Saturday, July 5, 2014

A History of Cosmology: Prehistory to Present

Ever since the dawn of human consciousness, it is an undisputed fact that people have been looking up to the stars with inquiring minds. Evidence for this comes in the form of primitive artwork, which depicts, among other things, the stars. Further proof of this obsession with the sky comes in the oral legends of people all over the world, which often use the stars to try and explain the world. In time, this curiosity about the stars would transform itself outright into organized religion.

So, why did humans care about the stars at all?.

Answer: the stars move with a regularity that does not change over the course of years and could be used to foretell the seasons, which were very important to early humans, whether they be hunter-gatherers or farmers. In a world fraught with danger, early people undoubtedly took comfort in this regularity. Naturally, not everyone would notice these cosmic patterns to existence but the people who did could amass a huge amount of power for themselves by their apparent skill in being able to 'predict' the seasons and thus the weather. By being able to forecast the seasons, these early astronomers would have become very respected for their skill. However, not being content with being the world's first weathermen, the early astronomers started inventing myths about the stars in order to explain the natural world, which made for great fireside tales.

With the coming of agriculture, stories such as this would come to serve as the basis for religion that would be used by the few to control the many.

In around 5,000 B.C., give or take a few thousand years depending on location, settled agriculture developed and the old hunter-gatherer way of life came to an end for many as farming now became the primary way to make a living. With the advent of farming, the entire way of life for people changed as timekeeping became a true obsession because determining the proper times to plant and harvest crops was, literally, a matter of life and death. With the dependency on farming also came an obsession with weather, which could help or hurt the harvests.

No one knows when the first god-sky association was made, but with the rise of civilization and writing in around 3,000 B.C., the organized religion centered on the sky could now be documented.

It is an almost universal idea that people believe God/the gods come from the sky. On the surface, this commonality among cultures completely unknown to each other seems puzzling. However, with some rational thought, the reason becomes obvious: the ancients were so orientated on the stars and the people who could seemingly predict the future that the stars became an object of worship. Think about it: ancient humans had very little control over their environment. So, with the discovery that the appearance of a given star or pattern of stars would herald, every time, some kind of natural occurrence that was advantageous to humans, it was, following the logic of our ancestors, only natural that the stars had some influence over what was taking place on Earth.

Around 3000 BC as the Ancient Egyptian civilization was coming into being, the stories that would come to make up Egyptian mythology were also being recorded in writing for the first time. For the Egyptians, the most important tale was the legend of Isis and Osiris. In a time that was probably more remote to the Ancient Egyptians than Ancient Egypt is to us, there was a time when the gods ruled here on Earth. In this time, a brother and sister served as king and queen of Egypt. Osiris was a just and popular king who was loved by all his subjects, save his jealous brother, Set. In time, Set murdered Osiris, cut his body into pieces, and cast them into the Nile. Being a dutiful wife. Isis went around Egypt and gathered the pieces of Osiris, bandaged them together (hence the origin of mummy wrappings), and briefly resurrected her husband on Earth before he became ruler of the Underworld, the land of the dead.

Okay, so what?

At the same time, the Egyptians noticed a curious coincidence. Every year at the start of summer (this no longer takes place thanks to precession), the bright star Sirius rose just ahead of the Sun. Shortly thereafter, the Nile would flood, bringing rich silt to the Egyptian fields, replenishing nutrients in the soil and thus ensuring a good harvest for the next farming season. Essentially, this flood would resurrect the land, which was barren and dry beforehand. Rising just ahead of Sirius was the man-like constellation of Orion, which the Egyptians also recognized. In time, Sirius would come to be associated with Isis because its helical rising would coincide with a resurrection of the land, similar as to what Isis did for her murdered brother/husband. Orion? That's an easy one, the Egyptians associated Orion with Osiris.

As time progressed, with the powers of the star gods expending all the time, the priests came up with the idea that the gods needed to be pleased through prayer and sacrifice. However, what seemed like a miracle to the masses was nothing more than nature taking its course. So, when the Mesoamerican cultures would start sacrificing to the gods upon the helical rising of the Pleiades in the hope for rain, the rain would always come but not because the star gods were pleased, but that every summer is the rainy season in the region. The priests knew this cosmic coincidence would happen and played the part to the hilt. In time, the people became so convinced that the sacrifices had everything to do with the coming of the rain that they would not dare stop listening to the priests and offering up the sacrifices. Playing their part, the priests would often demand more sacrifice, thus instilling fear in the populace while increasing their own power.

Needless to say, this vicious cycle would continue to repeat itself until the advent of science or the change of climate.

By 600 B.C. in the Western world, every major culture had either mythology or full-blown religion focused on the sky to explain the world. With this universally-accepted idea that the stars were divine, it seemed very unlikely that this belief system would ever be challenged, especially in a place so imaginative in its myths as Ancient Greece. Yet, that is exactly what happened in the 500s B.C.

