4 Astronomers Who Changed the World

The night sky was a fascination to the earliest humans and its study could probably be classed as the earliest science.

Astronomy enabled the early civilisations to develop the calendar and was of great importance for many aspects of daily life. There are many astronomers from all continents and civilisations. Here we look at the important contributions of just four of them.

1. Ptolemy (c.90 – 168 AD)

the astronomer Ptolemy.


Ptolemy produced the Almagest which was a book that dealt formally and systematically with the subject of astronomy. It wasn’t completely original but was based on work done by earlier astronomers. In his book, Ptolemy produced convenient tables of numbers that allowed astronomers to calculate the positions of celestial objects and their rising and setting times for many years in the future.

The book also contained a star catalogue, based on one made by Hipparchus almost 300 years earlier. But the world-changing aspect of this book was that it was written before the world was plunged into the Dark Ages and survived. If it had not, when the Dark Ages ended, European astronomy would have had to start from scratch.

2. Brahmagupta (c. 598 – 670 AD)

Brahmagupta changed the world of mathematics as well as astronomy in his major work Brahmasphutasiddhanta, which was one of the main sources of information for the Islamic astronomers.

It was common belief that the Moon was further away than the Sun, but he used observations of how shadows behaved on Earth to prove that this was not the case. He also developed a system of working out some lunar and solar eclipses and supported the idea of an earlier astronomer, Aryabhata, that a new day began at midnight. He saw that the other astronomical bodies were spheres and actively disputed the widely held beliefs that the Earth was flat or hollow.

It is also said that Brahmagupta came up with the idea that anything that had mass was attracted to the Earth, normally credited to Isaac Newton almost a thousand years later.

3. Al-Khwārizmī  (c.780 – 850 AD)


Whilst Europe was in the Dark Ages, it was the Golden Age of Islam, during which knowledge flourished in the Middle East. Al-Khwārizmī was one of many extremely talented medieval Islamic learned men and made lots of contributions to human knowledge, not just in the field of astronomy. His contribution to astronomy was to produce a similar work to that of Ptolemy,  called the Zij al-Sindhind, but based on work of Indian astronomers.

Al-Khwārizmī’s book contained tables that could be used to calculate the positions of the Sun and the five planets known at the time. How did he change the world? Prior to his book, Islamic astronomers had been more concerned with the translation of other works and learning the knowledge of others. Subsequent Islamic astronomers carried out their own independent research and began to come up with original ideas of their own.

4. Galileo (1564 – 1642)

Galileo Galilei


Most Early astronomy placed the Earth at the centre of the universe, however, a rival theory arose — the heliocentric theory which placed the Sun at the centre of things. Galileo was a learned man and supported it. But since this idea was against the teachings of the Roman Catholic Church, its followers were seen as heretics. Usually, heretics were executed, but Galileo was too well known to meet that fate so he was placed under house arrest.

Galileo was the first person to look at the sky through a telescope and systematically record what he saw. For this reason, he is widely seen as the ‘father of observational astronomy‘.

Taught science for 16 years at a secondary school in the East Midlands.