Universal Gravitation and Discovery Disputes

The work of Galileo had set in motion a new Scientific Revolution. Science and reason became fundamental cornerstones of the study of a natural world only before thought of philosophically. Empiricism - mathematical theory - would accommodate observation in the pursuit of new scientific discoveries. [1]

It has been argued by scholars that previous work done by Johannes Kepler was instrumental in the later discoveries of gravity and planetary motion expounded by the British scientist, Isaac Newton. However, although Kepler's laws regarding traditional astronomy were unprecedented, "few astronomers adopted them. There was no Keplerian cosmology or world system as there was Ptolemaic, Copernican, and Tychonic world systems. In many ways, Kepler's work was a historical dead end." [2]

Newton's now infamous epiphany was said to have occurred in the apple orchard of his family home. There under a tree, Newton is said (indeed, he told the story himself in his elder years) to have witnessed an apple falling, and the force of gravity was theorised. As one scholar (comically) noted however, "I'm extremely skeptical about the role of fruit in Newton's life." [3] Fable or not though, Newton's observations and experiments with gravitational force led to the simplification of motions, like velocity and acceleration. More importantly, "it was possible to calculate quantities that are constantly changing.... With this technique, Newton invented an entirely new branch of math called calculus." [4]

Newton also constructed a new and more compact version of a telescope. His refracting telescope, as the instrument is known, is the model used for contemporary telescopes used to peer into the deepest reaches of the visible universe. For Newton, the development served as a launching pad for his scientific career: "It brought Newton on to the world stage of science, and Newton became an overnight sensation." [5]

The greatest work attributed to Newton stems from a visit with the astronomer Edmond Halley. Halley, an astronomer who had studied at Oxford University, analysed the heavens from his colonial workspace on the South Atlantic island of St. Helena, and the most famous comet is named after him. Halley was a prognosticator of planetary orbits and transits, and therefore, an accomplished astronomer to discuss similar work with Newton. [6] During their meeting, Newton surprised Halley by explaining that ellipses formed the line of planetary motion. Though he could not provide documentation of his theory to Halley at the time, Newton devised a rule known as the 'inverse square law' to define this relationship in the heavens. Years of Newton's observations, experiments, and discoveries were published in a book, the Principia, soon after. "It is the most magnificent work, it is the most all-encompassing work, it is the most daring book of any scientific treatise ever written." [7] Within its pages, Newton outlined his three laws of motion, and within these laws, it was evident that the same gravitational forces on Earth operated in space as well: "Newton's breakthrough was to see that the Moon's orbit around the Earth and a cannonball's motion on Earth were governed by the same law of gravity." [8]

"It's so important because it really tells us how nature operates in a fundamentally new way. Newton

is saying, 'the same thing that is going on in the heavens is going on on Earth, and vice versa.' It gives

us a guidebook to answer the age-old question of what causes the rise and fall of the tides. It gives

us answers to the orbits of the planets and their positions. It's a tremendous act of intellectual triumph,

one of the great keystone, cornerstone pieces of our intellectual heritage." [9]

Newton's discovery of gravitation laid the foundation for modern science and the ways in which we humans perceive our place in the universe.

Of course, Newton was not without his critics. His rivalry with fellow scientist (and Royal Society member) Robert Hooke may not as well publicised today, but it was a constant stress for Newton to be exposed to criticism. "As soon as the Principia was published, Newton's old rival, Robert Hooke, claimed he had come up with some of the key ideas first. And later, others attacked it because Newton did not explain what gravity is, just how to calculate its strength." [10] Throughout his life, Newton was never entirely comfortable with publicising his works for fear of shame, ostracising, and negative reaction. [11]

Newton's primary challenge was of the ideas of Rene Descartes, a French philosopher who thought of the universe as a giant machine. Descartes argued that all universal motion was simply "the physical interactions of parts of this machine." [12] For much of the eighteenth century, the theories on physics put forth by Descartes and Newton were the main doctrines for evaluation. The use of different methodologies to come to a respective conclusion may explain part of the divide between British and European science in the second half of the 1700s: "Newton's loyal followers in England made little progress compared to scientists on the continent less tightly tied to geometrical proofs and more ready to take up algebraic methods (developed by Descartes)." [13]

Newton was also fiercely engaged in a copyright battle with the German mathematician and philosopher Gottfried Leibniz, who had also claimed to have invented calculus. Leibniz was a staunch supporter of Descartes' theories on planetary motion, and pitted the two on a fundamental war of physics: vortices vs. elliptical orbits. Leibniz argued that gravity was the result of revolving vortices around the Earth. [14]

Contrary to modern opinion, Newton was not a fervent opponent to the idea of a universe operating under the guise of an omnipotent and omnipresent being. As a member of Trinity College, Newton was expected to pursue theology and work as a Church representative at the University of Cambridge. It was not until a century later that "gangs of interpreters (most of them French) will take the 'God' out of Newton's world." [15] Perhaps this was part of the schism between British science and Continental science in the years following Newton's discoveries. As Newton maintained the idea of a universe with God in it, French and German scientists (like Descartes and Leibniz) attempted to explain a 'godless' universe in the latter years of the Enlightenment.

