Humanity has come a long way from its humble beginnings in caves hundreds of thousands of years ago. Much of our progress is thanks to the curiosity of bold men and women—people who dared to question the so-called "facts" of their time, even when doing so could get them arrested… or worse.
Throughout history, many brilliant thinkers introduced groundbreaking theories that challenged the status quo. For years, sometimes centuries or even millennia, these ideas stood firm as undeniable truths.
But, as science advanced, countless once-accepted facts were exposed as nothing more than myths, mistakes, or pseudoscience.
Today, we’re taking a fascinating trip back in time to uncover 15 former facts that are no longer facts. So, sit back, get comfortable, and prepare to unlearn everything you thought you knew.
Disproven Space Theories and Old Solar System Myths
Ever since humanity first gazed up at the stars, we’ve been obsessed with what lies beyond the clouds. For thousands of years, people crafted elaborate theories about the solar system and Earth’s place in the universe.
Many of these ideas weren’t just theories and were accepted as absolute facts, and opposing beliefs weren't just wrong—in some cases, they were considered dangerous heresy.
But as science and technology advanced, many of these once “undeniable truths” about space were shattered. Today, we know these old space facts were nothing more than myths and misunderstandings.
Here are some of the most famous disproven solar system theories once believed as fact:
1. The Flat Earth Theory: Why People Once Believed the Earth Was Flat
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| An Image of A Flat Earth |
Modern Homo sapiens first appeared on Earth as early as 300,000 years ago. However, in almost all of this long and brutal history of surviving deadly predators, weather catastrophes, and near-extinction events, no one thought to disprove a theory that had so much weight: the flatness of the Earth.
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Pinpointing the exact era when Homo sapiens first emerged as a distinct species is nearly impossible, especially with current technology. However, in 2016, scientists successfully sequenced DNA from the fossilized remains of early Neanderthals found in the 430,000-year-old Sima de los Huesos—also known as the "Pit of Bones"—deep in Spain’s Atapuerca Mountains. By comparing this ancient DNA to that of modern humans, researchers used a molecular clock to estimate when our evolutionary lines split. Their findings suggested that the last common ancestor of Homo sapiens, Neanderthals, and Denisovans likely lived between 550,000 and 765,000 years ago.
Read more about the study in the Smithsonian Magazine.
The Earth’s flatness was considered a fact throughout most of the ancient world. Many people held varying beliefs about it, from those who thought there was a physical edge of existence to others who believed the world was a disc.
It wasn’t until about the 3rd century BC that mathematicians calculated the circumference of the Earth. By the 5th century BC, the shape of the planet was undoubtedly a sphere. For those wondering how ancient the 5th century BC was, it’s about 2500 years.
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The idea that the people of medieval Europe believed the Earth was flat is a myth. Scholars already knew the world was spherical. However, the problem was that they believed the planet was much smaller than anticipated. When Christopher Columbus planned his voyage, he underestimated the distance to Asia due to faulty calculations. He eventually never reached Asia and instead discovered a new continent, the Americas.
2. How People Massively Miscalculated the Earth's Age by Billions of Years
If people thought the Earth was flat, beliefs about its age shouldn’t shock anyone. The Ussher chronology is a 17th-century chronology written by the Archbishop of Armagh, James Ussher. He stated that after meticulously reading the Bible, the Earth was 6000 years old.
The Church of England adopted Ussher’s work as fact. They added the chronology to the official Bible, and for many years, most of the Western world believed the planet was 6000 years old.
It wasn’t until the 19th century that many scholars and scientists disproved Ussher’s idea and relegated it to the dustbin of history. With the help of carbon dating techniques and advanced calculations, we know that our planet is roughly 4.5 billion years old. That means James was off by 4,499,994,000 years.
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The Earth and the Sun are nearly the same age, with the Sun being about 100 million years older. This is because the Sun’s formation triggered the gravitational clumping of matter that eventually led to the formation of the planets.
Learn more about the Sun's age BBC Sky at Night Magazine.
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3. The Myth of the Moon’s Perfect Shape—Debunked by Galileo
It’s no surprise that people in ancient times held varying beliefs regarding the moon. The ancient Egyptians worshipped and saw it as a symbol of fertility, while others thought it could make a person crazy. All these beliefs were disproven, but some were incredibly hard to change due to their elevated status.
When an astronomer named Galileo Galilei pointed his new invention, a telescope, towards the moon and showed the Catholic Church that the celestial body was not a perfect sphere but one with rough edges, everything went boom.
The Church, which had maintained the geocentric view of the world, stated Galileo’s evidence was false and heretical and sentenced him to house imprisonment for life. They believed his ideas contradicted God’s creation and wanted his punishment to serve as a deterrent to those who wanted to explore heavenly bodies.
