© Rob Kerby Guevarra/IAU OAE
Figure 1 – Image showing the motion of Mars from earth over time; notice how it moves backwards. All planets or wandering stars have similar motion, but the most noticeable is Mars.
Prologue
When commissioned to write this article by The Review of Religions, I was tasked with researching the extent to which the Heliocentric theory of the Solar System was rooted in Islamic foundations. However, as I researched this subject, I came across a secret that had lain uncovered for over 1400 years, despite being in plain sight. And it is this secret that was key to the Scientific Revolution in the West.
There is a chapter in the Holy Qur’an named Surah al-Taqwir (Chapter 81), which is commonly understood to relate to the ushering of the modern age, beginning in the 15th century. Whereas extensive commentary has been written about most of the verses in this chapter and how they relate to the changes in the modern era, the importance of two particular verses had lain secret:
‘Nay! I call to witness the planets that recede, go ahead and then hide.’ [1]
The reference in these verses is to five heavenly bodies, which we now know to be planets, but which were known to the ancients as the ‘five wandering stars’. These stars did not conform to the uniform circular motion of the other stars, and stood out in the heavens apart from the others. Sometimes they would seem to speed up, sometimes slow down; sometimes disappear from view and other times even go backwards or recede. In fact, the word planet is derived from a Greek word meaning ‘wanderer.’ [2]
In this entire chapter of the Holy Qur’an, which contains prophecies about the modern era, there are only two instances in which God bears witness by something: one in the verses above, and the other is a verse relating to this topic. This demonstrates that amongst all the prophecies mentioned in this chapter, the prophecy in these verses is of such an order of magnitude that it bears witness to God Himself, and stands out amongst the other signs given in this chapter.
This article will take you on a journey of understanding the enigma of these five wandering stars, and how humanity’s attempt to resolve the motion of these stars would fuel centuries of investigation, research and mathematics from the Babylonians, to the Greeks, to the Muslims, finally leading to Copernicus’ Heliocentric model in 1543, which placed the Sun at the centre of the solar system.
In many ways, the Heliocentric model marked the inception point for the scientific revolution of the modern day. Before this point, for many thousands of years, humanity had considered the Earth to be stationary and the centre of the universe – known as a Geocentric model. As we shall see, this Heliocentric model formed the basis for further advancements by Kepler and then by Newton, enabling the first grand theory of natural law in Newtonian mechanics. It was also an indispensable step in changing man’s perspective on himself and his place in the universe. Finally, it was the first thrust of a new priesthood – the scientific establishment – that would come to replace the Church in the West and become the focal point for a new religion.
The scientific revolution can be thought of as the overhaul of Aristotelian physics [3] and cosmology, and the development of the scientific method. To make any inroads in science, one needs to experiment repeatedly, and the greatest running experiment in the history of man, is the movement of the heavens and the earth. Therefore, it was this observation of the heavens and the continuous attempt to understand it that was pivotal in the development of mathematics and science. This is indeed adumbrated in the Qur’an:
‘And We have made the night and the day two Signs, and the Sign of night We have made dark, and the Sign of day We have made sight-giving, that you may seek bounty from your Lord, and that you may know the computation of years and the science of reckoning. And everything We have explained with a detailed explanation.’ [4]
As such, to understand this revolution and any Islamic influences, we must take a journey through scientific history into the world of astronomy and cosmology. In the Holy Qur’an we further read:
‘In the creation of the heavens and the earth and in the alternation of the night and the day there are indeed Signs for men of understanding’. [5]
It will become clear in this article how this verse, in a few words, encapsulates the entire basis of the scientific revolution.
In this article, we will examine the beginnings of the Scientific Revolution in Europe and analyse whether it has its foundations in the Islamic Scientific tradition that was developed in the centuries following the Holy Prophet Muhammad (sa), or whether it is purely based on the foundations of the Ancient Greek tradition. The treatise will restrict itself to the sciences of Astronomy and Cosmology, particularly focusing on the development of the Heliocentric model.
