The history of comets or more properly “cometary” discovery begins with humankinds curiosity of the heavens. For years ancient humans looked toward the heavens and wondered what was out there? Eventually as time progressed some cultures began to use the sun, moon, stars, and planets to keep track of seasons, construct a calendar, and to keep time. These “celestial objects” were used by ancient humans as a method to measure things. Indeed they provided well, for their “stability” and “predictability” never seemed to change. Celestial bodies rise, set, and behave in concise manners. So ancient humans just assumed that everything in the heavens behaved this way. Until one day, when the first comet was seen. This shattered the notion that the heavens always behaved in predictable ways. More importantly, it sparked the imaginations of ancient people to find away to explain the phenomena of this object which behaved like no other. What was this strange object? Why did it appear and then disappear? These were questions which would be answered by several cultures in many different ways over the course of history.

Among the first to try to decipher this mysterious celestial object were the Chaldeans, Egyptians, Greeks, and the Romans. Each of these cultures made some attempt to explain these objects. In fact, the Greek gave this “mysterious object” a name. They called it a “Comet”. Which is in their language means “long-haired one”. Although the Greeks gave the comet it name, not much is known about their actual views on the subject of these celestial phenomena because there are no known written records of their actual knowledge. In fact, the earliest known written record of comets comes from a Babylonian inscription in 1140 B.C. “A comet arose whose body was bright like the day, while from its luminous body a tail extended, like the sting of a scorpion” (Brandt, Chapman 4). This is the first known written record of a comet. Although, it is not all that revealing, it is certainly a starting point for us to begin the discussion of the early history of comets and cometary science.

Dominant Paradigm Of The Ancients

Starting about 300-400 B.C. there was a major debate going on in the world of cometary thought. Some people thought that comets were celestial objects, while others claimed that comets were some kind of atmospheric phenomena. The Babylonians were among those who claimed that comets were celestial objects. However, their ideas were superceded by Aristotle, who was among those to claim that comets were an atmospheric phenomena. This may seem silly to us today, but armed with the knowledge and assumptions of the day, which implied that the objects in the heavens never changed, his ideas were not so silly. Nevertheless, Aristotle’s guiding rationale behind his “atmospheric theory” was attributed to the fact that comets did not travel in the zodiac (like the planets did). Hence, comets could not possible be celestial objects. Unknowingly though, the miscalculation that Aristotle made was in his assumption that the heavens never changed. This caused him to infer that comets had to be of some other phenomena, because remember, celestial objects were believed to always behave in concise and predictable fashions. Aristotle, then published his work in a book called Meteorology and it was accepted as the most plausible explanation of comets. Thus the “atmospheric theory” became the dominant paradigm for cometary science during this time. However, just because this was the most commonly accepted way to think about comets and cometary science, does not mean that Aristotle’s ideas were accepted by everyone. There was a man named Seneca (4 B.C. – A.D. 65) who claimed that comets were indeed celestial objects. However, he could not prove this theory because he was missing some key information which would make the theory cohesive. So for the most part, Aristotle’s ideas ruled for some 2000 years until some major discoveries started to build upon new ways of looking at the universe that surrounds us.

Important Discoveries: Decomposition Of The Dominant Paradigm

Two thousand years is along time. It is hard for us to imagine that no revolutionary changes took place in cometary science for that long. However, you have to remember that Aristotle’s “atmospheric theory” dispelled comets as non-celestial objects. So interest in studying them simply became unattractive to the philosophers, astrologers, and astronomers who would have normally taken on the task. Why study about something that had already been explained? Why should you question one of the greatest scientist of all time? So it seems that a lack of interest in the topic was one of the main reasons why there was not much change in cometary science for almost 2000 years. Inquiring minds had simply become complacent, and there was basically no real incentive to for anyone to prove the dominant paradigm wrong. So what implemented the decomposition of the dominant paradigm? Well, like many things in history, it appears that important discoveries must take place which point people in the right direction. Something to spark their interest and curiosity enough to challenge the ideas and thoughts of the times. This is exactly what was begging to occur in the late 1400’s thru the late 1500’s. Starting with one simple discovery, then by another larger one, and then by another larger one. You get the point. There was basically a lot of discovery going on in the world of astronomy during this time which required people question the basic assumptions and theories of the world around them. Eventually all of these questions and discoveries lead to the development of a whole new way of looking at cometary science.

