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Science has undergone profound changes over the past millennia. Theories rose, fell, and often faced intense scrutiny. Many ideas that were once considered absolute truths in the scientific world now seem almost absurd. Some debates were swiftly settled, but others dragged on for decades, if not centuries, stubbornly resisting the tide of reason, unwilling to slip into the forgotten pages of history just yet.
10. Continental Drift
If you ask a group of random people how the continents separated, chances are many will mention Pangaea and the concept of continental drift. In the early 20th century, Alfred Wegener presented his groundbreaking theory on continental drift, suggesting that the earth's landmasses once formed a single supercontinent. Through his study of plants and animals along the coastlines, as well as comparing fossils, rocks, and discovering species like the mesosaurus (a freshwater reptile found in both South America and Southern Africa), he concluded that all landmasses were once connected. Though we know it as Pangaea today, Wegener originally referred to this supercontinent as “Urkontinent,” which means “original continent.”
Interestingly, Wegener's theory of continental drift did not address the mechanics behind how the continents moved. His ideas on this were vague, at one point even suggesting that it might have something to do with the forces created by the Earth's rotation.
The concept of continental drift, as it was once understood, is now outdated. Today, the term refers only to a small portion of plate tectonics theory, which explains how continents rest on shifting slabs of rock that constantly interact with each other—rising, falling, moving closer together, and drifting apart.
The idea of a single massive landmass, Pangaea, is also considered obsolete—sort of. Modern science not only recognizes Pangaea, but also identifies two other ancient supercontinents: Pannotia, which existed 600 million years ago, and Rodinia, which formed over a billion years ago.
9. The Emission Theory of Vision
For over 2,000 years, one of the dominant theories about how vision worked was that it resembled something out of X-Men, similar to Cyclops. In 450 BC, Alcmaeon of Croton proposed that vision occurred because the eye contained 'fire' that emitted beams to detect objects and send the information back to the brain. Plato supported this, stating that the fire originated in the eye and worked with external light to send images to the brain. Plato further suggested that this fire was an extension of the inner fire we all possess, not burning, but lighting our way. This idea seemed to be backed by physical evidence, as pressing on your eyes would reveal what appeared to be released fire.
A number of notable figures, including Euclid, who developed the geometry explaining the limits of our vision, and the poet Lucretius, who described images as separate from the objects themselves, likening them to the skin shed by a snake, were among the proponents of the emission theory.
This theory remained widely accepted until the 13th century when translations of works by 10th-century Islamic scientist Ibn al-Haythem (also known as Alhazen) began to circulate. His arguments helped to debunk the emission theory, such as the pain experienced in the eye when exposed to bright light, which would not occur if the eyes were emitting rays of fire. He also pointed out that relying on eye fire alone would make it impossible to see distant objects like stars, as no set of eyes could contain that much fire. Alhazen not only disproved the emission theory but also introduced his own, suggesting that the eye receives information and responds to the light that enters it, a theory that laid the foundation for our current understanding of vision.
8. Le Sage’s Theory of Gravity
Georges-Louis Le Sage questioned the entire concept of gravity. While gravity was understood to influence the entire universe, Le Sage couldn’t see how Newton’s widely accepted theory could explain the gravitational pull between two masses separated by vast distances in space. He came up with his own theory, which has mostly been discredited, but there are still a few scientists who support it today.
According to Le Sage’s theory, attraction isn’t caused by a direct interaction between two objects, but by the effect on the invisible particles filling the space between them. These particles move freely until two objects cast shadows on each other. The shadows reduce the number of particles between the bodies, causing them to move closer together—this, according to Le Sage, is gravity.
The major flaw in this theory is that it suggests size influences gravitational force more than mass. Larger objects would cast bigger shadows, and thus should have a stronger gravitational pull. Le Sage tried to address this by arguing that mass is mostly empty space, with only small clusters of actual matter. Since these mass clumps cast the gravity shadows, it follows that larger objects, with more mass clumps, would exert a greater gravitational effect.
Even though Le Sage's theory faded after Einstein’s theory of relativity, it has remained oddly popular in certain fringe circles. In 1954, experiments involving the Foucault pendulum and the Allais effect were cited by proponents of shadow gravity as potential evidence for the theory, though most scientists remain skeptical.