In the mid 500s B.C., Greece, or rather the Greek culture as represented by the city-states, was on the rise. In this early part of their history, the Greeks were not powerful beyond their localities, with the dominant power of Persia ever threatening their very existence. Naturally, living in such a dangerous world, the Greeks had to use their minds to make a living. It was an offshoot of this need for practical knowledge that the Greeks became the first people to embrace the scientific method as we know it today.

So far as we know, the first Greek scientist was a man named Thales who lived in the city-state of Miletus, located in modern Turkey. Thales was every bit of what we could call a “renaissance man” in that he was not only familiar with many fields, but an expert in them, too. In his life, Thales was a traveler, merchant, philosopher, historian, mathematician, and scientist. The knowledge of Thales was so great that he is considered, along with the great law giver, Solon, to be one of the legendary Seven Sages of Greece. The scientific theories and accomplishments of Thales were revolutionary, not so much for their being right, but for the fact that he was, so far as we know, the first person who attempted to explain the world without invoking the gods.

Also from Miletus was Anaxamander, a contemporary and student of Thales. Taking his teacher's ideas of the universe as a naturally-occurring creation, Anaxamander further demythologized the heavens by suggesting that the objects that we see in the sky were not gods, but physical places. So far as we know, Anaxamander was the first man to believe that Earth floated freely in space, that the rising of of the heavenly bodies was caused by their motions, and that the celestial objects were wheels with holes that allowed the light contained within to escape.

Rounding out the great trio of scientists from Miletus was Anaxamenes, a student of Anaxamander. While Anaxamander was the first man to suggest that the heavenly bodies we see in the sky were physical places, Anaxamenes was the first man to propose a coordinated, rational system describing the way in which the universe works. At the time of Anaxamenes, the universe consisted of the 5 naked eye planets, the Sun, Moon, and Stars. Through observation, Anaxamander reasoned that the Earth was at the center of this system and orbited by the Moon, Sun, and planets with the stars being farthest away, fixed like lights on the inside of a spherical vault. This basic idea of celestial spheres would go on to be refined and expanded upon for hundreds of years.

 In the late 300s B.C., Eudoxus refined the model of the solar system to a new level of sophistication, or cumbersomeness, your call there. In the model of Anaxamenes, the Earth was at the center and was orbited by the planets with the stars lining the inside of a spherical vault. However, in its simplicity, the old model of Anaxamenes failed to address some undeniable observations about solar and planetary motion. First, while the Sun moves through the sky from East to West, it also moves along the Zodiac. Why was that? Also, planets appear to slow, stop, reverse course, move backwards, stop again, and continue in their forward motion. Why could this be? These are the two questions Eudoxus sought to answer.

In explaining the seemingly inexplicable motions of the stars and planets, Eudoxus set them on multiple celestial spheres. Starting with the stars, whose motions were easiest to explain, Eudoxus set them on a single sphere that rotated from East to West once per day, easy enough. However, this simplicity wouldn't last long. The Sun, besides moving across the sky once a day, also moves through the Zodiac once per year and both of these motions had to be rectified in the model. So, to explain why the Sun does what it does, Eudoxus set the Sun on two spheres, one moving East to West once per day and the other going Eastward once per year to account for the movement through the Zodiac. Sound confusing? It gets better. The planets need four, (yes, four) spheres. Sphere 1 rotated Westward once per day for the daily motion of the planet. Sphere 2 rotated Eastward once a year to account for the planet's motion through the Zodiac. Spheres 3 and 4 were slightly inclined to each other and were used to explain retrograde motion of planets, which occurs in an elongated figure 8 motion if observed carefully. In retrospect, this model was needlessly cumbersome and failed to account for the sometimes very obvious change in planet brightness. However, at the time, it was the best thing going. 

The next great thinker in Western astronomy was Aristarchus of Samos, who lived from 310-230 B.C. Besides being an astronomer, Aristarchus was also a mathemitician and, so far as we know, the first man to try and measure the distances to the heavenly bodies, namely the Sun and Moon. Problem: no one knew how big the Earth was at the time. So, while Aristarchus used sound geometry, his incorrect assumed size for Earth resulting in his computations of distance being way off the mark. However, if Aristarchus had been lucky enough to known the sizes of the heavenly bodies, he would have been right on the mark.
However, while Aristarchus was the first man to try and find the distances to the heavens, his major achievement was that he was the first man to reason that the Sun, not the Earth, was at the center of the solar system. Sadly, no original works of Aristarchus survive, only mentions of his ideas by later writers. How thrilling it would be to read Aristarchus and discover his reasoning process that led him to discover how the solar system really worked. A start is with geometry. Thanks to later writers, we know that Aristarchus calculated the Sun to be about 7 times bigger than the Earth. So, as a start, Aristarchus may have reasoned that it made no sense for a giant Sun to orbit a tiny Earth. To finish his model where the Sun, not the Earth, stood at the center, Aristarchus argued that the motion of the sky was only apparent, caused by the motion of the Earth turning on its axis once a day. However, save Seleucus of Seleucia, the ideas of Aristarchus met a wall of resistance.
First, if Earth moved, why wasn't there a great wind caused by it speeding through the heavens? Second, if Earth rotated on its axis once a day, why do falling objects still land directly under from where they fell and not to the West? However, the third argument, the unchanging nature of the stars, was perhaps the most compelling. If the Earth moved and the stars remained still, according to mainstream Greek thought, two things should happen: first, the stars should move relative to each other (stellar parallax) and change in brightness as the Earth moved around the Sun. Unfortunately, the critics of Aristarchus never considered the idea that the stars could be almost infinitely far away, thus negating both stellar parallax and brightness changes. 

