“Some people become heroes against their will. Even though they may have ideas that are revolutionary, they may not know it, and if they know it, they may not completely believe them” (Gleiser, 68). The astronomers Aristarchus of Samos and Tycho Brahe are evident examples of scientific heroes because of their strong influence in the history of astronomy, and involvement in two paradigm shifts of scientific reasoning. Aristarchus of Samos and Tycho Brahe, though they existed in time periods vastly different from each other, produced earth-shattering discoveries far ahead of their time and beyond the capabilities of ancient astronomical instruments. Without their work, the foundation of modern astronomy may not have been formed.
Aristarchus was an ancient Greek astronomer, born in 310 BCE. Not much is known about his youth, besides his birthplace of Samos in Greece. Much of his work was lost over time as well, his only surviving work being On the Sizes and Distances of the Sun and Moon. The head of Aristotle’s Lyceum at the time was Strato of Lampsacus, and it is known that Aristarchus studied with Strato in Alexandria. As a “gifted mathematician, a meticulous observer, and clearly a courageous free-thinker” (Gleiser, 50), Aristarchus was destined to be a great scientist from the start. Aristarchus lived in Alexandria for most of his life, keeping all of his work in a library there. A fire destroyed the library as well as the scientific and cultural records, but some information on Aristarchus and his accomplishments still exist through ancient writings. After his studies of the sizes and distances of the sun and moon, Aristarchus died in 230 BCE with little recognition for all his hard work.
Aristarchus’s main observations in On the Sizes and Distances of the Sun and Moon showed three premises; the Earth’s distance to the Sun is approximately nineteen times larger than the Earth’s distance to the moon, the Sun’s diameter is 6.8 times larger than the Earth’s, and the Moon’s diameter is 0.36 times the Earth’s diameter. If it were not for the imprecise use of “naked-eye” observations, Aristarchus’s data would have been more accurate. Instead of being nineteen times further away, the Sun is actually three-hundred and ninety times further from Earth than the Moon. This mistake occurred from an incorrect angle Aristarchus received, due to his calculations taken with his naked eye. The second premise overestimates the Moon’s angular diameter, and the third premise was more of an estimate than a measurement. The blame for the validity of Aristarchus’s work should not be placed on himself; rather on the lack of technology available to ancient philosophers of his time.
Aristarchus inferred the sun must be at the center of the universe, or a heliocentric universe, because the Sun is so much larger than the Earth. It is odd that On the Sizes and Distances of the Sun and Moon follows a more geocentric view and does not mention the heliocentric model, and his mind changed with time. He was also the first to claim that the Earth moves on an axis. This statement was unheard of at the time but became a hot topic of discussion for many scientists. Aristarchus had six hypotheses for his heliocentric theory. First, the Moon receives light from the Sun. Second, the Moon moves in a sphere with Earth as a point in the center. Third, when there is a half Moon occurring, the circle dividing the light and dark sides of the Moon is Earth’s direction. Fourth, a half Moon’s angular distance from the Sun is under one-thirtieth piece of a quadrant. Fifth, the Earth's shadow has a diameter the size of two moons. Lastly, if including the Zodiac chart, the Moon appears to take up one-fifteenth of the Zodiac. Though his theory was backed with solid hypotheses, it is said that Aristarchus abandoned his concept of a heliocentric universe time and time again.
Scientists are shaped by those before them, by learning from their ideas and mistakes. Even though most of his work was lost, Aristarchus was still noted by many other scientists for his ideas. While later Greek astronomers like Hipparchus, Archimedes, or Ptolemy revisited Aristarchus’s premises to reap more accurate values on sizes and distances, the ancients typically underestimated how enormous the Sun is. Up until the seventeenth century, Aristarchus’s ratio for the Sun was widely accepted by scientific communities. Archimedes, for example, noted Aristarchus’s figures in his book The Sand Reckoner. Archimedes required measurements of the spherical universe’s size in order to calculate how many grains of sand would be needed to fill the universe, and Aristarchus’s figures held the biggest universal measurements.
Another scientist familiar with the work of Aristarchus was Copernicus, a sixteenth century astronomer who came back to the concept of the Sun in the center of the universe. Aristarchus’s heliocentric model was forgotten due to the lack of a stellar parallax in the studies, but later inspired Copernicus in Six Books Concerning the Revolutions of the Heavenly Orbs. Eighteen centuries after Aristarchus discovered the universe as heliocentric, people still believed in the geocentric solar system. But his ideas came back in Copernicus’s work, gradually changing the outlook of the people and Catholic Church. This shows how Aristarchus’s ideas, the ones remembered post-fire, were eye openers for many astronomers and philosophers such as he. As explained by James Burke in a 1983 NASA public lecture series at the College of William and Mary, “When paradigms start to shift, the unexpected way they go is a shock to the system”. It is hard to adapt after a paradigm shift, but that does not mean it is better to remain conservative in beliefs as new data disproves these beliefs. By opening the floor for discussion, others were able to learn from his theories and create their own conceptions of the cosmos.
