What is Coperican theory ?​

Copernican heliocentrism is the name given to the astronomical model developed by Nicolaus Copernicus and published in 1543. This model positioned the Sun at the center of the Universe, motionless, with Earth and the other planets orbiting around it in circular paths, modified by epicycles, and at uniform speeds.

The major features of Copernican theory are: Heavenly motions are uniform, eternal, and circular or compounded of several circles (epicycles). The center of the universe is near the Sun. Around the Sun, in order, are Mercury, Venus, the Earth and Moon, Mars, Jupiter, Saturn, and the fixed stars.

Allows calculation of planetary orbital periods around Sun. Allows geometric calculations of planetary distances from Sun. These show nice regularity: more distant planets have longer periods, move slower. Easier to calculate planetary positions than with Ptolemaic model.

I hope this helps!

Primary sources are usually  more accurate and are written by someone who experienced it or witnessed it. secondary sources are those who heard of it after the fact that can lose details and or twist the event in a light that benefits them.

1is using relevant evidence 2 is speaking