Going back a few centuries to Eudoxus (and discounting the ignored correct model of Aristarchus), the picture of the solar system hadn't really changed in several centuries despite the fact that the Eudoxus model was extremely complex to say the least. With Ptolemy, who lived from 90-168 A.D., what would be the final word on the solar system for nearly 1,500 years in the Western World would be written. Taking the failure of Eudoxus to explain the brightness change of the planets and the overall cumbersomeness of his model, Ptolemy streamlined the solar system and explained planetary brightness change in a single stroke. Like Eudoxus, Ptolemy put the Earth at the center of the solar system. Outside, the Moon was put in orbit around the Earth with the planets and Sun (in correct order) outside the Moon. Result: a much simpler, easier to understand model of the solar system. Now, as for the planets' change in brightness, Ptolemy solved this by adding epicycles to the orbits, which explained both retrograde motion and brightness changes at once. The system was so well received that was accepted without challenge for nearly 1,500 years. 
After Ptolemy, the Greco-Roman civilization would start into its long, slow decline thanks to political and then religious instability. In 180 A.D., Marcus Aurelius, the last of the 5 Good Emperors, died, leaving the throne to his mad son, Commodus, the first in a pretty much unbroken string of lunatics to rule Rome. At the same time that the secular government was going to pieces thanks to reckless spending, corruption, and murder, the religious fabric of the Roman Empire was being torn to shreds as the Christian Church started making inroads against the old Pagan faith. In time, Christianity would win out and, in order to consolidate their religious power, Church leaders did everything they could to stamp out Pagan culture, which included the free, inquisitive spirit that inspired the Greeks to set out to try and understand the world way back in the 6th century B.C., starting with the Ionian scientist Thales of Miletus. With the collapse of the Western Roman Empire in 476 A.D., the Catholic Church was unrivaled in power and, with eternity at stake, no one dared question Church position on anything, including the cosmos, which the Church deemed to be centered around a flat Earth that never moved and populated by a collection of perfect, unchanging heavenly bodies.

For the next 1,000 years, the center of scientific inquiry would move East.

The only reason we know anything about the Classical astronomers is by the efforts of Eastern scholars, the Byzantines and Arabs, who copied the ancient scientific literature (Byzantines) and later translated it (Arabs). Result: the knowledge of the ancients was preserved for posterity. Needless to say, we owe a great thanks to these Byzantine and Arab scholars for their efforts. With the old knowledge at their fingertips, Eastern astronomers would expand upon it to refine our understanding of the universe.

From the 5
th to 11th centuries, while Europe languished in its millennium-long, dreamless sleep, various Byzantine and Arab astronomers re-examined an old idea that had largely been ignored in the West: a heliocentric solar system.

First proposed by Aristarchus of Samos in the 200s B.C., the heliocentric model was discounted for some very practical objections. First, if Earth moved, why wasn't there a great wind caused by it speeding through the heavens? Second, if Earth rotated on its axis once a day, why do falling objects still land directly under from where they fell and not to the West? However, the third argument, the unchanging nature of the stars, was perhaps the most compelling. If the Earth moved and the stars remained still, according to mainstream Greek thought, two things should happen: first, the stars should move relative to each other (stellar parallax) and change in brightness as the Earth moved around the Sun. Unfortunately, the critics of Aristarchus never considered the idea that the stars could be almost infinitely far away, thus negating both stellar parallax and brightness changes. 

Nasr-al Din al-Tusi

In the 1200s, astronomer Nasr-al Din al-Tusi came to the realization that there was no more empirical evidence supporting the centuries-old idea that Earth was at rest than there was for the Earth being in motion. Now, while not a heliocentricist, per-se, al-Tusi did show that the arguments for the geocentric system, namely those voiced against Aristarchus, were, at the time, just as impossible to prove as those for a moving Earth. In the1400s, another scholar, Ali Qushji, would again reiterate this point of view.

During this time, other Islamic scholars were thinking far beyond the solar system.

