your distance determination is too large. c) False, standard candles produce the same measurement at the telescope no matter what distance they are. d) It depends on the standard candle: if they are Cepheid variables, they will still pulsate at the same rate no matter what distance they are from you.

6 Galaxy A is moving away twice as fast as Galaxy B, so Galaxy A must be Galaxy A is moving away twice as fast as Galaxy B, so Galaxy A must be When we look at the farthest galaxies in the Hubble Ultra Deep Field, we see galaxies that are When we look at the farthest galaxies in the Hubble Ultra Deep Field, we see galaxies that are a) twice as far away as Galaxy B. b) twice as close as Galaxy B. c) four times as far away as Galaxy B. d) four times as close as Galaxy B. a) twice as far away as Galaxy B. b) twice as close as Galaxy B. c) four times as far away as Galaxy B. d) four times as close as Galaxy B. a) about 12 or 13 billion years old. b) about 4.5 billion years old. c) about 1 or 2 billion years old. d) about 4 million years old. a) about 12 or 13 billion years old. b) about 4.5 billion years old. c) about 1 or 2 billion years old. d) about 4 million years old. What are possible reasons that galaxies differ in form? What are possible reasons that galaxies differ in form? What is likely to happen if two galaxies collide? What is likely to happen if two galaxies collide? a) Pre-galactic clouds have different densities. b) Pre-galactic clouds have different rotation rates. c) Galaxies collide with one another, creating different types.. a) Pre-galactic clouds have different densities. b) Pre-galactic clouds have different rotation rates. c) Galaxies collide with one another, creating different types.. a) Their stars will crash into each other. b) Their mutual gravitational pull will greatly distort each galaxy. c) Starbursts greatly enhanced star formation may occur. a) Their stars will crash into each other. b) Their mutual gravitational pull will greatly distort each galaxy. c) Starbursts greatly enhanced star formation may occur. What is found at the centers of many galaxies? What is found at the centers of many galaxies? Why should we not be surprised that galaxy collisions were common in the past? Why should we not be surprised that galaxy collisions were common in the past? a) a large central star b) a large central planet c) a cluster of stars d) a supermassive black hole e) a supernova a) a large central star b) a large central planet c) a cluster of stars d) a supermassive black hole e) a supernova a) Galaxies moved faster in the past and therefore collided more often. b) Galaxies were larger in the past and therefore collided more often. c) The universe was much denser in the past, so its galaxies were much closer together, making collisions much more frequent. d) Because elliptical galaxies are formed by the collision of two spiral galaxies, ellipticals are observed to be more common in the past. a) Galaxies moved faster in the past and therefore collided more often. b) Galaxies were larger in the past and therefore collided more often. c) The universe was much denser in the past, so its galaxies were much closer together, making collisions much more frequent. d) Because elliptical galaxies are formed by the collision of two spiral galaxies, ellipticals are observed to be more common in the past. True or False?: Starburst galaxies have been forming stars at the same furious pace since the universe was about a billion years old. True or False?: Starburst galaxies have been forming stars at the same furious pace since the universe was about a billion years old. Starburst galaxies have lots of gas and dust that hides their star formation. For this reason, Starburst galaxies have lots of gas and dust that hides their star formation. For this reason, a) True, starburst galaxies are the most prolific regions of star formation in the universe. b) False, after too many stars form, a black hole results and a galaxy stops forming stars. c) False, the bursts of star formation would use up all the gas in a galaxy in a much shorter period of time than the age of the universe. d) False, starburst galaxies are only found nearby, and are all very young. a) True, starburst galaxies are the most prolific regions of star formation in the universe. b) False, after too many stars form, a black hole results and a galaxy stops forming stars. c) False, the bursts of star formation would use up all the gas in a galaxy in a much shorter period of time than the age of the universe. d) False, starburst galaxies are only found nearby, and are all very young. a) we're not really sure how much star formation is occurring. b) we use infrared observations to penetrate the dust. c) we look for x-rays from very hot gas powered by many supernovae. a) we're not really sure how much star formation is occurring. b) we use infrared observations to penetrate the dust. c) we look for x-rays from very hot gas powered by many supernovae.