There are many names that are used for the Muslim Scientific tradition. Some refer to it as Arab Science. Others as Islamic Science. Yet others as ‘Middle Eastern Science’ – a misnomer if ever there was one. We prefer to use the term Islamic or Muslim Science. This, too, is a misnomer of sorts, for Jews and Christians were also a part of the story. But misnomers are, unfortunately, unavoidable. If one refers to it as Arab Science, an outraged Uzbek could legitimately point out that Avicenna was from modern-day Uzbekistan, as was Al-Khawarizmi. In reality, Islamic Science was a civilisational effort, combining the nationalities and religions of many. We have chosen to opt for the term ‘Islamic Science’ or ‘Muslim Science’ – not in an attempt to whitewash the history books of Christian or Jewish contributions, but to recognise that all such advances were made within the cultural and religious milieu of Islam. Without the advent of Islam, it is unlikely that the advances made during the period would have been achieved when they were, given its extraordinary feat of uniting nations as far-flung as Spain and India under a single language, religious outlook, and culture.
© Shutterstock
Figure 2 – The names and shapes of various star constellations.
In the Beginning
Let’s go back in time a few thousand years ago, to a world in which there are no telescopes but also no light pollution. [6] The night sky is lit up brightly with an array of objects – objects which we begin to call ‘stars’. They begin to form patterns in our mind, just as the clouds do during the daytime. However, whereas day after day or even hour after hour the cloud forms change, instead we would see the same star patterns night after night, with only a slight difference in position. We begin to find names for these patterns: Aries, Pisces, Capricorn etc. [7]
Aided by these star patterns, we begin to isolate and locate particular stars, monitoring how they move through the night. Our only form of direct measurement is to measure the angle and luminosity (the brightness) of the star. After measuring the angle of each star night after night, we would find that the stars seem to move in a circular pattern around the Earth – with one star, the pole star, seeming to stay fixed in place. This circular pattern is known as the Diurnal Circle. It is almost as if the stars are on the surface of a sphere or dome. This pattern of movement was known in the earliest times, even to the Babylonians.
© Shutterstock
Figure 3 – Star trails are the streaks of light from stars circling around Polaris that appear in the night sky as a result of Earth’s rotation. These patterns are called ‘diurnal circles.’
After further careful observation we would find that there are five ‘stars’ that do not conform to this spherical or circular motion. These would be known as the ‘wandering stars’ – ‘stars’ that would sometimes grow brighter, sometimes seemingly move ‘backwards’, as well as vary their speed of motion through the night sky.
Observing these phenomena, the following questions might have arisen in our minds: are the stars moving around the Earth, or is the Earth stationary, with the stars only appearing to move around the Earth, by virtue of the Earth’s own movement? What holds the stars aloft? What makes them move? What are the wandering stars, and why are they different? Why does their brightness vary? What paths do they follow?
The wandering stars are what we now know to be the five visible planets from Earth: Mercury, Venus, Mars, Jupiter and Saturn. The paths that these ‘Five Wandering Stars’ follow would prove to be the enigma fuelling scientific thought through the centuries. In an attempt to answer these questions, the Greeks, building upon the works of the Babylonians, [8] would attempt to build a cosmology to account for the astronomical observations of the heavens.
Here I would like to draw a distinction between two related fields of Science – Astronomy and Cosmology. The observation of the night sky and charting of the heavens can all be deemed Astronomy, but the physical nature of what is causing the motion or the underlying structure of the heavens is called Cosmology.
The questions and observations raised so far were not unique to Greek civilisation, but for the purposes of this article, we begin with the Greek tradition.
Aristotelian Cosmology & Physics
The questions relating to the five wandering stars bring us to the great philosopher and scientist of the ancient world Aristotle (384 – 322 BCE), a student of Plato who himself was the student of the Prophet Socrates. [9] Building on previous Greek thought, Aristotle would construct a scientific model that would dominate the world for almost 2,000 years. We can summarise Greek thought at the time of Aristotle through an examination of its answers to three key questions.
Question 1: Do the Stars Move, Or Does the Earth?
