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 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 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.

In my recent blog post, covering the history of immunological science and the development of vaccine technology, as well as in a patron bonus on germ theory, I found it interesting to explore both the hits and misses of scientific progress. It illustrates well the scientific principle that only through experimentation, collection of evidence, observation and comparison can truth be established. We see in the history of science the concept that, as Isaac Newton once wrote, each generation stands on the shoulders of giants, building upon what has already been proven and disproving what has not in order to achieve a more perfect understanding of our world and universe. I find this gratifying because of how very different it often seems from historiology. Don’t get me wrong. Professional historians work tirelessly to revise and perfect our understanding of the past. The term “revisionist history” in fact has unfairly developed a negative connotation, when in reality, every professional historian engages in measured and evidence-supported revision. But since history is often viewed as static and unchanging, our evolving understanding of it often takes a long time to catch up. Textbooks continue to disseminate oversimplified narratives rife with myths and misconceptions. That, of course, is the bread and butter of this blog. Take, for example, Copernicus and Galileo, about whom there remain a wealth of myths that even scientists like Carl Sagan were known to repeat. The first is the Demotion Myth, the idea that the heliocentric model represented a demotion of the Earth’s place in the universe. Actually, according to medieval and early modern beliefs, in which the center was the worst place to be, like the center of Dante’s model of hell, moving Earth away from the center was in reality something of a promotion according to contemporary philosophy. Further myths claim that Copernicus waited until his deathbed to publish his heliocentric model, but that was more of a coincidence. Likewise, many myths surround Galileo, from apocryphal experiments atop the Leaning Tower of Pisa wrongfully attributed to him, to erroneously crediting him with the invention of the telescope, the thermometer, and the scientific method. Folklore tells us Galileo was excommunicated, convicted of heresy, and immured in a dungeon. In fact, he was put on trial, but in reality it was for breach of an agreement with the Holy Office. As the Pope had endorsed his work, Galileo had agreed not to present the Copernican model as proven fact, but rather to discuss the pros and cons of all cosmological models. Pope Urban VIII was actually sympathetic to the Copernican model, but when Galileo broke his agreement and presented it as fact, it put the Pope in an awkward situation. Far from being tossed in a dungeon, though, Galileo was sentenced to live in a 5-room suite in the Palace of the Holy Office, was able to receive guests and, records show, could come and go at great liberty, if not as he pleased. These myths make it clear that, while the science to which they contributed was built upon and furthered, the history of their lives was muddled and misrepresented. So let us retire, this once, from the benighted realm of Historical Blindness, and bask in the light of empirical science, specifically the luminous realm of astronomy, where wrong ideas have also abounded, but have almost universally been overcome by reason.

Saturn depicted by Galileo (top), Huygens (middle), and Cassini (bottom). Image credit: RM Chapple — Saturn depicted by Galileo (top), Huygens (middle), and Cassini (bottom). Image credit: RM Chapple

One of Galileo’s wrong ideas had to do with Saturn. In 1610, he was the first to observe this planet using a telescope, and he saw what appeared to be a triple planet, or a large planet with two moons on either side. However, two years later, he observed that these moons had disappeared, and two years after that, seeing that they appeared to have returned, he speculated that they were some kind of arms. But the shape of Saturn would baffle astronomers for a long time, sometimes appearing as three bodies and sometimes as an egg on its side. Some fifty years after Galileo first spied it, Christiaan Huygens, a Dutch astronomer, discovered Saturn’s moon Titan using a telescope superior to Galileo’s and in the process, he observed these arms of Saturn, which appeared to pierce it through its center, making it look something like a spinning top, but then vanishing with time. It was Huygens who hypothesized that these arms were a ring around the planet that when viewed edge-on appeared to be arms, or moons with inferior optics, and became impossible to discern from other angles. Huygens’s ring theory was not widely accepted at first, but other astronomers came around to his way of thinking, coming to believe that Saturn had a ring around it… a solid ring, for if it were not entirely solid, how could it possibly hold together as the planet spun? A hint came 15 years later, when Giovanni Domenico Cassini observed a gap in the ring. This gap proved it was not some giant ring of stone, all of a piece, so the mystery deepened. How did the isolated masses within the ring remain in place? Perhaps it was gaseous or composed of fluid? Not until the mid-19th century did James Clerk Maxwell demonstrate through equations that none of these possibilities would have been stable. Thus it was discovered that Saturn’s ring was composed of small unconnected particles. Almost forty years later, in 1895, James Keeler would further our understanding, observing that there were actually multiple rings of Saturn, and the innermost did not move at the same speed as did the outermost. So the history of astronomical discovery shows us that even when we see something with our naked eye, what we are seeing may not be entirely apparent.

