Transcript The History of Astronomy

The History of Astronomy
Early Astronomers
The history of astronomy goes back several thousand years
ago. Almost all ancient cultures had stories about how the
universe was created, what it was like, who created it, and
how the earth and humans got here, but those stories are
usually not very believable. The early Egyptians believed that
the universe was a large rectangular box with Egypt at the
center of the bottom and with huge lamps which hung down
from the top for stars. The ideas of the other cultures which
were near Egypt usually had the same concept of an enclosed
space with that culture’s part of the world at the center.
One major factor holding the ancient cultures back from developing the
technology to look farther into the cosmos was their belief in many
unpredictable gods who controlled the universe. If the universe was
unpredictable because of gods, why try to understand it if what you
learned could become obsolete at the whim of the next god. The only
culture that worshipped one God who made a predictable universe at
that time were the Jews. The Bible, which came from that culture, later
had a profound positive impact on science.
Some of the astronomers in the ancient cultures kept records of their
observations. The Chinese have records going back to about the 1300s
B.C. By about 700 B.C., the Babylonians could predict certain heavenly
events. By about 600 B.C., the Greeks started to get interested in
astronomy.
The Greeks
The first ancient culture that usually comes to mind as being more
aware of the truth of their surroundings than other cultures of that time
period are the Greeks. In fact, our word astronomy comes from the
Greek words meaning "law and order". The Greeks were not the first
culture to try their hand at astronomy but the work of their
philosophers was widely distributed by the Romans and was the
accepted authority on that subject for hundreds of years. The Greeks
discovered that the earth was a sphere by several methods and the
philosopher Eratosthenes measured the circumference of the earth to
within about 300 kilometers of today’s generally accepted value. In
about 200 BC Aristarchus first stated that the earth revolves around the
sun but most philosophers argued that everything revolves around
earth.
There were apparently also some cultures about which we know little
who were interested in astronomy. Stonehenge and the various other
similar structures which appear to be ancient calendars are some
examples of monuments built by those groups.
Ptolemy
Around 150 A.D. Ptolemy (100?-165? A.D.), an Alexandrian astronomer,
invented the concentric system to explain the motions of the planets
around the earth. His work was the accepted authority on astronomy
until 1543.
To fully understand why some of the early modern astronomer’s ideas
were not accepted and why some of those ideas led the astronomers to
be ridiculed, it is helpful to have a background on what was happening
to the culture at that time.
For a time under the Romans, from about 300 BC to 476 AD, there was a
decline in the study of astronomy in favor of astrology and some of the
works of the Greek philosophers were destroyed.
Modern Astronomy
The modern history of astronomy starts in Europe in about 1300 AD.
Before that time, the Roman Catholic Church had been the dominant
religion in Europe and at times had more control over countries than did
the kings of those countries. The Roman Catholic Church started in
about 300 AD under the Roman emperor Constantine. Over time, the
popes started getting more powerful because of the fact they were the
heads of a religion followed by most of Europe and gradually replaced
the empire as the center of power. During that time, some of the popes
introduced some controversial beliefs to increase their power and the
popes and most of the clergy became corrupt. By the 1200s, it was
obvious that most of the clergy were more interested in gaining political
power than in helping the people spiritually.
In 324 AD, the Roman emperor Constantine moved the capital
of the Roman empire from Rome to the city of Byzantium,
present day Istanbul, and renamed it Constantinople. As he
built up his new capital, he collected and stored many of the
ancient writings of the Greek philosophers in libraries in the
city. In 395 AD, the empire split up into two parts. The eastern
half had its capital in Constantinople and was called the
Byzantine empire. The western half had its capital in Rome.
The church also split into two parts; the eastern half was
called the Eastern Orthodox Church and the western part was
called the Roman Catholic Church. Each church also had its
own pope and very different ideas. In about 476 AD the
western half of the empire was destroyed by the Visigoths,
Vandals, and other Germanic tribes.
Southern Europe was then plunged into what is now called
the Dark and Middle Ages, which was marked by frequent
wars and a lack of strong governments. During that time, not
much learning at all occurred and most of the population
lived under lords as serfs. The priests of the Roman Catholic
Church, however, kept education from dying out completely
during that time. The eastern empire stayed together for
another thousand years until 1453 when the Ottoman Turks
captured Constantinople. Before the Turks could capture
Constantinople and make it into Istanbul, however, most of
the population fled the city, taking with them the works of
the ancient Greek philosophers. As the knowledge from the
city spread throughout Europe, it helped start what is now
called the Renaissance.
The Renaissance
The Renaissance, which took place from the early 1300s to
about 1600, was a time in which people in southern Europe
began to learn, which had not taken place there much since
the western empire fell. As the people started to learn, they
saw the corruption of the Roman Catholic Church which led
them to turn away from it altogether and to start pursuing
the improvement of themselves with knowledge. They got
much of that knowledge from the monasteries of Catholic
Church which had preserved most of the books written before
that time.
