HIPPARCHUS OF NICE: BIOGRAPHY AND CONTRIBUTIONS TO SCIENCE - MATHS - 2025

Hipparchus of Nicaea was a Greek astronomer and mathematician known for his great contributions in both scientific areas. His life is quite unknown, although it is known that he was also known as Hipparchus of Rhodes for having lived part of his life on that Greek island.

The scientist was born in Nicea, in present-day Turkey, in 190 BC. C. approximately. The few known data on his biography seem to indicate that he worked in his hometown recording the annual weather patterns of the area. This work was quite common for Greek astronomers, as it was used to calculate the beginning of the rainy and stormy season.

Hipparchus of Nicea - Source: Transferred from de.wikipedia to Commons by Maksim - Under Public Domain

However, according to the references that authors such as Ptolemy left about Hipparchus' research, most of his professional life was developed in Rhodes. Only one work of those written by the scientist has been preserved. Unfortunately, according to experts, this is one of the least important.

The rest of the contributions made by Hipparchus were collected by other later scientists, such as the aforementioned Ptolemy. Among his most important achievements are the development of a catalog of stars, the calculation of the precession of the equinoxes and the distance between the Earth and the Moon or having been the father of trigonometry.

Biography

Hipparchus was born in Nicaea, Bithynia, the current Turkish town of Iznik. Although there are not too many data about his life, experts point out that his birth could have occurred around 190 BC. His death occurred around the year 127 BC. C, on the island of Rhodes.

His main field of work was astronomy, an area in which he is considered the most important figure of antiquity. Among other achievements, Hipparchus was the pioneer in creating quantitative models of the movements of the Moon and the Sun. Furthermore, the measurements made by the astronomer were extremely precise.

Hipparchus took advantage of the astronomical techniques that the scientists of Chaldea and Babylon had created. This knowledge and the quality of his work caused his discoveries to become the basis for the research of later astronomers.

Work in Nicaea

As has been pointed out, data on the life of Hipparchus are very scarce. All that is known comes from the writings of other later scholars who took it as a reference.

The first works of Hipparchus were carried out in his native town, Nicea. There I compile records of the area's annual weather patterns. This task, very common at the time, made it possible to develop meteorological calendars with which to synchronize the onset of rains and other natural phenomena.

Rhodes

It is not known when and why Hipparchus moved to the island of Rhodes. According to the available data, it was there that he developed most of his life.

On the Greek island he carried out an astronomical research and observation program that was repeatedly cited by Ptolemy. This scholar collected more than 20 observations made by Hipparchus between 147 and 127 BC. Likewise, he also cited three previous observations, dated between 162 and 158 BC. C.

However, experts consider that those observations cited by Ptolemy were only a small part of the total.

Hipparchus was also the author of several highly critical commentaries on the work of his predecessors and other contemporary astronomers.

Part of these criticisms can be found in the author's only book that has survived to this day: Commentary on Aratus and Eudoxus. It is a minor work according to his biographers and is full of corrections to the many errors contained in the Phaenomena of Aratus. Likewise, he was also very relentless with the mistakes that Estastothenes made in his geography works.

Hipparchus, as Ptolemy wrote, was a "lover of truth." In this sense, he highlighted his ability to recognize the mistakes made in his work and correct them according to the evidence that appeared.

Coins with his face

As with the more everyday aspects of Hipparchus's biography, it is not known what his appearance was. However, there are representations of his face, although elaborated long after his death.

Coins with his image were minted at Nicaea between 128 and 235 AD. This, given that the scientist had been dead for 250 years, does not guarantee that they were very precise, but it does offer proof that his work was recognized in his native town.

Hipparchus Contributions

Hipparchus of Nicea was already considered in ancient times as one of the most important scientists. His influence also lasted for centuries.

Despite its importance, his life is very little known. Of all his works only one has survived to this day, the aforementioned Commentary on Aratus and Eudoxus.

This lack of direct sources causes their contributions to be known thanks to the writings of Ptolemy and Strabo. The first, in particular, repeatedly quoted Hipparchus in his Almagest, a great astronomical compendium written in the second century AD. C.

