From the Greeks to Newton: How the Laws of Motion Were Discovered
In science, most discoveries are made over time by building on the works of others (AKA standing on the shoulder’s of giants). Sir Isaac Newton’s laws of motion were heavily inspired by René Descartes’s Laws of Motion as written in his Principles of Philosophy. Galileo’s Laws of Motion inspired both Descartes and Newton. While Aristotle and his laws of motion and physics inspired EVERYONE (including all the great and influential thinkers we didn’t mention)..
Truly, despite individual greatness, science is a collective effort, and it’s misleading to pretend otherwise and interesting to look at what that means in different instances.
General knowledge was of the utmost importance, especially in the scientific revolution. With the printing press being only a recent phenomena, our forefathers read the work of all the great thinkers. Each polymath built on the work of those who came before them, in a constant push toward enlightenment, and in this case, understanding the basics of physics including the laws of motion and gravity.
Although Newton was the first to present the laws of motion with accurate mathematical proofs, he didn’t “discover the laws of motion” alone. Newton “stood on the shoulders of giants” (specifically Aristotle, Galileo, Descartes) to create the foundation of classical physics. Later, when Albert Einstein “discovered” Special and General Relativity, he too built upon the work of others. These included Newton, who had accurately predicted earth’s local gravity, but not the exact rules that govern gravitational force.
Whether we call it inspiring or borrowing, we can conclude that it is a small world, especially when considering the great minds in Europe after the advent of the printing press and telescope which led to the scientific revolution. We explain the details, and importantly the laws of motion as presented by Aristotle, Galileo, Descartes, and Newton below.
TIP: Newton has a fascinating story that stretches far beyond physics. He spent 30 years at the end of his life working at the royal mint dabbling in economics: he invented calculus, and much more. Learn about Newton’s later years.
FACT: David Hume almost broke science with his “Hume’s Fork“, luckily Kant provided justification for the rationalism on which Newton’s science is built, while adding in the necessary skepticism and empiricism of Hume. Today this line of thinking has turned into what we call the scientific method.
Where Did Newton’s Laws of Motion Come From?
We like to credit Einstein with relativity (to which the laws of motion and Newton’s classical physics closely relate), but the concept goes back to Aristotle in ancient times and Galileo Galilei in modern times.
Aristotle’s Laws of Motion
One can argue the laws of motion, in general, go back to Aristotle, or earlier. Aristotle is the first to define some physics concepts related to motion, but since there is a big gap between Aristotle and Galileo (compared to Galileo, Descartes, and Newton, who all lived in the same century) we won’t go too deep into Aristotle here. Know simply that Galileo, Descartes, Newton, and others draw from the Greeks during the scientific revolution (and still do today). See Aristotle’s Laws of Motion and see The Physics of Aristotle versus The Physics of Galileo.
Galileo’s Laws of Motion
Galileo, with a telescope in hand (figuratively), clearly defines relative motion in 1632 in his Dialogue Concerning the Two Chief World Systems (read online). To sum up, the concepts presented in the book:
Galileo, building on earlier ideas, says the laws of motion are the same in all inertial frames (frames like earth), that “objects in motion tend to stay in motion unless they meet resistance AKA inertia” (Newton’s First Law), and that motion is relative. These are concepts Descartes, Newton, and Einstein would later adopt.
Comparing Descartes’ Laws of Motion to Newton’s Laws of Motion
About ten years later, in 1644, René Descartes fleshed everything out. He said, “in the absence of external forces, an object’s motion will be uniform and in a straight line” (Newton’s First Law) and a version of “for each force, there is an equal and opposite force” (Newton’s Third Law).
Descartes laws of motion are set out in Part 2: The principles of material things, luckily Descartes makes it easy by numbering everything. You are looking for, starting on page 28 (of this specific version) #23 – #40 (or really to the end of the chapter).
Newton borrowed a lot of ideas from Descartes, including his laws of motion.