However, Galileo’s ideas proved factually accurate centuries later.
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On October 31, 1992, Pope John Paul II formally apologized on behalf of the Vatican for the Church's treatment of Galileo. He acknowledged that theologians failed to separate faith from empirical inquiry. This marked a significant turning point in the relationship between science and Christianity.
Read more in the New York Times.
4. The Geocentric Theory: When People Believed Earth Was the Center of the Universe
Before humans believed the Sun was a massive spinning fusion reactor, they were busy thinking the Earth was the center of the solar system. The geocentric model declared that all planets were perfectly spherical and orbited the Earth, which was a stable body; this belief stemmed from religious exceptionalism.
The geocentric model lasted for thousands of years in the Western world and was only changed when the mathematician and catholic clergy, Nicolaus Copernicus, presented the heliocentric model (which had existed for a long time), which stated the Earth and planets revolved around the Sun. He said,
We revolve around the Sun like any other planet.
Years later, Johann Wolfgang von Goethe, a prominent writer, commented on how Copernicus's statement altered science forever.
He stated,
Of all discoveries and opinions, none may have exerted a greater effect on the human spirit than the doctrine of Copernicus. The world has scarcely become known as round and complete in itself when it was asked to waive the tremendous privilege of being the center of the universe.
Read more about humanity's journey away from geocentrism in NASA's Earth Observatory.
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| The Idea of Geocentrism |
5. Why Ancient Astronomers Thought the Sun Was a Planet (Debunked Solar System Fact)
Besides believing the Earth was the center of the universe, ancient people believed the Sun and the Moon were planets. According to the ancient world, the planets in the sky were the Sun, Moon, Venus, Mars, Jupiter, and Saturn. It took remarkable scientists like Galileo to disprove this long-standing fact.
Debunked Human Biology Myths and Old Medical Theories
Before the world was accustomed to the theory of evolution, reproduction, microbiology, and respiration, many fallacies stood as indisputable facts.
Here are some standouts:
6. Why Evolution Was Once Rejected by Scientists and Religions Worldwide
Before Charles Darwin and Alfred Russel Wallace published their journal on the theory of evolution, humanity had a myopic view of the history of its beginning. Many people believed in creationism, which said that God created all living beings; this idea fit perfectly into every belief system, as no one could have observed the gradual change of species due to adaptation and evolution.
For thousands of years, creationism was the dominant fact of the world, and no one could alter it until scientists poked holes and proved the world was much older than creationism stated.
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Though the theory of evolution provides significantly more evidence for its stance, it's still one of the most contested ideas to this day. According to a 2011 poll data compiled by the American Scientific Affiliation, only about 16% of respondents believed the theory of evolution was the best explanation for the origin of life. 40% believed God created all life in its present form 10,000 years ago, and 38% believed God guided a process by which humans developed over millions of years.
Read more on the study in the American Scientific Affiliation.
7. The Wrong Chromosome Count: When Scientists Believed Humans Had 48 Chromosomes
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| The Human Chromosome - Credit |
With the overwhelming success of the theory of evolution, biologists began peering into the human body to determine what it holds. After chromosomes were discovered, many scholars raced to learn how many humans have. In the 1920s, a breakthrough occurred when American Zoologist Theophilus Painter published findings saying humans have 48 chromosomes.
For the next thirty years, the chromosome count for humans was an indisputable fact. However, all that changed in April 1956, when J-H Tjio and A Levan at the University of Lund in Sweden discovered the correct figure was 46.
8. Lamarckism Explained: Why Scientists Once Believed Acquired Traits Were Inherited
Before Charles Darwin proposed the theory of evolution, another scientist, Jean-Baptiste Lamarck, proposed an idea that would serve as the foundation for evolutionary biology. He stated that the physical characteristics of an organism achieved throughout its lifetime could be passed to offspring; this idea meant that a bodybuilder could give birth to a child with an enhanced physique.
Throughout the 19th century, Lamarckism was a fact. However, with advancements in genetics, it was proven false
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9. The Four Humors Theory: The Old Medical Belief That Controlled Medicine for Centuries
Before people realized that health relied on many environmental and dietary factors, there was a leading factor concerning one’s well-being.
The four humors theory, developed by ancient Greek Philosophers, stated that good health relied on four bodily fluids being in equilibrium. The fluids were black bile, yellow bile, phlegm, and blood.
For many centuries, people believed this idea to be an indisputable fact. However, medicine and microbiology advancements proved that good health relies on nutrition, resistance to pathogens, and hygiene.
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The four humors theory is believed to have originated from Ancient Egyptian medicine. However, it was systemized by the Greeks when Hippocrates suggested the four vital fluids were black bile, yellow bile, phlegm, and blood. Humorism remained a dominant idea in the Western world for 2000 years until it was disproven.
