## HipparkhAncient Greek scientist, one of the founders of astronomy
Country:
Greece |

**Content:**

## Biography of Hipparchus

Hipparchus (circa 190-125 BCE) was an ancient Greek scientist and one of the founders of astronomy. He was born in the city of Nicaea and lived and worked in Alexandria and on the island of Rhodes.

## Contributions to Astronomy

Hipparchus is credited with creating the first mathematical theories of the apparent motion of the Sun and the Moon, as well as the theory of eclipses. He accurately determined the size of the Moon and its distance from the Earth. By comparing his own observations with those of his predecessors, he calculated the duration of the solar year with great precision (with an error of no more than 6 minutes).

Hipparchus and other ancient astronomers paid a lot of attention to observing the movements of planets. The observed motion of planets from Earth is quite complex, as their speed sometimes increases, decreases, and occasionally comes to a halt before moving in the opposite direction. At times, a planet describes loops in the sky. This complexity, as we now know, is due to the fact that observations are made from Earth, which itself revolves around the Sun.

Hipparchus, who considered the Earth to be stationary, believed that the observed motion of planets was real. He followed the theory of epicycles in explaining planetary motion. The theory of epicycles provided a purely formal, geometric representation of planetary motion with a certain approximation. The tables of positions of the Sun and the Moon compiled by Hipparchus allowed for the precalculation of the moments of their occurrence with an error of 1-2 hours.

## Advancements in Astronomical Techniques

Hipparchus was the first to employ spherical trigonometry in astronomy. He improved the accuracy of observations by using crosshairs to align instruments such as sextants and quadrants with celestial objects. The scientist also compiled a large catalog of positions of 850 stars, sorting them by brightness into six degrees (stellar magnitudes).

Furthermore, Hipparchus introduced geographic coordinates - latitude and longitude, making him the founder of mathematical geography.