The history of astronomy

Current research assumes that astronomy is almost as old as mankind itself. Astronomy was already practiced by the first advanced civilizations, for example in ancient Babylonia, where star constellations were observed from 3000 BC and recorded on clay tablets, as were the times of the rising and setting of stars and planets. However, the ancient Egyptians also had a relatively highly developed astronomy: a solar calendar could already be compiled based on years of systematic observations. Additionally, outside these advanced civilizations, which also included the Maya, the first astronomical cult centers existed, such as Stonehenge in England, which was built between 3000 and 2000 BC.

There were two main reasons why mankind began to study celestial bodies. Firstly, astrologers have always tried to predict future events by interpreting celestial phenomena. Secondly, it is impossible to create a calendar without basic astronomical knowledge, because every calendar, whether lunar or solar, must be preceded by long, systematic observations of the sky. A calendar is absolutely necessary to regulate life in highly developed cultures. For example, it would be very difficult to determine a date for sowing and harvesting without an exact calendar, as the seasonal weather changes are too unreliable for this in most areas.

Calendars are also needed in more highly developed religions to regulate the ritual year, as well as for civil administration and the drafting of contracts. These are all achievements without which an advanced civilization as we know it is practically impossible. Consequently, without calendars and previous astronomical observations, it would hardly have been possible for mankind to develop beyond the hunter-gatherer stage. Astronomy was therefore one of the cornerstones of the first civilizations. As important as it was, its role remained constant and essentially unchanged over the following millennia.

It was not until the Middle Ages that there was a change that altered the world of astronomy forever: Nicolaus Copernicus, presumably inspired by ancient models, no longer based his calculations of the position of celestial bodies on the earth as the center of the world. In his main work "De Revolutionibus Orbium Coelestium", he placed the sun at the center and can therefore be regarded as the founder of the heliocentric view of the world.

However, decades were to pass before two other researchers tackled this controversial subject: Galileo Galilei and Johannes Kepler. Galileo, the older of the two, was the first astronomer to use a telescope and publish what he observed. However, he did not invent this revolutionary instrument himself; it was a further development of telescopes already in use and originally built in the Netherlands. With this new instrument, he made a groundbreaking discovery. He was the first to observe the moons of Jupiter in 1609 and realized that they move in a kind of circular orbit around the largest planet in our solar system. This and a number of other discoveries led Galileo, like his predecessor Copernicus, to hold the view, which was not without danger at the time, that the earth orbited the sun and not the other way around.

Johannes Kepler followed a similar path. But unlike Copernicus and Galileo, he concentrated on evaluating the observations of somebody else, namely Tycho Brahe. During his time as a court scholar at the Danish royal court, Brahe compiled extremely precise catalogs of the locations of stars and planets. After his time in Denmark, Brahe took his observations to Prague and worked there as an imperial court mathematician. Brahe died in 1601, Kepler became his successor and thus gained access to the results of Brahe's observations. Kepler began to analyze the enormous amount of data at the time and published his results in 1609 and 1619. From this, Kepler's three famous laws were born. However, it was not until years later that Isaac Newton, who published his theory of gravitation at the end of the 17th century, which was partly based on Kepler's work, discovered the cause of the rules Kepler had found for the movements of the planets.

But as essential as the discoveries described above were, they did little to change the actual field of work of most astronomers. They continued to concentrate on observing the positions of stars and planets and recording them with ever greater accuracy in so-called ephemeris tables. These catalogs were used for calculating the orbits of planets, for calendars and for navigation on the high seas, but astrologers also waited for the latest, even more accurate results to be used for their lucrative business.

It was not until the middle of the 19th century that completely new fields of work were added to this millennia-old classical astronomy (positional astronomy) in a kind of revolutionary upheaval, for which the name astrophysics was introduced for better differentiation.

The basis for this were three fundamental developments for the future path of astronomy. Firstly, the invention of photography. For the first time, what was seen through a telescope no longer had to be laboriously drawn by hand. The arrival of cameras in observatories opened up completely new ways of working for astronomers. Secondly, the photometer, with which star brightness could now be measured objectively and no longer had to be estimated by eye. Thirdly, spectroscopy, which would not have been possible without photography and which made it possible for the first time to make statements about the physical and chemical properties of a star in addition to its position and brightness.

From the middle of the 19th century, this new branch of science spread steadily throughout the world. Just under a hundred years later, classical astronomy had almost been superseded and today there are only a few institutes worldwide that conduct pure positional astronomy.

However, although science is now almost exclusively concerned with astrophysical issues, technical systems, such as the American Global Positioning System (GPS), still require the most accurate star positions possible in order to function properly. But even our calendar is regularly readjusted on the basis of extremely precise star position data, which in principle is still the same process as performed by the ancient Babylonians.

Positional astronomy is therefore neither obsolete nor outdated, but the current scientific discourse is entirely astrophysical. And in order to gain new insights, astrophysics has required ever more powerful telescopes since its inception.