The first of these important discoveries occurred in 1472 when a man by the name of Johannes Muller (also known as Regiomontanus) attempted to systematically measure important aspects of the comet of 1472. He carefully measured the diameter, position, length, and thickness of the tail of this comet However, the methods he used were not good enough for him to prove much of anything. Nevertheless, his contribution is important because it was the first time that anyone really applied a systematic approach to classify, categorize, and study cometary phenomena.

The next important discovery that would bear some importance was an observation made by two people: Jerome Frocastor and Peter Apian; in the 1530’s. While observing a comet in 1531 (an appearance of what would later be known as Halley’s comet) both of them curiously enough noticed that the tail of the comet always pointed away from the sun. They compared this to observations made on earlier comets and found that the tail of comets always pointed away from the sun. What made the tail always point away from the sun? This seemed a little bit odd. Although they were not the first people to ever observe and notice this phenomena, they were contributors just as much, because they let the idea be widely known that the sun had some kind of effect on cometary behavior.

The first two discoveries that we have talked about thus far were very important to the betterment of cometary science. However, sometimes it takes a revolutionary idea to get people to disregard the previous way that they looked at comets. This was the kind of idea is what Nicholas Copernicus had been brewing up. In the 1540’s Copernicus came up with one of the most profound and important discoveries which really came to shape astronomical as well as cometary ideas. He was the first person to prove using systematic methods that Ptolemy’s model of the earth being at the center of the solar system was in fact false. Copernicus contended that the sun was at the center of our solar system. This was revolutionary at the time because no one had ever been able to prove that Ptolemy was wrong. As you can imagine this created quite a stir in the astronomical circles because if Ptolemy was wrong about the nature of our solar system; Then what other assumptions and notions of humankinds knowledge of the nature of the heavens could be wrong? Unfortunately, Copernicus like most revolutionaries, never lived to see the day when his thoughts were accepted. For he died on the same day that he received a copy of his greatest work On the Revolution of the Celestial Spheres, in 1543. It would take almost another century before his ideas were accepted by the majority of the educated populous. However, soon after his death, there would be a huge leap in the knowledge of cometary science.

The next big leap in the knowledge of cometary science took place in 1572 when Tycho Brahe, a man known for his keen observational skills, discovered the birth of a new star (which we now call a supernova). This was an important discovery because it shattered the notion that the heavens never changed. His observation proved that the heavens were dynamic in nature, and that there was room for change in the heavens. It may not seem like much, but combined with the idea of Copernicus, it was starting to appear as though many of the assumptions of ancient astronomers were wrong. However, this was not Tycho Brahe’s greatest accomplishment by far. After viewing and observing the comet of 1577, Tycho noticed some unusual things which didn’t seem to mesh up with Aristotle’s view of the heavens and comets. In1588 he published his work called De Mundi Aetherei Recentioribus Phaenomenis. In which he mainly questioned Aristotle’s notion that the heavens never changed. Secondly, he questioned Aristotle’s ideas that comets were “atmospheric objects”. So finally, curiosity got the best of Tycho, and he decided to use a “parallax” method to measure the how far the comet was from the earth. His conclusion was that the comet was much farther from our atmosphere than Aristotle could have ever dreamed. In fact, Tycho calculated the distance of this comet to be about 1 million km from earth. Finally, proof that comets were indeed true celestial objects existed. This was the final shake up which crumbled Aristotle’s theory that comets were “atmospheric objects” to the ground, and gave way to an entirely new way of thinking about comets.

By the early 1600’s the ideas and notions of comets and the heavens had changed significantly. Among the two most profound newly accepted ideas were: 1) Comets were now known to be celestial objects. And 2) The heavens were dynamic (that is, changes could take place). With all of this in mind, you must imagine that the world was a pretty exciting place at this time. The heavens were being opened up to reveal mysteries which had been concealed since the beginning of humankind. Was the world ready for more revelations? What new discovery would reveal the next great mystery of the heavens? We can only imagine that this is what went through the minds of the astronomers, mathematicians, philosophers, and poets who pondered some to the worlds toughest questions in the early 1600’s. In relation to cometary science, we know of one person who was especially hard at work to solve yet another mystery of the comet.