Another important figure during this time was Christopher Wren, a famous architect from the UK who also had a keen mind for astronomy. Educated at Oxford University, Wren discussed space and the planetary motions with Newton as early as 1677. Wren however, like Hooke, did not possess the mathematical acumen "or geometrical ability to show what orbit would result from an inverse square force of attraction: in effect, to derive Kepler's laws of planetary motion from principles of dynamics." [16]

In my opinion, scientific theories must be documented, tested, and verified multiple times by many reputable contemporaries before they can be recognised as 'discoveries'. This is why we have the 'scientific method' as a process of analysis. It legitimises the work of scientists and allows for the transparent circulation of their ideas amongst the intellectual community and the public at large. Of course, all sorts of problems can and will likely persist - from the destruction of evidence, to accusations of plagiarism, to conflicting research and ethical concerns. All of these possibilities are likely to occur as the work of scientists continues (and some could say, intensifies) in the social, economic, and political arenas of our global world. In Newton's time, these difficulties were even more problematic, as information was not as readily communicable and scientists could be threatened with heresy and put to the death (of course, this can still happen!) As a historian however, it is important to have documented proof of claims so that discoveries can be analysed fairly and attributed to their rightful 'owners'. Therefore, I believe in the scientific method as a necessary process.


End Notes:

[1] Chris Oxley (Director). Smith, George (Dibner Institute) (Contributor). (2005). Newton's Dark 
Secrets [YouTube video]. USA: PBS/Nova.

[2] Norriss S. Hetherington. (2006). Planetary Motions. Westport, CT: Greenwood Press, 148.

[3] Oxley (Dir.). Schaffer, Simon (University of Cambridge) (Contr.). Newton's Dark Secrets.

[4] Oxley (Dir.). Abraham, Murray F. (Narrator). Newton's Dark Secrets.

[5] Oxley (Dir.). Speaker unknown. Newton's Dark Secrets.

[6] Hetherington, Planetary Motions, 155: "Halley died before the predicted return of his comet in 1758. He also died before the predicted transits of Venus in 1761 and 1769, abut he left detailed instructions for calculating the size of the solar system from their observation."

[7] Oxley (Dir.). Christianson, Gale (Newton biographer) (Contr.). Newton's Dark Secrets.

[8] Oxley (Dir.). Abraham (Narr.). Newton's Dark Secrets.

[9] Oxley (Dir.). Christianson (Contr.). Newton's Dark Secrets.

[10] Oxley (Dir.). Abraham (Narr.). Newton's Dark Secrets.

[11] Oxley (Dir.). Newton's Dark Secrets.

[12] Oxley (Dir.). Abraham (Narr.) Newton's Dark Secrets.

[13] Hetherington, Planetary Motions, 165-66.

[14] Hetherington, Planetary Motions, 165.

[15] Oxley (Dir.) Schaffer (Contr.) Newton's Dark Secrets.

[16] Hetherington, Planetary Motions, 152.


References:

Hetherington, Norriss S. (2006). Planetary Motions. Westport, CT: Greenwood Press.

Oxley, Chris (Director). (2005). Newton's Dark Secrets [YouTube video]. USA: PBS/Nova. Narrated by Murray F. 
Abraham. https://www.youtube.com/watch?v=7n3RWAIlzAI.

Copernicus

In his most famous book De Revolutionibus, Nicolaus Copernicus argued that the Sun, not the Earth, was the centre of the universe. Printed in 1543, his heliocentric view of the solar system argued against nearly 2000 years of entrenched scientific theory, and proved to be the most important Copernican thesis. As this post will show, the Sun as the centre was a even more revolutionary idea for human comprehension than it was for astronomical precision.

