Hipparchus

Hipparchus

Hipparchus
Reading Level

	edHelper's suggested reading level:	grades 9 to 11
	Flesch-Kincaid grade level:	9.76

Vocabulary

	challenging words:		circa, critique, cyclic, ecliptic, orientation, precession, pliny, treatise, brightness, astronomical, invaluable, tremendous, groundbreaking, duration, appreciation, inspiration
	content words:		Natural History, European Space Agency, High Precision Parallax Collecting Satellite, Hipparcos Catalog

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Hipparchus
By Vickie Chao

¹     Suppose we could travel back in time to note the positions of all the stars relative to the Earth. We then compare our observations with the current positions of those stars. Right away, we would notice that the positions of the stars have actually shifted systematically. This strange phenomenon is caused by a cyclic wobbling in the orientation of the Earth's axis of rotation. The entire cycle takes about 26,000 years to complete.

²     Of course, even with today's technology, we have yet to find a way to travel back in time. Hence, we must make do with historical records. By pouring through volumes of data, we can still arrive at the same conclusion. What we are attempting to do here is actually nothing new. A Greek astronomer by the name of Hipparchus (or Hipparchos) did exactly that more than 2,000 years ago. He was the first in the world to discover the precession of the equinoxes.

³     Hipparchus was a rather obscure character in history. Of the scant information we have about him, we only know that he was born around 190 B.C. at Nicaea, Bithynia (modern-day Iznik, Turkey), and probably died in 120 B.C. He apparently dedicated most of his adult life to making astronomical observations on the island of Rhodes. He wrote at least fourteen books to conclude his findings. But, sadly, only one remains. That lone publication is known as Commentary on the Phaenomena of Aratus and Eudoxus. It was basically a critique of a popular poem (Phaenomena) composed by Aratus who in turn had gotten his inspiration from the work of Eudoxus of Cnidus, a Greek astronomer before Hipparchus' days.

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