Early Heliocentric Model

Timelines of Events

• 430 BCE
  • Philolaus of Craton: He proposed that there is a massive ball of fire at the center of the universe, around which the sun, moon, Earth, five planets, and stars revolve.
• 350 BCE
  • Aristotle says that Earth is at then center of the universe and every celestial bodies around revolves around it.
• 150 CE
  • Ptolemy claims an Earth-centered (geocentric) model of the universe.
• 1453
  • Nicolaus Copernicus proposes a sun-centered (heliocentric) universe.
• 1838
  • Friedrich Bessel of Germany is the first astronomer to measure a star's distance precisely using a technique called parallax.

The Early Heliocentric Universe

• Aristarchus of Samos: The first person to propose that the sun, rather than Earth, is at the center of the universe and that Earth revolves around it.
  • His thoughts were inspired by Archimedes.
• In Archimedes’ The Sand Reckoner, Aristarchus proposed that "the fixed stars and sun stay unmoved" and that "Earth revolves around the sun."
• Seleucus of Seleucia was persuaded of the truth of Aristarchus’ heliocentric view of the universe.
• In 150 CE, the geocentric viewpoint was still the prevailing one, and it persisted until Nicolaus Copernicus revived the heliocentric perspective in the 15th century.
• Aristarchus also thought that the distance between the stars was much greater than previously thought.
• He calculated the sizes of the sun, moon, and other celestial bodies in relation to Earth.
• His calculations for the moon's distance were largely accurate, but he underestimated the sun's distance due to an error in one of his measurements.

“Aristarchus was the real originator of the Copernican hypothesis.” — Sir Thomas Heath

Aristarchus of Samos

• He was born during the Hellenistic age. 
• The Catholic church had an unrivaled influence at this time.
• The majority of the information we have about Aristarchus comes from hearsay and one single piece of writing that has survived, and very little is known about his early life.
  • Although there isn't any proof to support it, it is only assumed that he was born on the Greek island of Samos.
• He was the first to examine the Sun and moon's sizes and distances in relation to Earth. 
• Some speculate that Aristarchus of Samos was one of the astronomers threatened with persecution because of their theories. 
• Although almost all of Aristarchus' theories were disregarded and even rejected, there is a completely opposing school of thought that contends that he was not in danger of being persecuted.
• He was the first person to propose a heliocentric model of the Solar System, which was revolutionary at the time but did not receive the acclaim it deserved.
• He is also credited with using the proper geometric method to calculate the sun's distances from the moon and the Earth.
• He also made an effort to measure the moon's and the sun's sizes.
• Even though the majority of his calculations were wrong, we can't really dispute his contributions to astronomy.
• In fact, famous ancient astronomers such as Copernicus credited Aristarchus' theory, proving that he was a genius of his time.
• Aristarchus of Samos is honored for this by having an entire lunar crater named in his honor.
• The heliocentrism theory that he advanced, essentially proposing that the sun was the center of the Solar System and that the planets and their moons revolved around it, is what is most commonly associated with him today.
• Additionally, he claimed that the fixed stars we believe make up the universe are actually suns that are located far from our own solar system.
• As the first person to appear to comprehend that the Earth rotated not only on its axis but also around the Sun, Aristarchus is also credited with this understanding.
• Science advancements took a while before they were able to prove the axial rotation and tilt models.