Nothing enforces humility more rigorously than science, the powerful idea that being wrong is not something to be ashamed about, but rather something to be openly embraced, as it has the potential to open up new doors to progression and innovation in the sciences. When scientists are wrong, they are motivated to change their views when some new evidence comes along that contradicts these views. This humble disposition tends to go against the grain of human nature, which assigns a high value to being right all the time and entails that being wrong is the worst of all outcomes and should therefore be avoided at all costs. Below are four prominent examples of scientific theories that were once widely accepted and held in high regard, and which were eventually proven wrong in the light of new scientific evidence, but which paved the way to advances in science which would never have been possible otherwise.
Heavy objects fall faster than lighter objects
It was the view of Aristotle in the fourth century BCE that an object falls with a speed proportionate to its weight, which follows that heavy objects fall faster than lighter objects. To some extent we can sympathise with Aristotle for maintaining this theory, as he certainly couldn’t be accused of lacking evidence for this claim. A heavy stone and a lighter stone are dropped from the same height somewhere in Ancient Greece, the heavy stone hits the ground first, therefore the natural conclusion from this observable evidence is that heavy objects fall faster than lighter objects. Consequently, this idea remained widely accepted until the sixteenth and seventeenth centuries, which brought an end to the near 2000 year dominance of Aristotelian physics.
It was the valuable contributions of Italian physicist and astronomer Galileo Galilei which provided the definitive proof that heavy objects don’t fall faster than lighter objects. He argued that if heavy objects did fall faster than lighter objects, then heavy stone A would fall faster than light stone B. If you then tied stone B to stone A, stone B would apply drag to stone A, which would slow stone A down, meaning stone A and B tied together should fall slower than stone A by itself. However, stone A tied to stone B is heavier than stone A by itself, meaning stone A and B tied together should fall faster than stone A by itself. So we end up with an irreconcilable contradiction, where stone A and B tied together falls both faster and slower than stone A by itself.
We now know that the two objects fall at different rates due to the effect of air resistance, which was conclusively demonstrated by an experiment carried out by American astronaut David Scott on the moon, which has no air resistance. He dropped a hammer and a feather from the same height, and both struck the surface of the moon at the exact same time. The same experiment can also be carried out within a laboratory vacuum, which produces the same observable effect. Aristotle was undoubtedly one of the greatest thinkers in western philosophy. He is credited with the invention of logic, and his discourses on physics, such as those found in his books Physics and On the Heavens, pervaded scientific thought right up until the time of Galileo. However, to quote Bertrand Russell, “hardly a sentence in either can be accepted in the light of modern science”.
Another theory straight out of the school of Aristotelian physics is the geocentric model, a description of the cosmos which holds that the planet Earth is at the centre of the universe and all celestial bodies, such as the sun, moon, stars and planets, orbit around the Earth. Similar to the notion that heavy objects fall faster than lighter objects, it’s easy to understand how early Greek astronomers arrived at this conclusion, with the sun appearing to orbit around the Earth once a day and the moon, planets and stars following a similar cyclical pattern. Add to this the apparent fixed, central and unmoving position of the Earth from the perspective of the observer, and it’s easy to see how the geocentric model forced itself irresistibly onto the minds of curious Greek astronomers as they looked up at the sky. Due to the wealth of observable evidence which seemingly supported its conclusions, the geocentric model served as the dominant theory to explain the cosmos and our position within it until the sixteenth century when the heliocentric model of Nicolaus Copernicus took the Earth away from the centre of the universe and replaced it with the sun.
The theory of heliocentrism, which holds that the sun is near the centre of the universe with the Earth and other planets orbiting around it in circular paths, was proposed as far back as the third century BCE by ancient Greek astronomer Aristarchus of Samos. However his theory never gained traction because there was no observable movement of the stars relative to each other, or stellar parallax, to suggest that the position of the Earth was continuously changing. In 1543 and the year of his death, Copernicus’ magnum opus De Revolutionibus Orbium Coelestium was published, in which he argued that the Earth has a twofold motion. A diurnal rotation on its axis and a yearly rotation around the sun. Copernicus, like Aristarchus of Samos, had to contend with the difficulty of reconciling a moving Earth with the absence of stellar parallax amongst the stars, but he correctly accounted for this by explaining that these fixed stars must therefore be greatly further away than the sun. Copernicus had little influence in his own lifetime, but his work would mark a monumental shift from thousands of years of geocentrism with the Earth at the centre of the universe.
