Let’s do a small exercise before going into what the misconception is. Try to remember what Newton's law is. Perhaps, you can remember every word. Is it “for every action, there is an equal and opposite reaction”? This is what we all remember when we hear about Newton right?
Let’s recall Newton’s first law of motion:
“Every body continues to be in its state of rest or of uniform motion in a straight line unless compelled by some external force to act otherwise."
Able to recollect? Let’s put this in more simple words. If you don’t disturb (touching, pushing, yanking and a few other annoying things can be defined as disturbing) a moving object, it will continue to travel in a straight line. If it is not moving, it will continue to be in the same state.
Does it make any sense? If I kick a ball, does it travel in a straight line forever? No. Eventually, it falls down due to the force of gravity. If a cart is moving in a straight line on the ground, does it continue to be in the same state of motion? It eventually stops because of the ground the cart rubs up against, and the air that it bumps into are both pushing it back. Then what about the moon? It goes in ellipses, not in a straight line and it travels in free space. Well, the moon isn’t force-free either. It is bound to the Earth’s gravity. So, nothing is ever in perfectly stable uniform linear motion. There is always some or other force that tries to stop the object that we’re trying to move.
Now it is more confusing, right? There could be literally no force-free bodies in the universe. Then what does Newton's first law of motion govern?
I recently read an article titled “Forced Changes Only: A New Take on the Law of Inertia” by Daniel Hoek and found that Newton's first law is a lie. Not what Newton told, but what everybody calls “Newton’s First Law”, the one they tell you about in school, the one physicists and scholars have for centuries attributed to Newton, is not what Newton meant in his Principia. According to Hoek, it is a clumsy mistranslation of the Latin principle that Isaac Newton labelled the First Law of Motion, an eighteenth-century mistake that somehow managed to fly under the radar.
What Newton meant and what we understood
Try to read the first law again. What does this principle say about bodies that are subject to forces?
Take, for example, the spinning top mentioned in the Principia. Its parts are not force-free and do not move in straight lines, yet they continue to rotate unless they are retarded by the air. According to Newton, their state of motion changes only to the extent that the forces impressed upon them compel them to. This is a perfect illustration of what the First Law actually says - that objects will only diverge from their state of rest or uniform rectilinear motion insofar as the impressed forces compel them to.
But what does this mean for objects that are not subject to forces? According to Daniel Hoek's thesis, there are two statements that help to clarify this. Statement 1 states that if no forces are impressed on a body, it will persevere in its state of uniform rectilinear motion. This is what we have learned so far - in the absence of forces, objects will maintain their state of motion.
However, Statement 2 is where things get more interesting. It states that every change in a body's state of uniform rectilinear motion is compelled by the forces impressed on that body. In other words, if an object changes its state of motion, it is due to the forces acting upon it. This highlights the fact that the First Law is not just about objects that are subject to forces, but also about the absence of forces and how they affect an object's motion.
In the end, the First Law of Motion is a complex and nuanced principle that requires careful consideration and interpretation. It serves as a reminder that even the most fundamental scientific principles can be open to interpretation and refinement and that the pursuit of knowledge is an ongoing process of discovery and exploration.
What went wrong?
Have you ever wondered how a tiny word could make big differences? Well, it turns out that a single word was responsible for a major oversight in one of the most important scientific works of all time - Isaac Newton's Principia. And the most surprising part? This error went unnoticed for centuries, even by some of the most brilliant minds in physics.
So, what was the error? It all comes down to a single word - "quatenus". This Latin word, which means "insofar," was omitted from the original translation of the Principia by Andrew Motte in 1729. As a result, the First Law was translated as "Every body perseveres in its state of rest, or of uniform motion in a right line, unless it is compelled to change that state by forces impressed thereon."
At first glance, this may not seem like a big deal. But the omission of "quatenus" actually changes the meaning of the First Law in a significant way. Instead of adding a qualification, Motte's translation makes it sound as though the law makes an exception for bodies subject to forces. In reality, the law states that an object will only continue to move in a straight line at a constant speed if there are no external forces acting upon it, except insofar as those forces may cause it to change direction or speed.
Despite the error going unnoticed for centuries, it was finally discovered during a re-examination of the original Latin text. The new translators, Cohen and Whitman, fixed Motte's mistake by adding the word "quatenus" back into the First Law. By doing so, they restored one of the fundamental principles of physics to its original splendour.
Conclusion
It is not like without Newton’s insofar, physics would have evolved differently. You see, for a long time, people had the wrong idea about Newton's First Law. They thought it only applied to imaginary situations, and that it wasn't really relevant to the real world. But in reality, every twist, turn, and jolt that we experience is actually governed by this law!
So, what exactly is the First Law of Motion all about? Well, it's quite simple: if a body changes its speed or direction, it's always due to a force.
In a nutshell, all changes in motion are forced.
While some may argue that Euler's reformulation of Newton's Second Law made the First Law somewhat redundant, it's important to remember that this law is still a crucial part of our understanding of physics.
By recognizing the true importance of Newton's First Law, we can gain a deeper appreciation for the role that forces play in our everyday lives. So the next time you experience a sudden change in motion, remember that it's all thanks to the power of forces and the laws of physics!
Resources:
- Forced Changes Only: A New Take on the Law of Inertia - https://philpapers.org
- NCERT XII Std Physics book - https://ncert.nic.in
- English Translation of Newton’s Principia - https://archive.org
Reviewers:
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