### „Proposition 6. The moon moves (in an orbit) lower than (that of) the sun, and, when it is halved, is distant less than a quadrant from the sun.“

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16 0## Aristarchus of Samos

Aristarchus of Samos was an ancient Greek astronomer and mathematician who presented the first known heliocentric model that placed the Sun at the center of the known universe with the Earth revolving around it. He was influenced by Philolaus of Croton, but Aristarchus identified the "central fire" with the Sun, and he put the other planets in their correct order of distance around the Sun. Like Anaxagoras before him, he suspected that the stars were just other bodies like the Sun, albeit further away from Earth. His astronomical ideas were often rejected in favor of the geocentric theories of Aristotle and Ptolemy. Nicolaus Copernicus attributed the heliocentric theory to Aristarchus. Wikipedia

Photo: Unknown artist (17th century), Atlas of Cellarius / Public domain

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On the Sizes and Distances of the Sun and the Moon (c. 250 BC)

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On the Sizes and Distances of the Sun and the Moon (c. 250 BC)

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On the Sizes and Distances of the Sun and the Moon (c. 250 BC)

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On the Sizes and Distances of the Sun and the Moon (c. 250 BC)

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On the Sizes and Distances of the Sun and the Moon (c. 250 BC)

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On the Sizes and Distances of the Sun and the Moon (c. 250 BC)

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On the Sizes and Distances of the Sun and the Moon (c. 250 BC)

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On the Sizes and Distances of the Sun and the Moon (c. 250 BC)

1. That the Moon receives its light from the sun.

2. That the earth is in the relation of a point and centre to the sphere in which the moon moves.

3. That, when the moon appears to us halved, the great circle which divides the dark and the bright portions of the moon is in the direction of our eye.

4. That, when the moon appears to us halved, its distance from the sun is then less than a quadrant by one-thirtieth of a quadrant.

5. That the breadth of the (earth's) shadow is (that) of two moons.

6. That the moon subtends one fifteenth part of a sign of the zodiac.“

Note "is less than a quadrant..." is less than 90° by l/30th of 90° or 3°, and is therefore equal to 87°.

On the Sizes and Distances of the Sun and the Moon (c. 250 BC)

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On the Sizes and Distances of the Sun and the Moon (c. 250 BC)

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On the Sizes and Distances of the Sun and the Moon (c. 250 BC)

Variant: Proposition 10. The sun has to the moon a ratio greater than that which 5832 has to 1, but less than that which 8000 has to 1.

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On the Sizes and Distances of the Sun and the Moon (c. 250 BC)

Variant: Proposition 17. The diameter of the earth is to the diameter of the moon in a ratio greater than that which 108 has to 43, but less than that which 60 has to 19.

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On the Sizes and Distances of the Sun and the Moon (c. 250 BC)

Variant: Proposition 7. The distance of the sun from the earth is greater than eighteen times, but less than twenty times, the distance of the moon from the earth.

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On the Sizes and Distances of the Sun and the Moon (c. 250 BC)