Historical Perspective Orbital Mechanics Historical Perspective

What is an Orbit Orbit refers to the motion of one body around another Although not always the case, one object is typically very large in relation to the other In this case, the smaller object is said to orbit around the larger, and the larger is typically presumed to be fixed in space

What is a Satellite? Today, we typically think of a satellite as something man-made that orbits the Earth This is true, but anything that orbits another body is a satellite The planets in our solar system are satellites of the Sun The Moon is also a satellite of the Earth

History of the Study of Orbital Mechanics – Ancient Greece Interest in orbital motion dates at least to ancient Greece Aristotle studied the motion of the planets in the night sky General understanding at the time was that the Earth was fixed in space and the heavenly bodies moved around it

History of the Study of Orbital Mechanics – Copernicus Nicolaus Copernicus (1473-1543) First to theorize that the Earth and other planets actually revolved about the Sun Assumed the motion to be circular Took accurate measurements and found that his assumption was not strictly accurate Theory was considered heretical at the time

History of the Study of Orbital Mechanics – Brahe Tycho Brahe (1546-1601) Lectured at University of Copenhagen Responsible for gathering a wealth of accurate planetary motion measurements

History of the Study of Orbital Mechanics – Kepler Johannes Kepler (1571-1630) Assistant to Brahe Proposed that planetary orbits were elliptical Proposed laws of orbital motion that are still used today

History of the Study of Orbital Mechanics – Hooke Robert Hooke (1635-1703) Member of the Royal Society Debated Newton on facts about orbital mechanics

History of the Study of Orbital Mechanics – Newton Isaac Newton (1643-1727) Grew interested in mathematics from reading about astonomy From Kepler’s work, deduced the existence of an inverse square law attractive force Proposed Theory of Universal Gravitation Wrote Principia, considered the greatest scientific book ever written Posits his three laws

Conclusion Interest in orbital motion dates back to ancient history First formal assertion that the earth was not the center of all things in mid-16th century Study of orbital motion led directly to Newton’s Principia and the three laws

Conclusion Study of orbital motion from 16th century until Newton focused on how the planet orbited the Sun Newton proposed why the planetary orbits exhibit the behavior they do with the Theory of Universal Gravitation Kepler’s and Newton’s laws govern our understanding of orbital mechanics still today