Because earth is at the barycenter of the universe and the only object that can be said to be still and not in motion. Consequently, everything else is in motion relative to the earth's position. God designed it that way.
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Now you have contradicted yourself. You say we cannot explain how gravity works,
therefore we cannot use it to explain the motion of the planets, Sun, or Earth.
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Then you say the barycenter explains how the Earth can be at the center of the Universe.
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However, to compute the barycenter, we need to use the formula for the attraction of
one body to another (their masses), but that formula uses the idea of gravity.
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So you say gravity cannot be used, but it must be used to compute barycenters.
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Furthermore, there are no bodies close enough to our solar system to affect the
barycenter of our solar system. The nearest star, being 4.3 light years from Earth,
could never exert any force on the barycenter.
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The formula for the attraction of two bodies depends on the distance squared as the
divisor. If you square a distance of 4.3 light years as the divisor, you get a value of
about zero, no matter what the masses are of the two bodies. Note, 4.3 light years
distance is 25,000,000,000,000 miles away (25 trillion miles).
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So, this imaginary barycenter idea cannot work.
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Question. Why did God want to make the Earth the center of the Universe?
And where is the evidence for that ?