Such was the case with Mars when William Herschel studied it with one of his homemade telescopes during the late 18th century. He made some important discoveries during his study, having to do with the rotation and axial tilt of the red planet. He also observed that the white spots on Mars’s poles, observed by both Cassini and Huygens and hypothesized earlier that century to be polar ice caps, changed size according to the season. This confirmation that ice existed on Mars helped to fuel Herschel’s speculation that the planet was inhabited. Herschel tended to vocally believe that all planets were inhabited, envisioning the moon as being akin to the English countryside, and even suggesting that the Sun supported life… not on its scorching surface, of course, but in some cooler underground realm, like a reverse Hollow Earth theory in which it is somehow hotter on the surface and more temperate within. Thus it’s no surprise that when Herschel viewed and mapped Mars in 1783, he asserted that all the visibly darker areas were oceans and declared the planet capable of supporting life, encouraging the perennial belief in Martians. With the 19th century construction of more and more advanced observatories, further mapping of Mars was accomplished, starting in 1877 by Giovanni Virginio Schiaparelli in Milan. It was he who named these supposed Martian continents and seas, giving them mythological names. Schiaparelli also observed something surprising. There appeared to be a network of pale lines in certain regions, which Schiaparelli called canali. When this news reached the English speaking world, his work was translated, and it was discovered that there were “canals” on Mars. At the time, canals were something of an engineering wonder, and the recent completion of the Suez Canal had been touted as a great accomplishment of mankind. So when the English speaking world heard “canal,” they thought massive artificial waterways, which would mean intelligent and industrious Martians. In reality, Schiaparelli’s word canali had been mistranslated. A more accurate translation would have been “channels,” a word less suggestive of engineering. But it was too late. The Martians were out of the bag. American astronomer Percival Lowell mapped what he saw as a network of canals with “oases” at certain intersections, speculating that the drying of the Martians’ planet had forced them to draw water from their polar ice caps. But again, what they had spied through their telescopes was not as clear as they believed. These features could be glimpsed only briefly and occasionally through Earth’s shimmering and shifting atmosphere, and as it turned out, they were an optical illusion. The lighter and darker regions were not oceans and continents, but rather what are called albedo features. Rather than bodies of water, or vegetation, as was an alternative theory, they didn’t correspond to topographical features at all and were likely just areas where wind had swept away the pale surface dust to reveal the darker ground beneath. As for the canali, they were an artifact of the human eye, creating phantom lines between briefly visible features, and the suggestion of infrastructure introduced by the English mistranslation added a psychological element, such that astronomers were looking for lines, expecting to find them, and staring until they saw them, making Mars something like the Magic Eye posters of the 1990s.

Martian canals depicted by Percival Lowell. Public Domain.

While sometimes astronomers were looking right at something and unable to discern what it was, or believed it was something it was not because of what others had told suggested, other times they searched and searched for something that wasn’t even there, again because some had insisted it would be there. The enduring search for a “phantom planet” is the perfect example of this. In the early 18th century, astronomers began to hypothesize about the regularity in distance between the planets in our solar system, concluding in 1772 with Bode’s Law, a formula for predicting the distance between planets that it was hoped would make the discovery of new planets possible. And indeed, it did. In 1781, William Herschel spotted Uranus, which he believed to be a comet, but of course it wasn’t. What it was was the 7th planet from the sun, right where Bode’s Law said it would be. After that, Johann Bode, one of the originators of the law, urged astronomers to search for another planet between Mars and Jupiter, as there was a gap there indicating the presence of another planet. This hypothetical planet was the subject of much interest at the turn of the century, and a group of astronomers who fancied themselves the Celestial Police devoted themselves to finding it. A discovery of a heavenly body in that slot between the orbits of Mars and Jupiter was made the next year, but not by one of the Celestial Police. One Giueseppe Piazzi discovered a heavenly body that he dubbed Ceres, and it was thought the predicted planet had been found. However, the next year, Heinrich Olbers discovered another body with about the same orbit: Pallas. After that came Juno and Vesta, and it became clear that numerous objects were in orbit there. Thus the asteroid belt was discovered, and a theory emerged that it represented the remains of a larger planet that had once orbited there where Bode’s Law had predicted a planet would be found. This “lost planet” was named Phaeton in an 1823 pamphlet by Johann Gottlieb Radlof, a German schoolteacher who took this theory and used it as a catastrophist explanation of certain myths and biblical incidents. In this way he was something of a predecessor of Immanuel Velikovsky, the catastrophist to whom I devoted an entire episode in my Chronological Revision Chronicles. But as usual, despite such pseudoscience, science marches on. Ceres and others of the largest asteroids in the belt are today considered dwarf planets at most, and the belt is believed to be material that simply never accreted into a planet because it was too perturbed by Jupiter’s gravitational influence.