In the 12
th century, Fakhr al-Din al-Razi became, so far as we know, the first man to raise the possibility of the plurality of worlds and multiple universes. More atheologian and philosopher than an astronomer in the true sense of the world, al-Razi based his argument for a plurality of worlds and a multiverse on a verse in the Koran, holy book of Islam, which read, in part: “ "All praise belongs to God, Lord of the Worlds." Writing in his book Matalib al-'Aliya, al-Razi states that “it is established by evidence that there exists beyond the world a void without a terminal limit, and it is established as well by evidence that God Most High has power over all contingent beings. Therefore He the Most High has the power to create a thousand thousand worlds beyond this world such that each one of those worlds be bigger and more massive than this world as well as having the like of what this world has of the throne, the chair, the heavens, the earth, the sun, and the moon. The arguments of the philosophers for establishing that the world is one are weak, flimsy arguments founded upon feeble premises.” Basically, al-Razi stated that beyond the known universe, there exists an infinite expanse of space, which God has the power to fill as He desires. Yes, while the impetus behind his idea was clearly not one based on science, al-Razi's theory of the true nature of the universe has proven to be closer to fact than one would expect for a theory beginning with theology.
For all of their efforts, all of these Eastern scholars are largely forgotten today thanks to a quirk of history. The Byzantine Empire (also known as the Eastern Roman Empire), which was instrumental in preserving the knowledge of the Western Greco-Roman world, was also the political continuation of Rome itself, flourishing for another 1,000 years after the 476AD fall of the last Western Roman emperor. However, as is the case with all great empires, they must fall. In the year 1453, its influence stretching little more than the walls of Constantinople itself, the Byzantine Empire fell to the Ottoman Turks.

With the fall of the Byzantine Empire, all of the learning began by the Greeks and continued through the Byzantines and Arabs came flooding out along the trade routes and to Western Europe. Additionally, another, more practical reason to care about astronomy came about thanks to the fall of the Byzantines: money.

For centuries, the Western European nobility had an insatiable appetite for goods from the Far East. Needless to say, traveling from Western Europe to China was a very expensive undertaking as such mercantile operations would take years from start to finish. Result: by the time the intrepid merchants returned to Europe, goods that could be acquired in China for a given price could commonly increase a hundred-fold in Europe thanks to both all the time, effort, and money put into making the trip as well as thanks to the law of supply and demand, which had rich aristocrats paying ridiculous prices to get small supplies of rare goods.

Cue the Turks.

The Turks, in addition to being conquerors, were saavy businessmen. One reason the Byzantine Empire lasted so long was thanks to the immense amount of trade coming through its capital of Constantinople, located on the Bosphorous Strait, which separates Europe and Asia. Throw in Africa and what do you get? A 3-way crossroads of the known world that became a mandatory way station for anyone and anything traveling from one continent to another. Realizing the strategic importance of their new capital, the Turks decided to make some money by dramatically hiking the fees to procure safe protection through the Ottoman Empire for travelers on their way to China.

Result: Western European monarchs did the math and came to the conclusion that, in the long run, it would be more cost-effective to find a new route to Asia than pay the outrageous prices the Turks were charging for guaranteed safe passage through their territory.

With their new-found impetus for exploration,
Europeans discovered a rather perplexing problem: all of the Byzantine/Islamic start charts showed the stars positioned differently than the European ones, (which turned out to be in error). The question of why the stars on the European charts were incorrectly placed (precession and the lack of Europeans' updating their charts for 1,000 years is why) was the spark that reignited long-suppressed curiosity of European intellectuals.
In the 1400s, sailing ships were like spacecraft are today. When a sailor left home port, he was, in effect, sailing to an uncharted new world far beyond the help of his home country, much the way astronauts in space do so today. In crossing the oceans to journey to distant lands, sailors might as well have been sailing to Mars. At the time, finding longitude was the biggest navigational challenge. Latitude was easy, simply look at what Northern stars you could see in a given location to tell approximately how far you had gone. Longitude? Well, that was tough. Traveling East-West had no easy answers, except, quite possibly, in the stars and in more accurate methods of timekeeping. With rich nobles wanting their exotic spices and fine silks, science, specifically astronomy, finally had a practical application.
At the same time, the Black Death was raging through Europe. First hitting in the “great mortality” of 1347, the Black Death would wipe out about a third of Europe's population in the years 1347-1352. While such a terrible, gruesome disease in itself would have been horrifying enough to an ignorant populace, the fact that the all-powerful Catholic Church could not do a thing to stop its spread increased the already terrible feelings of helplessness. When watching so many die and nothing being done to halt the spread of death, faith in the Church was shaken. Perhaps the Catholic Church that had dominated European life for 1,000 years wasn't so powerful after all.

In time, these three things, exposure to intellectual achievement, the collapse of Byzantium, and the loss of faith in the Catholic Church would lead to the Renaissance, the rebirth of Western Europe.
The first great astronomer of the Renaissance was Nicolaus Copernicus (1473-1543), who is widely considered to be the first great astronomer since antiquity (never mind those now-forgotten Eastern scholars) because it was Copernicus who proposed the idea of a heliocentric, or Sun-centered, solar system. Being a clergyman, Copernicus undoubtedly realized the offensive nature of such an idea (the Church favored the geocentric model) and thus waited until the end of his life to publish his book, On the Revolutions of the Heavenly Orbs. Copernicus himself received the first printed copy on the day he died.

