| The
Shapley-Curtis Debate:� 1920 |
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| � | Are spiral nebulae really other |
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| galaxies, or just swirling clouds of |
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| gas and dust within our own |
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| galaxy? |
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| � | Many spiral galaxies had much |
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| larger radial velocities than other |
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| objects within our own galaxy |
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| � | Answered by new observations: |
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| � | In 1923/4 Edwin Hubble photographed and
identified Cepheids in the |
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| Andromeda Galaxy: |
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| � | Distance to Cepheids cleared showed Andromeda was
outside our own |
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| galaxy |
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