It is a fact that we see Sun, Moon, stars and planets rise daily and after climbing to the South setting again. The planets are wandering stars, following their own paths.
These movements in the sky can be explained in three different ways (to the left the models of Ptolemy, Copernicus and Tycho Brahe are shown). But that's a mathematical truth: can all of these also live up to the laws of physics?
Eventually three models compete from about the 16th till the 18th century:
Arguments in the debate
Quite a few arguments were put forward:
More on velocities
If the Earth rotates daily around it's axis, you would cover a distance of about 40.000 km per day: that is 1667 km/hour. In Amsterdam it will be about 900 km/hour: that's about the cruising speed of an airplane!
The disctance between Earth and Sun is about 149 million kilometers. If the Earth orbits the Sun we cover a distance of about one billion kilometers a year - that's almost 30 km/second or 108.000 km/hour. Astronauts in the International Space Station orbit the Earth with a speed of about 28.000 km/hour.
He was very good in math. Using the exact observations of Tycho he could not get his calculations right assuming planets were orbiting in circles - as was assumed to be perfect, divine movement (a Greek thought). He concluded the planets orbit the Sun in ellipses and proposed some famous laws (used by Newton for his laws). He is considered to be one of the founding fathers of modern science.
The animation shows the second law of Kepler: in equal intervals the planet orbits equal surface areas (blue, the green arrow represents the speed)..
In this example you see the Sun a lot more off centre than in reality.
His contribution to the discussion seems to be vital. Two of his laws are essential:
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