In analyzing Copernicus, he had some important motivations for developing his heliocentric idea. First, Ptolemy's geocentric solar system was complicated and it was often at odds with observations. When it came to arguing for heliocentricism (and perhaps avoiding getting himself into trouble), Copernicus didn't flat out say that he was right and his opponents wrong, but that his theory was just that, a theory, and one that couldn't be proved or disproved any more than geocentricism. Unfortunately, just like with Aristarchus 2,000 years before, critics came out of the woodwork to argue against Copernicus. The fact that Copernicus himself was dead by the time his book was printed didn't help matters, either.

 The next great astronomer of the European Renaissance was a Danish nobleman named Tycho Brahe. Using his money to his advantage, Brahe built a permanent observatory filled with the world's most precise instruments, which he then staffed with trained assistants. Result: Brae is estimated to have collected 10 times the data of all the astronomers who lived before him, combined. Single-handedly, Brahe corrected the error-ridden astronomical charts compiled by previous generations of astronomers in a career that mared the pinnacle of pre-telescopic astronomy.

At the same time that Brahe was measuring the heavens, the next great astronomer, Johannes Kepler, was just getting his career started. Despite astronomy not being his profession (he was a math teacher), Kepler wrote a book on the topic, specifically planetary orbits. This work attracted the attention of many astronomers, including Brahe, who invited Kepler to join his staff.
Brahe was an astronomer, not a mathemitician, and he knew that he needed Kepler's mathematical genius to make sense of his volumes upon volumes of data. At the same time, Kepler knew he needed Brahe's data if he were to make any discoveries about planetary orbits. Unfortunately for Kepler, Brahe, probably rightly so, regarded his observational data as his life's work and wasn't about to start giving it out freely. Between the time he joined Brahe's staff in 1599 to the time Brae died in 1601, Kepler almost quit his position several times over frustration about not being granted access to the volumes of data Brahe had compiled in over 30 years of observations.

After Brahe died, though, Kepler would be appointed to Brahe's position of Imperial Mathemitician, which thus granted Kepler access to all of Brahe's data. Eagerly plunging into his work, Kepler immediately came across problems, specifically that the observational data could not be reconciled with planets having a circular orbit, as proposed by Copernicus. In the time that followed, Kepler tried various models for planetary movement in the hope of finding one that would fit the observations. Try as he might, Kepler just couldn't reconcile the models to the observations, especially in regards to the planet Mars, which exhibited the greatest irregularity in its orbit.. Finally, in desperation, Kepler, a deeply religious man who sought to find proof of a divine blueprint for the solar system, gave up the perfect circles that had so dominated astronomy for centuries. Upon calculating the orbits of the planets as ellipses (slightly elongated circles) the observation and theory finally agreed. It was this discovery that planets' orbits ere elliptical that inspired Kepler's 3 laws of planetary motion.

Law 1: All planets move in elliptical orbits with the Sun at one of the foci.
Law 2: All planets move through equal areas of space in equal times ()basically, planets move faster when closer to the Sun and slower when farther away).
Law 3: A planet's period of orbit is proportional to its distance (orbital period (in years) of the planet squared equals the semimajor axis (in AU) cubed). This discovery showed that there was some common force governing planetary motion (this force is gravity, but Kepler didn't know this yet).

Unfortunately, try as he might, Kepler, while he could explain “hows” of planetary motion, he couldn't explain the “whys.” This task would fall to the man whose ideas would be the final word in physics for 200 years.

 The story of Issac Newton is both a story of outright genius and pure luck. His intelligence recognized from an early age, Newton was sent to Cambridge University in order to get a college education, then in itself a rarity. In 1665, one of history's great ironies struck: the Plague arrived in London and Cambridge was shut down for the year, thus interrupting Newton's studies. Returning home, Newton allowed him mind to roam free. It was during this unplanned vacation that Newton invented calculus, discovered the laws of motion, and made fundamental discoveries in optics, all of which may have never happened had the Plague not struck and Newton had remained preoccupied with his formal studies. 

In his definitive work, the Principia (Mathematical Principles of Natural Philosophy), Newton laid out his three laws of motion that explained all motions in the universe. The laws are as follows:

1. Inertia: objects at rest remain at rest and objects in motion remain in motion unless acted upon by an outside force.
2. Force: forces act on an object, cause chances in acceleration (here used to den

3. Reaction: for every action, there is an equal and opposite reaction
Also, the law of universal gravitation was shown mathematically for the first time.
Long story short, after doing a lot of calculations, Newton found that his laws of motion perfectly explained the motion of the planets that Kepler so accurately described, but could not explain.

Overlapping Kepler and Newton, the fourth great figure in Renaissance astronomy was taking a more practical approach to science.