With the luxury of high resolution images from the Hubble Space Telescope and instruments that allow for more accurate measurements to be made, we can now see the absurdity of the geocentric model as a description of the universe. It did however serve as a rational explanation of the universe at the time, and it also pandered to a sense of self-importance, especially in a religious context, that humanity was also at the centre of the universe.
False tidal theory
In a letter to Cardinal Orsini in 1616 titled Discourse on the Tides, Galileo Galilei theorised that the rising and falling of water in the form of tides is the result of the Earth’s diurnal rotation on its axis and its yearly rotation around the sun. Galileo was a great proponent of heliocentrism and this was his attempt to connect the heliocentric model of the universe and the natural phenomenon occurring on Earth. The inspiration for Galileo’s tidal theory came in 1595 when he was aboard a ferry carrying freshwater from Padua to Venice. Whenever the ferry would change speed or direction, he observed that the fresh water contained in the barrels oscillated in accordance with this change. He inferred from this that the changing speed and direction of the Earth results in a similar effect on large bodies of water, with the Earth’s rotational forces causing the oceans to alternatively accelerate and decelerate, forming the tides.
In his book Astronomia Nova, published in 1609, German astronomer Johannes Kepler offered an alternative explanation of the tides. Kepler argued that it is the gravitational force of the moon that accounts for the rise and fall of water in the form of tides, and he based this theory largely on ancient observations such as those made by Claudius Ptolemy in Tetrabiblos. Galileo however remained unconvinced by Kepler’s assertions, pointing to a lack of empirical evidence in support of his claims. Galileo did end his Discourse on the Tides by conceding that his tidal theory may be incorrect, but he had no reservations about including it in his 1632 Dialogue Concerning the Two Chief World Systems and omitting any notion of a causation between gravitational forces and the tides. Galileo’s defence of Copernican heliocentrism, including his theory of the tides, led to public condemnation by the inquisition for blasphemy in 1633, and Galileo was placed under house arrest for the rest of his life.
In the end, Kepler’s theory was proven correct and it is now widely accepted that the rising and falling of water in the form of tides is attributable to the gravitational pull of the moon. However, despite the fact that Galileo’s tidal theory was erroneous, his revolutionary methods of scientific investigation and inquiry inspired generations of scientists to pursue advances in the fields of physics, astronomy and mathematics.
The Latin phrase tabula rasa, literally meaning “blank slate”, is an epistemological idea which posits that the mind at birth is devoid of all knowledge, ideas and beliefs, and that it is only through experience, perception and sensation that these qualities can be acquired. This theory stands in stark contrast to the doctrine of innatism which maintains that our mental hardware comes pre-installed with knowledge and ideas which are unlocked through experience. The concept of tabula rasa has its origins in the writings of Aristotle, and in his treatise On the Soul written in 350 BCE, he described the mind as “potentially whatever is thinkable” and “nothing until it has thought”. The Italian scholastic philosopher St. Thomas Aquinas, who was a great proponent of Aristotelian thought as the basis for Christian philosophy, expanded on Aristotle’s theory of the mind as a blank slate in his magnum opus Summa Theologica, asserting that “our intellectual faculties know only the impressions made on them”.
The modern idea of tabula rasa is most closely associated with the English philosopher John Locke, who is widely regarded as the founder of empiricism which postulates that all knowledge is derived from experience. In his 1689 work An Essay Concerning Human Understanding, Locke championed the idea of tabula rasa by stating that the mind contains no innate ideas or principles, similar to white paper void of all characters, and that the ideas we render from experience are derived from two sources, sensation and perception. Locke argued that since we can only think in term of ideas, and since all ideas are derived from experience, it is therefore self-evident that knowledge cannot precede experience. Locke’s theory of knowledge provided opposition to the Cartesian position that knowledge can be derived from innate ideas within the mind through the process of deductive reasoning.
The theory that the mind is a blank slate, upon which personality and other mental qualities are written through life experience, is a powerful idea that informs the way we think about free will, accountability, equality, politics, and many other important areas of life. It has also had a significant impact on the treatment of mental illness in particular, through the exploration of positive and negative life experiences and the extent to which they affect mental health. However, through many years of research and study in the fields of biology, psychology and genetics, it is now widely accepted that genetic and environmental factors wield substantial influence on cognition, personality and behaviour. For example, there is clear evidence to suggest that babies are not born with a blank slate, but rather have innate biological predispositions which directly affect their cognition, personality and behaviour. Still, whilst the blank slate theory of mind has been proven to be fundamentally wrong, the nature vs nurture debate is still hotly debated today.