Early theories about the Moon

140 BCE
- Hipparchus finds out how to predict eclipses.
1st century BCE
- Jing Fang rises the radiating influence theory, stating that the moon's light is just the sun's reflection in space.
150 CE
- Ptolemy creates tables for calculating celestial body positions.
11th century
- Shen Kuo’s Dream Pool Essays explains that celestial bodies are round rather than flat.
1609
- Johannes Kepler describes ellipses to explain how the planets move as free-floating bodies.

Zhang Heng: He’s the Chief Astrologer at the court of Chinese emperor An-ti; and was a mathematician and observer.
He recorded 2,500 stars that were "brightly shining," and he estimated that there were an additional 11,520 stars that were "very small."
In his treatise Ling Xian, or The Spiritual Constitution of the Universe, he positioned Earth at the center of the universe, saying that "Earth is the yolk of the egg, lying alone at the center, and the sky is like a hen's egg, and is as round as a crossbow pellet."
Zhang came to the conclusion that the moon did not have its own light and simply reflected the sun "like water."
He also described a lunar eclipse, in which the sun's light is blocked from reaching the moon due to Earth's presence.
- He realized that the planets were also affected by eclipses.
Shen Kuo, a Chinese astronomer, expanded on Zhang's work in the 11th century.
In Shen’s Dream Pool Essays, he explained that planets aren’t flat.
Shen showed how the moon's waxing and waning proved that the sun and moon were spheres.

Zhang Heng was a Chinese scientist who worked in a variety of fields. He lived during the Han dynasty. He was a skilled engineer, meteorologist, geologist, philosopher, mathematician, astronomer, writer, and other professions as well.
In 132 AD, Zhang invented the first seismometer, a device that gauges an earthquake's power. He is renowned for a wide range of other creations and writings.
Heng was the first cartographer in China to use a grid system for his maps, allowing for the calculation of positions and distances.
He held a number of positions, including chief minister under Moana's rule and chief astronomer at the Imperial Chancellery for Astronomical and Calendrical Science.
He also produced a wide range of writings, from poetry to books containing his scientific investigations.
One was his research book on astronomy, which discussed his hypotheses about celestial phenomena that had not yet been adequately explained.
- It proposed various ideas, including the idea that the Moon receives light from the Sun rather than producing its own.
- A lunar eclipse caused by the Earth's shadow was also suggested.