Another outstanding astronomer and philosopher was Tycho Brahe, though there is much more information on Tycho than Aristarchus. His birth and early life can be accounted for in more detail, as well as his upbringing as a future nobleman. Joergen Brahe desperately wanted a son, and his brother promised that Joergen could adopt his next son. The brother’s wife gave birth to twins on December 14th 1546, one stillborn and one surviving boy. The promise was broken, as the family wanted to keep Tycho, prompting Joergen to kidnap the son he felt entitled to. When Tycho was thirteen years old he attended the Lutheran University of Copenhagen for philosophy and rhetoric. This university is where Tycho’s interest in astronomy was born in August 1560, after he observed a partial solar eclipse that had been predicted by a handful of astronomers.
Joergen attempted to steal away his passion for astronomy by sending him to another school with a tutor named Anders Vedel. Anders Vedel would take Tycho’s astronomy books, but that did not stop Tycho from continuing to learn about space science. Anders Vedel realized Tycho’s passion could not be stolen away from him, and slowly gave up on his mission. While he was still young, Tycho got into a quarrel where part of his nose was sliced off. This piece of his nose was replaced by “a gold and silver alloy” (Gleiser, 83). He made many great discoveries as a man that have not been forgotten though modern astronomy surpasses the observations of scientists like Tycho. Tycho Brahe died on October 24, 1601.
Tycho Brahe made many scientific contributions to society during his time. While he is well regarded for his fairly accurate observations made using the best astronomical instruments available before telescopes, Tycho became highly renowned in the scientific community for his publications “De Nova Stella” (The New Star) and “De Mundi Aetherei Recentioribus Phaenomenis Liber Secundus” (The Second Book About Recent Phenomena in the Celestial World). Unlike Copernicus and Galileo’s astronomical work, Tycho’s publications were not banned by the Catholic Church.
Tycho’s first significant discovery was his observation of a star brighter than Venus. He was intrigued and studied it for a year, noticing its position relative to other stars did not change. Tycho later published the most comprehensive study of this supernova although he was not its only observer. Another observer of the supernova will later come into play as a long-lasting impact of Tycho’s work. Tycho’s publication included the supernova’s location compared with other stars. “De Nova Stella” was also a composition of astrological forecasts, poems, and meteorological diaries.
Tycho Brahe recorded The Great Comet of 1577 from November 1577 to January 1578, using Hipparchus’s parallax method to measure that the comet was approximately 6 times farther from Earth than the moon. He concluded that comets travel within the Earth’s atmosphere with its tail always pointed away from the sun. This statement also means the comet traveled on a path that correlates with the sun rather than the Earth. His conclusions inclined him to create a star catalogue based off Ptolemy’s work. Over time, Tycho’s star catalogue grew to record data for over 1,000 stars. Tycho’s work disproved the concept of Aristotelian spheres, a driving force keeping planets and stars in their orbit. Tycho also tried to make measurements for the stellar parallax but could not find a parallax for the stars. He concluded that either the earth was motionless or the stars were too far to measure its parallax. He decided the Earth had to be the center of the universe, and deemed it improbable for the stars to be as far away as they actually are. Although he was incorrect, Tycho was not entirely off-track.
In addition to the aforementioned recordings of stars and comets, Tycho Brahe formed his own model of the universe. Tycho found many inconsistences in both Ptolemy and Copernicus’ solar system models, though he found pieces of information he agreed with. Thus the Tychonic System was birthed, which positioned Earth at the center of the universe with the Moon, Sun, and stars orbiting the earth. While it is now known that the Sun in fact does not orbit the Earth, the Tychonic system correctly placed the five planets Mercury, Venus, Mars, Jupiter and Saturn orbiting the Sun rather than the Earth. The Tychonic system was a “hybrid between a pure geocentric Aristolean model and the Copernican heliocentric model” (Gleiser, 85), and was accepted in the scientific and religious communities for many years.
The quality of Tycho’s observations were important to future astronomers and the development of modern astronomy, and the influence of his work can still be seen today in new predictions and theories. Tycho Brahe was fairly accurate in his studies, however he was not always correct. A future astronomer with an interest in Tycho’s calculations was the German astronomer Michael Maestlin. He was another observer of the 1577 comet that intrigued Tycho, and gathered more details about its distances from the Earth. Maestlin built upon the same foundation as Tycho while studying the comet and furthering the ideas that astronomers use even today. The comets distance was measured as it moved from 3 times farther than the moon to 30 times further. Since Aristotle’s time people believed planets were held in orbit by heavenly crystal spheres, but Maestlin’s work implied the comet had to travel through the crystal spheres of Mercury and Venus. Scientists of the time believed crystal spheres were hard and clear, but soon after suspicions arose about the reality of crystal spheres. Once Michael Maestlin and Tycho Brahe began to wonder if crystal spheres existed at all, they sparked a domino effect. Others began to catch on, and wonder if their conceptions of the cosmos were as valid as they had believed. Scientists working off of each other’s data can lead to life-altering realizations; the questioning of crystal spheres was only the beginning of a scientific revolution.
In conclusion, both Aristarchus of Samos and Tycho Brahe made major scientific contributions during their lives to later cause massive scientific revolutions. Aristarchus discovered that the earth orbits the sun, rather than the other way around. His calculations significantly expanded the size of the universe, showing there is much more to the cosmos to explore! Tycho Brahe’s observations of planetary motion led to today’s model of the solar system in more ways than one. In the future there will be many more scientists, whose contributions go beyond anything Aristarchus or Tycho could dream of, but that does not make their contributions any smaller.