Nearly a hundred years after the formation of the Celestial Police and the search for the lost planet, astronomers found themselves again all aflutter in search of a theorized planet, this one between Mercury and the Sun. It all started in 1810, when French astronomer Urbain Le Verrier constructed a model of Mercury’s orbit of the Sun according to Newtonian laws. When he had a chance to verify his model by observing Mercury’s transit, or its crossing of the disk of the Sun, however, it failed to confirm his model. It appeared there was some excess value observed in its perihelion precession for which Le Verrier simply could not account. Le Verrier’s solution was that there must be another small planet between Mercury and the Sun that was affecting Mercury’s orbit. He called this theoretical planet Vulcan, not in some prescient anticipation of Star Trek but, of course, after a Roman fire god, from whose name we also derive the word “volcano.” It wasn’t long before he received some confirmation of his theory in the form of an amateur astronomer’s claim to have spotted this previously unseen planet crossing the Sun. Despite the fact that another astronomer expressed doubt owing to the fact that he had been observing the sun at the same moment and had seen nothing of the sort, Le Verrier accepted the account as evidence in favor of his theory, and the amateur astronomer was lauded for his sighting. Perhaps it’s no surprise, then, that afterward, many amateur astronomers began to come forward claiming without any corroborative evidence that they too had observed Vulcan in years past. What Le Verrier needed, though, were sightings of the planet in transit that were confirmed by more than one astronomer. Since a solar eclipse would provide the best conditions for such a sighting, the total solar eclipse of 1878 served as their best opportunity to confirm the existence of Vulcan. Astronomers from all over converged by rail on the American West, gathering at the summit of Pike’s Peak in Colorado or overrunning the small town of Separation, Wyoming, places that just happened to lie on the eclipse’s path of totality, where the shadow of the moon would sweep over the country. Respected astronomers at these different locations did indeed sight something they believed to be an intra-mercurial planet, and not just one, but two! Excitement built that not only Vulcan but also another unknown planet had been discovered. Unfortunately, none of their coordinates matched, and the idea that four new planets had been discovered between Mercury and the Sun simply beggared belief. So the search continued, especially during eclipses, until, in 1915, Einstein’s Theory of Relativity satisfactorily explained the excess precession of Mercury, which meant there was no longer any reason to believe that Vulcan existed. Now, it is thought that many of the objects supposedly spied in transit were sunspots or perhaps artifacts of telescopic optics that had been damaged, like Icarus, when pointed too close to the Sun.

Astronomers gather in Separation, Wyoming, in 1878 to observe a solar eclipse in hopes of confirming the existence of the planet Vulcan. Image courtesy of the Carbon County Museum.

Despite this difficulty in sighting even our closest planetary neighbors, humanity has long held the conviction that the number of planets in the cosmos was innumerable. Greek Philosopher Epicurus told Herodotus that “the universe is boundless both in the number of the bodies and in the extent of the void” and that “there are infinite worlds both like and unlike this world of ours.” But for much of human history the only things that could be spied beyond our immediate solar system were luminous bodies: stars. The very fact that planets do not emit light made it essentially impossible to see any so-called exoplanets beyond our solar system. Planets, of course, only reflect light, but when searching for planets that orbit other stars, the great distance and the faintness of their reflected light in comparison to the brightness of their stars’ light make them hidden bodies out there in the void. In fact, hard as it may seem to believe, we did not have any evidence for the existence of planets outside of our own solar system until the 20th century. Astronomer Peter Van De Kamp had begun to hypothesize that planets outside our solar system could be detected by their gravitational effect on the movement of the stars they orbited. His first couple of identifications resulted in hypothetical planets that seemed far too large to be planets, but in 1963, he detected a wobble in the movement of Barnard’s Star, 36 trillion miles from us, and thus the belief in extrasolar planets, and possibly planets that can support life, was bolstered. Currently, the existence of more than 4,000 exoplanets has been confirmed, but surprisingly, Van De Kamp’s discoveries are not among them. As it turns out, all of the star wobbles that Van De Kamp took as evidence for the presence of a planet were actually caused by adjustments to the optics of his telescope. The first real evidence for the existence exoplanets didn’t actually arrive until the early 1990s, a fact which I find astonishing.

Despite the evidence for the corruption of Van De Kamp’s calculations favoring a planet orbiting Barnard’s Star having appeared decades earlier, as recently as 2013 astronomers were still seeking to definitively rule out their existence, which they appear to have finally done. This is the strength and power of science. It takes nothing for granted. Although the existence of oceans and canals on Mars has been ruled out, the existence of water on the red planet remains a topic of much study. In 2011, high resolution images from the Mars Reconnaissance Orbiter showed dark streaks on some slopes indicating seasonal water flow over the surface of the planet, and just last year, radar data from the European Space Agency’s Mars Express spacecraft detected possible underground lakes. And while the Phaeton theory that the asteroid belt is the remains of a destroyed planet is only supported by fringe pseudoscientists like Zecharia Sitchin, ideas about phantom planet and other hidden bodies within our solar system continue to be entertained. The notion of a planet Vulcan is mostly extinct, but some astronomers still suggest that intramercurial objects, which they call vulcanoids, could still exist and help to explain the various mysterious sightings in the 19th century. There is even some support for an unseen “Planet X,” but since Pluto has been demoted to a mere dwarf planet in the Kuiper Belt beyond Neptune, it is typically referred to as Planet 9 these days. Indeed, the only credible theory for the existence of another planet within our solar system places it in the same neighborhood, for the unusual orbits of the objects in the Kuiper Belt have led astronomers to hypothesize that the presence of a large body hidden far beyond Pluto may account for it. So, in astronomy and science generally, as in history, it is unwise to suggest too soon that the truth has been entirely settled.

Hidden Bodies: A Brief and Incomplete History of Astronomical Discovery

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