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Name: David
Status: other
Age: 60s
Location: N/A
Country: N/A
Date: 1999 - 2000

I read a quote from Sir Fred Hoyle that said that because of the theory of relativity that it was just as true to say that the earth went around the sun as to say that the sun went around the earth. Is this true? Was the Copernican Revolution a mistake?

Well, no. The Earth does not go around the Sun, nor the Sun around the Earth, if you want to be very careful: they both revolve around their center of mass. Now, the Sun is much heavier than the Earth, so that the center of mass of the Earth-Sun system is almost at the center of the Sun. So the "orbit" of the Sun is just a little wobble which perhaps is undetectable, while the orbit of the Earth surely looks like it is centered on the Sun.

The larger issue here is what relativity means. Relativity does not mean everything looks the same from all viewpoints: it merely means that everything looks the same from all viewpoints that have no physical reason to be different. Stated that way, it's kind of obvious, isn't it? If you really want to see a planet-Sun system where it doesn't matter where you stand on the Sun or the planet, then you need a system where both have the same mass. See, because the Sun has a much larger mass, then its viewpoint has good reason to be different from that of the Earth. If you had a double Sun system, or double planet, and both were exactly the same mass, then I expect you find it easy to believe that both objects would revolve around a point midway between them (their center of mass) instead of one arbitrarily around the other.


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