Like his contemporary Johannes Kepler, Galileo Galalei was drawn to astronomy through mathematics. Unlike Kepler, who was motivated by a purely intellectual desire to discover, Galileo's initial motives were financial. Despite its high prestige, the position of university professor was not the best paying job in the world and Galileo was short on money and saw what he hoped would be a financial savior in a new invention called the spyglass.

Invented by an unknown Dutch lens maker who discovered that great magnifications could be achieved by the right pairing of lenses, the spyglass was the father of the telescope. Being a mechanical mind, Galileo resolved that, if he could get a spyglass and improve the design, he could make a lot of money by selling his design to the military. Well, Galileo did get a hold of and improve upon the spyglass, but his legacy would be far more than as a salesman.

Being naturally curious, Galileo gained worldwide fame for the fact that he was first to turn the improved spyglass, now dubbed the 'telescope,' to the sky, thus becoming the first telescopic, and thus modern observational astronomer in history. Finally, after centuries as a theoretical abstraction, the sky and the bodies it contained would become places. In his book, the Starry Messenger (written in the vernacular Italian, not Latin as all previous scientific works were), Galileo both forever changed the picture of the universe through undeniable visual observations and the way which people perceived science through writing in everyday language.

In the Starry Messenger, Galileo made several major discoveries. Starting with the least Earth-shaking, the Milky Way cloud transformed itself into rich fields of tiny stars, far more than the eyes could ever count. In the telescope, the stars looked the same as they did visually, with no details, which implied that Aristarchus and Copernicus were right, the stars were infinitely far away. Last, the angular sizes of the stars were greatly over-estimated by non-telescopic observers, including the great Tycho Brahe.

Galileo also discovered that the heavenly bodies were not perfect and unchanging. The Moon was found to have mountains, valleys, plains, and dark areas, hardly a perfect world. As for unchanging, Galileo found that the Sun was not some static, unchanging body, but a disc covered with dark sunspots that moved across the Sun itself. By watching the sunspots, Galileo deduced that the Sun spun on its axis about once a month.

When turning his telescope on Jupiter, Galileo found that the planet was accompanied by four tiny specks that moved with it through the stars, changing position relative to each other, but staying with the planet. It took no time for Galileo to realize that these tiny specks were moons, thus disproving the long-held idea that everything revolved around the Earth. However, this did not disprove geocentricicm because, although not everything orbited Earth, there was still no irrefutable proof that the Earth was a planet that went around the Sun.

Galileo's next discovery, the phases of Venus, provided such proof.

In a geocentric solar system, Venus would always be some sort of crescent thanks top the fact that the Sun orbited Earth with it. In a heliocentric solar system, Venus would go through a full range of phases, just like our Moon. Well, in turning his telescope on Venus, Galileo found that it did exhibit a full range of phases from a thin crescent to a nearly full disc (new and full are obscured by the Sun).
Now, these discoveries in themselves were disturbing enough for scholars and theologians but, to make matters “worse,” Galileo published all of these findings in the vernacular Italian, the language of the masses, rather than in Latin, the language of the educated. In doing so, Galileo became the first great popularizer of science, but the cost would, in time, be great.
When Galileo published the Starry Messenger, the Catholic Church, long the unchallenged, dominant religion of Europe, was in a bad way thakns to the Protestant Reformation, which had begun in 1517 when Martin Luther published his 95 Theses, which directly challenged the authority of the Catholic priesthood by stating the, at the time blasphemous idea, that salvation could be achieved through a personal relationship with God, thus negating the middleman that was the Catholic priest. Its authority challenged, the Church immediately clamped down on all teachings that ran contrary to Church doctrine, which included science.

Trying to avoid getting himself into trouble by openly professing heliocentricism (which the Church deemed heretical), Galileo proceeded to write the Dialogue, subtitled Concerning the Two Chief World Systems, the Ptolemaic and Copernican, which was published (also in the vernacular Italian) in 1632..
In the past when autocratic governments/religions were the norm, writing about controversial topics in the form of a dialogue (more accurately a debate) was a great way to avoid getting oneself in trouble, provided that the debate was actually balanced. Problem: Galileo's debate was anything but balanced, with the character supporting the Earth-centered model and using Church arguments even being named Simplicio (“simpleton” in Italian).

Needless to say, the Church wasn't happy and summoned Galileo before the (un)Holy Inquisition. Threatened with torture, Galileo, then 69 years old, confessed that his teachings had been in error and that he was guilty of religious crimes. The Church, in reality, came down rather lightly on Galileo, sentencing him to house arrest in his palatial villa for the rest of his life (they could have sent him to prison or, like Giordano Bruno, had him burned at the stake) and placed the Dialogue on the Church's list of forbidden books (where it would remain until 1822). While physically confined, Galileo's mind remained unfettered as he remained active in science for the remaining decade of his life.

