Apollonius of Perga and Hipparchus

            Apollonius of Perga was a Greek astronomer and geometer from 262 BC - 190 BC who immensely contributed to the geometry aspect of astronomy.  Not only is Apollonius most noted for his works on conic sections, but he is also the man who gives names to the conic sections – hence his nickname “The Great Geometer”.  Parabolas, hyperbolas, and ellipses, all imperative to both astronomy and geometry, were named by him.  The idea of using eccentric orbits to explain the motion of the planets and the speed of the Moon is also credited to him.  Very well-known future astronomers such as Isaac Newton, Johannes Kepler, and Ptolemy were all greatly influenced by his works.  Additionally, Apollonius is known for studying lunar history.  For this he is referred to as Epsilon and a crater on the moon has been named after him. 

Some of Apollonius' works.

Apollonius was born in Perga, Pamphylia, Greek Ionia which is now Murtina, Antalya, Turkey and died in Alexandria, Egypt.  During his time growing up in Perga, he was surrounded by strong culture including worshipping the nature goddess, Queen Artemis.  Later on, he moved to Alexandria, Egypt where he studied under Euclid, a successful geometer.  Euclid is one of the few people Apollonius credited for all of his discoveries.  

There is not much knowledge of Apollonius' life - in fact is not even certain if he was really born in 262 BC.  The main concept he is remembered for is his contributions to the geometric aspect of astronomy with his conic sections. 

Similarly, Hipparchus of Nicaea was an astounding Greek geometer, mathematician, geographer, and astronomer.  He is referred to as the founder of trigonometry and is famous for his discovery of the precession of the equinoxes.  There is much more knowledge on Hipparchus than Apollonius. 

            Hipparchus is thought to be the first to calculate a heliocentric system, but he gave up on his work because the calculations showed the orbits were not perfectly circular - as that was the only belief at that time.  Through his observations and mathematical methods developed by the Babylonians, he was the first to create accurate models for the motion of the Sun and Moon in addition to his creation of trigonometry, trigonometric tables, and a reliable technique that facilitates predictions of eclipses.

Additionally, he discovered and measured the Earth’s precession.  The Earth’s precession is caused by the gravitational force from the Sun and the Moon on the Earth. Essentially this involves how the Earth is very slowly spinning, like that of a top, on its axis.  Hipparchus estimated that the Earth rotates 1 degree every century, which is extremely close to the present-day theory of Earth rotating on its axis by 1.38 degrees every century.   

The Babylonians played a large role of influence in Hipparchus’ works.  He used Babylonian units of measure (ex: the pechus).  It is also noted that Ptolemy gave reason to believe Hipparchus was very much influenced by the Babylonians.  Hipparchus was able to confirm his eclipse predictions by comparing them to Babylonian records from 345 years before. 

Hipparchus’ lunar studies contributed to the present day knowledge of synodic days, which is the amount of time it takes for a planet to rotate once. For Earth, the synodic day is 24 hours long. The synodic day is distinguished from the sidereal day, which is one complete rotation in regards to stars.

Hipparchus’ and Apollonius’ contributions to astronomy and mathematics were absolutely astonishing and incredibly influential.  Their discoveries influenced some of the most famous astronomers over time.