7. Rain Follows the Plow
Following the US Civil War, there was a massive influx of settlers into the Midwest, an area known for its vast farmland but little else. Before it was cultivated, the region was even more barren and desolate. Much of this movement was driven by a piece of mythology that was believed to be scientific truth: The rain would follow the plow.
In the 1860s, it was widely reported that plowing land that had never been cultivated before would release fresh soil into the air, bringing rain. Ferdinand Hayden, the director of the US Geological and Geographical Survey of the Territories, made this idea seem like scientific fact. He claimed that the central US was dry because moisture couldn’t cross the Rockies, and if people planted trees, they would release moisture into the air, leading to more rainfall. Others joined in, and in 1870, the Smithsonian shared claims from the Kansas Pacific Railway, which promoted the idea that railways and power lines were attracting rain. The University of Nebraska also supported this, arguing that it was the people’s duty to cultivate the land to its fullest potential.
As a result, many people tried so-called 'dry farming' methods, hoping their actions would attract divine favor and bring the rains. Oddly enough, it appeared to work for a while. Unusually heavy rains during the 1870s and into the early 1880s convinced around two million people to settle in the plains. However, by the time a drought struck in 1887, many families had gambled everything on a theory that wasn’t really based on science, but rather promoted by real estate companies, railroad barons, and anyone else who stood to benefit from the influx of new settlers.
Even after the drought, the belief that human actions could influence rainfall persisted. The next rainmaking attempt involved using dynamite, based on the idea that the vibrations from explosions could trigger rainfall. As late as the 1930s, people still believed that human activity could control the weather. Ironically, we now know that human actions can indeed influence the weather, though not in the way that farmers had hoped.
6. Neptunism
As early as ancient Greece, it was clear that water had immense power and likely played a major role in shaping the world. In the 1770s, Prussian geologist Abraham Gottlob Werner introduced the theory of Neptunism, sparking heated debates within the geological community that would last for decades.
Werner's theory posited that the Earth was originally covered entirely by water. The ocean contained suspended particles that, over time, settled to form the first rocks. As the ocean gradually receded (although Werner didn’t explain how), the rocks that had settled at the bottom became the landmasses. More rocks formed as more sediment settled, and older rocks were worn down and resettled as the water continued to retreat. Eventually, a catastrophic flood was said to have eroded vast areas, laying down a fresh layer of sediment. This idea was particularly appealing to those seeking to reconcile the Biblical flood narrative with scientific understanding. However, when James Hutton proposed his theory of Plutonism, challenges to Neptunism began to emerge.
James Hutton, who had a diverse career as a doctor, farmer, chemical manufacturer, and geologist, spent two decades refining his theory before presenting it as an alternative to Werner’s. Hutton's theory, Plutonism, argued that the Earth's surface was shaped by ongoing natural processes like erosion and volcanic activity. Crucially, Hutton suggested that the Earth was still being shaped, and the processes responsible for this transformation could be observed in action. He provided detailed descriptions of how heat and pressure affected rocks, how seabeds were lifted, and how wind and water transported and deposited debris, such as at river mouths. Hutton named his theory in honor of Pluto, the god of the underworld, acknowledging the role of the Earth’s internal forces.
When it comes to who was closer to the truth, Hutton was undeniably more accurate. His work, published in 1795, laid the foundation, but it wasn’t until the 19th century that Charles Lyell took his ideas, refined them, corrected some inconsistencies, and presented them in a more polished form. Plutonism contradicted many religious beliefs, which made the debate even more drawn-out. Zoologist Georges Cuvier added fuel to the fire by arguing that the fossil record was proof of numerous mass extinction events caused by catastrophic floods, with the last one leaving some life on Earth untouched.
5. The Planet Vulcan
In the mid-19th century, astronomers struggled to explain Mercury's peculiar orbit. In 1846, one of the leading astronomers of the time, Urbain Jean Joseph Le Verrier, set out to solve the mystery. Already celebrated for his predictions leading to the discovery of Neptune, Le Verrier suggested that there was an undiscovered planet beyond Mercury. He theorized that this planet was responsible for the unusual orbit of Mercury, and his claim was met with excitement—after all, he had correctly predicted Neptune’s existence.
For twelve years, Le Verrier searched for this planet, which he named Vulcan, but found nothing. Just as he was about to abandon the quest, amateur astronomer Edmond Modeste Lescarbault claimed to have observed the elusive planet on March 26, 1859. Le Verrier, convinced by Lescarbault’s report, fully endorsed the discovery. He was so impressed by Lescarbault’s work that he recommended the astronomer for the Legion of Honor, which Napoleon III duly awarded.
