Celestial Mechanics


Celestial Mechanics is the study of the motion of heavenly bodies such as planets and stars. It has its origins in ancient time but known efforts describe the actual notion of these Ptolemy from the city of Alexandria. His model was geocentric with planets moving on various epicycles. centuries later Copernicus developed a simplified heliocentric model then place the sun at the center rater than the Earth. Galileo was fist person to provide observational evidence for a heliocentric. Trying to save the idea of geocentricity, Tycho developed a hybrid geocentric / heliocentric model that in a modified version is use by modern geocentricity. Ironically it turns out that according General Relativity both heliocentricity and geocentricity may be considered correct. General Relativity allows you to choose any frame of reference you want because all  frames of reference are equally valid. So this includes not only heliocentricity and geocentricity but Mars-centricity, Venus-centricity and even Kepler-62f-centricity. It is simply a matter of choosing the most convenient frame of reference.

It was however Kepler that first described basic sent of law to describe planetary motion.

  1. .All planets move in elliptical orbits, with the sun at one focus.'
  2. A line that connects a planet to the sun sweeps out equal areas in equal times.'
  3. The square of the period of any planet is proportional to the cube of the semi-major axis of its orbit

These laws helped Newton develop his law of Gravity. Which paved the way to a full understanding of orbital motion, not only helping us better understand how planets move by any object in space. It is this ability to precisely calculate orbits that makes space flight possible. It also makes it possible to understand the motion of every object in space.




Nicolaus Copernicus

Galileo Galilei

Tycho Brahe

Johannes Kepler

Isaac Newton

Planetary Motion

Stellar Motion

Galactic Rotation

Orbital Mechanics



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