7 Matter falling into supermassive black holes in the centers of galaxies is thought to be the source of Matter falling into supermassive black holes in the centers of galaxies is thought to be the source of Where does the energy released by a massive black hole come from? Where does the energy released by a massive black hole come from? a) jets that shoot far into space. b) active galactic nuclei. c) strong radio emissions. d) quasars. a) jets that shoot far into space. b) active galactic nuclei. c) strong radio emissions. d) quasars. a) supernovas b) gravity c) colliding stars near the black hole d) nuclear energy a) supernovas b) gravity c) colliding stars near the black hole d) nuclear energy True or False?: The black hole at the center of our own galaxy may once have powered an active galactic nucleus. True or False?: The black hole at the center of our own galaxy may once have powered an active galactic nucleus. Could Newton laws or Kepler's 3 rd law be applied to the hot gas orbiting the nucleus of M87 to determine the mass of the central black hole? Could Newton laws or Kepler's 3 rd law be applied to the hot gas orbiting the nucleus of M87 to determine the mass of the central black hole? a) True, active nuclei in other galaxies appear to be powered by accretion into similar sized black holes. b) True, the Milky Way has a very similar appearance to other galaxies with active nuclei. c) False, the Milky Way is a spiral galaxy and only elliptical galaxies have active nuclei. d) False, active nuclei in galaxies are only found in the distant universe. a) True, active nuclei in other galaxies appear to be powered by accretion into similar sized black holes. b) True, the Milky Way has a very similar appearance to other galaxies with active nuclei. c) False, the Milky Way is a spiral galaxy and only elliptical galaxies have active nuclei. d) False, active nuclei in galaxies are only found in the distant universe. a) No, those laws apply to planets. b) Yes. a) No, those laws apply to planets. b) Yes. Since quasars are mostly found at very great distances, Since quasars are mostly found at very great distances, What do we know about the beginning of the universe? What do we know about the beginning of the universe? a) there must have been more of them when the universe was young. b) we can use their light to study the intergalactic medium between us and them. c) they must have remained unchanged for at least 10 billion years. a) there must have been more of them when the universe was young. b) we can use their light to study the intergalactic medium between us and them. c) they must have remained unchanged for at least 10 billion years. a) It was about 6000 years ago. b) It was billions of years ago. c) It was extremely hot and dense. d) A and C a) It was about 6000 years ago. b) It was billions of years ago. c) It was extremely hot and dense. d) A and C At the beginning of the universe, At the beginning of the universe, What observed feature of the universe motivated scientists to propose the big bang theory? What observed feature of the universe motivated scientists to propose the big bang theory? a) the temperature was billions of degrees. b) the density was enormously high. c) matter could turn into energy and vice versa. a) the temperature was billions of degrees. b) the density was enormously high. c) matter could turn into energy and vice versa. a) There is lots of debris in space, as would be expected from an explosion. b) The universe is expanding, and the expansion must trace back to a specific point and time of origin in the past. c) Everything has a beginning, middle, and end. a) There is lots of debris in space, as would be expected from an explosion. b) The universe is expanding, and the expansion must trace back to a specific point and time of origin in the past. c) Everything has a beginning, middle, and end.

8 What does the big bang theory predict can be seen today if there really was a big bang? What does the big bang theory predict can be seen today if there really was a big bang? Which of the two main predictions of the big bang theory turned out to be true? Which of the two main predictions of the big bang theory turned out to be true? a) Radiation from the big bang might be detected. It was gamma rays 14 billion years ago, but today it is cooler and would look like weak microwaves coming from all of space. b) The Big Bang produced three elements, which might be seen in the oldest stars: 75% hydrogen, 25% helium, 1 part in a billion lithium. c) The universe must be finite in mass and dimension. a) Radiation from the big bang might be detected. It was gamma rays 14 billion years ago, but today it is cooler and would look like weak microwaves coming from all of space. b) The Big Bang produced three elements, which might be seen in the oldest stars: 75% hydrogen, 25% helium, 1 part in a billion lithium. c) The universe must be finite in mass and dimension. a) Radiation has been found coming from all of space, just as predicted. b) The oldest stars are made of hydrogen, helium, and lithium, in the proportions predicted. c) both A and B d) neither A nor B a) Radiation has been found coming from all of space, just as predicted. b) The oldest stars are made of hydrogen, helium, and lithium, in the proportions predicted. c) both A and B d) neither A nor B How do scientists test the idea that the four fundamental forces are aspects of a more general force that became separate ("froze out") during the big bang? How do scientists test the idea that the four fundamental forces are aspects of a more general force that became separate ("froze out") during the big bang? The cosmic background radiation from the big bang has been mapped in detail. What does it look like? The cosmic background radiation from the big bang has been mapped in detail. What does it look like? a) It can't be tested. b) They study far-away objects to see how forces behave at times early in the universe. c) Particle accelerators like Fermilab and the Large Hadron Collider have tested predictions that the weak and electromagnetic forces are related. a) It can't be tested. b) They study far-away objects to see how forces behave at times early in the universe. c) Particle accelerators like Fermilab and the Large Hadron Collider have tested predictions that the weak and electromagnetic forces are related. a) It is all over the sky. b) It is seen even where there is no matter. c) It is very uniform in overall distribution. d) If you look very closely, there are slight fluctuations from place to place. a) It is all over the sky. b) It is seen even where there is no matter. c) It is very uniform in overall distribution. d) If you look very closely, there are slight fluctuations from place to place. True