In the years that followed, Vulcan never appeared where calculations based on Lescarbault’s observations predicted it would be. Le Verrier, growing increasingly frustrated with the lack of confirmation, became so unpleasant that one of his colleagues remarked, “I do not know whether M. Le Verrier is actually the most detestable man in France—but I am quite certain that he is the most detested.” Le Verrier passed away in 1877, on the anniversary of Neptune’s discovery, but the search for Vulcan continued.
During a 1878 eclipse, astronomers in the United States eagerly waited for Vulcan to make an appearance. One observer, James Craig 'Tubby' Watson, reported that he had seen it, though others disagreed, claiming he had made a mistake. Watson became fixated on the idea of Vulcan’s existence, even going as far as digging a shaft in the ground to place his telescope in, thinking it would allow him to observe celestial bodies around the Sun in broad daylight (a theory that had already been debunked by earlier astronomers).
When Watson died before he could complete his underground observatory, interest in Vulcan began to wane. It wasn’t until 35 years later, when Albert Einstein’s theory of relativity explained Mercury’s motion, that all hopes of discovering the mysterious planet were definitively put to rest.
4. Imponderable Matter
The Victorian fascination with ghosts and the supernatural is well-documented, but at the time, it wasn’t necessarily about believing in the paranormal. Instead, people thought ghosts were made of something quite real: odyle. Chemist Baron Karl von Reichenbach described odyle as a substance produced by the heat and chemical reactions in a decaying body, with some individuals being more sensitive to it than others. Henry Morley stated that ghosts weren’t supernatural but instead formed from this very real, very common substance. It was a kind of imponderable matter with traits resembling electricity—heat and light. In 1839, Golding Bird described “imponderable matter” as the substance that fills the spaces between bodies, almost weightless, highly elastic, and responsible for transmitting light, heat, and magnetic forces.
As these theories spread, they were often invoked to explain anything that couldn’t easily be understood. There were numerous ideas about what these forms of imponderable matter were, but it was generally accepted that the entire universe was composed of it. These theories were influenced in no small part by Newton’s work, in which he suggested the existence of an ether to explain gravity. Michael Faraday lectured on the properties of imponderable matter, claiming the Sun was one of its largest sources. Psychologist Herbert Spencer argued that studying imponderable matter would offer insights into the workings of the human mind, another intangible phenomenon.
Victorian-era physics even ventured to use imponderable matter to explain the afterlife. Balfour Stewart and P.G. Tait theorized that imponderable matter signified the existence of an unseen world parallel to our own. Since they believed our world would eventually cease to exist, they argued that the energy released by it would be absorbed into this invisible realm, which would continue to exist beyond our understanding.
These early ideas about imponderable matter were later revisited under the concept of luminiferous ether. Throughout the Victorian period, nearly all scientific fields were built upon the theory of imponderable matter and its tangible counterpart, “ponderable matter.” However, the importance of imponderable matter extended beyond science, influencing economics, industry, and culture.
Imponderable matter spanned such a broad range of scientific disciplines that it’s nearly impossible to pinpoint when its decline occurred. By the 1860s, however, physicists began to redefine their concept of matter, and imponderable matter slowly faded into history.
3. Abiotic Oil Formation
Oil and petroleum were known long before the modern age, even in ancient Greece, where philosophers explored how the concept of the four fundamental elements applied to various natural phenomena. Oil was no exception, and Aristotle speculated that oil, along with other minerals, formed due to some sort of exchange of materials deep inside the Earth. He thought that petroleum was either a form of sulfur or closely related to it, since the two shared a similar odor.
This marked the beginning of the idea that petroleum and oil had abiotic, or abiogenic, origins. By the Renaissance, scholars such as Georgius Agricola took this theory further, suggesting that bitumen and petroleum were created through the Earth's forces acting on sulfur to compress it. This idea stood in direct contrast to the notion that fossil fuels originated from organic matter, a theory that would undergo many revisions over time.
In the 19th century, the prevailing theory was that petroleum formed similarly to coal. Although organic matter was already believed to be involved, it took time to connect this idea to petroleum. It wasn’t until the mid-20th century that scientists were able to analyze petroleum in more detail. When traces of substances like chlorophyll were discovered, it became clear that petroleum, like coal, had an origin in natural, once-living organisms.
