Newton's Laws: Perfect Balance from an Unbalanced Mind

 

 

Note: Replica of Isaac Newton's second reflecting telescope of 1672 by Andrew Dunn, 2004.
Wikimedia Commons (https://commons.wikimedia.org/wiki/File:NewtonsTelescopeReplica.jpg).
CC BY-SA 2.0.

 

Newton's Laws: Perfect Balance from an Unbalanced Mind
by Vicky L. Oldham, November 22, 2021

Isaac Newton is regarded among the greatest thinkers in the history of Western scientific discovery.  He deduced the nature of properties of the physical universe that laid the groundwork for countless advancements in science and technology.  He contributed to mathematics by helping to develop calculus (known in his time as "fluxions").  Most importantly, Newton created a framework for understanding our world by defining universal laws of motion and gravity, originally entitled Philosophiae Naturalis Principia Mathematica (1687), but best known as the Principia (Westfall, n.d.). His insights have led not just to practical innovation, but centuries later, promise future discovery.

Isaac Newton developed three mathematically defined laws of motion (CrashCourse, 2016).  Newton's first law of motion, commonly referred to as the law of inertia, describes how objects either stay in motion or at rest unless acted upon by an outside force.  Imagine a falling object hitting the ground (or someone's head, as in the apocryphal story of the apple falling on Newton while he sat beneath a tree) (Biography, n.d.).  This law states that still objects are also acted upon by forces like gravity but remain in equilibrium.  One typical example of Newton's first law may be experienced watching a sled sliding down a snowy hill.  The force pulling the sled downhill is gravity.  At the bottom of the hill, the sled meets resistance (friction) and stops due to the greater net force of friction and gravity.  A child riding on the sled may be thrown forward slightly when the sled stops because the child does not meet the same resistance as the sled at the same time—demonstrating the effect of inertia.  Conversely, if the child's feet hit the ground before the sled fully stops, the child may momentarily lean backward.

Newton's second law of motion describes the relationship of mass and acceleration to the net force (the sum of all forces acting on an object); the greater the mass, the stronger the force needed for acceleration.  Newton neatly packaged this idea in a mathematical formula stating that force is equal to mass times acceleration.  With the second law, one may determine the force required to accelerate the sled just by knowing the sled's mass and acceleration values.  Alternately, knowing the force and the mass, one may calculate acceleration. 

Newton's third law of motion says for every action, there is an equal but opposite reaction.  When the sled comes to a halt at the bottom of the hill, it's because gravity has exerted an equal but opposite force on the sled's mass.  The "equal but opposite force" concept may seem abstract because an upward force exerted by the sled and opposing the pull of gravity is hard to imagine.  As the sled is sitting still, the net forces (the sum of all the forces acting on the sled) are equalized, but if a child begins to pull the sled forward by a rope, the net force moving the sled becomes greater than that exerted by gravity.

Newton didn't just verbalize his laws.  He used precise mathematical formulas to describe his findings, enabling his work to be tested and used by others in countless practical applications.  Newton is also credited with significant improvements to the scientific method.  Judging by the extent of technological development that has changed our world since his time, it would be difficult to underestimate the benefit of his work to scientists and engineers: designers of cars, planes, aircraft carriers, submarines, and massive structures like suspension bridges.  Beyond the usefulness of Newtonian mechanics on Earth, Newton's contribution to understanding space and eventual space-related technologies is considered on par with Einstein's theory of relativity.

Newton believed the same mathematically defined laws that described the fall of apples could apply to the motions of planets, leading him to formulate a law for universal gravitation (CrashCourse, 2016).  In addition to confirming the truth of his findings through mathematical proofs, he felt compelled to look further into the depths of space through firsthand observation.  Not satisfied with the limitations of Galilean-type telescopes, Newton invented a new kind of telescope in 1668, the reflector, representing a quantum leap in viewing faraway objects in the solar system.  His novel design achieved 40x-magnification despite a length of just six inches, ten times smaller than the available refracting telescope of his day.  With his reflecting telescope, Newton could observe planets, including some Jovian planet's moons.  He further realized that the force of gravity drives planets along elliptical orbits and causes the rise and fall of ocean tides on Earth.

The profound nature of Newton's discoveries seems inconsistent with the life and personality of the man.  A brief inquiry into his past, including questions about his youth, education, and influences, reveals a darker nature with unexpected twists and turns.  Isaac Newton was born prematurely on Christmas Day 1642 in Lincolnshire, England.  It was a period of turbulence during civil wars in England and the waning days of the Thirty Years' War that consumed most of Europe.  Due to his frailty and tiny size, at first, he was not expected to live (Teach, BBC, n.d.).  Newton survived and, as a young boy, expressed a passion for mechanical devices.  Multiple sources from his youth reported that he built clocks and windmills (Britannica, n.d.).  He was admitted to Cambridge in 1661 (at age 19) when his brilliance in mathematics became known to his instructors.  However, once at Cambridge, the spread of the plague threatened the local population, and all students were sent home.  It was there that Newton developed many of his revolutionary ideas. 

