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 5th
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 12th
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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