Aristotle concluded that the Earth must be stationary and, therefore, it must be the stars that are in motion. This was not a new notion presented by Aristotle, but rather an agreement with his Greek predecessors. One of the justifications for this position can be illustrated with the following example: if you were to throw an apple in the air, where would it land? If the Earth was spinning or moving, then surely the apple would land behind you, because for all the time the apple was in the air, the Earth would have spun underneath it, thereby leaving the apple behind. As the apple lands in exactly the same place from where it was thrown in the air, we can conclude that the Earth is stationary. This objection would be a key factor in not accepting a Heliocentric model of the solar system and sticking to a Geocentric one.
Today, we know that the Earth has several motions including its movement around the Sun, its movement around its own axis and a wobble (‘precession’) about its axis. What we must understand is that the Greeks or other contemporary civilisations did not have a real understanding of two concepts that resolve this issue: gravity and inertia. The concept of inertia is that ‘a body continues in its existing state of rest or uniform motion’ unless it is acted upon by an external force. These concepts would not be realised until Newton, and would puzzle scientists throughout the ages.
Another point – besides the example of the apple – that convinced scientists before Copernicus that the heavenly bodies rotated around the Earth was the Stellar Parallax: the hypothesis that, if the Earth has motion with respect to the Sun, then the position of the stars on the stellar sphere should shift by an angle p as the Earth rotates around the Sun. Essentially, the position of the stars would change as the Earth moved around the Sun. However, this variation in angle could not be observed. The only other explanation could be if the stars were at an unimaginable distance from the Earth, thus making the parallax unimaginably small (which was the case). In fact, this variation was so miniscule that it would only be observed in 1838, requiring telescopes for its recognition. As this parallax was not observed with the naked eye, they logically concluded that the Earth was stationary and everything else was moving.
Finally, we should recognise that despite the above arguments, there were individuals who proposed a moving Earth theory. It is said Herakleides (c. 390 – 310 BCE), possibly a one-time student of Aristotle, proposed that the Earth turns on its axis; however, all his writings are lost. [10] According to Archimedes, a Greek astronomer named Aristarchus (c. 281 BCE) hypothesised that the Earth moved around the Sun in a circular fashion, and that the parallax was unnoticeable precisely because the stars were at a great distance from the Earth.[11]
© Wikimedia Commons | Booyabazooka
Figure 4 – A demonstration of the annual parallax of a star.
Question 2: What Holds the Stars Aloft and What Causes their Motion?
Earlier we described the stars orbiting the Earth in a circular motion as if they were on a moving sphere around it. This model actually accounts very accurately for the observed motion of the stars. As such, the Greeks turned this conceptual notion into an actual physical and cosmological explanation of why the stars moved.
They hypothesised that the stars are on a large sphere that rotates around the Earth at uniform speed. This was known as the celestial sphere. The speed has to be uniform since, if it is not uniform, one would have to postulate that there exists something which is speeding up or slowing down the spheres. The question naturally follows is: what are the celestial spheres made of, and what causes their uniform motion? For this, the Greeks hypothesised that the sphere is made up of a substance called ‘aether’, and that this substance naturally moves in a uniform circular motion. As such, whatever is on the celestial sphere will also be propelled with the same motion.
Question 3: What Are the ‘Five Wandering Stars’?
The third and final question was to do with the five wandering stars. What are they and why do they vary in brightness? What paths do they follow? What makes them different to everything else?
The Celestial Sphere could not explain the motion of the ‘Five Wandering Stars’. As such, to accommodate their individual motions, the Greeks extended the spherical model of the stars. They proposed that the five wandering stars, the Sun and the Moon were propelled around the Earth by each having a sphere of their own. This sphere was centred on the Earth. This is known as the homocentric (one centre) model, the Earth being the centre of each sphere.
© Wikimedia Commons | Fastfission
Figure 5 – a simplified depiction of Aristotle’s model of the Universe by Peter Apian, 1524.
It must be noted that this is a simplified version of Aristotle’s model. To account for the specific motions of the heavenly bodies and particularly the five wandering stars, sphere after sphere had to be added to the model, ending up with a grand total of 55 spheres.[12]
Summary of Aristotelian Cosmology
We can summarise the Aristotelian cosmological understanding as follows:
Firstly, the universe is made of five forms of matter: earth, fire, water, air and aether.
Secondly, all matter has an internal capacity of motion.
Thirdly, bodies made of ‘earth’ and ‘water’ naturally move towards the centre of the universe, which is the Earth.
