Astronomy: Myth and Science

Timelines of Events

• 550 BCE
  • Anaximander of Miletus: He produced attempts to explain the science of the universe.
• 530 BCE
  • Pythagoras: He established a school in Croton and promoted the idea of a cosmos in which bodies move in perfect spheres.
• 350 BCE
  • Aristotle: In his On the Heavens, he outlined an Earth-centered model of the universe. Many of his ideas will dominate thinking for 2,000 years.
• 220 BCE
  • Aristarchus of Samos: He proposed a sun-centered model of the universe, but his concept is not widely accepted.
• 200 BCE
  • Eratothenes of Alexandria: He calculated the distance to the sun by measuring the circumference of the Earth.
• 150 CE
  • Ptolemy: He wrote the Almagest, setting out an Earth-centered model of the universe that which are widely accepted.
• 499 CE
  • Aryabhata of Aryabhatiya: An Indian astronomer, claims that the stars move across the sky because the Earth rotates.
• 1025
  • Ibn al-Haytham creates a work that criticizes the complexity of the Ptolemaic model of the universe.
• 1180
  • Gerard of Cremona made Arabic texts, including the Almagest, which made it accessible in Europe and translated them to Latin.
• 1279
  • Guo Shoujing, a Chinese astronomer, he determined the length of the solar year with precision.
• 1437
  • Ulugh Beg, a Mongol Rule, corrected many of the postions of stars found in the Almagest.
• 1543
  • Nicolaus Copernicus: His book De revolutionibus orbium coelestium is published, outlining a sun-centered cosmos.

Ancient Greece and its colonies are where the traditions that form the foundation of modern astronomy.

• In Mesopotamia, astronomy was based on mythology, and divining the future was a major concern.
• Thales of Miletus: He was the first in a long line of philosophers who believed that logical reasoning could reveal the immutable laws of nature.

Aristotle’s beliefs

• Aristotle was a student of Plato, and both shared Pythagoras' ideas, which held that the natural world was a "cosmos" as opposed to a "chaos."
• Aristotle claimed that the heavenly realms are perfect and unchanging, but he also supported ideas that made "common sense" sense.
• His philosophy was adopted as the overall framework of ideas for science that was the most agreeable, and it was later incorporated into Christian theology.

Geometrical order

• In 150 CE, Ptolemy compiled the ultimate compendium of Greek astronomy.
• By 500 CE, the Greek approach to astronomy had lost momentum.
• After Ptolemy, there were no significant astronomical innovations in this tradition for nearly 1,400 years.
• Large civilizations like those in China, India, and the Islamic world all created their own traditions.
  • Astronomers from China, the Arab world, and Japan documented the 1054 supernova, which created the well-known Crab nebula in the constellation Taurus.
• “It is the duty of an astronomer to compose the history of the celestial motions through careful and expert study.” — Nicolaus Copernicus

The spread of learning

• Greek science made a circuitous journey back to Europe.
• In 740 CE, Baghdad grew into an important learning center for the Islamic world.
• Ptolemy’s Almagest, his great compendium was translated into Arabic.
• In the 12th century, many Arabic texts were translated into Latin, allowing the legacy of Greek philosophers as well as Islamic scholars to reach Western Europe.
• Throughout his life, Nicolaus Copernicus collected books, including Ptolemy's works.
• Copernicus believed that Ptolemy's geometrical constructions fell short of the goal that the original Greek philosophers had set for them: to describe nature through the discovery of basic principles.
• Even though Copernicus intuitively understood that a sun-centered approach could result in a much simpler system, his unwillingness to give up circular motion ultimately prevented him from achieving true success.