That Copernicus was the first to interpret the universe as revolving around the Sun, or that the Earth spun on its own axis were not brand new ideas. Jean Buridan (c. 1300-1358), Nicole Oresme (c. 1320-1382), and Nicholas of Cusa (1401-1464) were all medieval polymaths who had developed a diurnal conception of the Earth in the fourteenth and fifteenth centuries - before Copernicus's time - and even an ancient Greek astronomer, Herakleides, proposed such a theory. Another, Aristarchus of Samos, also believed in a heliocentric universe and a daily spinning Earth motion. It seemed far more plausible that the tiny Earth, not the gigantic universe around it, could rotate within a 24-hour period. Copernicus is such an influential figure in this field because he was the first to construct "a mathematical system of planetary motion from a heliocentric perspective." Though he (incorrectly) assumed that the Sun was stationary (his protege Johannes Kepler later corrected this view), "Copernicus was the first to develop a detailed account of the astronomical consequences of the Earth's motion." His system provided something that the long traditional Ptolemeic model did not - coherence. With Copernicus's heliocentric model, "the retrograde motions of the (inner and outer) planets become a natural consequence of the motion of the Earth around the (mean) sun" and the motion of the planets was uniform. Here, "Copernicus's solution is only partially successful because he still assumes uniform circular motion" but "the major irregularities of the planetary motions are only apparent. These appearances are produced by the orbital motion of the Earth. As the sun is stationary in the heliocentric system, it does not have retrograde motion" (Weinert, 21-5; Margolis, 87, 106 [note 10]).

Copernicus's model also enabled him to measure the distances between planets. Adopting mathematical methodologies used since antiquity and updated observations of planetary orbits, Copernicus could determine the relative distance of the planets from the Sun and from each other. 

[The Copernican Model of the Solar System; source: Google Images] 

Here again, we see a coherent system that could do away with the antiquated beliefs of celestial spheres. That being said however, Copernicus's observations did not totally disprove the ancient Greek astronomical observations nor, especially, Ptolemy's heavily entrenched geocentric model:

"The Greeks sought to fit the appearances they observed to their prior beliefs about celestial phenomena.

Copernicus claims that his work is based on long and numerous observations, his own and those of the

Greek tradition.... Nevertheless Copernicus's observations do not establish any new facts. The Copernican

observations do not go beyond the discoveries of the Greeks. They do not cast in doubt Greek

presuppositions about circular motion. It is therefore fair to say that from an observational point of view,

the Copernican and Ptolemaic systems were equivalent" (Weinert, 25).

Modern astronomers cannot disregard the observations and theories proposed by the ancient astronomers just because of the updated 'discoveries' of Copernicus, Kepler, and other more recent astronomers. For without Ptolemy's model to establish a 'base theory,' Copernicus could not have expanded upon those ideas and eventually develop his own model.

Explaining the season was another conundrum which the Greeks were aware of, but still required an astronomical model for comprehension. In a geocentric universe, the variations in weather and temperature which corresponded with the four seasons in a year could not be definitively explained. So Ptolemy, using observations by Hipparchus, devised a system with eccentric or displaced circles. At a 23.5 degree angle, the Sun would orbit the Earth on a tilt. Copernicus's model attained a more difficult theory concerning this phenomenon - a third motion, or "deflexion of the Earth's axis." Because the planets lay within celestial spheres (again, disproved by Kepler, who argued that astronomy could do "without the useless furniture of fictitious spheres and circles"), and moved as part of a system, the seasons and the length of days fit a symmetrical pattern (Weinert, 25-8).

Copernicus's theory of a heliocentric universe was fundamental to the establishment of a humanist approach to science. Although humans were no longer the centre of the universe, they could however apply a mathematical and geometrical methodology to rationalising the vast wonders of the cosmos. "By making Earth a planet, Copernicus revolutionized humanity's view of its place in the universe and triggered a controversy that would eventually bring the astronomer Galileo Galilei before the Inquisition."  To arrive at such a conclusion meant the opening of other radical ideas. It signified the beginning of a new scientific paradigm, displacing nearly 2000 years of entrenched astronomical thought. Simon Stevin, William Gilbert, Thomas Digges, Kepler and Galileo were all contemporary astronomers of Copernicus to encourage this new paradigm shift (Weinert, 1, 20; Backman, Seeds, et al, 53-4; Margolis 70]

A mobile Earth could naturally explain retrograde motions, the seasons, and the relative distance of planets from the Sun within a heliocentric universe. Thus, Copernicus's system proved to be another launching pad for further research and quantitative data on our solar system. More importantly, it fundamentally changed the way we humans viewed our place in the universe.

Sources:

Backman, Dana E, Michael A. Seeds, et al. Astro. Toronto: Nelson Education, 2013.

Margolis, Howard. It Started with Copernicus: How Turning the World Inside Out Led to the Scientific Revolution. New York: McGraw-Hill, 2002.

Weinert, Friedel. Copernicus, Darwin, & Freud: Revolutions in the History and Philosophy of Science. Chichester: Wiley-Blackwell, 2009.