Fourthly, fire and air move away from the centre, as evidenced by flames always flickering upwards and bubbles always moving upward.
Fifthly, the heavens are made of the aether. These are indestructible and make up the spheres upon which the heavenly bodies move. The aether moves in uniform circular motion.
Sixthly, the heavens are immutable; the stars will not change.
Seventhly, a vacuum is impossible.
Eighthly, gravity is movement towards a natural place.
Ninthly, uniform circular motion, i.e., the heavens orbit at uniform speed. This is a logical assumption, as from a rational point of view, they asked, ‘why would their speed change?’ It would mean something needs to be speeding them up or slowing them down, which required the positing of a new elemental structure. This would be crucial in trying to map out the path the heavenly bodies take. The assumption of the uniform circular speed of the heavenly bodies would be a central pillar in the cosmological formulation of the Solar System and universe. To illustrate this, one can imagine the circumambulation of the Ka’bah. This act of moving around the Ka’bah at a uniform speed would be considered a ‘uniform circle motion’.
Aristotle had provided a physical explanation for the astronomical observations made. Aristotle’s reasoning was such that, in general, it would remain the dominant physical and cosmological explanation of the universe for almost 2,000 years.
Ptolemy
In the next 450 years after Aristotle, subsequent Greek Astronomers would build an astronomical model of the universe based on the cosmological principles presented by Aristotle, outlined above. Three figures stand out: Appolonius (240 BCE), Hipparchus (190 BCE) and Ptolemy (100 CE). [13]
It would be Ptolemy’s work, the famous Almagest, which would be the epitome of Ancient Greek astronomical thought. Ptolemy’s work was originally called Mathematike Syntaxis, ‘The Mathematical Arrangement’. [14] In Muslim hands it would take on the name The Almagest, a contraction of an Arabic word al and majisti from Greek megistē, meaning the ‘greatest’ [treatise]. [15] Ptolemy would combine and enhance previous Greek thought, making observations and attempting to apply mathematical models to those observations. However, being a staunch Aristotelian, he would try to build a model of the universe that maintained three core principles:
1. Circular/Spherical motion.
2. Motion of heavenly bodies at uniform speed.
3. A geo-centric model i.e., that the Earth was at the centre of the universe, and all heavenly bodies orbited around the Earth.
However, in what would otherwise have been a simple model, complexity was added by the five wandering stars, specifically relating to two inequalities or anomalies in their motion. This is summarised in the Almagest:
‘The fact that there are two anomalies appearing for each of the planets, and that they are unequal in magnitude and in the times of their returns, works a good deal of confusion. For one of the anomalies is seen to have relation to the Sun, and the other to the parts of the zodiac, but both are mixed together so it is very hard to determine what belongs to each.[16]
Anomaly One
The first anomaly/inequality which is a ‘more difficult problem than the second inequality’, [17] is the non-uniform motion of the ‘wandering stars’ around the Earth. These ‘stars’ do not move with uniform speed or around the Earth as a centre. So how could observation be reconciled with the cosmology of Aristotle? To account for these various anomalies, Ptolemy would employ the following four instruments (see Figure 6): deferent, epicycle, equant and eccentric.
The Instruments of Ptolemy
Deferent – We can view this as the generalised motion of the five wandering stars around the Earth.
Epicycle – As mentioned before, the five wandering stars do not go around the Earth in a circular motion, rather sometimes they have retrograde motion, i.e., they appear to move backwards. To account for this, an epicycle was added onto the deferent for each wandering star. This means that while the wandering star moves around the Earth on the deferent, it also moves around another circle, separate to the Earth, known as an epicycle. This, as can be seen from Figure 5, would allow for apparent retrograde motion, while orbiting the Earth.
Equant and Eccentric – The final two pieces are considered the most controversial parts of the jigsaw, known as the equant and eccentric. As mentioned before, the planets not only appear to have retrograde motion but also appear to speed up and slow down, and also become nearer or further away. This means that the planets moved with non-uniform motion with respect to the Earth, and therefore contradicted one of Aristotle’s cosmological principles. To find a resolution to this issue, Ptolemy removed the Earth from the centre of the universe, and created a ‘false’ centre; this would be the centre around which the wandering star’s deferent would move, known as the eccentric. Furthermore, the equant point would be that point around which the motion of the wandering star is at a constant speed. In this way, the motion of the ‘wandering star’ would be considered to be circular and uniform around two fictitious points.
