Before such a thing was proven to be fact, heliocentrism was the theory that the Earth revolved around the sun, instead of vice versa. It seems obvious now, what with our telescopes and modern book learnin’, but when it was first suggested, the heliocentric model of the solar systems was frowned upon hard. Like, “excommunicate you” hard. Yes, because most folks at the time were still so convinced that God and Jesus had built the universe with humans as its center-point, people were permanently shunned or house-arrested for suggesting—based on scientific reasoning—that maybe that wasn’t the case.
Fortunately for him, Seleucus of Seleucia did not meet that fate. However, his work did go a long way toward advancing the heliocentric model. He also sussed out the cause of the Earth’s tides. A right smart chap, he was.
The Mad Man of Mesopotamia
Born circa 190 BCE in Seleucia on the Tigris in Mesopotamia (in what is now Iraq), Seleucus was an astronomer, a philosopher, and, as has been noted, an early proponent of heliocentrism. Following the teachings of Aristarchus of Samos, which suggested that the Earth turns on its own axis whilst simultaneously revolving around the sun, Seleucus was the first to demonstrate the workings of a heliocentric system using reason. Unfortunately, the exact arguments he used to state his case have been lost to the sands of time.
The excellently named 20th Century CE Dutch mathematician and mathematical historian Bartel Leendert van der Waerden suggested that Seleucus likely arrived at his heliocentric view of the universe by first determining the constraints of a geometric model, then developing methods to compute the positions of the planets using said model. If that sounds somewhat familiar, it’s because Nicolaus “Big Nick” Copernicus used essentially the same process to create his own heliocentric model in the 16th Century CE.
Lucio “Big Luke” Rosso, a modern-day Italian physicist, mathematician, professor, and scientific historian, has suggested that Seleucus’ interest in heliocentric theory was likely related to Earth’s tides. Seleucus closely studied our planet’s yearly tidal cycle, and found that it could not be adequately explained in a geocentric system. Seleucus was the first to hypothesize that tides are caused by the Moon’s gravitational interaction with Earth, and the first to suss out that the “height” of the tides is dependent on the Moon’s position relative to the Sun.
Not too shabby for a punk kid outta Mesopotamia.