I am continuing this fixation with the heliocentric theory because I feel there remains a lot for budding theoreticians to learn from it. Obviously we know the planets do go around the sun, but that is not the point. Rather, I am hoping to show how things can go wrong in forming theories, and what sort of things make it right. The most likely place to go wrong can be summarized simply: if you start with a wrong premise, you may draw a wrong conclusion. Your conclusion may agree with observation, because a wrong premise can do that, as Aristotle pointed out. A wrong premise that brings considerable agreement with observation is extremely difficult to get rid of, because it has pervasive effects.
 
One reason why, in classical times, it was felt that the Earth must be stationary was that if the Earth moved, because of the premise that air rises, hence the fact that we have air at all must be because the Universe is full of it, means that through logic the Earth must move through air. If so, there would be a contrary wind, the speed difference of which on either side would depend on the rate of rotation. Note this argument holds even if the air is orbiting as well. There was no such wind, therefore no such orbit. We can forgive Aristotle here, but we forgive those who followed Archimedes less well. Had Aristotle known of Archimedes Principle, this argument would probably never have been made.
 
An important observation was that the Sun's output was known to have been constant for several thousand years, and a quick calculation showed that had it been powered by combustion, it should have faded. It had not. There was only one possible explanation the ancients could see: the Sun had to be moving, and by moving, it generated a lot of friction, because such friction would be the only physical means of powering the star. The earth did not generate heat, therefore it was not moving. Note that it was Aristotle, or someone earlier, who established that friction generated heat, not Rumford. It was too much to expect them to guess nuclear fusion, but it shows that when developing a theory, every now and again something turns up that should not be explained. There is no fault in admitting you do not know everything. Newton is often quoted as saying there should be no hypotheses. I do not think Newton really believed that. I think what Newton meant was, there should be no hypotheses unsupported by observational evidence. Unfortunately, in this case there was observational evidence; the problem lay with the use of the word "only".
 
Another problem with the heliocentric theory was that it did not calculate anything of interest. We had to wait for Newton.
 
There was also a final problem. Aristotle had stated that heavier things fall faster than light things. The ancients appreciated that orbital motion required the planet to be under constant acceleration towards the star, i.e. falling. If heavier things fell faster than light ones, the planet should fall to pieces, with light matter streaming off behind the planet. That did not happen, therefore the Earth could not be falling. The only way it could not be falling is if it were fixed at the centre. Therefore the heliocentric theory was wrong. It is here that Aristotle failed in his own methodology. He was always stating that only observation counts, and he advocated experimenting. Unfortunately, he never bothered to test this because it was obvious.
 
There was a deeper problem. He divided motion into two classes: eternal and constrained. Constrained motion caused the body to stop moving, and Aristotle assumed that it was a property of the body because some objects, when thrown, went further than others. What he should have done is to use his own methodology: either the constraint came from within the body, or was external to it. A few experiments would show it was external, for example, a stone dropping in air goes faster than one dropped in water. That in itself is not enough, and some further tests are required. Can you see why?
 
To summarize, get off to the wrong start with a theory and you can get into trouble. The question is, can this happen now? In my opinion, it has. I find the Copenhagen interpretation of quantum mechanics to be difficult to believe. How can the fact you observe something be the cause of it? Very homocentric! What do you think?