© Wikimedia Commons | Fastfission
Figure 6 – Diagram showing Epicycle (smaller dashed circle), deferent (larger dashed circle), eccentric (x) and equant (•).
In this manner, Ptolemy had created a system that described the motion of the heavens and the earth, whilst at the same time attempting to remain faithful to Aristotelian cosmological principles. Although it is a very convoluted and complicated system, it provided surprisingly accurate observations.
Anomaly Two
The second anomaly relates to the strange coincidence between the motion of the wandering stars with the Sun – they move fastest when they are in conjunction with the Sun, and in retrograde motion when in opposition to the Sun. Conjunction and opposition are terms which refer to the alignment of the Sun, Earth, and the ‘wandering star’, with one key difference: when we are in conjunction, it means that the Sun is in between the Earth and the wandering star, whereas in opposition, the Earth is in between the Sun and the wandering star (see Figure 7).
© Wikimedia Commons | en:WP
Figure 7 – A diagram showing the point of conjunction and opposition.
Ptolemy found that Anomaly Two could be mitigated by taking observations at opposition, leaving only Anomaly One. We will see that it is Anomaly One, the more difficult anomaly, that Islamic Scientists will pick up and resolve with respect to the Earth. The key take-home point here is that Anomaly Two demonstrates that there is a link between the motion of the planets and the Sun. Why does that link even exist? Find out in the next part of this series, ‘The Five Wandering Stars’.
Serialisation of this article will continue in the next edition.
……………………………………………………….
About the Author: Zafar Bhatti earned a Master’s degree in Physics from Imperial College London and has since gone on to build a career in the IT industry.
……………………………………………………….
ENDNOTES
1. The Holy Qur’an, 81:16-17.
2. Thomas Kuhn, The Copernican Revolution: Planetary Astronomy in the Development of Western Thought (Cambridge, Ma: Harvard University Press, 1970), 45.
3. By Aristotelian Physics is meant the understanding of physics as proposed by the great Greek philosopher Aristotle. This will be elaborated later in the article.
4. The Holy Qur’an, 17:13.
5. The Holy Qur’an, 3:191.
6. This refers to light from homes, streetlamps and buildings that ‘dilute’ the visible light from the stars at night. In the past it was much easier to view the stars at night. This was due to much less artificial night polluting the skies. Today we can still find areas which contain minimal light pollution, allowing the stars at night to be viewed very clearly. For example, the South Downs National Park in the UK is one of only 13 International Dark Sky Reserves.
7. My review ‘In the beginning’, is inspired by Thomas S. Kuhn’s work The Copernican Revolution, an excellent read, although in some ways very much rooted in outdated views tracing any cosmological attempt at understanding of the heavens to be the monopoly of Western Europe.
8. Leonard W. Clarke, “Greek Astronomy and It’s Debt to the Babylonians,” The British Journal for the History of Science 1, no. 1 (June 1962): 65–77.
9. Hazrat Mirza Tahir Ahmad (rh), Revelation, Rationality, Knowledge and Truth (Tilford: Islam International, 1998), 73.
10. John Louis Emil Preyer, History of the Planetary Systems: From Thales to Kepler (Cambridge: Cambridge Univ. Press, 2014), 123.
11. Ibid., p. 137.
12. N.R Hanson, Constellations and Conjectures (Springer Science & Business Media, 2012), 69.
13. John Louis Emil Preyer, History of the Planetary Systems: From Thales to Kepler (Cambridge: Cambridge Univ. Press, 2014), 149.
14.https://www.britannica.com/topic/Almagest
15.https://www.collinsdictionary.com/dictionary/english/almagest
16.https://science.larouchepac.com/kepler/newastronomy/part1/5/index.html
17.N.M. Swerdlow, “An Essay on Thomas Kuhn’s First Scientific Revolution,” The University of Chicago 148, no. 1 (March 2004): 112.
Add Comment