or False?: When we look at the cosmic background radiation, we are looking farther into space further back in time then when we look at the farthest galaxies. True or False?: When we look at the cosmic background radiation, we are looking farther into space further back in time then when we look at the farthest galaxies. What are the slight fluctuations seen in maps of the cosmic background radiation? What are the slight fluctuations seen in maps of the cosmic background radiation? a) true b) false a) true b) false a) uncertainties in the map b) variations in the instrument's sensitivity c) the beginning of the formation of galaxies and clusters of galaxies d) dark matter a) uncertainties in the map b) variations in the instrument's sensitivity c) the beginning of the formation of galaxies and clusters of galaxies d) dark matter Grand unified theories of physics (GUTs) predict that the very early universe (10-32 seconds after the big bang) may have had a phase transition, releasing energy and causing Grand unified theories of physics (GUTs) predict that the very early universe (10-32 seconds after the big bang) may have had a phase transition, releasing energy and causing Can the idea of an enormous early inflation of the universe be tested? Can the idea of an enormous early inflation of the universe be tested? a) a period of rapid expansion (inflation). b) tiny fluctuations predicted by quantum mechanics to expand large enough to contribute to the fluctuations we see in the cosmic background radiation. c) a reduction in the curvature of space. a) a period of rapid expansion (inflation). b) tiny fluctuations predicted by quantum mechanics to expand large enough to contribute to the fluctuations we see in the cosmic background radiation. c) a reduction in the curvature of space. a) No, it happened too long ago. b) Yes, inflation affects the tiny fluctuations in the cosmic background. If we measure them precisely, we can test inflation theories. a) No, it happened too long ago. b) Yes, inflation affects the tiny fluctuations in the cosmic background. If we measure them precisely, we can test inflation theories.

9 True or False?: Inflation couldn't have happened because it means that matter would have moved faster than the speed of light, and relativity says this is impossible. True or False?: Inflation couldn't have happened because it means that matter would have moved faster than the speed of light, and relativity says this is impossible. Models of the universe that include inflation and match the details of the cosmic background radiation say the universe is about Models of the universe that include inflation and match the details of the cosmic background radiation say the universe is about a) true b) false-matter isn't moving through space, space itself is expanding a) true b) false-matter isn't moving through space, space itself is expanding a) 4.6 billion years old. b) 10 billion years old. c) 13.7 billion years old. d) Infinitely old. a) 4.6 billion years old. b) 10 billion years old. c) 13.7 billion years old. d) Infinitely old. If the expansion of the galaxies is traced backwards in time, it indicates the universe began about If the expansion of the galaxies is traced backwards in time, it indicates the universe began about The age of the oldest stars in our galaxy appears to be about The age of the oldest stars in our galaxy appears to be about a) 6000 years ago. b) 4.6 billion years ago. c) 10 billion years old. d) billion years. a) 6000 years ago. b) 4.6 billion years ago. c) 10 billion years old. d) billion years. a) 6000 years old. b) 4.6 billion years old. c) 10 billion years old. d) 13 billion years old. a) 6000 years old. b) 4.6 billion years old. c) 10 billion years old. d) 13 billion years old. The best current estimate for what the universe is made of is The best current estimate for what the universe is made of is What is Olbers' paradox? What is Olbers' paradox? a) about 4% ordinary visible matter. b) about 23% dark matter. c) about 73% dark energy. d) All of the above a) about 4% ordinary visible matter. b) about 23% dark matter. c) about 73% dark energy. d) All of the above a) If the universe was infinite, any direction you looked you would eventually see a star. b) If the universe was infinitely old, the starlight would have time to get here. c) The sky should look bright at night because all areas of the sky should have a star, and time for the starlight to reach us. a) If the universe was infinite, any direction you looked you would eventually see a star. b) If the universe was infinitely old, the starlight would have time to get here. c) The sky should look bright at night because all areas of the sky should have a star, and time for the starlight to reach us. Since the sky is dark at night, what's wrong with Olbers' paradox? Since the sky is dark at night, what's wrong with Olbers' paradox? Why should it not be surprising that some galaxies contain a little more than 25% helium, but it would be very surprising if some galaxies contained less. Why should it not be surprising that some galaxies contain a little more than 25% helium, but it would be very surprising if some galaxies contained less. a) The universe is not infinite in size. b) There's not an infinite number of stars. c) The universe is not infinitely old. a) The universe is not infinite in size. b) There's not an infinite number of stars. c) The universe is not infinitely old. a) A star converts about 25% of its hydrogen into helium before it dies, so galaxies with multiple generations of star formation can have a higher percentage of helium. b) The big bang fused 25% of normal matter in the universe into helium, and stellar nucleosynthesis can increase, but not decrease, this amount. c) The helium fraction decreases with age, so younger galaxies have more than 25%, but galaxies with less helium would be older than the estimated age of the universe. d) Helium is more massive than hydrogen so it cannot readily escape the gravitational field of a galaxy. A percentage lower than 25% would indicate that the galaxy had no dark matter. a) A star converts about 25% of its hydrogen into helium before it dies, so galaxies with multiple generations of star formation can have a higher percentage of helium. b) The big bang fused 25% of normal matter in the universe into helium, and stellar nucleosynthesis can increase, but not decrease, this amount. c) The helium fraction decreases with age, so younger galaxies have more than 25%, but galaxies with less helium would be older than the estimated age of the universe. d) Helium is more massive than hydrogen so it cannot readily escape the gravitational field of a galaxy. A percentage lower than 25% would indicate that the galaxy had no dark matter.

