Like people even today, the ancients had to deal with verisimilitude: the appearance of truth. Something that appears true may indeed be true – or it may not be. Earth being motionless is a verisimilitude, an appearance. It seemed true. It still seems true. It would have taken extraordinary insight and courage to question publicly whether it is actually an illusion. With the tools at hand 2,300 years ago (none), how could anyone possibly turn such a longstanding belief on its head?
Yet that is exactly what one Greek accomplished. I write about him proudly, because he is my earliest hero – so much so, that at this moment I’m on his island of Samos in the Aegean Sea, searching for anything more that I can learn about him.
Aristarchus of Samos, born in 310 BCE, pondered the sky and arrived at correct conclusions 18 centuries ahead of everyone else. Aristarchus was a mathematician and astronomer, and the very first person to write and preach that the Sun is the center of the solar system, and that Earth orbits around it while also spinning like a top. To his contemporaries, it must have seemed nothing short of crazy.
Aristarchus arrived at this heresy by observing the Half Moon, measuring whether it truly sat at right angles to the Sun at that time, and then figuring out what relative distances would produce such shading. Without the benefit of optics, the Half Moon’s sky location has a typical error of a few degrees, and Aristarchus calculated that the Sun lies 18 times farther than the Moon. Since both discs appear the same size – a wondrous coincidence that is somehow lost on most people – it must mean that the Sun is actually 18 times larger.
No matter that the Sun’s true size is not 18 but 400 times wider than the Moon. Either way, it was a major solar upgrade over the prevailing view. For example, his contemporary Samos native Epicurus (yes, that Epicurus, who was fond of life’s pleasures) claimed that the Sun was two feet in diameter. Two feet! Early evidence, perhaps, that hedonistic ouzo sessions were incompatible with mathematical reasoning.
Even if it merely boasted the breadth of 18 Moons, as Aristarchus claimed, this still meant that the Sun is several times bigger than the Earth. This made it logical to him that it, and not Earth, should be the motionless entity. A smaller body should logically orbit a larger one. Moreover, Venus and Mercury clearly circled the Sun like a moth around a flame. If they do so, why not us?
Aristarchus preached this “heliocentric” model of motion 72 generations ahead of Copernicus and Galileo, the Renaissance geniuses who are today popularly credited with the idea. Shouldn’t the first person who revealed our planet’s true motion be known by all, his name remembered before any American Idol contestant? Shouldn’t some of us have attended Aristarchus High? (I checked. None of the 37,100 public or private secondary schools in the US has the name Aristarchus High. Then again, there isn’t a Richard Nixon High either, and he was the one who delivered the line “I am not a crook,” which may be right up there with finding Earth’s rotation.)
Aristarchus’ widespread anonymity and general mistreatment by history was partially due to his personal life being largely wrapped in mystery. He’s known to have studied at the Lyceum, but no one is sure whether he attended the Athens or the Alexandria campus, for example.
In any case, it was all for naught. The moving-Earth idea never gained any traction. When Plato later insisted that our world doesn’t budge, it became the literal gospel for the next 18 centuries. So much for getting it right way ahead of everyone else.