Starting in the 1500s, the learning from southern Europe
began to enlighten the people in the north. In northern
Europe, however, when they saw the corruption of the
church, instead of turning away from the church, they tried to
reform it. This period is called the Reformation. During the
Reformation, people began to read the Bible for themselves,
which the Roman Catholic Church was supposed to be based
on, and found beliefs in the Bible which they thought were
contrary to the beliefs of the church. Some of these people
started the Protestant movement. Many thousands of people
were killed, usually being burned as heretics, because of their
belief in things which were contrary to what the pope, who
set the beliefs of the Catholic Church, said.
The Catholic Church was still very powerful and one of the beliefs
that the pope set is that the earth itself is the center of the universe and
that all other heavenly bodies revolve around it. This is the reason that
the church persecuted those who believed Copernicus’s ideas about the
sun being the center of the solar system.
The printing press was invented in the year 1430 which helped spread
information about all of the sciences. This made the common man able
to afford a book, which before then had to be handwritten and thus
were very expensive. By this time, most educated people were aware
that the earth was a sphere.
Copernicus
About that time a Polish canon of ecclesiastic law and astronomer
named Copernicus (1473-1543) began to wonder if there could be a
more aesthetically pleasing and reasonable arrangement for the planets
than the concentric system. He studies Aristarchus’s heliocentric ideas
and built a new system out of it. He developed a system where all of the
planets, including earth, orbit the sun and where each one of these
orbits was in the shape of a circle with the sun at its center. After almost
forty years of study, he published his monumental book On the
Revolutions of the Heavenly Orbs in 1543, the year he died. He was
never able to prove his ideas but later advances in physics would make it
possible to prove a version of those ideas.
Copernicus’s ideas were not perfect because, since he believed that
the planets move in perfect circles, he had to insert some epicycles and
other mathematical structures into his theory which made it about as
inaccurate as Ptolemy’s system. However, Copernicus’s theory was a
tremendous leap in astronomy.
The next person to make an advance in astronomy was Tyco Brahe
(1546-1601). With help from King Frederick II, he built an observatory
on the Island of Hveen that was equipped with the most accurate pretelescopic instruments for observing space ever built. He was able to
determine positions of objects to within one minute of an arc, far more
accurate than any previous attempt. Brahe constructed an
uninterrupted record of the positions of many planets and other bodies
for several years, but he did not accept Copernicus’s ideas. His idea of
the universe was a compromise, he believed that the five planets
orbited the sun, but the sun orbited the earth. He reasoned that the
motion of the earth would be felt and he thought that Copernicus’s
ideas were unscriptural.
Kepler
As the Renaissance was coming to and end, a German man named
Johannes Kepler (1571-1630), who believed Copernicus, started looking
at the records of Brahe’s observations. He discovered that none of the
ideas presented thus far about the motions of heavenly bodies lined up
to the evidence in Brahe’s records so he formulated his own ideas. After
seventeen years of work, he finally came up with the true motions of
the planets and published them in two books in 1609 and 1619. He
discovered that the planets move around the sun in ellipses with one
focus of the ellipse at the center of the sun and the other focus at a
usually unoccupied point in space. He also came up with rules for their
movements called Kepler’s laws.
Because of Kepler and Brahe, astronomers now had a model for the
solar system that actually fit the evidence and that could be used to
predict future events or reconstruct past ones. This was a giant leap for
astronomy but the work still remained to give reasons for what Kepler
observed.
Galileo
Living at the same time as Kepler, an Italian named Galileo Galilei (15641642) made the next breakthrough for astronomy. Galileo is probably
best known for some experiments with falling objects from the leaning
tower in Pisa, his home town, but he also made some exciting discoveries
with his homemade telescopes and experimented with pendulums.
Galileo was also a believer in the Copernican theory. Since Ptolemy first
made up his concentric model, many people argued that Ptolemy’s
theory must be true because they reasoned that the earth would leave
the moon behind if it traveled around the sun.
In 1610, Galileo made the discovery with his telescope, which
was the most advanced at that time, that Jupiter had at least
four moons orbiting it. This was proof against the concentric
system because Jupiter’s moons were orbiting Jupiter and not
the Earth, which everything orbited according to Ptolemy’s
concentric model. If Jupiter could retain its satellites, then the
Earth could retain the moon as it went around the sun. He
published a paper about his findings and got in trouble twice
with the Roman Catholic Church which placed him under
house arrest until his death for advocating the Copernican
theory.
Newton
The science of astronomy still needed one more piece in its foundation
for others to build upon. This piece was contributed by an English man
named Sir Isaac Newton (1642-1727). Newton was an astronomer,
scientist, and mathematician who investigated the laws of gravity and
made spectacular discoveries about light. He formulated laws which
explained how objects move and how gravity operates. He also laid the
ground work for the study of spectrum analysis. He also made the first
reflecting telescope which made possible the huge observatory
telescopes of today.
The laws provided by Kepler, Galileo, and Newton were not perfect but
they had a good degree of reliability and were used for many years.
There have been revisions of their laws by Albert Einstein and others but
the original laws are still used by many for calculations that do not need
an extremely high degree of precision.
