Astrodynamics/History
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[edit] History of Astrodynamics
The study of the sun, moon, and stars has been a subject of prominence among humans for many thousands of years. Because the revolution of the earth and other planets around the sun, and the daily rotation of the earth on it's axis create regular patterns of motion, the study of the stars and planets was used as a method to tell time. The location of the north star, polaris, and the constellation "the southern cross" were used by ocean navigators to travel the seas in the times before magnetic compasses. Many religious ceremonies and beliefs also grew around the stars and their constellations.
The study of the motions of the stars and planets has also been a major driving force behind mathematics and science. Some of the fruits of this study are the optical lense (for use in telescopes) and the field of calculus. Many modern inventions and technologies were also furthered because of modern space exploration. It is for all these reasons that we are studying astrodynamics.
[edit] Early History
The most early view of the solar system that gained any popularity was the Ptolemic system, which viewed the earth as the center of the universe, with the sun, stars, and all the planets revolving around the earth in perfectly circular orbits. Planets were known to diverge from this model, and it is from the Greek word "Wanderer" that the word "planet" first derived.
[edit] The Renaissance
Nickolaus Copernicus, having taken several measurements of the motions of various planets, came to the conclusion that the sun was the center of the universe, and that the earth rotated around the sun. Copernicus' model also assumed that the orbits of the planets were circular, which left a few inconsistencies from his measurements, but the model was much more simplistic then the Ptolemaic model.
Urban myth holds that Copernicus' theory was dismissed by the Catholic church, when in reality Copernicus' book was funded by a church cardinal, and was dedicated to the current pope. It wasnt for nearly 100 years later, after Kepler had begun publishing that the church denounced the idea as heretical.
After Copernicus, Galileo constructed the first telescope and viewed the moons of Jupiter, which revolved around Jupiter and not around the Sun. This was not proof of Copernicus' theory, but it was evidence that there were bodies in existence that did not rotate around the earth.
[edit] Kepler and Newton
Tycho Brahe, a danish nobleman, was a keen observer and machinist, and used his talents to compile a listing of the most accurate observations of stars and planets that had ever been taken up to that point. However, Brahe lacked the intuition to fit that data to a mathematical model. Brahe's acquaintance, Johannes Kepler, an accomplished mathematician was able to do just that.
While Kepler did not understand the mathematical basis behind his discoveries, he was still able to publish three laws of planetary motion that still bear his name today.
Isaac Newton, the famous mathematician and physicist, used his new invention calculus to derive the orbital motion of a planet as an ellipse. However, it wasn't until after being prodded by Edmond Halley, a fellow scientist, that he was persuaded to publish his work, Principia Mathematica with his results.
Halley, Newton's only contemporary that was able to understand the new calculus, was able to use Newtons results to predict the path and the time of return for the comet that still bears his name.
[edit] Lagrange and Gauss
Gauss is known as an amazing mathematician, but many of the results he produced were due to his study of astronomy. Gauss developed many of the mathematical tools that we use today to study orbits. One of his developments, Least Mean Squares curve fitting, was developed to apply an orbit to a series of inexact measurements, but has since found uses in nearly every branch of engineering, science, and mathematics.