Despite growing evidence against it, the abiotic theory continued to hold sway. In 1877, Mendeleev proposed that when surface water descended deep into the Earth, it would react with metallic carbides, producing acetylene, which then condensed into petroleum. Though this theory was gradually debunked, some scientists, particularly those in the Soviet Union, persisted in backing Mendeleev’s hypothesis well into the 1960s. They argued that petroleum could only form in the high-pressure, high-temperature conditions found deep within the Earth. Meanwhile, astronomers in the West also leaned towards abiotic theory, suggesting that since hydrocarbons were discovered in space, it was reasonable to assume that the Earth was made of the same materials, reinforcing the theory's validity. Today, however, the evidence overwhelmingly supports the biogenic origin of petroleum.
2. The Firmament
In his writings, Augustine offered an interpretation of what the firmament truly was. Initially, he compared it to the distinction between the physical waters of Earth and a spiritual sea located above us. However, his views evolved, and he later depicted the heavenly firmament as the expanse stretching from the air that supports the clouds to the fiery sphere beyond it.
The firmament has long been a focal point in both Biblical and astronomical discussions, with St. Augustine offering varied interpretations of its nature. His earliest description compared it to the space between earthly waters and an ethereal sea, but later he revised this to envision the firmament as the vast area between the clouds and the fiery realm beyond.
The concept of the firmament as a tangible, real entity persisted far longer than one might expect, with some of the most renowned figures in astronomy supporting it. Copernicus, for instance, acknowledged that Earth wasn’t at the center of the universe, but it remained the center of gravity and its own sphere. He also referenced the firmament when defining Earth’s distance to the Sun, asserting that the gap between them was nearly negligible compared to the vastness of the firmament, which he believed to be the home of all the other stars in the cosmos.
The first person to challenge the notion of a giant, enclosing sphere around the Earth was the 15th-century German scholar Nicolaus of Cusa. He was the first to propose the idea of an infinite universe, not driven by scientific observation but by theological reasoning. Given God's omnipotence, why wouldn't He create a universe without boundaries?
Despite Nicolaus of Cusa's revolutionary idea, the firmament still held sway until Giordano Bruno advanced the theory that there was, in fact, no firmament at all. He wrote about an infinite universe, suggesting that we were not alone in the vast expanse of space. While he included a note clarifying that acknowledging God's superiority to the firmament was in no way heretical, his ideas attracted the wrong kind of attention. His efforts were futile, and in 1592, he was denounced to the Inquisition for heresy. After seven years of imprisonment and trial, Bruno was found guilty and tragically burned at the stake on February 8, 1600.
1. The Open Polar Sea
For centuries, humanity has been fascinated by what lies beyond the horizon, and the poles of the Earth have remained some of its greatest mysteries. In the 16th century, various scientific theories, based on what was then considered factual, proposed that the North Pole was home to a warm, open sea. This belief dates back as far as 1360, documented in the manuscript Inventio Fortunata. According to this text, a man named Nicholas of Lynn allegedly sailed to the North Pole and described its climate as being as mild as that of Amsterdam.
One of the supporting theories came from British explorer John Davis, who argued that only freshwater environments could support massive ice formations. Since the sea was believed to be saltwater all the way to the North Pole, it was logical to assume that ice wouldn't accumulate there. Additionally, it was understood that the North Pole experienced months of summer days and sunlight, making it likely warm enough to melt any ice that might form.
Explorers and their financial backers were so convinced of the validity of this theory that they invested large sums of money attempting to establish trade routes between Europe and Asia based on the belief in an open polar sea. British explorers even secured the backing of Henry VIII in 1527, and despite all expeditions returning with only tales of icy seas, the conviction that open water lay just beyond the ice continued to persist.
In 1850, an expedition led by William Morton claimed to have discovered a break in the ice and open sea. Although no such breakthrough was found, this sparked renewed interest in the idea. Three years later, American explorer Elisha Kent Kane embarked on a mission to locate the missing British explorer John Franklin and his 128-man crew, who had vanished eight years prior while attempting to find a northwest passage between Europe and Asia. Despite the eight years that had passed, some still hoped Franklin’s crew had found refuge on a lush, green island within the open polar sea. The final expedition searching for this sea took place in 1879, and after spending 14 months trapped in the polar ice, the theory was ultimately abandoned.
