| 11. | These apply to the apparent revolutions of the planets and fixed stars as well.
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| 12. | Do any of them know how much variation is needed in the fixed stars?
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| 13. | The outermost consisted of motionless, fixed stars, with the Sun motionless at the center.
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| 14. | As we now know, the fixed stars are not fixed.
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| 15. | If there is any fixed star in our constitutional constellation,
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| 16. | Hipparchus thought it was caused by the motion of the sphere of fixed stars.
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| 17. | In the 4th century, Eudoxus of Cnidus wrote a book on the fixed stars.
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| 18. | He established the idea of a sphere of fixed stars that rotated about the earth.
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| 19. | The fixed stars exhibit real motion as well, however.
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| 20. | In 1718 Edmund Halley announced his discovery that the fixed stars actually have proper motion.
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