10 True or False? Although the universe today appears to be made mostly of matter and not antimatter, the big bang theory suggests that the early universe had nearly equal amounts of matter and antimatter. a) True, the Big Bang theory predicts that high temperatures in the early universe generated matter-antimatter pairs, and the amounts of each were therefore virtually equal. b) True, the Big Bang was started by the mutual annihilation of virtually equal numbers of matter and antimatter particles. c) False, the amount of matter and antimatter in the early universe should be exactly the same as it is today. d) False, the amount of matter and antimatter in the early universe should be in the same proportion as it is today. True or False? Although the universe today appears to be made mostly of matter and not antimatter, the big bang theory suggests that the early universe had nearly equal amounts of matter and antimatter. a) True, the Big Bang theory predicts that high temperatures in the early universe generated matter-antimatter pairs, and the amounts of each were therefore virtually equal. b) True, the Big Bang was started by the mutual annihilation of virtually equal numbers of matter and antimatter particles. c) False, the amount of matter and antimatter in the early universe should be exactly the same as it is today. d) False, the amount of matter and antimatter in the early universe should be in the same proportion as it is today. True or False?: The theory of inflation suggests that the structure of the universe may have originated as tiny quantum fluctuations. a) True, tiny quantum fluctuations were stretched to enormous sizes by inflation and became large enough to grow into galaxies and galaxy clusters. b) True, quantum uncertainty meant that some regions of the universe expanded more slowly than other regions and these slower moving regions eventually became galaxies and galaxy clusters. c) False, the theory of inflation suggests that the structure of the universe arose when radiation decoupled from matter. d) False, quantum fluctuations are on an atomic scale and the structure of the universe is on the scale of galaxies. True or False?: The theory of inflation suggests that the structure of the universe may have originated as tiny quantum fluctuations. a) True, tiny quantum fluctuations were stretched to enormous sizes by inflation and became large enough to grow into galaxies and galaxy clusters. b) True, quantum uncertainty meant that some regions of the universe expanded more slowly than other regions and these slower moving regions eventually became galaxies and galaxy clusters. c) False, the theory of inflation suggests that the structure of the universe arose when radiation decoupled from matter. d) False, quantum fluctuations are on an atomic scale and the structure of the universe is on the scale of galaxies. True or False?: The fact that the night sky is dark tells us that the universe cannot be infinite, unchanging, and the same everywhere. True or False?: The fact that the night sky is dark tells us that the universe cannot be infinite, unchanging, and the same everywhere. a) True, the dark night sky shows that the Big Bang theory must be modified by allowing for an initial period of inflation. b) True, if the universe were infinite, unchanging, and the same everywhere, the night sky would be as bright as the surface as the Sun. c) False, the night sky is dark at optical wavelengths but is blazing at microwave wavelengths. d) False, the night sky is dark simply because the Sun is on the opposite side of Earth! a) True, the dark night sky shows that the Big Bang theory must be modified by allowing for an initial period of inflation. b) True, if the universe were infinite, unchanging, and the same everywhere, the night sky would be as bright as the surface as the Sun. c) False, the night sky is dark at optical wavelengths but is blazing at microwave wavelengths. d) False, the night sky is dark simply because the Sun is on the opposite side of Earth!