Einstein
One of the most profound impacts on science were two theories
proposed by Albert Einstein. Albert Einstein (1879-1955) realized that all
motion was relative, that is, coordinates and the descriptions of
movements meant nothing unless the reference body was defined. He
also had evidence that the speed of light was a constant, being the same
speed no matter how fast an observer is moving, which violates the
Newtonian laws of motions but was later demonstrated experimentally.
In creating his theory, he made the requirements that all defined laws
must work with respect to all bodies of reference and that the speed of
light with respect to all bodies was the same. To bring the requirements
into one theory, he used a set of mathematical formulas called the
Lorentz transformation.
The Lorentz transformation defined the formulas to use when
converting coordinates from one reference body to another when the
first body is moving at a constant speed with respect to the second.
With these formulas, he discovered that time and mass cannot be
constant for the speed of light to be constant; thus, time can not be
separated from space so the two must exist together in a four
dimensional space-time continuum. For instance, if two trains are
moving on two parallel tracks in the same direction at different speeds
toward a light source, and the speed of light from the light source is the
same for both of them, then time for the faster train must be slightly
slowed. In 1905, Einstein published his findings in his Special Theory of
Relativity. The Special Theory of Relativity could only be used in the
absence of gravitational fields so he published his General Theory of
Relativity in 1916. The General Theory of Relativity basically says that all
matter curves space, and in turn, how space is curved affects the
movement of matter, which explains gravitational fields. This theory is
constantly being validated by modern scientific experiments.
Space Exploration
The history of space exploration starts at about this time. In 1926, an
American scientist named Robert H. Goddard built and flew the first
successful liquid propelled rocket. By 1930, groups were being formed
which experimented with rockets and by the early 1940s, the United
States and the Soviet Union were both researching high altitude rockets.
The Space Race
During the cold war in the 1950s, both the United States and the Soviet Union
announced plans to launch earth-orbiting satellites. This began what is called
the "space race". At first, Dwight Eisenhower, the president of the U.S. at the
time, was reluctant to get involved in the race because he thought that an
American satellite orbiting the earth above the Soviet Union’s territory would
be seen as a threat and start a war.
At this time, the U.S. military had a high altitude rocket called the Jupiter. On a
missile test flight on September 20, 1956, the Jupiter rocket was flying over the
South Atlantic when its nose cone briefly went into space before arching down
to the ocean. The Jupiter’s designer and a few others knew that the nose cone,
if detached, could have gone fast enough to orbit the earth. The Pentagon
suspected that the Army might try to "accidentally" put another Jupiter nose
cone into orbit so they ordered the Army to fill the nose cones with sand and
to disable the Jupiter’s fourth stage.
Sputnik 1 and Explorer
One year and 14 days later, on October 4, 1957, the Russians put a small
sphere with a radio transmitter into orbit, which was the first manmade
satellite to orbit the earth. They named this small satellite Sputnik 1 and
it prompted the Americans to put their own satellite into orbit. On
January 31, 1958, the American satellite Explorer, which had some
scientific equipment, was put into orbit with a Jupiter C rocket. Explorer
had been fitted with a special Geiger counter from physicist James Van
Allen which recorded the previously unknown Van Allen belts of
radiation around earth.
Sputnik 1
Explorer
Human Exploration
On January 20, 1961, John F. Kennedy became president and on May 25 of that same
year announced the goal of sending an American to moon and bringing him back
safely. To reach this goal, he executed the Apollo program. Before humans could go to
the moon, however, humans needed to at least get into orbit. Before humans went
into orbit, each country used animals to test the technology.
The Soviets were the first ones to send an animal into space. In 1957, they sent a
dog named Laika into orbit in a capsule named Sputnik 2. She survived for a week
before running out of oxygen.
The Americans were next, on January 31, 1961, they shot a chimpanzee named
Ham in a Mercury capsule to an altitude of 157 miles. The chimp was recovered in
good health.
That year, on April 12, the Soviet Yuri Gagarin was the first person in
space. The Americans followed on May 5 with Alan Shepard being the
first American in space. Gagarin’s flight lasted 1 hour and 48 minutes
and he was in orbit 89 minutes. His highest altitude was 203 miles above
the earth. Shepard’s flight lasted 15 minutes and he rocketed to 117
miles above the earth but did not make it to orbit.
On February 20 1962, John Glen became the first American to orbit the
earth. His trip lasted 4 hours and 55 minutes and he orbited the earth
three times. His highest altitude was 162.5 miles.
Soviet Yuri Gagarin
John Glen
For years after that, the space race between the Soviets and the
Americans continued and many more people orbited the earth as the
technology progressed. The race finally ended on July 20, 1969 when
Apollo 11 successfully landed on the moon and Americans Neil
Armstrong and Edwin Aldrin became the first humans to walk on the
moon. The United States sent a total of 12 men to the moon, the last
being Eugene Cernan on the Apollo 17 mission on December 14, 1972.
No human has walked on the moon since. The Soviets never made it to
the moon.
Since then, many scientists have made discoveries and developed the
technology to look farther into the cosmos, but not much could have
happened without those first astronomers, philosophers, and scientists
taking time to look at our universe for what it really was.