Starship Asterisk*

Calling all astronomers,

Copernicus devised the concentrics orbits of the known planets centered around the Sun. How did he know the order of the planetary distances?

Know you sky,

I going to try and dredge-up a reply from Neufer with his treasure trove of trivia. I am guessing each planet is tracked across the sky and the number of days is tabulated for its return at the same longitude for the planets outside Earth's orbit. The longer the period the farther the planet is from the Sun. That is a lot of tracking and dedication for Jupiter takes 11 years to complete its orbit. So Neufer, how did Copernicus get his idea? Was it from deducing the Moon orbiting the Earth in a similar fashion as the planets orbit the Sun ?

Doug

These pictures show the idyllic island of Ven or Hven, where Danish astronomer Tycho Brahe lived and worked in the late 16th century. Brahe was by far the best observer and recorder of the sky that had existed up until then. Brahe carefully measured and recorded how the planets seemed to move across the sky.

Tycho Brahe was forced to leave Ven and Denmark and move to Prague, where he met Kepler. Brahe died a few years after arriving in Prague, and today some people say that Kepler poisoned Brahe in order to get his hands on Brahe's observations! In any case, Kepler, who was a much better mathematician than Brahe, studied Brahe's observations of the planets and found the only description that fitted Brahe's data: Kepler's laws of orbital motion.

It had been known since antiquity that Mercury moves faster than any of the other planets (hence the word "mercurial") and Saturn moves more slowly than any of the other by-then known planets, which in Kepler's days did not include Uranus and Neptune. Kepler showed that a larger orbit means a slower orbital speed, even though an incredibly elliptical orbit will force the orbiting body to move extremely fast during the part of its orbit which is closest to the body that it is orbiting.

Ann

Thanks for the reply,

Copernicus preceded Brahe and Kepler. How did he surmise the order of the planets from the Sun?

Doug

Hello Owlice,

Thank you for finding a tailor-made answer for my question. I wonder if Copernicus actually collected all the data for conjunctions, elongations, oppositions, and quadratures, especially for Saturn. Perhaps he used data handed down from past generations. He also had to be a student of algebra, trigonometry, and Euclidian geometry. I also wonder what ancient texts were available to him to study and obtain a grounding in mathematics without the help of a state required education. I am sure he studied Ptolemy to know there was a better way of understanding the "wanderers". He needed Ptolemy's writings for questioning current thinking in his time. He needed the church to feed him and give him time for his query. He also knew to keep his mouth shut so he could continue with his fun of discovery.

Such a secretive and fun-loving person must have been re-incarnated several times. I sometimes feel like I am one of those incarnations. Of course, there is a better chance Copernicus' current incarnation is Neufer or the Cloudbait Man.

This forum is pure pleasure,
Doug