Who were the the People who made the most important Contributions to Astronomy?

9/29/16 / by Troy Wilson

          From ancient times to modern reality, people have been studying the various objects in the sky for thousands of years. The way that these people have studied the stars has affected our view of our place in the universe. Not only have these people affected our view of our place in the universe, but they have also affected the techniques and pieces of technology used in the science of astronomy. Theories, telescopes, proven statistics, etc. have formed from astronomers all around the world throughout time. These key pieces have affected man in many ways to describe. There are so many to tell, it is hard to list all of them. So many different astronomers have been known all around the world during various centuries. Probably the most important astronomers to date are Edwin Hubble, Hipparchus, and Galileo Galilei. Let us go in order of time periods they were in…

Hipparchus (190 B.C. – 120 B.C.)

Hipparchus (Bergman)

          The time period of Aristotelian cosmology overflowed the minds of Grecian’s. This was the time period that Hipparchus was born in. The model during this time of the early astronomer Aristotle believed in the model idea that earth was the center of the universe and the circular planet motions are uniform. This model, however, it was “a rigid model that could not account for certain observations such as the changes in the brightness of the planets, their retrograde motions, and changes in their speeds: these observations clearly contradicted the Aristotelian model”(Violatti). Therefore, Hipparchus created accurate, proven statements and theories that described more than this.

          Hipparchus made an absolute sacrifice of his thinking to produce huge contributions on the world of astronomy. Hipparchus calculated the length of a lunar month with one error of less than one second and estimated the solar year with an error of six minutes. Pretty good for his time. He improved astrolabes and quadrants, both used as astronomical instruments. Hipparchus thankfully rejected the sun-centered system said believed by Aristarchus. Hipparchus then concluded that the geocentric model better explained many observations. Even though the geocentric model explains how Earth is in the center of the universe, it actually helped to “[expand] the size of the universe far beyond the accepted size, which was also an implication difficult to accept”(Violatti). Hipparchus improved the original calculations of the sizes and distances of the sun and the moon.

          Possibly his most greatest feat was measuring the equinoctial precession. On one evening, Hipparchus saw the appearance of a star where he himself was absolutely certain there had been none before. It was absolutely necessary for him to determine whether or not this appearance was real. While being determined to certify possible later changes, Hipparchus made a catalogue of the sky giving the positions of 1080 stars by giving their

The solstices and equinoxes that occur throughout one year are shown above. Equinoxes practically mark the halfway point of a solstice. They occur on September 23 (Autumnal Equinox) and on March 21 (Vernal Equinox. (Williams)

precise celestial latitude and longitude. With the chart he created from this, he made the statement that the stars had shifted their apparent position by around two degrees. This is how he himself discovered and measured the precision of the equinoxes.




Galileo Galilei (1564 – 1642)

Galileo Galilei (Huang)

          Galileo Galilei was a mathematics professor who made revolutionary observations of space and the nature around him with long-lasting ideas that would be brought to the top of the list to reference to. He is nicknamed “The Father of Modern Science” in many parts of the world. Supporting many ideas brought up by scientists and astronomers around the world helped to contribute to many of Galileo’s accomplishments in his lifetime. He entered the world with the mindset to do better than others and accomplish what others have never accomplished before.

          Galileo was born the 15th of February in 1564 in Pisa, being only one of six children. In 1583, Galileo enrolled at the University of Pisa, which is when he began to have a love for the subjects mathematics, physics, and astronomy. While at this university, he was exposed to the  Aristotelian view of the world. He agreed with the views at first, but due to financial issues, he had to leave the university before earning a degree. Galileo then moved on to the University of Padua, where he taught to others about his teachings in geometry, mechanics, and astronomy.

          Galileo published many books and or small booklets explaining his personal findings, using the vast knowledge capability he already had from studying at the universities. Some of which were controversial. In 1604, Galileo published The Operations of the Geometrical and Military Compass, which “revealed his skills with experiments and practical technological applications”(Editors). While at this, he created a hydrostatic balance for measuring small objects and smoothed his findings on theories of motion and falling objects; all of which began to bring him more income and recognition. In July 1609, he studied simple

Dialogue Concerning the Two Chief World Systems (Galilei)

telescopes built by Dutch eyeglass makers, leading him to develop one of his own. Turning his telescope to the heavens, he published a small booklet in March 1610, The Starry Messenger, making his point on how the moon is not flat and smooth, but a sphere with mountains and craters. Galileo published his own observations on the sun’s sunspots. In 1632, he published the Dialogue Concerning the Two Chief World SystemsGetting caught in his own arguments, it battled between Copernicus’s heliocentric theory of the universe and some Aristotelian beliefs of the heavens.


          Galileo died in Arcetri, Italy on January 8, 1642. In 1785, the church lifted the ban on most of the works supporting Copernican theory, and by 1835 dropped all of the opposition to heliocentrism. In the 20th century, several popes acknowledged the great findings and discoveries by Galileo. In 1992, Pope John Paul II honored Galileo for his accomplishments. Overall, Galileo’s contribution to our understanding of the universe was not in his discoveries, but the methods he developed to use mathematics to prove them.   


Edwin Powell Hubble (1889 – 1953)

Edwin Hubble (Hubble)



          Edwin Powell Hubble is often called the father of modern cosmology. He has made several different discoveries the changed how scientists view the universe. He briefly began his life as a lawyer and then exploded into a career of astronomy. The commitments he made to finding more about our universe still captivates us to this day on how he did it.