It was only now between Newton's laws of motion and Galileo's observations that the heliocentric solar system proposed by Aristarchus of Samos in the 200s B.C. was proven to be true. However, science being a continuous process, it was only a matter of time before man would come to realize that there was much more to the universe than our immediate neighborhood.

Ever since the invention of the telescope literally opened up new views to the cosmos, astronomers had been studying a lot of objects that were previously unknown without optical aid. One of these newly-discovered celestial bodies were strange “spiral nebulae,” faint patches of light in the sky that seemed to be shaped like cosmic whirlpools. What were they? No one could say as there was no way to definitively examine them with the state of technology at the time.

However, that didn't stop people from floating explanations.

 Immanuel Kant, a German, was the first man to propose the idea that the spiral nebulae were, in fact, island universes outside pour own Milky Way Galaxy. When Kant first proposed his idea in 1755, he was building upon deductions based on other telescopic work that led him to, correctly, deduce that the Milky Way was actually a spiral-shaped, spinning collection of stars held together by gravity just like the solar system, but on a much greater scale. Kant further reasoned that the spiral would be seen as a band of stars in the sky from a vantage point from within the galaxy itself. Taking his speculation about the Milky Way farther, Kant reasoned that the spiral nebulae seen by astronomers were galaxies just like our own Milky Way, but unimaginably far away from us. 

The idea proposed by Kant would serve as a basis of debate among astronomers for over 150 years as the technology available from 1755 until the early 1900s was simply incapable of resolving the question about what the spiral nebulae actually were.

 In the early 1900s, a man burst onto the physics scene, virtually overnight, who, for the first time in nearly 250 years, ushered in a revolution that would represent the first overhaul of Newton's physics and, to this day, remain the model on which all current physics are based. This man was Albert Einstein. Much could be said about Einstein, but for the sake of brevity, we will focus purely on one of his seminal ideas: namely General Relativity, which had a direct bearing on our perception of the universe.

Already world-famous for, among other things, Special Relativity (1905), which had to do with WHAT, Einstein would later go on to to expand upon these ideas with his theory of General Relativity, which he published in 1915. In developing General Relativity, Einstein devised some equations, 10 of them, that explained the universe. These became known as the Field Equations for General Relativity and sought to explain how gravity works as a result of space-time being curved by both matter and energy.

Up until Einstein, it was almost universally assumed that the universe was static and infinitely old. However, upon the examination of Einstein's Field Equations, there was a problem: Einstein's equations indicated at a dynamic, rather than a static universe because it was determined that the force of gravity could cause a formerly static universe to contract upon itself. As great of a genius as Einstein was, he was not perfect. Unable to comprehend a contracting universe, Einstein inserted his “cosmological constant” as a perfect counterbalance to gravity in order bring the universe to rest and achieve a static universe.

At the same time, other scientists were using the same equations with the result being completely opposite. In 1922, Alexander Friedmann, a Russian who is largely unknown in the West, published a paper wherein his interpretations of Einstein's equations indicated not a contracting, but an expanding universe.

At the same time, technology was evolving to the point to where, for the first time, the distance to stars could accurately be measured. Result: any discoveries came in quick succession that, virtually overnight, reshaped our understanding of the universe as a whole.

By the early 1900s, astronomers finally had the capability to accurately measure the distance to the stars by way of a special class of star called a Type II Cepheid. What is a Type II Cepheid? It is a variable star whose pulsation period is directly proportional to its luminosity, which allowed it to be used as a “standard candle” to determine cosmic distances. With this newly-found capability, it was only a matter of time before the question of whether the Milky Way was the known universe or whether the universe extended far beyond would be answered.
That debate was settled in 1923 when Edwin Hubble started observing a prominent spiral nebulae in the constellation of Andromeda. Finding Cepheids in the nebulae, Hubble used the standard candle method to calculate its distance. Result: the nebulae turned out to be over 2 million light years distant, a distance far in excess of any star ever previously measured. Taking the same method to other spiral nebulae, Hubble was able to determine that these objects also resided at a previously unimaginable distance. Conclusion: the nature of the spiral nebulae was settled: the nebulae were, in fact, galaxies just like our own Milky Way. Needless to say, the universe had just gotten a lot bigger.

However, there was another unexpected finding: the light from this distant galaxy was shifted to the red end of the spectrum.

In 1927, a Western scientist, Belgian George Lemaitre, would independently come to the same conclusion as the Russian Friedmann: Einstein's equations hinted at an expanding universe. Additionally, Lemaitre would propose what was essentially the Big Bang Theory over two decades before the term itself was coined by Fred Hoyle. The following year, Howard Percy Robertson would propose the idea that the red-shift was directly related to the distance of an object.

Come 1929, Hubble would again make the headlines. Expanding upon his earlier work to measure the distance to the spiral nebulae, now confirmed to be galaxies separate from the Milky Way, Hubble sought to test the hypothesis proposing a direct relationship between red-shift and distance. In that year, Hubble, along with observatory assistant Milton Humason, would measure the distance to 46 galaxies. Result: the relationship between red-shift and distance was confirmed, which would lead Hubble to propose the Red-Shift Distance Law, now more commonly known as Hubble's Law. The law simply states this: the farther away the galaxy, the faster it is moving away from us.