Read more about humorism on Wikipedia.
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| An Image of the Vitruvian Man |
10. The Miasma Theory: How 'Bad Air' Was Once Blamed for Diseases (Now Debunked)
Like the four humors theory, the miasma theory states that bad air originating from rotting corpses causes diseases.
Though the theory proved true because hygiene prevented diseases, it was a flawed idea that was eventually disproven by the advent of microbiology, which showed tiny organisms called germs caused diseases.
Disproven Physical Science Theories That Once Shaped the World
The physical sciences world has always advanced through numerous ideas thought to be factual; these leaps were only possible through the creation of peer-to-peer review, where scientists rigorously tested theories for fallacies. Some former ideas thought to be fact include:
11. The Four Classical Elements: Why People Believed Everything Was Made of Earth, Air, Fire, and Water
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| The Periodic Table of Elements With Their Atomic Spectra |
Before the discovery of the periodic table, ancient philosophers believed that the universe comprised four fundamental elements: air, water, fire, and earth. Empedocles proposed the theory and convinced his peers about the fundamental forces.
The four classical elements became fact throughout medieval and even modern times until scientists discovered smaller substances within the four classical elements.
12. Newton’s Gravity Theory: How Einstein’s Relativity Changed the Old Laws of Gravity
The science community nearly exploded when Isaac Newton brought the laws of gravitation. The formulas were so accurate that they could predict the motion of planetary bodies in space. For many years, scientists saw gravity as a force of attraction between bodies.
However, everything changed when Einstein introduced the theory of relativity. Einstein’s theory expanded the previous ideas of gravity and showed that it exists because of the curvature of space-time.
Einstein’s theory radicalized physics and pushed humanity into a new age of enlightenment.
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Many think Einstein’s theory of relativity erased Newton’s laws, but it didn’t. Newton’s equations still work perfectly for everyday tasks like predicting planetary motion or launching rockets, and NASA still uses them! Einstein’s theory revealed that Newton’s laws break down under extreme conditions like near black holes, at light speeds, or even in GPS technologies. Without Einstein’s corrections, GPS would be off by 10 kilometers every day.
Read more about how Einstein's theory enables GPS at NASA.
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| An Image Representing Relativity - Credit |
13. The Indivisible Atom Myth: Why Atoms Were Once Believed to Be the Smallest Particles
After the atom's discovery, many scientists thought it was the tiniest thing in existence. For many decades, it was a fact that atoms were the smallest and most indivisible parts of matter. However, all that changed when Ernest Rutherford used radioactive beta particles to split an atom.
With Rutherford’s experiment, the long-held idea of the atom’s indivisibility was shattered, paving the way for a new field called particle physics.
Old Sex and Reproduction Myths That Science Disproved
Many societies avoid talking about sex like the plague. Because of this connotation, many theories and myths about it have stayed in history as fact. However, with scientific advancement, many have been disproven. Some of these former facts include:
14. Sperm Cells as Parasites? The Old Scientific Myth About Reproduction
When Anton van Leeuwenhoek pointed his microscope at a semen sample, he observed tiny organisms swimming in it. Shocked, he called the organisms spermatozoa, meaning sperm animals.
Anton initially believed that sperm cells were parasites. His idea remained for years until scientists studied embryonic development in sea urchin eggs and learned the importance of sperm cells in reproduction.
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The idea that sperm cells were parasites remained a fact for over 100 years. Most scholars thought it had no use in fertilization. While Anton van Leeuwenhoek studied the human semen sample, he expected to find a preformed embryo and was disappointed when he couldn't find one. At that time, the popular belief was that human semen contained an embryo, and the female body only served as a nutrient provider.
Read more in the National Library of Medicine.
15. The "One Sex" Theory: The Bizarre Belief That Men and Women Had the Same Reproductive Organs
Before people accepted that men and women were different, some philosophers, like Aristotle, formulated the idea that both male and female organs were identical except for the womb. This idea lingered for years until scientists disproved it and showed that men and women possess different organs.
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| Timeline of Evolution |
Conclusion
We hope you enjoyed discovering these 15 fascinating facts that were once believed to be true but are now completely debunked.
Ready to challenge your knowledge even more? Try playing our weird fact game, Truthoria, and see how many strange myths you can spot!
You can also explore more mind-bending articles, such as:
- 10 Outrageous True Stories That Sound Fake—but Aren’t.
- 15 Evil Facts About Dolphins You Never Knew.
- 10 Unknown Facts About the Craziest and Evilest People in History.
Don’t forget to share this article and drop your thoughts in the comments—we love hearing from curious minds like yours!
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