What were Nicolaus Copernicus Galileo Galilei Tycho Brahe Johannes Kepler?

Answer 1

Copernicus 1473-1543 was a Polish priest who reworked the Ptolemaic model of the planets which had the Earth at the centre (geocentric) by instead placing the Sun at the centre (heliocentric).

Both models used circles and epicycles to represent the planets' orbits, which was a reasonably good model for elliptical orbits of low eccentricity.

Predictions from these theories were accepted until the quality of measurements of actual positions eventually showed problems.

Tycho 1546-1601 was a Danish nobleman who set up the best and most accurate measuring systems ever known for observing the positions of stars and planets, with higher accuracy than ever before achieved.

Galileo 1564-1642 adopted the Copernican theory and had a famous battle with the catholic church authorities over whether the heliocentric theory was the absolute truth rather than the geocentric theory as taught by the church at that time.

He was eventually forced to accept the church's teaching for lack of evidence to support the heliocentric theory, but long after his death the heliocentric theory became accepted everywhere.

Kepler 1571-1630 was a mathematical assistant to Tycho, an employee, who used the new measurements to calculate that the planets' orbits are elliptical and that the orbits obey three laws known as Kepler's Laws.

These were later combined mathematically with Newton's law of gravity and the laws of motion, using differential calculus, to show why Kepler's laws were correct. They were also used to find the planet's masses and the Sun's mass.