Delving into Newton's life story, most will imagine a famous, universally admired man, lauded and followed by fellow scientists and thinkers of his time.  However, upon learning more details about his personality, a typical reaction is to recoil with a sense of shock and disappointment.  It turns out that Newton was emotionally unstable, vindictive, and wildly accusatory in dealings with colleagues, including distinguished intellectuals of his day who he imagined to be covetous of his work.  At times he displayed intense paranoia and was known to pursue and threaten perceived enemies relentlessly.  He was gripped by unfounded suspicions, even accusing his closest friends, like the renowned English philosopher John Locke of conspiring against him (Iliffe & Mandelbrote, 2021).  Residing in London, Newton became warden of the mint in 1696 and later master, a position enabling him to acquire great wealth.  Reputed to be the "terror of counterfeiters," he sent scores of people to the gallows, finding "a socially acceptable target on which to vent the rage that continued to well up within him" (Westfall, n.d., Section: Warden of the mint, para. 3).  Historians today speculate that Newton suffered from a form of mental illness, possibly bipolar disorder.  Others attribute Newton's erratic behavior to mercury poisoning due to his fascination with alchemy, which included vaporizing toxic metals to explore their properties.

Newton died in 1727, leaving behind a massive stack of papers. The papers found their way to Cambridge in the late 1800s, where preeminent scientists John Couch Adams and George Stokes finally examined them.  According to an article in Wired Magazine, they were "horrified and dismayed. Here was this great scientific hero. But he also wrote about alchemy and even more about religious matters" (Mann, 2014, para. 17).  The revelation that Newton was intrigued by pseudoscience is even more perplexing, considering his crowning achievement, mathematically deciphering the laws of motion and gravity.

Despite standing the test of time for most applications, classical Newtonian laws have been challenged by scientists puzzled by inaccuracies in predictions related to some objects in space.  For example, Mercury's orbit has shifted faster than predicted by Newton's laws.  Einstein later solved the problem of Mercury's orbit, showing how space-time influences planets and stars by curving around them.  Still, Einstein's predictions fall short when studying massive objects like black holes (Deaton, 2019).  A recent article published in SciTechDaily by Case Western Reserve University (2021) discusses the growing interest in "Modified Newtonian Dynamics" or "MOND" for modified gravity.  MOND offers a "viable explanation for a cosmological dilemma: that galaxies appear to buck the long-accepted rules of gravity traced to Sir Isaac Newton in the late 1600's" (para. 3).  Part of the evidence swaying scientists to regard MOND seriously comes from observations of over 150 galaxies.  A StarTalk episode from 2015 features an interview with celebrity astrophysicist Neil deGrasse Tyson.  The interviewer asks if the information about MOND is considered "fringe" science.  Dr. Tyson assures the listening audience it is a viable discovery confirmed by other astronomers and based on data collected from the 1980s to the present (StarTalk, 2015).  Although MOND has proven accurate in observing specific galaxies, it fails to explain other phenomena in galaxy clusters.  The process of modifying preexisting theories is nothing new: it simply reflects the natural and historical process required to forge new pathways to discovery.  It would not be the first time that long-accepted views are later modified or even replaced due to advancements in data collection tools.

Regardless of the ongoing challenge to adapt to new information, there is no question that Newton's laws of motion and gravity have helped humans advance over the past few centuries in immeasurable ways.  One can only wonder how Isaac Newton would react if he could time-travel to our 21st-century world.  Perhaps after first feeling overcome by sheer awe beholding the technological world to which his ideas gave rise, his focus would turn to explore beyond the Earth, lured by the mysteries of space—and the chance to test and improve his ideas firsthand.

 

 

References

Biography (n.d.). Isaac Newton. Biography. https://www.biography.com/scientist/isaac-newton

CrashCourse (2016, April 28). Newton's laws: Crash course physics #5 [Video]. YouTube. https://youtu.be/kKKM8Y-u7ds

CrashCourse (2016, May 19). Newtonian gravity: Crash course physics #8 [Video]. YouTube. https://youtu.be/7gf6YpdvtE0  

Case Western Reserve University (2020, December 17). What if Dark Matter Doesn’t Exist? Unique Prediction of “Modified Gravity” Challenges Dark Matter Hypothesis. SciTechDaily. https://scitechdaily.com/what-if-dark-matter-doesnt-exist-unique-prediction-of-modified-gravity-challenges-dark-matter-hypothesis/

Deaton, J. (2019, August 3). Einstein showed Newton was wrong about gravity. Now scientists are coming for Einstein. NBC News. https://www.nbcnews.com/mach/science/einstein-showed-newton-was-wrong-about-gravity-now-scientists-are-ncna1038671 

Dunn, A. (2004). Replica of Isaac Newton's second reflecting telescope of 1672. Wikimedia Commons
https://commons.wikimedia.org/wiki/File:NewtonsTelescopeReplica.jpg 

Mann, A. (2014, May 14). The strange, secret history of Isaac Newton's papers. Wired. https://www.wired.com/2014/05/newton-papers-q-and-a/

StarTalk (2015, January 21). Neil deGrasse Tyson explains modified Newtonian dynamics [Video]. YouTube. https://youtu.be/Qkl2ASn9yyA

Teach, BBC (n.d.). Isaac Newton: The man who discovered gravity. BBC. https://www.bbc.co.uk/teach/isaac-newton-the-man-who-discovered-gravity/zh8792p

Westfall, R. S. (n.d.). Isaac Newton. Encyclopedia Britannica. https://www.britannica.com/biography/Isaac-Newton