Presentation on theme: "The History of Astronomy Early Astronomers The history of astronomy goes back several thousand years ago. Almost all ancient cultures had stories."— Presentation transcript:
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 cultures 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 todays 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 astronomers 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 Copernicuss 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 Aristarchuss 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. Copernicuss 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 Ptolemys system. However, Copernicuss 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 pre- telescopic 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 Copernicuss 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 Copernicuss 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 Brahes observations. He discovered that none of the ideas presented thus far about the motions of heavenly bodies lined up to the evidence in Brahes 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 Keplers 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 (1564- 1642) 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 Ptolemys 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 Jupiters moons were orbiting Jupiter and not the Earth, which everything orbited according to Ptolemys 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 Unions 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 Jupiters 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 Jupiters 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. Gagarins flight lasted 1 hour and 48 minutes and he was in orbit 89 minutes. His highest altitude was 203 miles above the earth. Shepards 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.