Law 1. Each thing, in so far as it is simple and undivided, always remains in the same state, as far as it can, and never changes except as a result of external causes… Hence, we must conclude that what is in motion always, so far as it can, continues to move. (Principles Part II, art. 37)
Law 2. Every piece of matter, considered in itself, always tends to continue moving, not in any oblique path but only in a straight line. (Principles Part II, art. 39)
Law 3. When a moving body collides with another, if its power of continuing in a straight line is less than the resistance of the other body, it is deflected so that, while the quantity of motion is retained, the direction is altered; but if its power of continuing is greater than the resistance of the other body, it carries that body along with it, and loses a quantity of motion equal to that which it imparts to the other body. (Principles Part II, art. 40)
Remembering none of the aforementioned wrote their works in English, Newton’s laws can be translated to
Law I. Every body continues in its state of rest, or of uniform motion in a right line, unless it is compelled to change that state by forces impressed upon it.
Law II. The change of motion is proportional to the motive force impressed and is made in the direction of the right line in which that force is impressed. (F=ma)
Law III. To every action there is always opposed an equal reaction; or, the mutual actions of two bodies upon each other are always equal, and directed to contrary parts.
TIP: Note that in #17 Descartes says there is no such thing as empty space. This is one of many things Descartes gets right in this chapter that is far ahead of its time; of course, Aristotle said much the same almost 2,000 years earlier. Descartes was summing up all prior knowledge in his aptly named Principles of Philosophy. The book was meant to be a replacement for the Greek texts.
TIP: When two people discover something in and around the same time it is called “multiple discovery.” This is what happened when Newton and Gottfried Leibniz invented infinitesimal calculus around the same time. It is different from what Einstein and Newton did with physics. They built on old theories and then make new breakthroughs. Although it is partially a matter of semantics, after reading Aristotle’s, Galileo’s, and Desecrates’ laws of physics the difference becomes clear.
Understanding Aristotle, Galileo, Descartes, and Newton
To say that Descartes wasn’t a mathematician would be disregarding La Géométrie and the invention of analytical geometry and the Cartesian coordinate system, so that doesn’t work. The same thing goes for Galileo; he certainly had a grasp, but in truth, the major players of the time period tended to focus on general knowledge and writing great works in math, astronomy, physics, philosophy, and economics. The same thing goes for Aristotle whose works comprise a book on just about every academic subject.
Newton is the same, but Newton’s Principia: the mathematical principles of natural philosophy specifically is a heady math-laden tome which includes the invention of calculus alongside modern physics.
The Principles of Philosophy is a comparatively easy read that is more focused on philosophy and metaphysics while Galileo’s work is arguably less metaphysical but also less mathematical, and as mentioned so is Aristotle’s.
Certainly, and partially because he comes later, one would have the most luck building a bridge with Newton, and by Newton’s admission he sees furthest as, coming later, he can “stand on the shoulder’s of giants.”
This story is meant to illustrate the collective nature of wisdom; the awesome impact of the printing press and university on the scientific revolution; the importance of studying classics and general knowledge; and ultimately the importance of the great thinkers who contributed to “classical mechanics,” mathematics, physics, and knowledge in general.
Some would assume that Newton created his own laws of motion, but that isn’t really how science works. Newton borrows the concept of calculus and the laws of motion, but refines them in such a way that “Newton’s Laws” (even today) encapsulate the laws of physics from an inertial frame.
Just like Einstein and relativity, there is a lot more to the laws of motion than just Newton. Still, with these facts in mind, Newton refined the laws of motion and is not mis-credited.
We can confidently say Sir Isaac Newton Discovered the Laws of Motion, but we have to make sure we are telling the whole story. If we forget the greats, it makes it that much harder to stand on the shoulder’s of giants, as we don’t have the whole story.
Author: Thomas DeMichele
Thomas DeMichele is the content creator behind ObamaCareFacts.com, FactMyth.com, CryptocurrencyFacts.com, and other DogMediaSolutions.com and Massive Dog properties. He also contributes to MakerDAO and other cryptocurrency-based projects. Tom's focus in all...