11.3 The Discovery that the Earth Rotates Around the Sun

The first known person to propose that the earth revolved around the sun was Aristarchus of Samos.

He calculated how the size of the earth compared to that of the moon by the curvature of the earths shadow on the moon as shown in the picture below.  We can see that the earth is about 3 times the size of the moon by looking at the shadow.

Once he knew how big the moon was he was able to estimate how far away it was from earth because the further away an object is the smaller it appears so he could calculate by how small it appeared how far away it must be.  When half the moon is visible in the sky the sun is at right angles to it as seen in the diagram below.

In the diagram above L is the distance between the earth and the moon, S is the distance between the earth and the sun and w is the angle between imaginary lines connecting the earth to the moon and the earth to the sun.

If you could see the sun and the moon at the same time you would be able to measure angle w.  I'm guessing that he must have seen both the sun and moon at the same time and measured w that way.  He knew the distance to the moon L and he estimated the angle to the sun.  Once you have the angle and L you can calculate the distance to the sun S.  He calculated the distance to the sun to be much bigger than the distance to the moon.  The sun looks to be about the size of the moon but after taking into account how much further it was than the moon he realized that the sun must be a lot bigger than both the earth and the moon.  If the sun was a lot bigger than earth it seemed more likely that the earth was revolving around the sun than the other way around. 

People preferred to believe that the sun revolved around the earth and continued to believe that.  1700 years later the Polish astronomer Copernicus provided even more evidence that the earth goes around the sun.  Another astronomer, Giordano Bruno pointed out that if the earth isn't the center of the universe and the stars in the sky are other suns, their could be planets going around those stars and there could be life on those planets. 

According to church doctrine God made man on the 7th day and then rested and that was it.  What Giordano said could lead people to start thinking that what the church people told them was not true.  Then the church would lose power and money and people might even turn against the church leaders.  So the church leaders, leaders who convinced people that they were righteous and just and close to God, turned against Giordano and killed him. 

Galileo Galilei was another astronomer who agreed with Copernicus.  He was forced by the church inquisition to say he was wrong and then was placed under house arrest.  If he hadn't said he was wrong he probably would have been killed also.

The astronomers showed that the church doctrine was wrong.  The church leaders of the time, by their terrible behavior show us that they were not good people and that power was more important to them that truth.  That doesn't mean that there aren't many very good church leaders but it does mean that just because someone is an important person in the church does not mean that person is a good person.



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