However, for all the evidence supporting an expanding universe, some die-hard adherents to the Steady State Theory were unwilling to give up on their ideas. To make the Steady State conform to Hubble's findings, Steady State adherents came up with some interesting ideas to explain what Hubble found. first of all, the Steady State Theory evolved to include spontaneous creation, which is used to explain the perceived expansion of the universe. One claim made by adherents of the Steady State was more profound than all the others: if there was a Big Bang, where was the proof?

It was the inability to answer this question that would create a debate for the better part of 40 years.

 It was only in 1964 that the final nail in the coffin of the Steady State Theory would be smashed into place. Working out of Bell Labs, Arno Penzias and Robert Wilson were tasked with a job: measure radio waves bounced off of balloon satellites. To do this, Penzias and Wilson had to eliminate all background interference. To do this, they cooled the receiver to -269 Celsius, only 4 Kelvin above absolute zero. Unfortunately, for all this effort, Penzias and Wilson were unable to eliminate a steady, low-pitch noise of a wavelength of 7.35cm that persisted in the receiver day and night, no matter where the antenna was pointed. In order to make sure that something natural, namely something in the antenna, wasn't responsible for the noise, Penzias and Wilson cleaned out the antenna, but the noise persisted. 

Interestingly, it was only when a friend of Arno Penzias told him that a study into looking for cosmic background radiation from the Big Bang was about to get underway at Princeton that Penzias and Wilson realized the importance of their finding. In the spirit of scientific cooperation, Penzias and Wilson contacted the researchers at Princeton and invited them to examine their findings. Result: the findings of Penzias and Wilson perfectly fit the predictions of what the cosmic background radiation would look like as proposed in the Princeton study. In 1965: Penzias and Wilson published their findings jointly with the Princeton team. In 1978, Penzias and Wilson won the Nobel Prize for their efforts.

It was only with this discovery that the Steady State Theory was finally put to rest. However, the discovery of cosmic background radiation would raise even more questions, namely one of what was the ultimate fate of the universe.

Before that, though, let's examine what is now agreed upon:

All matter in the universe was initially concentrated in an infinitely dense area less than the size of an atom. At the Big Bang, this matter was blasted out in all directions, creating the universe and time as as know it, too. At creation, the universe was all hydrogen, with heavier concentrations contracting to form the first stars, which, through mutual gravitational attraction, gathered to produce the first galaxies. In time, stars exploded in supernovae, creating all of the heavier elements while providing the fuel for future stars. All the while, the expansion of the universe and time has continued to this very day.

As for the ultimate fate of the universe, it is now the main question asked by cosmologists. The key consideration: the tug of war between expansion and gravity. The hinge point: the density of the universe, namely whether gravity will overcome expansion, expansion over gravity, or neither. Note: the point at which gravity and expansion cancel each other is termed the critical density of the universe.

As of now, the three major theories about the ultimate fate of the universe are as follows:

1. The Big Crunch: The actual density of the universe is greater than the critical density. In short, there is more matter with mutual gravity in the universe than the expansion set in motion by the Big Bang will be able to overcome. The process: expansion of the universe will start to slow and will eventually come to a halt before reversing into a collapse wherein the gravity of everything contained within the universe will start attracting all the matter back unto itself. End result: the universe will eventually collapse into itself, eventually reaching a black hole-like singularity like at the point of the Big Bang. As an addendum, some theorists believe that such a contraction could result into another Big Bang, thus creating an oscillating universe.

2. The Big Freeze/Heat Death: The actual density of the universe is equal to that of the critical density. In short, the expansion set in motion by the Big Bang and the mutual gravity of everything in the universe cancels out the other. The process: expansion starts to slow and eventually comes to a stop. The process involving the births and deaths of stars continues to the point where the universe eventually becomes so filled with heavy elements (Iron and heavier) that stars no longer have enough fuel to form. The result: in time, all of the existing stars burn out and the universe goes cold, eventually reaching a temperature near absolute zero.

3. The Big Rip: The actual density of the universe is less than the critical density. In short, the expansion not only continues, but picks up speed over time. The process: expansion of the universe accelerates in an uncontrolled manner. The result: expansion eventually becomes so fast that the very atoms that create the universes itself will, at the last moment before the universe is destroyed, be ripped to shreds by the expansion.

What will happen?

As of now, it's hard to say. However, there is growing agreement based on the latest data that the Big Crunch/Oscillating Universe is looking more unlikely than it was seen to be in the past as current data suggests either a universe with density equal to (Big Freeze) or less than (Big Rip) critical density. On the other hand, as instruments become more precise and theories revised, this may change again in the continually-updating process that is science.

Bottom line: stay tuned . . .

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