Some biographers point out that Hipparchus built an astronomical observatory in Rhodes in order to carry out his research. However, the instruments he used are hardly known.

Again Ptolemy pointed out that he had built a theodolite in order to measure angles, as well as a device to calculate the distance between the Sun and the Moon.

First catalog of stars

Hipparchus discovered a new star, located in the constellation of Scorpio, in 134 BC. This finding inspired him to create a catalog that included some 850 stars, classified according to their luminosity according to a six-magnitude system. This method is very similar to the one currently used.

Along with this stellar catalog, Hipparchus built a celestial globe that showed the constellations and stars, all arranged in a sphere.

In addition to the already mentioned six magnitudes of luminosity of the stars (in which 1 corresponded to a very high brightness and 6 to almost invisible), Hipparchus indicated in his catalog the position in the sky of each star.

Unfortunately, this original catalog has not reached our days. What is known about this work comes from the work of Ptolemy, who 300 years later, used it as the basis for creating his own catalog: Almagest. According to experts, Ptolemy copied what had already been discovered by Hipparchus and expanded it with his own discoveries.

Precession of the equinoxes

Precession is defined as the movement of the equinoxes along the ecliptic motivated by the cyclical precession of the Earth's axis of rotation.

When Hipparchus was building his star catalog, he noticed that some of the stars had shifted compared to previous measurements, especially those made by Chaldean astronomers.

This circumstance made him think that it was not the stars that were moving. His conclusion was that it was the Earth that had changed its position.

This modification is caused by the movement called precession. It is, in general terms, a kind of cyclical wobble that affects the orientation of the Earth's axis of rotation. Each cycle consists of 25,772 years.

In this way, precession became the third type of movement discovered on Earth, after rotation and translation.

The cause of this movement is the effect of the gravity of the Sun and the Moon on the Earth. This gravitational force affects the equatorial bulge of the planet.

Distinction between the sidereal year and the tropic year

The measurement of the value of the precession of the equinoxes led Hipparchus to affirm that there were two types of year: the sidereal and the tropic.

Likewise, he also calculated the duration of both. Thus, the sidereal year, according to their research, lasts 365 days, 6 hours and 10 minutes. For its part, the tropical year lasts 365 days, 5 hours and 55 minutes.

His calculations are striking for their precision. Current instruments have shown that, in the first case, Hipparchus' error was only 1 hour, while in the second he was only wrong by 6 minutes and 15 seconds.

Hipparchus declared that the tropic year should be adopted, since it is the one in harmony with the seasons.

Earth-Moon Distance

Another of Hipparchus' contributions was his measurement of the distance between the Earth and the Moon. Previously, Aristarchus of Samos had tried to measure it, but Hipparchus demonstrated very considerable precision.

Using the observation of an eclipse that occurred on March 14, 190 BC. C, calculated that the distance was 30 times the Earth's diameter, which is equal to 384,000 kilometers. Currently, this distance has been established at 384,400 km.

Trigonometry

Hipparchus has also gone down in history as the father of trigonometry. This field of mathematics consists of relating linear and angular measurements and is widely used in astronomy.

Thanks to the use of trigonometry, the mathematics of triangles is done more simply, something that facilitates astronomical calculations. Hipparchus made a table of angle chords and then made it public for other scientists to use.

Parallels and meridians

The Nicaea researcher was also a pioneer in the division of the Earth into parallels and meridians. In this way, he made the use of longitude and latitude common.

Among other practical functions, this allowed him to attempt a reliable two-dimensional map of the Earth.

References

1. Astromy. Hipparchus, the measure of the year and a catalog of stars. Obtained from astromia.com
2. Biographies and Lives. Hipparchus of Nicaea. Obtained from biografiasyvidas.com
3. Euston96. Hipparchus of Nicaea. Retrieved from euston96.com
4. Violatti, Cristian. Hipparchus of Nicea. Retrieved from ancient.eu
5. Jones, Alexander Raymond. Hipparchus. Retrieved from britannica.com
6. Famous Scientists. Hipparchus. Retrieved from famousscientists.org
7. Darling, David. Hipparchus of Nicaea (190–125 BC). Retrieved from daviddarling.info