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1 | | Why do astronomers believe the Universe is expanding? |
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2 | | What is meant by a cosmic horizon? |
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3 | | What is Olbers’ paradox? |
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4 | | What is the cosmic microwave background? What is its origin? |
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5 | | Why do astronomers believe the early Universe was hot and dense? |
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6 | | What is meant by the age of the Universe? How old is it? How is its age found? |
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7 | | How was helium formed from hydrogen in the early Universe? |
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8 | | What explanation do astronomers offer for why the relative abundance of hydrogen and helium is uniform? |
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9 | | Is our cosmic horizon the same as that of beings in another galaxy? Why? |
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10 | | What is meant by inflation in cosmology? |
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11 | | What is the Big Bang? What are some of its properties? |
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12 | | What problems of the Big Bang theory are resolved by inflationary models? |
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13 | | What is meant by open and closed universes? |
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14 | | How do the shapes of open, closed, and flat universes differ? How does their energy content differ? |
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15 | | What is “unified” in grand unified theories? |
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16 | | What is meant by dark matter? |
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17 | | What role does the cosmological constant play in cosmology? What evidence makes astronomers think it may exist? |
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