          After graduation from school, Hubble branched off his career into the world of astronomy. He was invited to work at the Mount Wilson Observatory in California, but “he had to delay the acceptance while he served as a soldier in World War I”(Redd). When he arrived back from the war, he took the position at the observatory.

          Hubble worked with the two biggest telescopes in the world at the time. They were 60-inch and 100-inch Hooker reflector telescopes. He oversaw the construction of the 200-inch Hale Telescope on Palomar Mountain before his death in 1953 at the age of 63, which was the largest telescope on Earth until the Russian BTA-6 was built in 1976. With using the power of some of these telescopes, he observed the night sky. In 1920, small diffuse patches in the sky were termed nebulae, and they were thought to have existed in the Milky Way. With Hubble noticing a pulsating star called a Cepheid variable in each nebulae, they allowed for the precise measurement of distance. He thus calculated how far each nebulae was from each-other. This proved that these were not in the Milky Way galaxy. Scientists remarkably noticed that these nebulae were actually different galaxies apart from each-other, emphasizing then on how much the universe has been expanding.

          During this time, Hubble published a standard classification system to use for the galaxies. Hubble’s method of organizing the classes “focuses on three galactic types: ellipticals, spirals, and barred spirals, and irregulars”(Redd). The method, known as the “tuning fork” diagram organizes ellipticals by how stretched out they are from a perfect circle, while spirals and barred spirals become less tightly wound as they progress. He originally thought that elliptical galaxies evolved to spirals, but now scientists believe that galaxies are classified from the start.

The Hubble Tuning Fork Diagram shows how different types of galaxies are classified. The chart organizes the different types using the shape of a tuning fork (for a piano). (Gomez)

          In studying many galaxies, Hubble wanted to discover that they did not stay in one stationary place in space. Every galaxy is actually rushing away from Earth. Some galaxies were moving 90 million miles per hour away from the Milky Way Galaxy. With all the discoveries being made about the passing and flying-by of galaxies away from our galaxy, the “calculation to determine the rate at which the universe is expanding is known as Hubble’s Law”(Redd). As stated by the calculation, the universe is expanding at a constant rate, known as the Hubble constant. Einstein actually visited Hubble at Mount Wilson to discuss the expansion of the universe at a constant rate.


Hubble’s Constant will prove and describe the reason we see galaxies from a distance. Galaxies are expanding at a constant rate, and the constant proves to calculate the speed at which the galaxies are moving. (Riess)

          Hubble labored in vain for a change that would allow astronomers such as himself to be recognized. He never received a Nobel Peace Prize, despite his role in understanding the vast expanse of our universe. He was recognized the year he died, 1953, for the prize but then became ineligible because the award cannot be awarded posthumously. In 1990, NASA launched the Hubble Space telescope into orbit around the Earth. The telescope, named after Hubble himself, has provided thousands of images about the deep parts of the cosmos. It played a key role in discovering dark energy and the force causing the universe to expand. To this day, the telescope is honored in space and remains in orbit, exploring the vast expanse of our surroundings.  


Works Cited:


Bergman, Jennifer. “Hipparchus.” Windows to the Universe. Windows to the Universe, 25

          July 2001. Web. 29 Sept. 2016



Dickinson, David. “Review: The Journey to Palomar.” Astro Guyz. AstroyGuyz, 25 June 2010.

          Web. 29 Sept. 2016. <http://astroguyz.com/2010/06/25/review-the-journey-to-



Galilei, Galileo. “The Operations of the Geometrical and Military Compass, 1606.”

          University Libraries: The University of Oaklahoma. The University of Oaklaoma, 2014.

          Web. 29 Sept. 2016. <https://galileo.ou.edu/exhibits/operations-geometrical-and-



Gomez, Edward. “Create a Hubble Tuning Fork Diagram.” LCOGT.net. LCOGT, 2016. Web. 29

          Sept. 2016. <https://lcogt.net/education/activity/create-hubble-tuning-fork-




          YELLOWSOLARSYSTEM, 4 Feb. 2015. Web. 29 Sept. 2016.



Hubble, Edwin. “Free Daily Quotes.” Quotes Gram. Quotesgram, 2016. Web. 29 Sept. 2016.



Riess, A. “Refined Hubble Constant Narrows Possible Explanations for Dark Energy.”


          NASA, 7 May 2009. Web. 29 Sept. 2016.



Williams, Matt. “PRECESSION OF THE EQUINOXES.” Universe Today. Universe Today, 24

          Dec. 2015. Web. 29 Sept. 2016. <http://www.universetoday.com/77640/precession-    




Biography.com Editors. “Galileo Biography.” Biography.com. A&E Television Networks, 2

          Dec. 2015. Web. 29 Sept. 2016. <http://www.biography.com/people/galileo-



Cristian Violatti. “Hipparchus of Nicea,” Ancient History Encyclopedia. Last modified April

          02, 2013. http://www.ancient.eu /Hipparchus_of_Nicea/.


Redd, Nola. “Edwin Powell Hubble: Biography.” Space.com. Space.com, 12 May 2012. Web.

          29 Sept. 2016. <http://www.space.com/15665-edwin-powell-hubble.html>.



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