Aristotle Didn’t Know Sh*t About Physics
The absolute nonsense of Aristotelian physics.
In case you’ve lived under a rock your whole life and have never heard of Aristotle, he was a Greek philosopher that lived between 384 and 322 B.C.E. His works in philosophy, psychology, politics, ethics, and many other fields of thought are held in high regards to this day. However, there is one field in which he dabbled that he is most certainly not well respected in: physics, or natural philosophy as it would have been called in his day. Whereas great minds like Galileo Galilei and Isaac Newton are still highly regarded for their work in physics to the present, we know that a majority of what Aristotle put forth as truth regarding physics was just plain wrong. It’s not even that he was just wrong, it’s that he was very, very wrong.
See, Aristotle didn’t do many experiments. He was more of a sit around and think about it kind of guy. He liked to make claims about how things worked but didn’t fancy actually testing said claims in the real world. This way of working suits more abstract fields that deal with human behavior and the mind, such as ethics, but doesn’t sit well with things that involve the physical realm. A lot of the physical concepts that Aristotle believed in could have been disproved by simply testing it out and seeing if things behaved the way he predicted.
One of the most classic examples of Aristotle being proven wrong happened when Galileo showed that objects fall at the same rate independent of their weight. All objects accelerate toward Earth at 9.8m/s² (Earth’s gravitational constant). The only reason some light objects, such as feathers, fall more slowly is because their acceleration down toward the Earth is countered by air resistance pushing up on the object as it falls, causing it to meander instead of falling straight down. In a vacuum, where air resistance is nonexistent, all objects, such as feathers and hammers, fall at the exact same rate, proving that weight has nothing to do with the speed at which objects fall.
This is in direct conflict with the Aristotelian point of view which says that objects fall toward the Earth because they are trying to reach their “natural place.” Every object had its natural place in which it wished to rest based on what it was made of. Aristotle believed that the speed at which objects fall depended on their weight, and he claimed that heavier objects would therefore fall faster than lighter objects and that the speed at which their fall varied would be proportional to their difference in weight.
We know today, thanks to countless experiments, that this simply isn’t true; it’s not how gravity works at all. An experiment proving that Galileo was correct on this issue has even been performed on the Moon, which is a near-vacuum environment where air resistance can be practically disregarded. Objects do not fall toward Earth because they are seeking their natural place within it, they fall toward Earth because the mass of the Earth warps the spacetime around it (according to Einstein), and they are simply falling down Earth’s gravitational well.
In fact, if you take items sufficiently far enough away from Earth or close enough to another massive body they will not fall toward Earth at all, like in the Moon example. Earth in itself has nothing to do with why objects fall; gravity does, and gravity is an effect produced by anything that has mass, even you. If Aristotle was correct, both the feather and the hammer dropped by astronaut David Scott during the Apollo 15 mission would have flown in the direction of Earth rather than down toward the lunar surface, and the hammer would have won the race.
Another thing that Aristotle believed was that the solar system, or “the heavens” — which was thought to be the entirety of the universe at the time — followed a geocentric model. That is, that the Earth was at the center of the universe and all other heavenly bodies orbited around it. Most people believed that Earth was the center of the universe at the time, but what made Aristotle’s model interesting is that he concluded that the planets and stars where each imprinted onto separate crystalline concentric spheres which moved in constant motion; making each of the heavenly bodies orbit Earth in perfect circles. In other words, spheres within spheres within spheres. In his model, the Earth was motionless in the center.
Today, it is common knowledge that we live in a star system in which Earth is one of multiple planets orbiting around the Sun — a heliocentric model. Earth orbits around the Sun due to a gravity well created by the Sun’s mass, as we established earlier. There are no spheres into which the heavenly bodies are imprinted. We know that every part of our solar system is in motion: Earth rotates on its axis, the Moon orbits Earth, Earth orbits the Sun along with the other planets, the Sun orbits the center of the Milky Way galaxy, the Milky Way galaxy is in motion, etc. We also know that planets do not orbit the Sun in perfect circles with constant motion; rather they have elliptical orbits and their orbital speed increases as they approach the Sun and decreases as they move away from it in such a way that a line drawn from the Sun to the planet covers equal areas in equal lengths of time.
Nicolaus Copernicus first described the heliocentric model of the solar system in 1543, but it wasn’t verified until Galileo used observations of Venus’ phases and Jupiter’s moons to prove Copernicus’ model was correct. Galileo would later be vilified by the church for such thoughts, even though he was correct.
Was Aristotle a bender of the elements? Of course not, but he did believe that everything was made of unique combinations of four elements: earth, fire, water, and air; of which contained four elementary qualities (hot, cold, dry, and wet). In his mind, every object was created from a finely tuned balance of these elements and qualities. If you were able to take an object and swap out one of its elements for another, it would transform into a different object. The elements of which objects were made of gave rise to their tendency to move toward their natural place. For example, objects like rocks would be made primarily of the earth element whose natural place was at the center of the Earth. Therefore, rocks fell toward the Earth in an attempt to reach their natural place.
Anyone who has taken a chemistry class knows that this view of matter is incorrect. Elements do exist, but they are not the kind of elements described by Aristotle. Instead, there are many elements that make up the periodic table of elements, each with different chemical properties based on their number of particles that create their atoms — which are the smallest pieces of an element. For example, the smallest element, hydrogen, has a nucleus made of a single proton with a single electron orbiting it. Add another proton; you get helium, the second smallest element. Continue to add more protons and you climb up the periodic table creating larger and larger elements. If you take an atom of the smallest element, hydrogen, and rip it apart, you no longer have an atom, and therefore you no longer have an element. Instead, you simply have subatomic particles (particles that are smaller than an atom). Even some of the subatomic particles can be broken down further into their constituent parts (elementary particles), though we won’t go too in-depth with that in this article. There are far more than four elements, and the elements have many qualities based on the specific combinations of their constituent particles; which is why different elements have different chemical properties and combine in different ways. The elements that make up objects have nothing to do with how fast they fall in a gravitational field like Aristotle believed.
Okay, so it’s not exactly fair to hold Aristotle to today’s standards. People simply didn’t do real-world experiments in his day like they do in the present. Sitting around and contemplating how the world works using logic was simply the way people did things back then. It was thought that you could understand the world around you using your mind alone. The idea of actually testing things didn’t matter much as long as you were able to come up with a logical way to describe what you saw around you. Aristotle saw that light-weight objects, like feathers, meandered to the ground while heavier objects, like rocks, fell straight down. From his point of view, the feather fell slower.
It wasn’t until the 1500s that people like Francis Bacon or Galileo came along and decided that there should be a method of figuring things out; one that took the observer’s own senses out of the equation and tested one’s predictions empirically. Today, we call this the scientific method. Galileo figured out how fast things fell to the ground and showed that some things orbit other things that aren’t Earth. It wasn’t until Newton came along in the 1600s that we were able to get a semi-complete description of gravity and why things orbit other things. Even still, it wasn’t until Einstein came along in the 1900s that we figured out the actual physical mechanism which causes the phenomenon. To this very day, there are still things regarding gravity that we don’t fully understand. How does it manifest in the quantum realm? What happens at the singularity of a black hole? We weren’t able to probe the inner workings of atoms and prove Aristotle wrong until we had sufficient technology available roughly 2,000 years after his death.
The fact that he even had the forethought to ask questions regarding physics showed that Aristotle was a great thinker with a great mind, even if he didn’t come to right conclusions very often.
This article is dedicated to David Andrew Taylor.
