50 how has the concept of a "planet" changed since the 16th century? do you think this shows scientific accuracy or disproves future facts, as one assumes that they will be discredited in time too?

The Earth-centered Universe of Aristotle and Ptolemy held sway on Western thinking for almost 2000 years. Then, in the 16th century a new idea was proposed by the Polish astronomer Nicolai Copernicus.  By the 17th century, astronomers realized that the sun was the celestial object around which all the planets orbit, and that moons orbit planets. 

I believe that it shows BOTH. Scientists are improving their understanding of this universe, yet some theories are still inaccurate. I don't think that these theories about this universe will soon become completely wrong, bnut some changes will be made.

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