Johannes Kepler came of age in the early 1600’s and was a “fan” of Tycho’s work. Kepler was also very confident in Tycho’s observations, measurements, and his accuracy. Thus he used many of the same methods that Tycho used to figure out how planets orbited the sun. After working really hard and long, he finally came up with an answer that the planets orbited the sun in an elongated pattern which best resembled an ellipse. However, his work wasn’t done there. He went on to create two scientific laws which could be used to predict the orbits of the planets. 1) The “Laws of Areas” which states that the line from a planet to the sun sweeps out in equal areas in equal times; the plants move faster when nearer to the sun (Whipple 26). 2) The “Harmonic Law” which states that the squares of the periods of the planets are proportional to the cubes of the long axes of their ellipses (Whipple 26). These two laws along with another, were very important indeed, because they are the “rules” which govern Copernicus theory that the planets revolve around the sun. The laws of Kepler then, simply complement the model of Copernicus —giving it more meaning that ever before. It is also an interesting tidbit to know that although Kepler developed these “laws” which govern planetary motion, that he was somewhat reluctant to apply the same rules to comets. In fact, he thought that comets were kind of “straywanders” which traveled in a straight line. It is kind of ironic, because as it turns out, Kepler’s two laws would some day help another famous scientist predict the return of the first comet.

Another man who was equally important and influential during the 1600’s was Galileo Galilei. His discovery and experiments with falling bodies concluded that there was a force called “friction” which impedes an objects motion. This would later become an important input into another theory which was not far down the road. Also, one of the most significant of Galileo’s accomplishments was his construction of a primitive “telescope”. Although he did not invent the telescope (which is a common myth) he did greatly popularize it’s use after he used it to look at the moon and other planets. He discovered that these objects were not perfect as they were said to be by the ancients. And yet, another mystery of the heavens revealed had been revealed.

Construction: The Foundation Of Modern Cometary Physics

During the late 1600’s to begging of the 1700’s the construction of the foundation of cometary physics was under way. The former dominant paradigm of the ancients had been crushed and room had been cleared for new ideas and theories. However, much was still unknown, and furthermore, it takes time for the great ideas of the resent past to digest properly.

The first inroad which made a lot of the transformations possible during this time would have to be attributed to the advent and wide spread use of the telescope. By far this was the biggest advancement in both astronomy and cometary science. The telescope allowed people to see things which could have never been seen with the naked eye. This tool forever changed the face of astronomy. And it forever changed cometary science, because it finally allowed astronomers to get a good look at these celestial objects. Making the study of comets easier and more fun than ever before.

With the birth of a new paradigm on the horizon, there were still many mysteries of comets. Furthermore, some important aspects of the their behavior were yet unknown. Namely, there seemed to be something major missing. Something “unknown” which could shed some more light on the subject of cometary science. Sir Isaac Newton was the man with that missing piece which filled in the gaps. Among his greatest discoveries were the laws of motion and gravity. These ideas were published in a work called Principiain 1687. Principia was for the most part complementary to both Copernicus and Kepler’s previous work. The thing that made this revolutionary was the fact that Newton’s concept of gravity was the only thing that was missing to complete the mystery behind the movements of planetary objects. Once Newton introduced this, he stated that if these law and rules applied to the planets, that there should be no reason that they cannot apply to comets as well. One of the most extraordinary things that Newton accomplished was the tying together of his ideas with Kepler’s and Galileo’s. His method of deduction was very slick. Starting with Kepler’s laws of planetary motion, he noted that a force is directed at the sun and that it varies as the inverse square of the distance (Whipple 35)—Which was his universal law of gravitation. There was a complement, and his ideas seemed to mesh with Kepler. However, Newton’s idea spawned from Galileo’s theory that bodies can move freely in space (Whipple 35). Wow, that is a lot to comprehend—This is exactly what most people thought in the early 1700’s. Even the best scientist were skeptical because it is very hard to fully understand. So to sum it all up, Newton’s theory was basically the foundation for modern cometary physics.

Newton, as strong and wise as he was needed a little more help to secure a foundation for this newly emerging paradigm. It just so happened, that while he was working with Edmond Halley to publish his works, that Halley became interested in trying to figure out the orbits of comets. Halley dug thru many records of comets of the past, and noticed that there seemed to be some sort of pattern. In one particular case, it became more than apparent that this one comet in particular, seemed to be visible every seventy-six years or so (plus or minus a few). Why could this be Halley wondered? And his answer was not far off. Halley barrowed and idea from his colleague, Sir Isaac Newton. If Newton’s law of gravity was correct, there might be some kind of force which is exerted on the comet as it passed Jupiter and Saturn which would account for the slight variations from each apparition of the comet. Taking a chance, from what he had deducted from all of the evidence, Halley made a bold prediction that the comet would return in 1758. Sure enough, on Christmas in 1758 the comet was sighted in the skies over Dresden, Germany (Brandt, Chapman 18). Thus we have an instance of the first successful prediction of the return of a comet. All of which was made possible from the wealth of knowledge which was built upon since the begging of the late 1400’s. So here we have the foundation upon which modern cometary science is based.