Hidden Bodies: A Brief and Incomplete History of Astronomical Discovery

It is not certain when Aristotle wrote his book On the Heavens, but it is thought to have been written sometime around 350 BCE. In it, he addresses the debates on the cosmogony of his day, for example asserting the weakness of the argument of flat-earthers. As I’ve discussed before, the view of the Earth as spherical was common, even popular, all the way back then, and championed by Aristotle. However, in laying out his model of the universe, he favored a geocentric cosmology, viewing Earth as the center of the universe, an immutable and eternal constant with other planets, the Sun, and the stars revolving around it, and beyond the stars, a spiritual plane that he called the Sphere of the Prime Mover. Even then, though, there were alternative views. As Aristotle notes, the Pythagorean philosopher Philolaus believed that the Earth revolved around a Central Fire. However, this Central Fire was not the Sun, in his view, which he said also revolved around the center with the Earth, and he further believed that on the other side of this Central Fire at the universe’s center was an Antichthon, or Counter-Earth, a strange idea that survived long enough to become the fodder of sci-fi.

Modern astronomers have even been obliged to disprove the existence of such a phantom planet, which would be detectable because of its gravitational influence on other planetary bodies. But Philolaus’s model influenced Aristarchus, who saw the Central Fire as being one and the same as the Sun, building a heliocentric model of the universe and even suggesting that the stars were themselves other suns. But Aristarchus’s model was often rejected in favor of the Aristotelian geocentric model, thereafter developed by Hipparchus of Nicaea and Ptolemy of Alexandria, who tweaked the model to suggest that each heavenly body, in its orbit of Earth, also moved in an epicycle, or a small circle, performing little loop-de-loops as it revolved around us.

The heliocentric view of the universe would not rise again, as it were, until the 16th century, when Polish monk Nicolaus Copernicus’s On the Revolution of the Celestial Spheres set forth a model of the universe that the Church rejected. Then in 1610, when Galileo recognized that the planetary bodies he’d been observing were moons orbiting Jupiter, not revolving around Earth, the geocentric model of the universe was in its death throes. However, this new model still held that we were very close to the center of the universe: our sun, Sol. This notion would not be shattered until the 20th century, when the head of the Harvard College Observatory, Harlow Shapley, placed our solar system in the boondocks of the Milky Way galaxy. Still, the Milky Way, it was thought, even by Shapley, was the only galaxy there was. Until Edwin Hubble showed that there were other galaxies beyond ours, proving it to Shapley in what Shapley described as a “letter that destroyed my universe.” Thus goes the march of scientific progress. When we believe we understand something, our illusions are obliterated by the next discovery. Today, we have the multiverse theory to suggest that our universe may not even be the only one, making our existence feel more and more insignificant.

Further Reading

  1. Bakker, Frederick A. “The End of Epicurean Infinity: Critical Reflections on the Epicurean Infinite Universe_.” Space, Imagination and the Cosmos from Antiquity to the Early Modern Period_, edited by Bakker F., Bellis D., Palmerino C., Studies in History and Philosophy of Science, vol 48, Springer, 2018, pp. 41-67. SpringerLink, link.springer.com/chapter/10.1007/978-3-030-02765-0_3.
  2. Baron, David. “The American Eclipse of 1878 and the Scientists Who Raced West to See It.” Mental Floss, 28 July 2017, www.mentalfloss.com/article/503114/american-eclipse-1878-and-scientists-who-raced-west-see-it.
  3. Bartusiak, Marcia. Dispatches from Planet 3: Thirty-Two (Brief) Tales on the Solar System, the Milky Way, and Beyond. Yale University Press, 2018.
  4. Basalla, George. Civilized Life in the Universe: Scientists on Intelligent Extraterrestrials. Oxford University Press, 2006. Internet Archive, archive.org/details/civilizedlifeinu0000basa/page/n3/mode/2up.
  5. Choi, Jieun, et al. “Precise Doppler Monitoring of Barnard’s Star.” The Astrophysical Journal, vol. 764, no. 2, 31 Jan. 2013, pp. 131-142. IOPScience, iopscience.iop.org/article/10.1088/0004-637X/764/2/131.
  6. Matson, John. “50 Years Ago an Astronomer Discovered the First Unambiguous Exoplanet (or So He Thought).” Scientific American, 30 May 2013, blogs.scientificamerican.com/observations/50-years-ago-an-astronomer-discovered-the-first-unambiguous-exoplanet-or-so-he-thought/.
  7. O’Callaghan, Jonathan. “Water on Mars: Discovery of Three Buried Lakes Intrigues Scientists.” Nature, 28 Sep. 2020, www.nature.com/articles/d41586-020-02751-1.
  8. Sant, Joseph. “The Copernican Myths.” Scientus.org, 2019, www.scientus.org/Copernicus-Myths.html.
  9. “The Galileo Myths.” Scientus.org, 2020. www.scientus.org/Galileo-Myths.html.