Our Fascination with Movement

Most people like me, who were fortunate enough to have access to some form of schooling while growing up, have most probably come across the ‘Newton’s Laws of Motion’ in Physics. And a lot of us, including me, sometimes take these brilliant observations for granted. However, I believe that we all to some extent have this joint fascination with the idea of moving things. Although Newton’s work in his book Principia Mathematica was a phenomenal breakthrough in physical sciences at the time, humans have been trying to understand motion of physical bodies for almost as long as the civilization has existed.

This study of motion of physical bodies due to external influences (forces or displacements), and their resulting effects, is more commonly known as Mechanics. This area of study traces its origins all the way back to ancient Greece, and has its root planted in the holy cradle of Greek Philosophy. Aristotle was among the first to propose the idea that there are specific laws governing the behavior of physical bodies in nature. This was around 4th century BC. Although, most of his ideas and principles were not based on controlled and quantitative scientific experiments, they still wielded a considerable amount of influence at the time. And it was his ideas (including the one where he thought the Earth was the center of the universe) that most people largely disproved, and gave way to a better understanding of the natural principles at work all around us. This does not mean at all that most of his believes were flawed, after all he was the one who provided evidence for a spherical Earth at a time where most people were flat-earthers. He also had this conceived notion of “natural” vs “un-natural” motion, and was one of the first to realize the idea of a vacuum. And in a sense he was one of the first to approach something close to the law of inertia. All his great work now is known in the history books as Aristotelian Physics/Mechanics.

His work was further complimented by the work of people like Archimedes, Alexandria’s Hero, the Babylonians etc. However, during the Medieval ages Aristotelian ideas were heavily criticized, rejected, modified and disproved in most cases. John Philoponus tested the equivalence principle by observing that two balls of different weights will fall at the same speed from the same height. He along with Hipparchus of Nicaea extensively studied the principles behind projectile motions, which eventually led to the development of the Theory of Impetus by Jean Buridan, which forms the basis of modern ideas like, inertia, velocity, acceleration and momentum. All this was happening around 13th and 14th century and was developed on the back of the work of Al-Baeruni, Al-Hazaan, Abu-Siina, Al-Khazini, Al-Baghdaadi etc.

Then towards the end of the 15th century and early 16th century, with the development of the telescope by Galileo Galilei, the idea of a static unchanging universe was threatened. With the Copernican Revolution in full swing, this was just about the right time where Galileo’s observational prowess provided another solid evidence that the Earth was just another plant in our solar system with the Sun being at the center (although this brought some trouble for him from the Church at the time…oh well). He also is believed to have performed the famous experiment at the Tower of Pisa. And was the first to point out that uniform motion is indistinguishable from rest, and hence in some sense forms the basis of modern ideas of relativity. Johannes Kepler was another fellow whose work led to the modern laws of planetary orbits and the laws of gravitation.

But it was Sir Isaac Newton in 1687, who unified the three laws of motion (the inertial law, the acceleration law, and the law of action and reaction) and gave way to the birth of what is known as Classical Mechanics (aka Newtonian Mechanics). He argued that these laws govern both earthly and celestial bodies, and hoped that they would explain all entities and their behavior including light. In the process Newton also developed what is known as Calculus, and his dot notation for derivatives is still used today. However, around the same time and independently, German polymath and philosopher Gottfried Leibniz, developed the derivative and integral notation of calculus which is still in use to date. He also developed the ideas of conservation of energy and the principle of least action. This was also the time during which the Bernoulli Family (James -aka Jacob, Johann and Daniel) made some very important contributions to the field.

Next up Swiss Mathematician (and much more), Leonhard Euler provided two more extensions to Newton’s laws of motion. He was also among the first ones to dive into the realm of what is now known as Solid Mechanics (which concerns itself with the effect of forces on solid bodies in terms of their deformations). Other notable contributions came from the likes of Thomas Young, Simeon Poisson, Gabriel Lame and Giordano Riccati.

Although Newton’s laws were very powerful in dealing with the explanation of a large array of problems, some reformulations along the way proved to be very beneficial in explaining physical phenomenas with far greater ease. Joseph Louis Lagrange in 1788 introduced his ideas of the path of least action and the calculus of variations, which are part of now whats knows as Lagrangian Mechanics. This was further refined by the Irish Mathematician William Rowan Hamilton, whose work culminated in what came to be known as Hamiltonian Mechanics. Both of these fellows did not really inject new physical ideas or laws but merely reformulated Newton’s laws and provided alternative mathematical expressions which were in some cases much easier to use and understand. Most Hamiltonian frameworks are still used in a lot of quantum mechanical explanations and derivations.

Even with the perceived completeness of the Newton’s Laws, it had some trouble explaining a lot physical phenomena. And these were exposed in the late 19th, paving the way for modern day physics. Although, classical mechanics was in line with most of the statistical mechanics (which explained most of thermodynamics and electrodynamics), as soon as we went down to the level of atoms and went up farther in the sky with massive celestial bodies traveling at great speeds, some short-comings were discovered. This paved the way for Relativistic Mechanics and Quantum Mechanics.

During the 20th century, we saw two major developments in mechanics, Theory of Relativity (Special and General) by Albert Einstein, and some re-formulations and formalization of the early 19th century quantum theory into whats now known as Quantum Mechanics and Quantum Field Theory based on the work of people like Erwin Schrödinger, Werner Heisenberg, Louis de Broglie, Enrico Fermi, Niels Bohr, John von Neumann and others.

Now this might be getting confusing, since so many different frameworks have evolved in the field of mechanics and so many buzzwords are being thrown around everywhere. Someone like me would probably be lost, but with the above history in mind we can boil down this fascination of ours to all the curious mathematical and conceptual tools we have developed as a civilization over time. The following diagram is my attempt to roughly depict whats the current state of understanding and frameworks in the world of moving stuff.


Figure 1: How to explain movement of stuff!?

This finally brings us to today as we ride along in the early 21st century, and we have a plethora of unsolved and unexplained problems and physical phenomenas. However, based on the work of brilliant people before us we also have several tools to help us solve these mysteries, and if the future is anything like our history I am confident we are all in for a surprise.



Figure 2: Our collective historical effort!

Many prominent thinkers throughout history dedicated their lives to answering the fundamental questions about the universe and its working principles. These ideas have influenced all aspects of civilization throughout history, and wield a lot of subtle influence on our modern societies. If the history is any proof to what’s yet to come, we can expect more exciting discoveries and school of thoughts propping up as we progress.

Written on February 21, 2019